How Nuclear Reactors Work, And How They Fail

"Sure! But it's not as effective as unplugging a rogue kitchen appliance, mostly due to some chemical reactions inherent in the fission reaction"

Um...yea NO. Chemical reactions? Listen popsci, I expect this from gizmodo, really I do, and I'm ok with that. But from you guys I do expect a bit more. It's a NUCLEAR reaction. One of the main differences between nuclear reaction and chemical reaction is related to how the reaction takes place in the atom. While nuclear reaction takes place in the atom’s nucleus, the electrons in the atom are responsible for Chemical reactions. Chemical reactions involve the transfer, loss, gain and sharing of electrons and nothing takes place in the nucleus. Nuclear reactions involve the decomposition of the nucleus and have nothing to do with the electrons.

So next time. Please do your research.

By chemical reactions, he means the the reactions such as the rust, zirconium, and hydrogen reaction. A nuclear reactor has plenty of components that can undergo chemical reactions under the extreme heat. The reactors themselves have been shut down.

@ adamsulik1988
Dude its just an informative guide on the trems meltdown and how reactors work, there is no need to rant about the electron and neclear reaction differences. I respect your knowledge and I actually learned something, but people make mistakes, okay

Very informative and easy to understand. Thank you, Dan Nosowitz and PopSci. Let's hope TEPCO can get their reactors under control.

I am a retired Metallurgical and Nuclear engineer and am familiar with the two oldest Fukushima reactors, as the company I worked for offered a different (more expensive) design for the 1974 and later installations.
The Fukushima reactors are BWR (boiling water reactors) of which the early Mark I and Mark II installations had and have basic design problems. These design problems have been known and have been written about since 1972 by AEC officials.

The surprising issue is why the power company was not forced to increase the reliability of the emergency cooling system, in a highly seismic operating environment.

Very similar problems exist in similar US installations and the gov. officials (like the financial meltdown guardians) do not seem to be stepping up to the issues.

The primary issue in Japan is not specifically that the reactors are BWR units, but that the emergency cooling systems and the reactor are mounted on separate concrete pads which in the case of a bad earthquake can move relative to each other and break the emergency cooling piping. At this point, it makes no difference if the pumps work or not.

Nuclear "accidents" are caused by relatively boring but very specific technical details, a "valve failed". Fine but exactly how? We are talking about big valves (some bigger than a limo) that are mechanical devices, motor or hydraulically operated, electrically actuated and electronically controlled. So when we speak of "X failed", exactly what happened? Mechanical problem? What kind of mechanical problem? and so on and so forth. When we finally get the answers -- we will see that something or a series of something really quite stupid happened.

With regard to future nuclear accidents, lets make a few things points: 1)a truly 100% failsafe installation is probably too expensive. 2)the thick concrete pad containing the reactor can sort of "float" during a bad earthquake. 3)the emergency cooling systems MUST work even after normal shutdown. 4)a bigger more expensive containment building is better. 5)the emergency pumps and as much cooling piping as possible must be on the same "floating" concrete pad as the reactor. 6) chose something other than just the cheapest design and give it better maintenance than the Davis-Besse installation.

Bad car accidents are always caused by at least 3 or 4 issues. Bad tires, bad brakes and rain do not cause an accident ----- until you need to stop.

Nuclear accidents are not necessarily ENGINEERING problems as often as they are accounting problems. How many nuclear ships have blown up? The stakes are a little higher than private company profit.

Until we know in great detail all of the boring technical elements of the cooling failure, we cannot properly criticize anyone. However design shortcomings have been known for almost 40 years and should be a wake-up call for the US.

regards

I am playing arm chair quarter about what went wrong with the Japanese nuclear reactors like most people are doing right now but if I am right maybe it will help.

I'm not in the least bit surprised they having a meltdown problem. Throwing salt water on the reactor is like throwing gas onto a fire or trying to put out a magnesium fire with a fire extinguisher ingredients made out of CO2...

Salt water ions very easily splits water molecules, H2O, in a current at a lower temperature than pure H2O, into its elementary hydrogen and oxygen components. Salt water is a much better conductor of electricity than plain old water. Pure water is an electrical insulator not a electrical conductor, through some other ingredients in the water and it quickly changes into a electrical conductor, with salt it is a very good electrical conductor. Therefore the buildup of hydrogen in the containment building is mostly caused by them trying to cool the radiation down with salt water. The fuel rods would have to get over 2500 C to split pure water molecules into hydrogen and oxygen, with saltwater the temperature can be much lower...

Ron Bennett

@ rlb2
Had to comment. That's a nice basic description of electrolysis, but has nothing to do with what’s going on here. The Article mentions how the Zirconium in the fuel cladding reacts with the minimal water/steam present to create Zirconium dioxide and hydrogen. That hydrogen out-gassing is what caused the explosions. There is no current(amperes) present in the core that would cause electrolysis, and the introduction of seawater is purely for heat transfer away from the core and to keep it covered with water (below the temps that cause the H2 gassing, and ‘further’ core damage) Steam voids in a core = bad. Seawater is used primarily because there is nearly an infinite supply. I won't even touch the inaccuracies of: "trying to cool the radiation down with salt water."

formerNuke - I'm just playing armchair nuclear quarter back here and trying to see if there was a link between the salt water they used to cool the nuclear reactor and the overabundance of hydrogen gas leak. I am not in any way a nuke engineer although I do have several other engineering degrees. My hunch is that it also may be a product of what John Kanzius discovered last year where radio waves were used on salt water that caused an intense flame, that reaction was not conventional electrolysis as we know it.
See here:

www.youtube.com/watch?v=e8utkoK2DhA

With nuclear fission classical decay you have alpha decay, beta decay, and gamma radiation those different types of radiation interacting with salt water may also produce hydrogen gas, we just haven't discovered it yet, at least that is with the limited knowledge I have about what type of coolants are used today. Do they use salt water in nuclear submarines to cool them down, from all I read they use liquid metals. If you know of some other time salt water was used to cool a nuclear reactor down please enlighten me?

Ron Bennett

Ron Bennet.

The sub and other marine reactors are not BWR units but rather PWR units. Pressure Water Reactors as well as the Fukushima installations are "light water reactors" light water meaning regular distilled water. However the Fukushima 1 to 8 are all BWR units. Liquid metals are normally used in "breeder reactors", with several isolated cooling loops.

The BWR, Boiling Water Reactors use the water that cools the reactor (and turns to steam, hence "boiling") to power the turbines. The BWR units are ALL cheaper and from a design point of view less safe in a seismic area, because the reactor water goes into a long loop outside of the reactor building, to the turbine building. (please read above comment)

A sub nuke is a PWR (pressurized water reactor) in which the reactor cooling water goes into a steam generator (big heat exchanger) then the second loop goes to the turbine. After the steam leaves the turbine, it then passes into another heat exchanger which has sea water on one side and the turbine steam / water on the other side. So no nuke water goes either into the turbine or the ocean. In a BWR the turbine becomes contaminated and all pipes and turbines must be shrouded. In a PWR the reactor pressure is higher, but does not leave the reactor building.

Next is a general statement, which is my opinion. A PWR is a safer, higher cost and higher tech system as compared to a BWR. The pressure inside the reactor is about 75 bar in a BWR and about 160 bar in a PWR. Generally A PWR has higher installation cost and higher maint. cost than a BWR. And due to the high pressure, dead sure maint. must be done. My opinion is that low cooling pipe rupture probability indicates a BWR. A high piping rupture possibility (as a war ship or highly seismic area) indicates a PWR unit.

Aside from all the "experts" who have been on TV lately, real down to earth issues are the ones that count. A nuke PHD can explain ad nausium nuclear reactions, but most problems are based on other issues ----- which in many cases are REALLY difficult to know, but once you know them - seem pretty stupid not to have been known.

For example, neutrons will always perform as the experts describe. But in a system involving tens of thousands of welds and thousands of yards of electrical cable, exactly which weld was marginal and how do you find it? or exactly which of several million electrical connections was a bit loose??. Light water cooling sounds pretty safe, and it is up to the point that it can have a drop dead guarantee. It seems as though everyone knows that the nuke reactions get upset in the absence of cooling. But the cooling guarantee is not "drop dead", particularly so in a BWR. Nuke plant designers and builders are limited by accounting (read Money) issues to a "most likely" scenario, we are kidding ourselves if we think that anything (except maybe NASA and the US Navy)gets real "drop dead" engineering. So I am really sorry for Davis-Besse, Three Mile Island and Fukushima, but "drop dead" quality usually means eliminating the accountants.

This creates a bigger problem however, the human race has to fork over the money or put up with the occasional disaster, or live in the dark or live with fossil fuel pollution. Wind, sea wave, river and other renewable power is great but I do not think there will ever be enough.

There are about 450 nuclear installations world wide, this almost means we are still in the "prototype" or "preproduction" phase. The world wide nuke issue REQUIRES standardized modular plants and should not be proposed and sold as either cheap to build or cheap to run or cheap to dismantle --- I wished I could see an alternative.

Regards

i say that we should make the containment vessel out of tungsten carbide it has the highest melting point 3410 °C (6170 °F)this should in the case of a melt down keep the corium contained. if im wrong about that feel free to viciously critisize me as us pop sci people tend to do

here is a site that shows what element react with and below is the link to the page talking about tungsten. oh and i didnt mean tungsten carbide i ment just pure tungsten.
http://www.webelements.com/tungsten/chemistry.html

I'm not a very technical person who looks more onto the details of these things and has fights about technicalities of the matter but all I have to say about this is what if it DOES go into full meltdown? My friend and I had a conversation about how dangerous it could be if all those nice gases came flying out of the core. Let's just say it wasn't a very good outcome.

@hackerslayer787.

Please read my two posts.

Good basic idea, unfortunately that which makes Tungsten ideal for a lot of things --- makes it impossible to create the big forgings necessary for nuclear reaction chambers.

I am a both a Metallurgical and Nuclear engineer, but I have relatively little practical experience with pure Tungsten. Usually the inside of the reactor vessel is lined with 3/16 inch thick high chrome stainless steel. Even this thickness is due to economic / "most likely" considerations.

I honestly do not know, but have colleagues who claim it would not be possible to line the reactor with pure tungsten.

In the real world, accountants and financial issues often take precedence over real "drop dead" 100% or even 99% safe engineering solutions.

Perhaps a SS / Tungsten alloy (decidedly more expensive) could be used for the reactor lining. Based on my 35 years of experience, this solution is not in the "most likely" category of anticipated problems to protect against. So even if technically doable, probably not within the economic limits of a profitable power plant.

regards

very true i would never have thought of that as i am a high school student and not an engineer but thanks for the review

Riccio or others,

One thing I don't understand is the long term need for cooling. Obviously, when the core/fuel rods are hot (just after shut down), cooling was needed so they wouldn't degrade or melt. And this cooling must be active, I think, in that the cool water must be injected and warm water removed in a circulating process. Since circulating, it must be driven by an electric or diesel pump.

How long does this cooling need to continue? Is there ever a point or temperature or state of radioactivity where the rods can be left alone with no water circulation cooling need? (Though maybe submerged under water.)

Larry

LMarv

i belive at the moment they brought in another smaller pump/generator to cycle salt water through the reactor

circulation needs to continue until radio active decay is complete and until nuclear fission stops at that point the rods should be cool and should allow for removal and or repair of the reactor.

feel free to correct me if im wrong Riccio

couldnt you simply pump some liquid nitrogen into the cooling chamber or would that be to cold and crack somthing vital?

