Thorium-fueled Molten Salt Reactors

I think Electic is nearly 100% correct in post 39. To answer your question: The same thing that would happen if a brick at 600C were tossed into a pan with a little water in it as the brick does not chemically react with the hot water, any more than the metal salt does, as I understand the (lack of) chemical reaction, but as Electric notes, the metal salt would not be going into water it could greatly expand as steam, but into H2O that is already steam!

I don't know the pressure in the primary and secondary loops of the heat exchanger, but would not be surprised if when a hole develops, it is the steam which passes / leaks into the primary loop, not the other way round.

 

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I did not read all the replies. Sorry if there are redundant remarks here.

I think there is a level of hysteria relating to nuclear reactors. Chernobyl & the Japanese disaster were due to faulty design & safety measures. USA, England, & especially France have had few serious problems.

Note that France gets over 50% of its energy from reactors & I do not know of any serious problems.​

An example of hysteria was a remark by politician Deneberg similar to the following.

Perhaps Deneberg (? spelling) was ignorant enough to think that a reactor could explode like a nuclear weapon. Perhaps he did not know that a nuclear weapon is incapable of destroying one third of Pennsylvania (not even a fusion weapon could do that). Perhaps he was merely being a politician making a sound byte hoping for more votes at the next election, knowing that the typical voter is too ignorant to have knowledge of the consequences of a reactor melt down.

England had a Chernobyl-type reactor at least a decade prior to the Chernobyl reactor. Due to known potential problems, they took precautions. A chernobyl-like problem occurred, but caused no serious problems. Some low level radioactive material was wind blown over the country side. Due to this minor incident, Chernobyl type reactors were abandoned in USA, England, France. Russia did not learn from (or did not know about) the English incident & took no precautions.

The Japaneses apparently ignored the fact that they were buiding their reactor in the Ring of Fire. I am sure that the USA would either not build a reactor in the vicinity of the San Adreas Fault or would make it fail safe in the event of an earth quake.​

BTW: I do not remember the seriousness of the consequences due the Japanese reactor incident. Aside from damage to the reactor, were there other serious damages/injuries?

 

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TOKYO (Reuters) - Japan will dramatically raise its warning about the severity of a toxic water leak at the Fukushima nuclear plant, its nuclear watchdog said on Wednesday, its most serious action since the plant was destroyed by an earthquake and tsunami in 2011.

The deepening crisis at the Fukushima plant will be upgraded from a level 1 "anomaly" to a level three "serious incident" on an international scale for radiological releases, a spokesman for Japan's Nuclear Regulation Authority (NRA) said.

That will mark the first time Japan has issued a warning on the International Nuclear Event Scale (INES) since three reactor meltdowns after the massive quake in March 2011.

Water still leaking from the plant is so contaminated that a person standing close to it for an hour would receive five times the annual recommended limit for nuclear workers in a year.

A maximum level 7 was declared at the battered plant after explosions led to a loss of power and cooling two years ago, confirming Fukushima as the worst nuclear accident since Chernobyl a quarter of a century earlier.

 

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There a good reason for that: France's "AEC" has its primary responsibility as Safety, not like the US's AEC's promotion of nuclear power. Thus things are done differently in France. For example, the reactor designs are mainly done by the government and one of the requirements is that all have identical control rooms so if a problem is developing the experts arrive knowing exactly what all the gages are telling, etc.

In the case of "three mile Island" problem the experts did exactly the wrong thing for nearly two days as they misunderstood what the gages were telling them. They thought a "hydrogen bubble" was growing and forcing the moderating water level in the core down, exposing parts of the fuel rods.

In the US there are a several different companies selling their own reactor designs, and more than a dozen different ones are now making power. Worse is EVERY US CONTROL ROOM IS UNIQUE. At three mile island all the controls were along one wall so that people in the gallery (high on the other side) could look thur the windows and see every thing but the experts on the floor could only see a the few gages that were on the wall in front of them (which they did not immediately know the meanings being presented by the gages). The relative placement of each gage was unique to Three Mile Island and not correctly understood for nearly two days - so instead of being a minor incident the public never heard of, for two days the experts (not understanding what the gages were telling) vented the non-existent hydrogen bubble to let the water rise and keep the fuel rods from over heating. I.e. they needlessly and intentionally released isotopes into the air, thinking they were preventing a serous melt down!