It is important to realize there are two different key objects within the reactor vessel: Fuel Cells, and Control Rods. The Control Rods were inserted in between Fuel Cells to stop the fission process (neutron flux)that is ongoing (this is call a SCRAM) That basically kills the reaction, but as the article states (and hackerslayer787 is correct) the decay heat and SELF fission of radioactive isotopes keeps generating heat within the vessel. If proper cooling is maintained and the fission process is kept shut down, after a good amount of time, you don't need to continue to supply cooling water...just maintain a water blanket over the core. Any residual decay heat will be lost to the ambient environment (i.e. to the vessel, piping, air in the Reactor compartment, etc.) It will reach an equilibrium. The time it takes to reach equilibrium depends on things like reactor size, operational temps/press, fuel loading, etc.

as for the nitrogen...yes too cold...at that point you'd be worried about brittle fracture of the reactor vessel due to temp stresses...and then you just cause a release from the primary protection closure

Thank-you for the replies!
L

What if you dumped Liquid Nitrogen in at he top of the pool, and it didnt freeze the water? Just super cool the top half?

Corium - more wackadoodle stuff. No moderation no nuclear reacton and temperatures well under the melting temperature of steel. This was what happened at TMI when the cooling system shut off.

Barely scraped the inside of the vessel.

@LMarv

The example I would like to use is not exactly correct, but simple and sort of correct. Technical experts, please bear with an oversimplified story.

Perhaps almost everyone knows that when you cook food in a microwave oven, you should let the food "rest" for about 1.5 minutes per inch of thickness. Why?

A microwave heats food by bombarding the water molecules with a "microwave" that due to being "micro" and a multiple of the atomic bond between the hydrogen and oxygen atoms --- "excites" or increases the vibration of the water molecule components (H and O2. this vibration heats up the food.

** so microwaves excite and heat the water in the food, which is why you can cook in paper or some plastic plates that do not contain atomic bonds similar to water**

But immediately after the microwave shuts off, the atoms are still vibrating and a bite of hot microwave food too soon out of the oven will burn you --- and sucking air or drinking a sip of water will not immediately stop the atomic vibration.

Now without getting into some messy and complicated descriptions - another short example. A flame is a slow explosion. And an explosion is a very rapid flame. But the atoms do not disintegrate - they just recombine to form other molecules with less energy, releasing molecular energy as heat.

Now to the nukes. Nuclear heat is not generated by recombining molecules --- which on it's own can be difficult to slowdown or stop. As in a forest or house fire, which is just hydro-carbon atoms recombining to create carbon dioxide, acid rain etc.

Nuclear heat is instead created by the "explosion of atoms", but not just the simple explosion of electrons jumping around. A nuclear explosion (however slow or fast, regulated or not) is serious business because it basically explodes the nucleus of the atom -- hence "Nuclear".

Now sometimes in your microwave, you hear little "pops", this is a small group of water molecules "exploding" or boiling, because the vibration is too great and the strength of the atomic bonds holding the molecule together can no longer retain it's structure as a liquid and becomes a gas (steam).

In a nuclear "reaction", the "re" part of the action is as a result or "reaction" to having too many radioactive particles close together. And the atomic nuclei are "exploding" because they are being "bombarded" by fast moving sub atomic particles in nearby Uranium or other "nuclear" material. Just as a big fire cannot be stopped immediately. A serious explosion cannot be halted immediately. And an explosion involving atomic nuclei is very serious.

The carbon rods (or whatever they are made of, for different types of nuclear fuel) are pushed in between the fuel rods, they slow the sub atomic particles that were flying around.
When there are sufficient of these "moderator" rods in place, the speed of the "acting" particles is slowed to the point where they do not have sufficient energy to "explode" any more nuclei. But this takes quite a while, because the nuclei that just previously exploded are VERY fast and the moderator rods do not slow them down immediately.

So depending on the density of the radioactive nuclear fuel and the exact reactor construction, it can take a couple of weeks of normal (substantial) cooling to actually stop (and cool)the reactor core. Different designs have different cooling temperature curves with respect to time --- but there are NO nuclear power plants that can be either stopped to "cold" or started from "cold" in less than a week or so.

This is why newer generation designs rely on so called "passive", "gravity" or some other theoretically "natural" force that does not require human intervention to stop.

Unfortunately the real "worst case" ability of these designs to actually stop by themselves is very discuss-able.
Meaning that I would have to see it to be convinced.

Three mile Island had a partial meltdown and it is still locked up, so there are still fast sub-atomic particles jumping around.

This is why storing "expended" fuel is such a HOT topic. Expended fuel is not dead, just not sufficiently active to be used as fuel. But is still really serious stuff that can't be swept under the rug, and must be treated almost as carefully as usable nuclear fuel.

Sorry, this is probably pretty boring, but "reasonably" safe or "once in 100 years" is not "drop dead" safe. Especially if the once in 100 or once in 500 years happens "on your watch" when you are 20 years old. When did the 500 years start?, and two "once in 500 year" incidents can happen in year 500 and 501. Bad timing on your part, from 1511 to 2511 everybody else got off Scott free, you just got fried.

I do believe that truly "drop dead" safe nuclear reactors can be built --- but they probably do not conform to a high corporate profit or to back room politics.

Regards

More boring technical comments, that I think are correct.

My understanding is that 3 reactors were "shutdown" for maintenance. This means that their fuel cores were perhaps in the spent fuel storage pools. Even spent or exhausted fuel is not dead, and for sure the stored fuel from the deactivated reactors is still active. The storage pools have to be cooled. If cooling is not possible, perhaps the explosion that blew off the top of the reactor building was due to excessive hydrogen buildup in the upper part of the reactor building where the spent fuel rods are stored.

Quite a bit of conjecture here, but I do not believe that we really know and I don't trust either the authorities or the operating company to explain that they made a series of mistakes.

I would like to go on record at this time by saying that in addition to the reactor problems, I think that there are spent fuel rod storage pool cooling problems.

Bottom line is that we could be in for something of which we have seen only the beginning. The old fuel rods can eventually cause hydrogen explosions if exposed due to low water level. So while a true "meltdown" may be avoided, repeated hydrogen explosions due to excess hydrogen accumulation in both the reactor building and the fuel storage pools are likely.

Don't be surprised if it gets a lot worse.

Regards.

If this Corium can burn through pretty much everything, whats to stop it from going straight through the ground forever? I know it sounds silly but if this stuff is that hot it almost seems like it can really create something catastrophic. Can the Corium then set off another natural disaster?

Riccio, thank-you for the new explanation. The idea of active pumping needed essentially all the time is crazy--there are so many scenarios that could lead to loss of the pumps, electricity, diesel fuel, people to run the pumps. It's shocking to think we allow designs like this. Passive sounds better, but, even if it works there are 100's of multi-billion dollar facilities that we'll never shut down.

I see many articles and discussions of the probability of something happening at a nuke power plant, like 10000 to 1 or something like that. But one of the things that I think is little discussed is the potential risks from nuclear power from these supposedly unlikely plant problems.

If there is an 0.0001 chance for a problem to occur that kills no one and destroys $1 million in equipment and facilities, that is bad. However, if you have an 0.0001 chance for a problem to occur that kills dozens, causes cancer in 1000's, destroys $billions in equipment, costs 10's of billions in associated costs and requires decades of human exclusion from vast areas, that's REALLY bad. Some might say unacceptable, even at 10000 to 1.

But I guess 1 in 10,000 sounds good as a sound bite.

although corium is hot i do not think its gonna melt through the whole earth nor do i think it can cause much more than some mutated Japanese workers.

And this is why we have CANDU (heavy water) reactors... Fewer parts = lower risk, to a point.

On a more relevant note, what bothers me most is when the media says "...radioactive steam has been released...". The steam is not any more radioactive than the cup of tea I put in my microwave. Just because something has come into contact with radiation doesn't mean that it becomes radioactive too. If that were the case the Japanese would all be glowing!

I am no scientist so this may be very naive. I have two questions in regards to the reactor problems in Japan.

1. Could workers use a fire hose type system to spray water on the reactors from the air? I heard they tried to dump water from the air but could not get above the reactors because of the radioactive steam.

Years (30+) ago working in landscape construction on interstate highways we used tanker with a water / hydro-muclh mix to protect grass seed on hillsides. It seems a similar type of solution could be used to get water to the reactors.

2. Could some type of foam be used to contain the fuel rods and protect the Japanese from radiation?

Thanks for listening.

@dennisely

The nuclear power plant and reactor construct that make it safe also makes it hard to fix.

The GE designed and Mitsubishi constructed power plant reactor building has a very heavy "reactor vessel" at the center. This is pretty tough, from 6 to 10 inch thick steel with a 3/16 inch stainless steel liner. This sets on top of a big donut shaped expansion tank, and everything is supported be a thick concrete floor that allows the building to sort of "float" during a big quake. At a distance of a few yards all around, this is covered by the primary "reactor containment building", (with the general shape of an inverted light bulb) this is also a tough nut, made of 3 foot thick steel reinforced concrete (the reinforcement bars are not coat hangers, but heavy, big and not junk steel).

The water that cools the reactor, actually boils - creates steam and is piped out of the reactor vessel, past the open space around the reactor vessel and through the reactor containment building wall. Then these pipes (for some reactors as big as 30 inches in diameter) are supported by the big heavy floor of the turbine building, and into the turbines.

Thus the two primary equipment platforms are big and heavy (hundreds of tons) but during a quake as bad as the one experienced, these two pads can move with respect to one another. This ruptures the pipe going to the turbine and the pipe going back to the reactor.

The regular cooling is dead. The emergency cooling is inside the reactor building and needs power for the pump motors. Apparently another bad design placed the emergency generators where the tidal wave either swept them away or rendered them unusable.

The spent fuel storage pools are near the top of the reactor building, on either side of the narrow top. Spent fuel is not dead and must be kept cool. The rectangular top of the containment building is really not part of the containment building but is simply a heavy sheet metal shed to protect the spent fuel storage pools, the crane and other misc. equipment.

Now to your question, The reactor core is of course inside the reactor vessel, which is inside the reactor containment building. For some reason the emergency pumping and cooling system doesn't work and things are getting hot. Probably some radiation is escaping from the broken regular cooling pipes.

Now to complicate things, I think that the fuel pool cooling pipes were sheared along with the reactor pipes. Maybe even the pool walls cracked. In any case the water begins to boil, but boiling is not just bubbling - boiling separates the water into hydrogen and oxygen. After a while the stored fuel rods peek out of the water, now high velocity rusting of the rod protection tubes starts, and the water boils faster. Eventually the steel shed fills with hydrogen and starts to bulge at the seams. When this happens, the trapped hydrogen escapes and recombines with the oxygen in the atmosphere --- this creates a nice big orange fire ball (which maybe you saw in the first film clips). This fireball is a fast moving flame or a slow explosion, but it blows the shed on top of the containment building to bits and probably blows out a few ton of radioactive water and maybe even some fuel rod material.

This is why only the top of the building blew up. The bottom part is the heavy cement structure.

My opinion is that this secondary outside radiation is making it almost impossible to get close to or inside the reactor containment building to start correcting / cooling the reactor vessel.

Unfortunately the heat inside the reactor is very high and I do not think that small amounts of anything (foam or liquid salt is going to work - they just need lots and lots of water.

If you are not already bored to death, please read some of my earlier posts.

Keep in mind that, the spent fuel pools in other reactor buildings could go the same way, but even as serious as this is --- it has almost nothing to do with a melt down or radioactive stuff escaping from either the reactor vessel or the reactor containment building. But some brave soul has to get inside and at least cool down the outside of the reactor vessel if it is not possible to rig temporary cooling through the broken reactor / turbine pipes.

Regards

The seeker of knowledge who seeks to reach beyond the stars to go where no mans gone before to see things no man has seen and bring these experiences back for the whole world to hear and see.

from Ricco posts all of them i understand what he is saying i believe their best bet is to pump in sea water in high volume with liquid nitrogen this is dangerouse yes but it will speed the cooling process up then they need put a large amount of Palladium into the dome or where the hydrogen gas tends to go to this will absorb the hydrogen and change the palladium into quasi liquid. I think this is their best solution to prob. and on another note do to this event i will post an rticle from my collegues research data i think all you energy nuts might find a little interesting here read this..........

After palladium absorbs enough hydrogen Water begins behaving like quasi-liquid at low distance scale too due the presence of water clusters, which are held together firmly - but they're still elastic and fluous. One of applications of this behavior (between creation of various homeopathic medicals, etc.) is to put a radiowaves into such clusters. If you balance the frequency of standing waves at the surface and volume of clusters well, a resonance breaking of water molecules will occur at the energy density, which is million-times lower, then the energy density required for splitting of water molecules. Even better, the metastable mixture of hydrogen and hydrogen peroxide will be formed, which could never appear during splitting of water at high temperatures.

And the memo is, if you create a quasi-liquid deuterium clusters in palladium and put the proper microwave frequency into it, then the standing waves at the surface of clusters would resonate with volume of atoms in such a way, a beta capture may occur, which could initiate a nuclear reaction at the energy density million-times lower, then it's required for production of unlimited energy in expensive & dirty tokamaks. Even bettter, during such reaction the metastable channel of nuclear reaction will occur without formation of neutrons - which is something, what could never occur during hot fusion.

Again this could lead to a limitless and engergy and a clean alternative to nuclear hot fision which is highly dengerouse and very hazerdouse.

It's interesting to note the comparisons being made between the Chernobyl reactor incident and BWR reactors. The Chernobyl reactor had a positive temperature coefficient, while BWR's and PWR's have a negative temper coefficient. In other words, when a reactor using U235 loses it's moderator, the majority of the neutrons leak out, causing the reactor to shut down. This of course, as has been noted, does not stop decay heat or destruction of the core. Chernobyl used plutonium 239 and U238, which require high energy neutrons for fission. Lose the moderator and reactor still lives. Operating with a positive temperature coefficient is a bit like driving a car where you need to step on the gas to slow down. The main comparison between the two types of reactors is their ability to produce fission products and scare the public.

Has anyone seen the idiotic news that helicopters are dumping water on the reactors???

This is like trying to flush the toilet in a bomb shelter by dumping water on it.

The helicopters are trying (but tons of junk are in the way) to dump water into or on to the spent fuel storage tanks.

No one can even get to the reactor containment building, much less inside - near the reactor, with the spent fuel pools spitting out radiation.

Hope everyone here understands that the reactor core is a box, inside a box (reactor vessel) - that is inside another box (reactor containment building), that is sitting under another box (the spent fuel pools) - which are spiting out bad stuff.

You can't just walk up to the front door and say "madam, I am here to fix your furnace". This place is like a war zone.

I wish the news media would all get together and hire at least one person who knows the difference between the gas tank and the engine.

I keep seeing this stuff on TV over and over first it was the fact oh big earthquake and tsunami but now its this its just one thing or another with Japan I mean really gotta feel bad for them. Anyway I have a question. My friend that kinda goes off about stuff like this was whining and complaining how if all the gases were released from this thing he said it was enough to travel around the world and make everything covered in radiation. I personally didn't think this but I want people who actually study this stuff to tell me cause in a way it COULD be possible (not very at that) but it's not so I'm just stuck in a corner here.

I'm curious to know what the plan is. Is the plan to restore power and startup the 'regular' cooling system? Why was it not possible to bring in those semi-trailer size generators and run the systems off of that?

On the flipside, if the cooling system was not damaged in the quake and just lost power, wouldn't it have been better to restart the reactor to generate the power to run the pumps? Or is the reactor not plugged in to its own power? Or would the heat increase at a rate faster then the pumps could cool it and would not be able to catch up.

I'm obviously no nuclear scientist, just curious.

To some extent the problem of hydrogen buildup in the containment buildings is a self-correcting one (albeit dangerous). Once the hydrogen explosion blows the skin off the building, any future hydrogen generated will just escape into the atmosphere rather than build up to explosive concentrations.

It seems like since they knew this was going to be an issue, they needed to punch some holes in the walls to vent the gas. This probably could have been accomplished in time under normal circumstances, but with all of the other earthquake and tsunami damage it was too much to get the resources/equipment in place to do it.

On a separate note, I too find it puzzling that if all they needed was simply power and/or pumps that these things couldn't have been flown in by helicopter. Surely these sort of things are available in many places, not least of which being military bases. Any of the decent sized naval bases is sure to have some pretty big pumps available. And mobile generators are used in many circumstances. Any one have any insight into this? Is it just that the power requirements are so great that mobile generators aren't up to the task?

Hi Riccio,

Yeah, I've seen the videos of the two helicopters trying to dump water on top of reactors 3 and 4. Virtually all of the water wasn't even hitting the tops of the reactor buildings they were trying to hit. It looked like a futile attempt.

@Loocster05
The only radioactive stuff in that building is the fissile material contained in the fuel rods. Any water/steam/other gasses coming out of there is not radioactive.

The only way for truly radioactive material to come out of there would be having the fuel rods to explode or vaporize,or some free neutrons to convert something already in the atmosphere to one of its radioactive isotopes. The most likely incidence of the latter would be some hydrogen in the steam coming out of there to become tritium, which is only ever created in trace amounts anyway.

So no, the reactor could not release enough radioactive gasses to cover the globe, not by a long shot. You've got nothing to worry about.

Nuclear fission power plants will be ever unsafe representing a constant menace for mankind because it was initially designed for breeding plutonium for nuclear weapons. On the other hand, the aneutronic fusion almost doesn't emit neutrons being unsuitable to breed radioactive materials. Furthermore, it can generate an awesome electric power using small areas without radiation hazards, doing this kind of energy, in my opinion, the most dense and environmentally friendly energy than ever. www.crossfirefusion.com/nuclear-fusion-reactor/overview.html

Yeah, there's just on teensie weensie problem with fusion, though: nobody's ever broken net zero (produced as much electricity as they put in) with fusion. Also, did nobody ever tell you that the H-bomb was a fusion bomb? Yes, fission can be used to produce plutonium to use in nukes, but it is primarily used to produce electricity. And so long as we here in Canada remain the world's primary producer of uranium, we intend to keep it that way.

Robert1234: Doesn't anyone recognize the real problem? If the cooling water is flowing, NONE of this happens. The cooling water is NOT flowing because the pumps, power, valves, etc. are not functioning. If the cooling water were ABOVE the reactor, it could be gravity fed, and if properly designed, naturally circulated, and NO PROBLEM WOULD EXIST. The idiots designing these systems have it backwards in the most critical phase. COOLING WATER ABOVE, REACTOR BELOW.

Steel mills use this system and in 200 years it never failed. In nuke plants, emergency cooling has NEVER WORKED right yet.

The good thing about this is that solar will certainly be used by the Japanese to a much greater extent in their rebuilding. The safety and long term benefits (free energy from the sun) are undeniable. Nuclear will become an energy of the past as millions of solar rooftops dot the landscape.
Their economy will grow quickly as the cost of electricity (including transmission) is eliminated from every citizen and small business budget.
Industry may also take the cue from the Ford Focus factory and use solar assisted power for robotic mass production. The vehicles destroyed will be replaced by lower cost electrics. The solar charging will totally eliminate the cost of gasoline for the life of the vehicles.

I have been following the posts for this article for several days now, and I want to thank all who have contributed. I want to especially thank Riccio for his very informative posts! It seems to me that a system that is so dependent on an always working power grid is one that shows profit always trumps safety. The backup system only had fuel for hours, so if the grid doesn't come back you are in real trouble. Since the tsunami destroyed the backup system, they didn't even have that! I am sure, they thought that they could truck in any fuel or replacement generators that were needed if the backup systems didn't work or were about to run out of fuel, but this was after an earthquake, and a tsunami. The Japanese who seem so good in improving existing technology, incredibly have done little to nothing to refine these nuclear plants in the last 40 years, shows me that even they have been corrupted by the pursuit of profits. I am not against capitalism, but unchecked greed cannot be allowed in any country. I think safety should always be placed ahead of profits. If I am wrong in any of my conclusions, please let me know. Thanks!!!

Robert1234: TrulyVisionary, you're full of crap. The stuff you posted is crap. I can't imagine why you bothered to waste your and my time posting it. "...could lead to a limitless and engergy and a clean alternative to nuclear hot fision..."

Your proposal simply makes no sense at all. Give it up.

With Chernobyl, the Russians pumped concrete into the reactor building and created a "sarcophagus" to contain the radiation. Chernobyl wasn't a BWR but was based on graphite (like Fermi's first reactor?). Creating a sarcophagus for Fukushima Naiishi wouldn't work, would it?

Also, some of the spent fuel pools are heating up (increasing fission?) and giving off radiation, and I assume that the reactor or reactors which are not being cooled correctly are radiating more. Does the additional radiation from these outside sources speed up the reactions in any one of the fissioning sites?

Riccio,

I had a couple of questions, if you wouldn't mind taking the time to answer them. By the way, I appreciate all of the time and trouble that you have already taken, in providing the rest of us non-nuclear-types, such as myself, with a lot of interesting information and viewpoints.

Question #1: As stated, I'm certainly not a nuclear engineer, but it seems like a "no-brainer" to avoid the design which they implemented at Fukushima, in which they stored the spent fuels rods right next to a working nuclear core. It would be like asking for some kind of a "domino effect." That seems, to me, to be kind of analogous to piling hundreds of old, half-full gas cans adjacent to the huge fire that you've built, while burning your backyard brush. No one can forsee an accident, of course, and that's why they call'em "accidents," but doesn't common sense tell you to be prudent, and store such dangerous materials away from harm's way, in case of an accident, such as the ones (earthquake and tsunami) that we just witnessed? It wouldn't seem like it would require a PhD in nuclear engineering, to figure such an obvious thing out. Where is the common sense, in all of this? Or am I missing something, here? I'd be willing to bet that, whatever the answer to such an obvious question, it's eventually going to come back to nothing more than money; just a jaded, pessimistic guess, though, of course.

Queston #2: A few years ago, I read an article, in either Popular Science or Discover magazine, about a nuclear reactor that the Chinese were building, based on a design created by the Germans. In this design, it was stated that the reactor would not be able to go critical, in the case of an accident, due to the design of the fuel, itself. As I remember, it entailed the use of small spheres of radioactive material, instead of the usual "Tootsie Roll" pellets that are currently employed in the fuel rods. By using a spherical configuration, the article stated that, in the event of an accident, the fuel-laden spheres would heat, thereby expanding, which would separate them from each other enough to cool the whole process down to the point of going critical. I guess the idea, there, would be to reduce the flux density, thereby "slowing" the overall reaction. This would be, obviously, a simplified version of what teams of German nuclear engineers had in mind, but it all sounded great, as though being some sort of perfect compromise: we get power from the atom (thereby weaning ourselves from oil), all the while keeping safe from the hazards of a nuclear meltdown, such as what we're now experiencing. Obviously, being in a "pulp science" magazine intended for the lay public, it certainly wasn't a technical tour de'force, but it, nevertheless, sounded good to a layman, such as myself. Do you know of this design? And, if so, what ever happened to it? I haven't heard or read any more about it, since then. Thanks, again, for your time and trouble, in shedding light on this stuff.

@adamsulik1988

Actually, Adam, there are several ways an atom undergoing nuclear decay can have its electrons affected by this decay. Some atoms undergo a form of ß-decay in which an electron emitted from the nucleus becomes entrapped in an electron shell. So yes, nuclear reactions can have an effect on the electrons. Besides, what they are saying is that the residual heat being released is do PRIMARILY to exothermic chemical reactions and not nuclear decay.