It silly nonsense to let the company's public relations people design how the control room is laid out! Every one should be EXACTLY THE SAME as in France.

 

While that may be true (I don't know) it presents a somewhat false impression. The "cold war" is responsible for the Chernobyl reactor design. It made power only as a buy-product. Its real purpose was to make plutonium which can be chemically purified, not requiring the expensive separation of U235 from U238.

That design has an inherently less safe "positive temperature coefficient" - reaction rate increases with the core temperature.* The US's early design are also selected by the cold war. Very early at Oak Ridge a safe thorium reactor was run for almost two years, but the generals learned you cannot make an A bomb with thorium, so the funding for exploring the potential of the thorium reactor was terminated and only available for research on uranium reactor was funded. They were US funded, and very secretly, to justify exploration of the two separation methods used make bomb grade Uranium 235 "Power too cheap to measure" was promised to Congress to keep the dollars coming.

Fortunately other governments wanted safe nuclear power more than bombs, so Canada developed the heavy water moderated Candu (Canada+ Deuterium) reactor which can run on natural uranium's less than 1% U235 - no enrichment plants required. India and four or so other peace loving countries are now going down the thorium reactor road.

* A greed deal of operator stupidity was also required to make the disaster: They had turned off almost all the automatic safety controls one night to intentionally measure the positive temperature coefficient. - I.e. they did not want those controls preventing a temperature rise big enough to accurately measure.

PS the main reason I don't believe Iran's nuclear program is only for peaceful purposes is that they don't go down the Candu or Thorium roads. It is not because the US claims they are wanting to make a bomb, even though that probably is true. The US fabricates lies to help its claims about the intentions of others. The worse example was the letter from the Nigerian "AEC" replying to Saddam's supposed request for more information on the availability of uranium ore. It was very well done, except for one detail: It was on the stationary of the Nigerian AEC, but that agency had changed its stationary about two years earlier than the letter's date.

 

? Thorium breeds to U-233, which is one of the easiest materials to make bombs from. You can make a gun-type bomb from U-233 with a minimum of expertise.

(Thorium ALONE cannot make a bomb; but then again, thorium ALONE cannot fuel a reactor, either.)

Uh, you do realize that heavy water is required for many breeder reactor designs, right? With it reactors can more easily produce plutonium (for atomic bombs) and tritium (for thermonuclear bombs.) It was one of the reasons that the US was able to develop atomic bombs before Germany did.

 

But it also breeds U232 which does a nasty to anyone trying to make a bomb with it. Two devices with U233 have been detonated. One was a 50:50 blend of U233 and Pu. It produced half the anticipated yield. The other was a .2kT yield device but the DESIGN yield is unknown to me.

Since Thorium is available world wide, why hasn't it happened before?
The members of the "Nuclear Club" have had seven decades of practice at making nuclear weapons. If it were so easy, explain this.
The current score card:
Weapons derived from Uranium ~20,000
Weapons derived from Thorium =ZERO!
If they haven't done it by now, that should tell you something.

 

Yes the U-232 is the "denaturing agent" in preventing making bombs from U-233, now it does not make it impossible, just very expensive. I should be noted though the molten salt fuelled reactors could really reduce U-232 production and produce very pure U-233, also modern robotics could be brought to task such the humans can be kept away from such a highly radioactive production process.

The weapons production argument is a silly one to me, it as if we stopped chemical manufacture just because it "could" be used to make VX and Sarin, or that we stop biotechnology industry because it "could" be used to make hyper deadly plague. Nuclear fuel technology can be regulated to safely produce fuel and considering the most countries with the financing to develop or buy new fangled thorium molten salt reactors will likely already be armed with atomic bombs its a moot point! If one is uncertain about a nation then sell them many small "battery" molten lead cooled reactors and then you handle all the fuel production and recycling of reactor cores.

 

I agree with Electric & kiteman's posts, but want to also note that the energy required ("separation work units") to separate two isotopes falls faster than linearly with the mass difference. Thus separating U235 from U238, a mass difference of three, is at least four times less expensive than separating U232 from U233. a mass difference of only one.

Also I think Bilvon is also wrong in saying : "Thorium alone can not fuel a reactor." True you need some decaying neutron sources to get it running but once it is you only need to add pure Thorium fuel as it is making the rapidly decaying U232.

 

Well supposedly molten salt fueled reactors can sieve out Pa233 fast enough to keep the production of U232 low enough. If not removed Pa233 will absorb more neutrons and decay into U232, if removed it decays into U233.

 

Because plutonium is far more available due to the current design of breeder reactors. (If we didn't have breeders we'd be using U235 for all our weapons.)

?? It's not easy. Neither is making and separating plutonium, but that was the first breeder technology developed. Weapons designers work with the materials they have, not with the materials they don't have. It's like asking why no one makes bombs with antimatter.

 

Right; this is generally done with a seed of U235 or similar fissile material. The alternative is to transmute some thorium to U233 via a neutron/proton beam but this would require a beam intensity far higher than anything we currently have available. The U233 then functions as the seed to start the reaction. (A more general term for the above is "energy amplifier" since you are effectively amplifying the power of the already-powerful particle beam.)

 

I'm not well versed in thorium reactor processes, but thought the neutrons in the reactor were making more U232 (?) than needed to keep it running with only pure thorium fuel replacing the older fuel when needed. I'm nearly sure, India and others making thorium reactors have no plans to make neutron beams too.

 

Right. Thorium alone is insufficient to start the reactor, so a seed of fissile material (usually U235 or plutonium) is placed in the reactor with a "blanket" of thorium around it. The reactor is started up with the seed material and initially it operates as a normal LWR. As it operates, the blanket absorbs the excess neutrons, and thorium is transmuted to U233. Once enough U233 has been bred, then it becomes the fissile fuel and the seed is no longer needed.

However it should be noted that the seed has to be large enough to power the entire plant while U233 is being bred (or alternatively the reactor has to be idled while a smaller seed breeds U233.)

 

Reactors can be designed to produce weapons grade Plutonium. Nuclear Power Plants don't. They are not designed too. Yes it is possible to design a plant to produce weapons grade U233. No responsible Nuclear Power Plant would. Indeed, all the designs I've seen specifically work to PREVENT it.

 

There are other factors that just the "first thru the gate" argument. There are some very nasty radiations from U232 decay products that have deleterious effects on mechanisms and especially explosives needed to detonate a bomb.

 

Nope. The Thorium 232 absorbs a thermal neutron and becomes Th233 which decays to Pa233 quite quickly. With a half-life of about 29 days it decays to U233. However, with a fast neutron, Pa233 will undergo a n,2n reaction Pa233(n,2n)Pa232 which then decays into U232. Also, the U233 will occasionally undergo the U233(n,2n)U232 reaction too.

 

I don't think your second option will work.
None-the-less, you have described why the Liquid Fluoride Thorium Reactor is better than the LWR, it needs the smallest seed charge of fissile material and the pellets don't need to be re-processed to get the bred fuel into operation.
LFTRs work very well with PuF3 as the fissile seed, PuFFF the magic fuel!

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Thorium ALONE can fuel an OPERATING Liquid Fluoride Thorium Reactor.

The trick is, to get it operating, you need a starter load of FISSILE material. MSRs have been started on all three fissile materials, U233, U235, and Pu239.

 

Agreed. It is definitely not easy. It would be a mistake to ignore the possibility, though; proliferation is a serious problem in the world arena today.

I guess that's a semantics argument. Thorium alone is non-fissile. You need U233 to actually operate the reactor (or build a bomb.)