Alright, after ashamedly asking myself why I haven't researched the answer to my own, second, question, I did so, discovering the following on Google:

en.wikipedia.org/wiki/Pebble_bed_reactor -

For anyone who's interested, it's a fascinating description of the so-called "pebble reactor" technology that the Germans developed. I guess they cancelled the project due to economic considerations, whereas the Chinese are going ahead with it, and, according to the article, plan to go on-line soon, with plans of something like twenty reactors being proposed, if the current prototype, which is being built at a university in Beijing, is viable. Yikes! And, just as I had guessed, the reason for the design being inherently safe is not as simplistic as I describe (reducing flux, due to thermal expansion of fuel beads). Instead, it involves a more complex concept, called "Doppler broadening," which evidently acts as a negative feedback loop, preventing the uranium in the core from overheating, due to a change in the number and type of available neutrons being absorbed by the uranium nuclei; fascinating stuff, for sure. The article stated that the Germans had actually removed all of the moderator rods and stopped all flow of coolant, to test the reactor's self-regulating capability...and the thing rose only to what they called an "idling" heat level, during which they could then work on it, removing the fuel and doing whatever. Why haven't we heard more about this?!

And, if you're reading this, Riccio, I'd still like to know the answer to my first question, if you don't mind. There must be a good answer, if a layman, like myself, can see the obvious hazard involved with storing dangerous materials next to each other. Any thoughts on that?

@Chrisbap & Robert123 (please ck some of my earlier posts)

You are absolutely correct, most explosions require some kind of container to maintain the concentration of the explosive. Pouring gasoline or even black powder on the ground where the wind can blow away the fumes is only going to create an impressive flame. Maybe a real quick flame that goes whoof, but does not explode.

Here is my opinion on the cooling:

The reactor, in it's reactor building and super heavy floor, weigh several hundred ton. The turbine and generator building would weigh more than double.

During a "normal" or "designed for" quake of say 7.5, everything vibrates like hell but basically doesn't move very far horizontally. I was in Japan visiting an old gas fired (smaller) power plant after a bad quake in (I think) 1977 the heavy but not as heavy turbine building foundation moved about 1.5 centimeter from the steam generator building.

The big (up to 30 inch diameter) pipes are built with a gigantic "omega" shaped expansion loop - which should be good for a few inch movement.

In this quake, 9.0 on a log scale is not just a little more it is several multiples more than 7.0. So I think the reactor building and the turbine building moved with respect to each other (maybe moved back) and sheared the big main reactor cooling pipes and the 12 or 16 inch diameter spent fuel pool cooling pipes.

So if you have a reactor vessel with the main in and out pipes sheared, it is like having a couple of holes (admittedly 3/4 of the way up the reactor and above the core). But if this is not correct then there must be a similar problem with the pumps and / or pipes.

Because like you say: if the emergency cooling pump motors need juice - it is a no brainer. If the pump is broken or the motor is burned out - it gets tougher. If the cooling water just runs out the other end of the broken pipe - and there in no radiation --- it seems that while difficult it is possible to weld it shut.

So we must be looking at something pretty serious with the pipework, maybe the heavy power cables, possible even the pumps and maybe some big valves didn't open or close.

Some valves are bigger than a hearse (no pun intended).

My guess is that the emergency pump motors are less than 500 hp each - so a 1500 hp gen set could be lifted in pretty easily.

The cooling of the spent fuel pools seems to be the current problem - limiting access to the containment building to check the nuts and bolts AND get on with the real job.

By now you are probably coming to my conclusion: Lots of "very authoritative" experts from every continent are flapping their gums about things of zero consequence. Is the pump broke?? or not?? Is the pipe broke or not?? Is the door jammed shut or not?? Did you lose the key??

I think that with four or five straight answers, my mom (88) could tell us how deep the crap is.

Just a little side note to Chrisb66: I have spent several years working with Japanese engineers, who in general are more serious about their work than Americans. Unfortunately when the boss says "no", they bow, say "HAI" (yes) and for the next 1000 years it never gets mentioned again. The bosses NEVER make a mistake - so if you have a closed boss - you get a sort of Hitler system of truthful information flowing.

Probably the damned accountants are to blame, you can't blame the politicians - they'll just whip up a special tax law for you.

Now the really great news for all three of you guys:

Go to Google and look up "GE Mark I" then "GE Mark I USA", you might have one of these (23 in the US) sweethearts in your back yard. Don't let wikileaks convince you that the problems were known just since 2006.

At this group of sites, you can see why (at my first nuke employer) we called them "Old and unimproved Brand X" - remember the old soap commercials?

After you digest this, Fukushima gets closer.

With almost 15 years directly in the nuke industry and another 20 in metallurgical consulting, I think good reliable nuke plants can be built and run.

But probably not by politicians, accountants, the Mafia or ding dongs. Maybe we need to have something different than a hand & glove relationship with regulators and industry. Or is it a hand in the pocket relationship???

Maybe the plants are actually performing miracles, with respect to the love and care they are getting. Remember Davis-Besse, these were ding dongs or the Mafia - accountants are smarter than to wreck the equipment.

Chris66, with almost any technical product, you get the safety you pay for -- seems to me cars kill a lot of people - but the last execution wasn't a Toyota or Ford truck - what gives??

Regards & pleasant reading

We CANNOT stop our intergalactic search for “intelligent life”, because it is becoming increasingly clear that none exists here on earth.

We repeatedly find that every decision is made on the basis of convenience and profit.

Why aren’t nuclear reactors made with a 10-fold or 100-fold safety back-up redundancy knowing that any failure results in 1000-plus year consequences?

Why isn’t every oil tanker built with a double hull?

Why is every plastic product made to be recyclable AND recycled?

Why isn’t all our garbage and hazardous product recycled, and our sewage treated, rather than it be simply dumped into our oceans?

Our water was clean, our air pure, our resources seemingly boundless, and room enough for us all on this planet – it is as perfect a world as we could ever want! Yet, how do we treat this perfect planet, …like we’ll get another if we screw this one up, …like we’ll be able to easily turn Mars into a second earth, …like this other (and hopefully truly intelligent) alien life will save us from ourselves?

HURRY UP ALIENS, but then again, maybe you’ve seen us already and you are keeping your distance.

We may pride ourselves in our knowledge, but we’re as stupid as it gets.

@popscifirefox

Well maybe you have seem my multiple posts.

Having considerable nuke and metallurgical engineering experience,I would like to give you an honest (grim) answer.

I see quakes in the middle east, india, china etc in which all the stone houses cave in (because there are no reinforcing rods) and everyone gets killed. And the whole world (especially the $media$) makes a big deal about the disaster. But, they lived fine for years in houses that they could not afford -- the other part of the bill finally came due.

In Japan and the whole modern world, there are nuke plants (and lots of other neat stuff) - probably not perfectly designed, probably not perfectly built and maybe not even perfectly operated. But we could afford it, because it was cheap. Haven't you ever asked yourself why a horse power hour or a manpower hour is practically free? - less than 25 cents. So we have enjoyed an easy, very high quality lifestyle.

So, really if a little nuke disaster kills off 10,000 or 20,000 every 10 years or so (because the bill finally came due) - where is the disaster?? This is only a fraction of the car deaths, and I sure don't see the Emperor, Barak Obama, Bill Clinton etc. clamoring for the death penalty for my Ford truck.

So why all the fuss??

But if we want electrical power at a price too low for the technology, sooner or later the bill will come due. No tragedy, bad contract.

Being as we are a bunch of dumb shits,apparently we can't afford the Concord, NASA, really safe cars, clean air and drop dead secure nuke (or puke) power plants - yet we want all this neat stuff. Helps us keep ahead of the neighbors.

So, I am just thinking that most big technical "disasters" (including living below sea level, living too close to un-dredged rivers (dredging kills the stones) and living on a muddy hill in California) are not disasters at all - but just getting the other half of the bill.

When everyone digests this, maybe it will be easier to get the correct amount of upfront money - to save the bacon later.

You know every so often too many people in India get on a ferry - maybe it gets top heave and flips over. Is this a surprise?? Maybe 100 times it goes perfect, then a little side ways wave and you get the bill.

Just a few thoughts on hysteria, the boogie man, (lack of) education and delayed payment projects. Stop.

***********************************************************
Isn't there a Japan trench just off the coast of Japan?

Aren't trenches caused by continents colliding?

Aren't trench mechanisms called subduction?

Isn't north Japan on the North American plate and the southern island on the Eurasian plate??

Isn't subduction in this area due to the fact that the Pacific plate is bending down and sliding under the trailing edge of the North American plate and also sliding under the leading edge of the Eurasian plate just in front of Japan?? (Alaska also has quakes and a pipeline)

Isn't plate subduction sort of "jerky" and not smooth??

Isn't it more likely that quakes occur at plate edges rather than internal to the plates??

Aren't the plate edges in the water??

Don't quakes in the water create waves??

Don't big quakes create big waves??

Didn't this big quake move the Japanese coastal GPS beam about 8 feet??

Is this tidal wave a surprise??

Are the broken toys a surprise??

They just got the bill.

When are we going to get the bill??

Regards

I do so love this magazine, but it sometimes still amazes me to see the knee-jerk responses by many of the supposed technophiles who populate its readership. However, the voice of reason expressed by the intellectuals and technical experts who comment on this topic do bring some sense and calm to the discussion. First, on the "off switch" topic, inserting the control rods fully, in this case, dropping the rods as part of a proscribed casualty procedure effectively stops the addition of heat to the system, this, in concert with then keeping the core covered with water (of any type) absolutely prevent any additional heat added to the system. In other words, the total heat gain will be negative, especially if the core remains covered with water, even the seawater currently being used as the final boundary to total loss of primary coolant volume. Granted the seawater creates any number of problems in relation to the future use of those reactors the possibility for total meltdown, or meltdown nomenclature (since meltdown by definition is the uncontrolled continuous loss of coolant and thus fuel coverage is self sustaining) is avoided with its use and is the last defense in many coastal reactor casualty plans. Even in the event of total meltdown it is still much more likely that some type of water can be applied to either the reactor vessel or internally to the containment building still resulting in the total final containment of any fissionable material to the outside world. As far as the comments surrounding the lining of reactor vessels with pure tungsten as an ultimate protective measure materials engineers will tell you that is prohibited by the brittle fracture characteristics of that material. The various steels used in the primary and secondary systems in nuclear power plants are chosen solely for their ability to meet the stringent engineering structural and material loads inherent to the various high pressure, high temperature, and corrosive demands placed on the materials. Many materials do not respond favorably to the extreme heating and cooling ranges inherent in the operation of nuclear power reactors, specifically the extreme stresses involved in the structural matrices of metals when ranged between ambient and nearly 600 degrees F. In fact those types of temperature extremes are exactly like those experienced by metals when undergoing designed hardening and softening procedures in industrial manufacturing processes--not something you want in your reactor vessel--relative softening under heat load. Nuclear power can definitely be safer and should always be held to the highest standards of scientific integrity and scrutiny but the fact remains that it is the safest method of steam cogeneration plain and simple--there are literally hundreds more industrial accidents which threaten public safety at the "other" power generation facilities be they powered by coal, fuel oil, diesel, or natural gas.

If Japan had used LFTRs there would have been no problems. LFTRs have a very simple fail-safe shutdown, all it requires is a loss of power to a cooling fan and gravity. A frozen plug is kept frozen by the cooling fan, and when it melts the liquid flouride drains into catch chamber. This is so simple and safe that the researchers in the late 1960s would turn off the fan when they went home Friday night and restart the reactor Monday morning.
I think our best choice is the Liquid Fluoride Thorium Reactor. LFTRs are a proven technology, research was terminated in 1975. New advances with better heat exchangers and the Brayton cycle turbines make this a highly desirable option. LFTRs can burn our stockpile of radio-active waste from existing nuclear power plants. (Because LFTRs are so efficient it would take over 100 years to do this). LFTRs produce little long term radio active waste, or products suitable for making bombs. The radio-active waste produced has a short half life and requires only 300 years of storage as compared to the uranium waste which has to be stored for 10,000 years. There is also much less radio-active waste, 0.3% for equivalent power from uranium. Thorium is plentiful, there is enough in coal ash and mine tailings to power the world for 100 years, and a million years supply can be dug out of the earth. See:
http://neinuclearnotes.blogspot.com/2008/11/thorium-at-googles-tech-talk.html
and also:
http://energyfromthorium.com/
We should build a factory to build these in a size small enough to ship on trucks (200MW) and an assembly line will bring down costs. These could be set up all over the world (no worries about nuclear proliferation) and first locations should be to replace coal and oil fired electrical generating plants, because there is already power distribution set up at these locations. Pollution from these sources will be terminated.

Sorry for the language and spelling, i'm from Denmark, a country without Nuklear power.

Nuklear fission chain reaction.
Uranium 235 will split when it catch a neutron (not hit by an neutrone), at that proces there will be a small loss of mass, mass is energi. ΔE=Δm*c2 , E: energi, m: mass, c: speed of light (Einstein). 1 kg mass is 10 eksponetial 17 joule, around the same as burning 3 million tons of coal. The uranium is not split by a neutron bombardment, it is not like a bullet hitting china. The neutrones has to be slowed down and then uranium will catch a neutrone and split. The neutrones has to bump into something that will slow down the speed. The best slow down is to let the neutrones bump into something with the same weight, the speed will slown down in a weight ratio (a tabletennis ball will not slow much down by bumping into a poolball, it will change direction but the speed will be nearly the same after the bump). To slow down speed of a neutrone in a nuklear reactor is used light water H2O, the H-nukleon is the same weight as the neutrone. In the CANDU reactor is used D2O, the D-nukleon is twice the weight of the neutrone, and in some reactors are used graffite. In the Fukushima reactor is used light water, H2O, to moderate the speed of the neutrones, there has to be around 1” of water between the fuelrods to slow the neutrones down to the speed where uranium is able to catch the neutrone and split. When the uranium split it will free in average 2,5 neutrones, the neutrones travells trough the fuelrod, slows down in the water between the rods and then it will be caught by an uraniumnukleon in another fuelrod, this will spilt and free 2,5 neutrones ...............the chainreaction is started and will go on to all the uranium 235 is split.
If the water used as moderator inside the reactor disappear, evaporate, the chainreaction will stop because the neutrones will not be slowed down, and the uranium will not be able to catch a neutrone, but the decay will continue, and cause fuelrods to melt inside the reactor. A nuklear power plant is not a potential atombomb, it can't create a nuklearexplosion, the critical mass is much higher. The chain reaktion will stop if not moderated by the moderator (water). When the rods melt down there will not be space for moderation the neutrones speed, so worst case is radiation, not restart and a process out of control.
To control and stop the chainreactions is used controlrods made of something that will absorbe neutrones, bor and cadmium is often used.

Nuklear Decay
Used nuklear fuel has a lot of unstable nukleons. In the decay process the nukleons stabilize them selves, it is a nuklear-process but not a nuklear chain proces, the proces produce stable nukleons, alpha-, beta-, and gammaradiation.
When a nuklear power plant is shut down for maintenance, the chainreaktion (splitting uranium 235) is stopped and the used and partialy used fuelrods (zirkoniumtubes with uraium pellets) are placed in an open water pool inside the contaiment, there is a couple of meters water over and around the rods. The water has 2 functions, it absorbes the energi (heat) produced in the decay proces and it is shielding against the radiation.
It is that proces going wrong at Fukushima, the waterlevel in the pool is under the top of the fuelrods, therefor the top of the rods are heating up and starting to melt. The melt it self is not a problem, everything melts when it gets to hot, the proces will stop when the nukleons get stable and not produce enough energi to melt. The problem is that the decay process produce a lot of radiation which is not shielded by the water and when the energi falls the melted fuelrods is not rods anymore but something lavalike at the bottom of the pool, maybe melted into the steal and concrete, it can't be handled, but have to be shielded at the place.
At the Fukushima they try to cool down with helikopters pooring water over the plant, it indicates that the melting is going on and they now are trying to cool down the containment so that it is not collapsing. If it is the rods they try to cool down, it indicates that the pool is outside the contaimant, and therefor open to the sky, then it is as worse as Chernobyl, and it would be better to try shielding with conctrete, enclosure forever.
Watermist as from an helikopter is a relatively good metodfor cooling, the watermist is smal partikels of water and when they hit something varm they evaporate, it takes more energi (heat) to evaporate water than the floating water is able to contain.

SC

This is so interesting, but I'm not quite getting one thing. Does the fission take place in the water or is it isolated in the rods, and if it is the latter, how exactly do the free neutrons get to the control rods?

Riccio: Have you got a proof-reader and fact-checker working for you? Furthermore, are you the reincarnation of Michael Crichton? 'Cause I'm getting an education here. Man, you are GOOD.
I was in high school living in the Detroit area when the Enrico Fermi breeder reactor had a partial meltdown (which took decades to diagnose the cause of, BTW) and I'd have to say at that time the "authorities" were less than candid, let's say, in informing the public of the actual gravity of the situation. That particular plant was "cooled" by means of liquid sodium, which, and I'm by no means an engineer, but I think that is the traditionally accepted ambient temperature for the Ninth Circle of Hell. But I've always believed that with that reactor, and the type of fuel they used, that a "full" or sufficiently substantial melt-down could plausably result in a critical mass situation. Am I correct about that? And if so, let's be glad the Japanese apparently don't have any breeders, like France does.
And Best Regards To You.

@ucpinky
The fission takes place solely in the fuel rods. This is because the only fissile material available is in the fuel rods. The reason that the free neutrons are able to get from one fuel rod to another is as follows: one neutron has an atomic mass of effectively 1. Uranium-235 (the primary fissile material) and Uranium-238 (what makes up most of the fuel rod's mass) have atomic masses of 235 and 238 respectively. So, essentially, you have a little free neutron floating around with other particles over 200 times its size. This leaves enormous gaps for that neutron to get through, and this is in a solid, where the atoms are closer together than in any other state of matter. Now, as this neutron makes its way through the fuel rod wall and into the moderator around it. It then (hopefully) bumps into one of the hydrogen atoms in a water molecule, which slows it down. It then keeps going until it arrives back inside a fuel rod. Finally, it (hopefully) collides with a U-235 atom, which absorbs it and splits (fission) releasing two or three more free neutrons.
Hope that helps.

@Dr Joey
The type of reactor to which you are referring is a LMFBR, or liquid metal fast breeder reactor. Yes, they do use liquid sodium as a coolant and moderator in the reactor vessel. However, you could not achieve critical mass of the grade of fuel used without having a moderator. Actually, your average BWR, PWR, CANDU reactor, etc. might be even more susceptible to going critical during a meltdown than a breeder reactor, simply because a breeder reactor uses the spent fuel from those reactors to power itself. There really is no such thing as radioactive waste. The spent fuel from one reactor can always be used to power another.

@Pippin
If that were the case than any fuel rod would decay whether or not in the presence of the neutron moderator. I'm pretty sure the fission takes place between the fuel rods, because of the fact that you need a critical mass to start the reaction. Unless I am misunderstanding you, so I'll try to summarize. The fission itself takes place within the rods, but neutrons can escape one rod and travel to another to spur more decays. That way, putting control rods between the fuel rods slow this process down, since these rods are made of a neutron poison. As for the water, the primary reason it's there is to cool the reactor and generate steam all at once.

@Dr. Joey, Thanks - I just have been in the wrong place at the wrong time -- several times.

@criffic, you are mostly right, the non mostly part is:

The fuel rods are hydraulically pushed up in A Mark I and II, small point and with pressurized hydraulic accumulators, usually works. Down, with the magnetic latch is the Navy and other PWR's.

After the control rods are "in" either up or down, the reaction drops to 1% to 2% of full power (and heat) but 1% of a big number is still a lot of heat. If you do not take away the heat, the fuel gets upset and melts things, not to China though. Car engines don't melt, but idling for a couple of weeks without water and it sort of looks melted. Spent fuel storage is no joke - I'll cover that below. Please read my post of 3/15/11 to LMarv, and the microwave story. Stop.

******************

I have not seen any information yet that would lead me to think that anyone actually knows what the real situation is inside the reactor building, or they are not talking, and maybe not walking.

Sorry but I know almost nothing about LFTR's, pebble bed, or heavy water reactors, I have worked in breeder reactor facilities and know a little. Although I am smart enough to know it, and not discuss the fountain of youth, Aladdin's lamp or other neat power sources.

Comparing what I know, and I KNOW about BWR's and PWR's, to all the slick published info - they look better than they are. I hope everyone is not getting ALL their alternate nuke info only from Internet.
So my poor brain makes the assumption that the other type of reactors (being in the distinct minority) have their own set of problems - and are probably not as good as their proponents would like you to think. The early "infomercials" (to the industry)for the GE Mark I and II were better than sex, sliced bread etc. and they are not!!!!!!!!!!!!!!!!!!!!

The Candu (heavy water reactors) that Canada uses, seem safe from the distance from which I have checked. (primarily reading real tech. operating manuals and other info etc.)

Guys, remember scientists are correct, the atoms, electrons, Uranium x,y and z has no choice but to follow it's appropriate laws.

The problems pop out when mortals build machines like nukes and the concord AND try to do it without breaking the bank.

Bottle caps are easy to make, less easy for 1/100 of a cent each. So you get some bad bottle caps. Is this a surprise??

On the down, side go to Google, ring up "GE Mark I" then "GE Mark I USA", (zip down the to the danger part of the list), then ring up your Senator.

The Fukushima issue is probably like a bad cold, it's going to get worse for another 10 days and then start getting better. We need antibodies and a few suicide workers and things will get better.

@rayroshi,

Storing spent fuel has always been a big discussion.

However here we run into word definition problems.

1) spent fuel is NOT wood ashes.

2) spent fuel is still warm.

3) even if left "on" an electric blanket is not dangerous, but if you fold it double, you get hot spots and a fire.

4) spent fuel can be recovered, recycled, densified for storage of the non radioactive part.

5) typical and historical methods are:
PUREX
TRUEX
DIAMEX
SANEX
and UREX (pissing on it doesn't help)

6) so called spent fuel is kept in the spent fuel cooling pool, until it is appropriate for recovery - but it still MUST be cooled.

7) For all the "experts", here is the really great part.
After a typical usable life of from 3 to 6 years, the "spent" (sounds like a burnt - cold match) fuel must be stored in a cooling pool for a minimum of 8 years and sometimes as much as 20 years before recovery etc. Check out the appropriate DOE docs if you don't think so.

8) the US tends toward dry storage, after the cooling pool, China, India, Pakistan, Japan, Russia, France and the UK are recyclers. and there is probably Internet info on it. I seem to recall that Italy, Germany, Belgium and of course the US opted out.

9)most countries require the individual power plants to store temporarily, their own spent fuel rods. (the gov. doesn't want this junk, you made the profit, the junk is yours)

10) it doesn't take a rocket scientist to figure that if the stuff lasts about 4 years and you store in the backyard pool for 20 years, then you need a pool equal to at least 5 changes in the reactor vessel. So ---------------- if something goes seriously wrong with the swimming pool, you get some nasty alga. And, whether or not the house is on fire doesn't count. Unless of course as in the Fukushima, GE Mark units the swimming pool is on top of the house and the bad alga is falling on your head and you cannot concentrate on the house fire.

Sort of like storing your dirty socks under the bed for 20 years and wondering what the hell stinks.

11) So, storage of spent fuel, until reprocessing is NOT a casual past time - and if it falls out of bed - you get roasted - is this shocking, probably so! But it shouldn't be a surprise.

12) Ask Wikileaks to get you some DOE docs

Regards

@Dreka
That's mostly correct. There is a third reason for the water to be in between the fuel rods, though, that being as a moderator. The moderator's job in a reactor that uses U-235 as fuel is to slow down neutrons (not stop them like a control rod) as they pass through it from on fuel rod to another. It has to do this for the reaction to continue because of an odd property of uranium: U-235 cannot absorb a high speed neutron, which is what is released by the fission of uranium. To produce fission in U-235, it must absorb a low speed neutron, something that can only be produced in the presence of a moderator. Thus, a neutron that stays inside the fuel rod in originated in will not induce the fission of another U-235 atom.

The reason that there are control rods is that they are capable of absorbing neutrons no matter what their speed. This allows the engineers to quickly stop the chain reaction simply by denying access from one fuel rod to another, cutting off the flow of neutrons that keep the reaction going.
Hope that helps.

The Fukushima Dai-ichi plant in Japan actually shows
the safety of a well designed nuclear power plant, as it
withstood what was essentially a worst case seismic event.
(even though ground motion could be worse depending on the
local distance to the earthquake fault) without much loss
of plant integrity.

There is a new reality for nuclear plant operators
though, that is independent of any safety calculations or
inspections and that is; “You may be required to continue
to operate your reactor and your physical plant despite
a critical loss of cooling capability for a time until
those systems can be restored. This means your plant
may essentially suffer fatal internal damage, while you
will be required to continue to operate it in a way as
to preserve public safety.”

We need to understand that nuclear power plant designs
are never intentionally tested to destruction so our
experience at operating them in that mode comes in dribs
based in real world experience. From my perspective what
went wrong at the Fukushima Dai-ichi plant is probably
correctable at other sites in terms of additional
procedures and equipment without excessive additional
net costs. Newer reactor designs will probably eliminate
dynamic cooling concerns from consideration entirely –
but the new information is you must still consider cooling
requirements for stored nuclear fuel in the rest of the
plant to suppress the results of unintentional nuclear
and/or chemical reactions.

Thank you for the interesting article.

More good news:

How much wood would a wood chuck, chuck? If a wood chuck could chuck wood, well of course a wood chuck would chuck all the wood that a wood chuck would chuck?

How much "spent fuel" do we have in the pools at Fukushima, meaning hot stuff.

Reactor # Tons
1 50
2 81
3 88
4 135
5 142
6 150
Plus 1097 ton in a local ground pool.

Plus 70 ton in dry storage, meaning after recovery etc.

A recent replacement of the fuel rods in reactor # 4, means that at least 20% of the hot stuff (26 ton) is fresh from the reactor and nice and radioactive. "The better to fry you my dear" "Got some good fresh Gammas here"

Total reactor fuel is about 100 tons.

Primary info source:"The Mainichi Daily News"

Water in the dry pools was evaporated by Zirconium very high speed rusting, (slow burning) at 1800 degrees Celsius.
(the fuel rods sticking out of the water)

Now, why would water evaporate at just 1800 degrees Celsius?? Maybe we have a failure to communicate. I thought spent fuel was dangerous? And we have 1500 ton under the bed??

I think maybe I missed something - do we need to restart this film?

Regards

Regards

Nuclear fusion is old 70's technology being used to run today's technology. It's over priced and it's all about making money in the long run. Indian Point sits between two fault lines and is less than 25 miles from New York City. It's been shut down more times than it's been actively on line. Due to allot of complications and looking for solutions by banging their heads against the wall. The spare rods are not disposable nor recyclable. The best solution to all these problems would be Biomass energy. To clear most of the radiation at the Chernobyl disaster, Hemp was planted to help with the cleanup. Hemp is an old technology that still fumbles scientists. It has over 250,000 uses and it's all positive results for the ecosystem, health and technology. All it takes is a little common sense. As a retired control room operator at the power houses I've found that keeping it simple got me great results much faster in trouble shooting problems that arouse at the power generation plants.

Look up Tsinghua University, China, pebble bed gas reactors. They have one, at least, up and running at this date. China has committed Billions of Yuan, not to trouncing Iraq as a favor to the Saudis, but for research into Thorium fueled reactors, for safer, more efficient, cheaper operation.
Japanese reactors were designed at the American Empire's peak, when Oldsmobiles were the car of the day, and inch, foot, pound, ounce, were the measurements of the day. Have you driven and Oldsmobile lately? But, you still measure temperatures by archaic Fahrenheit don't you! Even your simple-minded inferiors in Canada speak at least two languages, enjoy hundreds of cultures and think metric, can you imagine?
America, in moratorium on nuclear research for over thirty years, has fallen far behind in this field of engineering as well as the automotive and other fields of engineering. China appears to have taken the Nuclear lead with Russia a close second.
The Japanese nuclear disaster will not help in the future sales of America's 'tea-pot' style reactors, no matter how many generations or reiterations of the same, patent bound, accountancy determined, shareholder profits limited, designs are produced. The latest GE, Phase III plants are essentially the same as went before, plus a myriad of complex, and expensive control technology added - Like a Chevrolet evolves into an Oldsmobile, or even a Cadillac, as do-dads are added, but you are still buying the same basic car. This is old-school engineering at best.
Chinese/Asian engineers have goals designated by government decree, by committee decisions, not by accountants with shareholders best interests as primary focus. For this reason, Chinese engineers are allowed to 'think outside the box' and do so. Asian/Chinese engineers are drawn from a much larger gene pool, and on scholastic merit alone, not the candidate's families' abilities to pay for higher education, or prowess on the foot ball field and sports scholarships. This yields a very much smarter engineering pool, a pool with much higher potential, higher group IQ than is possible in America. Intellectual back-up sciences, technologies, for the engineering pool are selected by the same criteria, yielding a better, more intelligent intellectual floor on which to base engineers. Chinese schools are much more rigorous, and admittedly superior by the large gap as shamefully confessed by President Obama recently, American schools rating only 39th in the world.
Asia, for these reasons and others, such as America's fiat dollar manipulations, will pull away from American influence in the coming decades,and stand united and on her own, likely based on the Yuan, or and Asian group of currencies, not including the mistrusted U.S. Dollar and its Bankster's manipulations.
Expect this Japanese reactor situation to be the last of American involvement in Asia. Expect the next generation of reactors in Japan to come from China.
We are witnessing the final days of the last, and greatest, Caucasian Empire the world will ever know. America. we will miss you dearly, but we will survive without you.

@UncleB

Good point.

Don't know how old you are, or where you live. (you sound almost as old and nasty as I am)

But if you are young and live in the US, you are in for big problems.

I tried (and I might add) valiantly to change things in the early 1970's. After 15 years of trying to talk sense to upper management (fortunately not at GE), I was forced by my conscience and desire to improve, to leave the US nuke industry. At that time Europe was a carbon copy so it was the only game.

Unfortunately you can not, not know what you know. And therein lies the problem, because it will pop out when you least expect it. Others, less gifted with insight will think you are a smart ass and stop cooperating. Your boss will think you are angling for his job and put you in an office under the stairs.

I've seen this film.

I realize that it is a small drop in the bucket but a few companies,CAT comes to mind saw the light 25 years ago. So now for the dumb shits, the prints are just double dimensioned --- if not now, at least for years.

But all things considered, lets not brag up too much the Chinese. I was in China for 3 years in the late 1980's, and the most notable attribute is that the good people must pass through a much finer sieve. The net result is the same, but China is chock full of stupid people, the US does not have the corner on the market.

Repeat, after a while, I began to understand that I was the problem, so I went elsewhere. A couple of years in Australia, a couple in the UK, three in China, one year in Russia (when it was almost impossible for Americans to go), another year in India, two in Japan and several in Italy.

I never really had constraints on ideas that could help, because the boss was there to help facilitate, not stonewall.

Hope you can do as well.

As for America -- my two daughters are both studying foreign languages.

Several empires have vanished, this is not the first or last. A little sad though.

Regards

Heh, I just wish Canada wasn't going to crash and burn along with the U.S. whenever it happens. Rural Canada is difficult enough with six months of snow at a time and all the money being sucked up by population centres. At least our economy is based on raw materials, which will be in demand even when commodities aren't...

Too bad that while capitalism flourishes the world will be governed by greed... Ah well, life will move on.

Critical Mass.
The critical mass for a fission is the mass and density where the nuklear chain reaction goes on by it self, and only just.
In nature uranium is 99,3 % uranium 238 and 0,7% uranium 235, it is uranium 235 that splits by cathching an neutrone and creates the chain reaction, the fission. The naturel uranium is not able to fission in a light water reactor, the neutrones “get lost” in all the uranium 238. The uranium is enriched (i'm not sure its the correct word in english), in that process the uranium 235 content is rised to 3%-5%, the remaning uranium 238 is depleted (high density, not radioaktive and would be a good shield against radioaktive radiation, but only 5% is used).
The enrichment(?) process is a simple weight separating process, centrifugal, the uranium 235 is around 1,27% lighter than the uranium 238.The process is done over and over again to the needed enrichment(?) is reached.
To make a bomb is needed around 80 % enriched(?) uranium, and the critical mass is around 55 kg, 121 lb at normal pressure, pressure can lower the critical mass. In the Hiroshima bomb 2 pieces, each 2/3 of the critical mass, was placed at opposite ends of a tube an shot together by a TNT detonator. The result was not 4/3 of the critical mass, but because of the pressure, around 3 times the critical mass.
In a nuklear reactor using 3%-5% uranium 235 the critical mass is very high, and i don't believe any reactor is containing that amount of fuel, so the only way to have a chainreaction in 3%-5% uranium 235 is to moderate the neutrones. Water is a good moderator and it is the primary reason to use water around the fuel rods in a nuklear reactor. Cooling can be done in many other ways, in small reactors there can be a “water jacket” for cooling around the reactor.
Because the mass in a nuklear reactor is lower than the critical mass a loss of cooling and a melt down of the fuel rods will not start an fission, the plant is not going into a bomb.
The enrichment process is a simple weight separating process, centrifugal, the uranium 235 is around 1,27% lighter than the uranium 238.The process is done over and over again to the needed enrichment is reached.

Decay is nearly the opposite of a chainreaktion. Decay is the nuklearreaction where unstable nukleons are falling down to stable nukleons, it is in that process it create radioaktivity. The decay process starts just after the first splitting and going on long time after the splitting has stopped. The decay process produce energi as well as the splitting. But not in the same scale as the fission and the energi producing slows down.

SC

@unclB

But then again, asian engineers in Japan are not able to get a waterhose into the pool. A pool the size of a swimmingpool, 2000 tons of water, or what is needed to flod my house. My rainwaterpump for erigating my garden gives 2 tons of water at 5 bar every hour, it's 336 tons a week lifted 50 m, 166 foot. They can build a man-like robot but it takes a week to drag 1000 m of cable.
RC plains are used for nuklear bombs, but no one is able to make a RC truck in a week.

The creativity is not an engineer worthy, i think more of someone without education. Water, valves and cooling is not rocket science.
I'am not impressed of the asian japanese engineers, i think more they are copy-paste engineers.

I think more and more it's some kind of stunt or just panik.

SC

As an aside to the above superb discussion, some years ago (mid-1970’s) I had an Irish friend who was a chief pilot flying 747’s for Japan Airlines. When I asked him how he, as a non-Japanese, warranted working for Japan Airlines, here’s what he told me.

He said that due to a string of fatal airline accidents during that era it had been determined that no Asian pilots should sit in the first and second chair in the cockpit of their major airlines, because their entire culture from kindergarten on up discouraged the responsible on-the-spot free-thinking and quick emergency reactions sometimes demanded of the captain of a large jumbo jet. In his words, he said that schoolchildren had it drummed into them from an early age, the concept that “The nail that sticks up, is the one that gets pounded down.”

For example, he cited an instance where a large passenger plane with two Asian pilots had crashed, only because the chief pilot had suddenly developed a medical problem, and the copilot froze at the controls because he suddenly didn’t have anyone to give him orders on what to do in a dire emergency. My friend said that there were enough incidents of similar nature to warrant the wholesale hiring of caucasian chief pilots.

There’s also the Japanese obsession with ‘saving face.’ In late 1975 in Anchorage, Alaska, a Japan Airlines 747 was taxiing west on the taxiway towards the end of Runway 7R for takeoff. A recent freezing rain had coated the taxiway with slick ice and there was a strong south wind blowing. The runway maintenance crew hadn’t sanded the taxiway, so when a strong gust of wind smacked the tail of that 747 it abruptly turned 90 degrees to the left on that narrow taxiway. The pilot hit the brakes but the wheels just skidded on that slick ice, and the wind pushed the plane backwards (north) off the taxiway and down into a small gully, coming to rest about two plane-lengths off of the taxiway.

Everyone was safely evacuated and the plane was undamaged to the degree that it was eventually towed up out of there and repaired, after which it was put back into service as a cargo plane.

Point being, just two days after that incident I had occasion to fly out of Anchorage, bound for Paris on a vacation. As we taxied past that 747 we saw that it had NO JAL markings on it, because one of the first things that JAL did was to spray-paint their company logos over, with white paint.

I had the pleasure of living in Japan for three years, in the mid-1960’s. I like most aspects of their honorable, civilized culture, but the ‘saving face’ part of it was hard to understand. For example, the Tokyo news once spoke highly of a suicide victim – a college student - who had stuck his head under a pile-driver (SPLAT!!) to keep his family from being disgraced, JUST BECAUSE HE’D FAILED HIS UNIVERSITY EXAMS. I had some young friends who spoke of his deed in glowing terms, like he was their hero.

--Because of the above described concepts of deep-seated irresponsibility, self abnegation and propitiation as a cornerstone of their traditional culture, I sincerely do not believe that we will get the absolute straight story from Japan regarding everything that happens with this nuclear plant disaster. I’ll be pleasantly surprised if they become completely transparent regarding everything that happens, and I won’t be surprised if we hear about some employees who handily jump right into that cauldron without a radiation suit and sacrifice their lives in order to ‘save face’ for their boss.

It’s in their genes.

Maybe not a good idea to store the spent fuel rods on the coast? Seems to me they should be stored in the heart of a mountain until we stop using this barbaric form of energy generation.

@Old Curmudgeon,

Exactly dead on.

I have had similar experiences.

My first trip to Japan (Fukushima) was in 1972 as part (the bottom part) of a negotiating team from a GE competitor to try to obtain a contract for one or more of the projected 7 remaining reactors.

Keeping in mind that we were there, because we were invited!

After about 10 days, I developed a sort of friendship with young Japanese engineer (educated in the US). He secretly told me that we might as well pack up and go home because we were just wasting money.

He explained that to give the impression that things were open and up front, they were (in their opinion) obligated to go through this charade. And that for us to get the contract - the Japanese negotiating team would all have to kill themselves to avoid admitting to having made a mistake on the first reactor. We received some nice little gifts and went home two weeks later, nice trip though.

I lived in Japan for two years which I liked a lot, but they all thought that I was an unbelievable egotistic barbarian (though I really tried) and I was convinced that they were trained ants.

Then I spent three years in China - lots of fake shit and a lot of cover-ups, but not by the people on the same team. By the time I returned 20 years later China had changed, but Japan was still little robots smiling, bowing and saying Hai (yes) to everything, and letting you flounder around trying to understand what they had in mind.

I survived and was successful by not being surprised by anything, smiling ("closing my face"), bowing and saying yes. Strange way to run a railroad.

So we should not be surprised if we get facts that contradict the previous facts and in the end we'll not know much more than now.

@Riccio - Like everyone else, I first have to thank you for the light you've shed on the many aspects of this crisis. I may have simply missed a previous comment or explanation of yours, as there have been many. But could you comment on this "radioactive steam" that everyone (MSNBC, CNN, and FOXNEWS to name a few) have been freaking out about? From my understanding, the only steam or gas being released is boiling water and hydrogen (from oxidation of zirconium). So to put it simply, is there any sort of gas being released that actually is capable of transmitting harmful decaying particles? The article briefly mentioned cesium and iodine, but failed to go into any more detail.

I'm not even remotely educated in the field of nuclear power, but I feel as though it takes a "special" kind of person to panic and bulk up on iodine pills when you live over 5000 miles away from an event like this. Feel free to correct me.

Thanks

Can somebody tell me what kind of motors have the circulation cooling pumps?? By what I seem to read they are synchronous motors spead regulated by theyristors?!. Voltage??

If so, it must be assumed that the thyristors and/or control circuits also were damaged by the tsunami. Then, what sense it made to install a (I assume) a medium voltage cable to provide Energy??

Thanks

@Irienow
Barbaric? Hardly. Look up the following web site: http://nextbigfuture.com/2011/03/deaths-per-twh-by-energy-source.html.
Then come back and explain how exactly nuclear energy is more barbaric than coal or oil.

@chipper89
To put it simply, the media is (as usual) just trying to push everyone's "Panic!" button. You are correct in believing that the only things coming out of there are normal steam and hydrogen gas. There hasn't even been a great increase in the radiation coming from the now exposed fuel rods. The CBC interviewed a doctor who works just 20km from the plant yesterday, and he said there had been no significant change in the amount of radiation coming out of there, and that he felt fairly safe. (I'm paraphrasing, obviously) Considering the Japanese's "save face" attitude, I don't know for sure how true all of that is, but there's really nothing to say it isn't. Fore sure there will be some small increase in the amount of radiation exiting the plant, but the steam and other gasses being released are by no means radioactive.

Hope that helps.

Oh, great. Now there are higher than normal concentrations of I-131 in areas around Fukushima. So at least one fuel rod has rusted through its zirconium casing, and is releasing radioactive iodine into the atmosphere. Absolutely terrific.

@WikiRiccio - Thanks

So do you think we'll see some serious developments in Remotely Operated Vehicles (Machinery) to clean and contain this? It seems to me that eventually they are going to need to remove some portion of the buildings and debris from atop the rods. Once cooled, is it possible to extract the rods and get them into a containment vessel and off site?

Seriously - How do you expect things to play out in Japan?
If you get the call to put together a Red Adair-like team for nuclear disasters - I'm in.

Eric

@chipper89:

The short (and honest) answer is that I don't know. I have built, helped build, designed and repaired several nuke facilities, but I am not a nuclear scientist or expert regarding the health issues. That said, lets try to look at a few easy things that I do know.

1) News agencies go broke if they don't have advertisers.

2) Advertisers want their name under your nose.

3) News agencies grab the first guy with grey or white hair they can find. Who looks pensively into the camera and tells you that pimples are dangerous.

4)Radioactivity is radiation emitted by unstable atomic nuclei.

5) Radiation is in the form of sub-atomic particles (alpha and beta particles) and or energy in the form of gamma rays.

**this is clear as mud, so lets proceed**

6)An alpha particle is the loose nucleus of a helium atom, made up of two protons and two neutrons.

7) the nucleus is the center of an atom around which orbit the electrons.

8)Nuclei means more than one nucleus.

9)A beta particle is the loose electron that escapes from an atomic nucleus.

10) A fine point that we really don't care about is that some electrons spin one way and others spin the other way, nitpickers call this plus beta and negative beta. Also there other sub atomic particles discussed by people who want to impress you: neutrino, anti neutrino, head lights and tail lights etc., just kidding about the turn signals.

11) Gamma rays, are a very high form of electromagnetic radiation, the next step up from X-rays. This electromagnetic radiation is formed or caused by sub-atomic particle interaction, which could be electron / positron annihilation (they run into each other and create a spark),neutron pion decay, fusion or (and here it is) FISSION.

12) Now we are getting somewhere, fusion means you smack two things together and they stick (we are not smart enough to do this yet), FISSION is breaking apart atoms. We are pretty good at splitting and smashing up stuff.

13)Fission of heavy (with relatively large diameter nuclei) elements (like uranium, thorium, actinium, radium etc.)in a contained vessel (because it sort of explodes) and properly cooled because it gets hot, is how a nuclear reactor works.

14)Fission is one of a number of EXOTHERMIC (ex meaning it gets rid of something, like your ex for instance) reactions which when it explodes gives off all kinds of things we don't want ( gamma rays, betas and alphas) along with a lot of heat that we want. The heat creates steam, which when piped to the turbines, expands rapidly and turns the turbines. The turbines are attached to big - big generators and produce electricity.

15) But now we have all this stuff we don't want:
a) beta particles (high speed protons or electrons)
b) Alpha particles (helium nucleus)
c) Gamma rays (high powered x-rays)
*** all three of these are called Ionizing radiation,
because they are high energy and break chemical
bonds, creating ions, which means they are bad
for living cells.

16) So the fact is, all three are bad for your health.
Beta particles can penetrate human flesh sufficiently to cause burns and locally cause spontaneous DNA mutation.
Alpha particles, from cosmic rays are higher energy
than Alphas from fission, but can still penetrate a couple of millimeters, and of course are bad news for your DNA.
Gammas are the real sweethearts, they innocently zap right through you, don't create any burns, screw up the DNA, create cancer, create radiation sickness in the meantime while they are killing you.

17) There is some high level discussion by people who think about this stuff, that there may be some distinction of the three types of radiation depending on exactly how and from what material it originated. All we care about is that it kills you, or in the least it gives you really bad burns that almost never heal, because the cell DNA is altered.

18)Now some good news:
A) Beta particles are electrons or protons and as such have a negative or positive charge (and they are not very heavy), so having a charge, they interact with everything they run into. So they penetrate only about 2 meters of air or a sheet of paper or 1 millimeter to 1 centimeter of skin (depending how close you are to the source).
Beta emitters are: Tritium, cobalt-??, strontium-90, iodine?? (maybe 129) and cesium-13?. The iodine emitter is often used to treat thyroid problems. Carbon-14 is a weak emitter that has a half life of about 5750 years and is used to date organic things up to about 30,000 years. Through beta decay, it eventually becomes nitrogen-14.

B) The alpha particle, being a helium nucleus, is about 2000 times as heavy as a beta particle and has a lower velocity and is not generally dangerous (unless you are very close) because they travel less than a foot in air. Being heavier, however if you breath them they can create more cell damage than the beta particles.

c) Gamma radiation, I remember a general rule of thumb for fall out shelters. The really safe shield thickness is equal to 10 thicknesses for halving the radiation. So about 4 inches of lead, 24 inches of concrete, 6 feet of water or approx. 1 mile of air, will keep you safe. The reactor vessel is min. 6 inches of steel and the containment building is about 3 feet of special concrete.

** Just a note, another word that you hear from people who know too much is "Isotope", which just means an atom that contains the same number of protons - but a different number of neutrons than the primary atom, so you can have uranium and uranium isotopes.

d) To minimize all radiation, 1)increase the distance, 2)minimize the time of exposure and 3)hide behind something heavy, see above.

19)The historical fuel at Fukushima is uranium. I understand that a recent "improvement" was to use a plutonium / uranium mix, but this is probably not in the fuel pools. It might be in the most recently refueled reactor (number 4). From a potentially radioactive point of view it is much worse. Check out MOX fuel.

20) A commercial nuclear reactor can produce the following:
A) about 2 grams of tritium, which can cause cancer.
b) small amounts of cobalt-60, which causes cancer.
c) about 6% of U235 becomes Strontium-90, bone cancer.
d) radioactive iodine 129 & 131, in high concentrations
can cause thyroid cancer, but reactors do not
produce much. Taking stable iodine supplements can
prevent the thyroid from absorbing unstable iodine.
These pills can help, only if competent health
officials have determined that the concentration
of unstable iodine is too high.
e) Cesium 137 is also a by product of nuke reactors,
I was in Italy when the Chernobyl reactor melted
down. The Soviets estimated that Cesium 137 would
cause 3 times as many cancers as all others combined.

21) Everything produced by a Light Water Reactor; Fukushima, will be in the reactors - and in the spent fuel rods in the storage pools. Even though a relatively short distance, effectively isolates you. The bad point is that the radioactive material can be swept up with the steam, the steam is not exactly radioactive but it contains radioactive dust particles. The dust (debris) contains the actual (macro)radioactive particles that can emit the Gamma rays and the radioactive sub atomic particles.

22)At the concentrations that the dust could be pushed to the US west coast, it should not be a health problem. There are probably internet articles about the radioactivity concentrations EVERYWHERE due to the atomic testing in the 1950's and 1960's, and some comparison with current.
If the reactor containment building / shields are not cracked or leaking, even if the reactor does leak - there should be less radiation than from the water vapor, dust and cooling water blown into the air from the storage pool related explosions. Obviously this junk is going to be in the air until sufficient rain and snow clean the air - then it will be in the soil and eventually in the sea water. This area is probably done for growing food for 30 years. Cesium half life is about 30 years - I think.

So your common sense is probably right, live up wind and up stream of risky nuke plants. To be honest not many are risky, but for you, it only takes one.

Regards

@Scar17,

Like Old Curmudgeon and others have said, the Japanese are strange folks, and capable of anything. In the States, Three mile island was just locked up. Chernobyl was covered with cement and sand. To "save face" they could make park.

Personally I don't think that the reactors are ruined,(supposedly only three reactors have problems) if they are, then those buildings will probably not be placed in operation. But the associated turbine and generator could be salvaged.

If just the reactor cores are damaged, they could probably repair a plant in a little less than 30 months.

Regards.

This article was great for a person to understand the basics of how a reactor works. Do I understand correctly that the fission is caused from the reaction of the rods with each other and the control rods can stop the reaction by being placed between the fuel rods? The fission occurs inside the rods but they do not cool down for years?

@electrictoys
Not exatly. The Fission can take place in only one rod, if there is a Tamper (a mirror for neutrones) in the water around the fuel rods or if the mass of the rod is over the critical mass (a nuklear bomb).
The decay process, the proces where undstable nucleis fall down to stable nucleis, is also producing energy. It's this energy that keeps the earth floating inside.
SC

@TomWhittmann.

Please see previous, earlier posts.

First, let's be sure what we are talking about.

The BWR, Boiling Water Reactors at Fukushima and elsewhere, produce oddly enough boiling water. Specifically at about?? 560 to 580 degrees F. This of course is steam. In some other type of reactors the cooling media in the reactor core goes into an intermediate loop before going to the turbine or turbines. In A BWR the steam goes directly to the turbines.

Sometimes the turbines (even BWR's) are in series - a high pressure and then a lower pressure turbine, to get more spinning energy out of the same amount of steam.

Someone in a prior post said that the steam was not radioactive. Well even the steam from the reactor during normal operation IS radioactive, and the turbines and pipes must have minimum shielding. (this radiation is probably N-16 and fortunately has a half life of only a few minutes) To a lesser degree, everything in the loop that goes from and returns to the reactor is radioactive. And per my above post, the steam from the storage pools is at least carrying radioactive debris.

Pumps do not pump steam, so the normal cooling pumps are actually after the turbines, and after the condenser but usually before the return water preheaters.

The emergency cooling pumps are schematically on a separate loop, if this is physically the case in these early installations, I have no information.

So, it is safe to assume that "normal" operation, start up and shutdown uses the operational cooling pumps. But during the different phases of start, run and stop, different quantities of water are required. This means that the normal pump motors must be variable speed motors.

A more recent installation, I visited, had three pumps in parallel, to accommodate repairs on one and still have a back-up.

I am not an electrical engineer, so I do not know exactly which system, wave cutters, thyristors, etc. is more robust. My opinion is that constant voltage, variable frequency may be better than transforming AC to DC. Although frequency control is usually used for really high speed applications.

Regardless of the system, variable speed drives are very expensive - in this kw or Hp range, we are probably looking at a minimum of $50 per Hp for 2000 installed hp, So the controls must be robust and protected from any type of power spike, and be easily reset.

But if the pipes break, or the power stops, you have to go to the batteries for 6 to 10 hours on the emergency loop.

Regards

There are lots of comments here, and I've only read a few. The thing that struck me was in inappropriate diagram used to describe "how a plant works". There would normally be a secondary heat transfer loop where steam was generated to power the turbines that drive the generator, rather than having the primary steam produced in the reactor go directly to the turbines. Some reactors use working fluids other than water (or heavy water), such as molten sodium and potassium (named NaK). These molten metals would react chemically in water, but can be used effectively as the primary heat transfer medium, with a "secondary loop" heating water to provide steam to drive a turbine.

@jonrO

Please read prior posts.

Sorry --- no secondary loop at Fukushima.

Sodium, and liquid metals are generally for breeder reactors.

Approximately 85% of all world reactors are LWR, Light Water Reactors. Almost 100% of light water reactors are either PWR or BWR units.

Fukushima and almost half of the 83% of the LWR are Boiling Water Reactors AND send dried steam directly from the reactor vessel to the turbines.

Almost all military reactors and the other half of the 85% above are PWR, Pressurized Water Reactors -- AND have an intermediate cooling loop.

The schematic is incorrect only in that it does not show the emergency cooling loop, pumps, emergency power and emergency batteries. (of course it does not show the dog sleeping by the gate)

*** Read
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Regards

Riccio, first of all, I thank you greatly for your comments this far: they have been enlightening and insightful (and I've read them all.) And, secondly, I have a question about something I've been thinking about for years now, so here goes.

From your experience, and in your opinion, does technology exist that would enable us to make "small" nuclear power plants?
If so, then what would you say is the smallest feasible size?
Which are the components that limit the "diminution?"
Yes, I am talking about the entire power plant, cooling system, and generator also.

Thank you for your time and forgive me for my limitless questions.

Simon

The seeker of knowledge who seeks to reach beyond the stars to go where no mans gone before to see things no man has seen and bring these experiences back for the whole world to hear and see.

I have this to say is it not the dumbest thing in the world to poor salt watter but not only that but dirty salt water on a nuclear reactor two very bad things i can think of can only come of that A. the dirty sea water will cu rode important and needed machinery inside the reactor and 2. when the water boil out whats left SALT which then solidifies around the nuclear rods increasing them in a shell further risking over heating or a possible restart of nuclear reaction process if enough heat stay the nuclear process will resume i think this will end up being another Chernobyl i swear their is nothing nothing at all in the whole entire world that has safety procedures for this kind of disaster and the worst thing anyone can do is make blind decisions that can affect the lives of are Eco system hence the large body of water surrounding the plant cof cof OCEAN and delicacy of it and the people living in japan this disaster needs to me more well thot out and world leaders should step up this disaster can and will affect the us and other neighboring nations within the possible blast radius of a exploding plutonium bomb basically for you un familiars out their another Chernobyl

holy typos batman !

Maybe I’m being overly simplistic: Why not build robust smaller modular units capable of generating a few MW apiece, each encased in multiple layers of redundant concrete-steel-etc. and buried well underground to avoid terrorist activities. Engineer it so that most of the plumbing, ductwork etc. is fully encased in the heavy unbreakable walls of the module, and work out a simple leakproof way to circulate inert fluid and/or gas into and out of the module so as to extract a great quantity of usable heat without getting near the source of radiation.

Build a redundant safety factor into the fuel compartment which would allow common gravity to pull the fuel elements a safe distance apart – and lock them there – in case of an emergency, catastrophe or seismic event, thus bypassing this stupid reliance on backup generators, pumps, batteries etc.

If the ground starts shaking past a certain G-force it releases a latch, and gravity pulls the fuel plug. If the plant’s electricity output gets hit with an extreme overload it releases the latch, and gravity pulls the fuel plug. If the plant operator receives notice of an impending catastrophe he hits the red button which releases the latch, and gravity pulls the fuel plug, etc. etc. In all cases whenever the plug gets pulled, the module’s power output winds down all by itself, in a safe, predictable manner. What’s so hard about that?

Will the fuel not generate any heat at all, unless it’s jammed into an almost-critical mass right at the edge of melt-down? Is the resultant heat (power) production linear, related to proximity of the fuel, or is it exponential? Why be greedy and insist upon maximizing the heat production, if excess heat is the only real problem? Dial the heat (and your profits) down a bit so as to make the modules more stout and reliable, and move on.

Sten C. wrote a nice description of fission and nuklear chain reaction AND radiation.

The Fukishima plant is destroyed, monday morning quarterbacks.

Why the Russians don't bother with 'containment' structures ? Is it because they prevent access for backup cooling water and will blow their tops off anyway and cause violent damage ?

Nuclear radiation biodegrades (and so does crude oil).

What's the dilema with nuclear power ? The water. The water stops radiation too. Without water a meltdown occurs and radiation escapes into the atmosphere AND lava pollutes the ground. If a backup water supply is introduced, it slows escaping radiation but the water becomes contaminated and pollutes the ground too.

What about the flowing lava ? It's as harmful as the contaminated water. Is that why the Russians never bothered to build containment structures. I think so.

The most dangerous aspect of a disaster is used fuel rods that are not SPENT (rods that were removed but would be placed back into the RPV.) Place those rods in a very durable container of water. Keep this container near those rods at all times when the rods are in the RPV. It's not foolproof.

I can't imagine handling active but scrammed fuel rods after a disaster, but it could be done, and consider all the (very heroic) activity at Fukishima.

A large capacity flexible cooling hose should be attached to or near the RPV if a disaster happens. Emergency pumps could then pump water into the RPV from a great distance of the facility.

OK, so most water coming out is not radioactive, oxygen does have a radio isotope, but the steam and water can carry larghe amounts of radioactive materials with it. Now as far as wether the "corium" becomes more reactive, chemically? or any other way, : as the partially molten or not radioactive material is dissolved into the titanium / zirconium / nickel melt the heat necessary to keep the "new" alloy molten becomes higher. But as the number of reactions goes down with time, the heat necessary to accomplish this is no longer being generated. So the material hardens into a solid alloy which should be more resistant dissolving. The material which did not enter this "elephants foot" or blob at the bottom of the reactors is however much more soluble min seawater. Any fuel pellets exposed directly to seawater would have a large portion of their surface radioactive materials dissolved out and would leave the reactor with any leaking water. And if I remember correctly some of the fission byproducts that are most radioactive are also the most soluble. so you have the poisonous material leaking out and showing very high readings outside the reactor and the uranium still inside. As far as a melt through; 9" of steel can absorb and disssipate a lot of heat, especially when water is flowing around the outside from leaks and being sprayed on it. When water boils it absorbs a TREMENDOUS amount of heat. The video of number 2 inside the containment chamber does not show ANY sign of material having melted through the reactor vessel. Only showed corrosion from water running down the side of the reactor vessel, and down the pushrods for the control rods. Every one of which was still in place! No molten material outside the reactor vessel, NO melt through. so-called Corium cant melt very far down from the reactor because as it melts new material this gets mixed with it diluting the radioactivity per cubic inch and cooling the entire mess below melting point. I E it stops partway through the concrete. The only way a " China" syndrome could occur is if the "hot material" did not alloy with the other metals, remained seperate and continued to generate enough heat to melt through whatever it came to. Cant happen, molten metals like nothing better than mixing to form an alloy, Very Few will seperate and only at specific heats, anything else and they are alloyed, diluting the reactions and the het generation. With 14" to 16" of steel at the bottom of the reactor vessel, and the control rods in place, I have to say there is a 100% certainty no meltthrough at #2 reactor. taking all this into consideration, and the evidence from 3 Mile Island, I would bet that #3 and #4 dsid not melt through either. Maybe reactors are safer than we thought. The fuel pools maybe they should be contained like the fuel in the reactor is, inside a more hardened container. Or maybe a transport container filled with circulating water to move them from the reactor building to a below ground level pool some distance away. One thing is certain ther will be much ne knowledge gained from this, and probably still some surprises yet.