CERN Dr. Michael Dittmar, a CERN Physicist, has posted Part IV of his essay on the Future of Nuclear Energy, on the Oil Drum. In many respects Dr/ Dittmar's conclusions track the conclusions of thorium advocates.Dr. Ditmann has some interesting observations on LMFBRs. He claims that
the IAEA data base for fast reactors does not present any evidence that a positive breeding gain has been obtained with past and present FBR reactors. On the contrary, the presented data indicate at best that a more efficient nuclear fuel use than in standard PWR reactors can be achieved during normal running conditions. However, once the short and inefficient running times of FBR's, in comparison with large scale PWR's, are taken into account, even this better fuel use has not been demonstrated. In fact, the required initial fuel load in FBR's contains at least twice as much natural uranium equivalent and with a fissile material enrichment that is roughly 5 times larger than that in a comparable PWR. A fair comparison of the fuel efficiency should include the efficiency to recycle fissile material from used nuclear fuel in both reactor types.In addition Dittmar notes that there are three areas of further concern about LMFBRs"
Fast reactors are known for their worrying safety record. For example, it might be true that serious incidents, like the one that happened with the Chernobyl graphite moderated reactor, cannot happen with modern PWR's. However, only very few nuclear experts would agree to such a statement for sodium cooled FBR's.Indeed Dittmar's view seems to be that
FBR’s are known for their huge construction costs relative to PWR's, and it might be tempting to compare some of the past FBR's to a monetary "black hole." An equivalent of 3.5 billion Euros has been invested in the construction of the SNR-300 in Germany. Because of safety concerns related to sodium leaks and other problems, this small FBR has never started operation. This amount of money corresponds to the price tag for a five times more powerful modern PWR reactor.
A third problem is related to the FBR requirements to have a large inventory of high purity fissile material. The amount of fissile material listed in Table 3 should be compared to the few tenths of kgs required for a Pu239 bomb. This problem makes even small experimental FBR reactors highly sensitive to the proliferation problem.
* The breeding of Pu239 with fast neutrons has huge problems, and it would be great if another nuclear fuel could be found.
* Thorium breeding shows interesting potential if the remaining large number of problems can be mastered in the long term, . . .Dittmar nots evidence for thorium breeding in the Shippingport LWBR experiment. Dittmar also noted some advantages for thorium breeding:
- The possibility of utilizing an abundantly available resource that has hitherto been of so little interest that it has never even been properly quantified.
- The production of power with few long-lived transuranic elements in the waste.
- A reduction of radioactive waste, in general.
- The high cost of fuel fabrication due partly to the high radioactivity of U233 chemically sepa rated from the irradiated thorium fuel.
- Separated U233 is always contaminated with traces of U232 (69 year half-life but whose daugh ter products such as thallium-208 are strong gamma emitters with very short half-lives). Although this confers proliferation resistance to the fuel cycle, it results in increased costs.
- The similar problems in recycling thorium itself due to highly radioactive Th-228 (an alpha emitter with two-year half life) present.
- Some concern over weapons proliferation risk of U233 (if it could be separated on its own), although many designs such as the Radkowsky Thorium Reactor address this concern. The tech nical problems in reprocessing solid fuels are not yet satisfactorily solved. However with some designs, in particular the molten salt reactor (MSR), these problems are likely to largely disap pear.
- Much development work is still required, before the thorium fuel cycle can be commercialized, and the effort required seems unlikely while (or where) abundant uranium is available. In this respect, recent international moves to bring India into the ambit of international trade might result in the country ceasing to persist with the thorium cycle, as it now has ready access to traded uranium and conventional reactor designs.
The well known use of nuclear fission energy in PWR's is unsustainable. The problems related to long-lived transuranic elements, e.g. plutonium and heavier elements, as well as nuclear waste in general, are unsolved. The concern with nuclear weapon proliferation cannot be dismissed either.
"Much development work is still required, before the thorium fuel cycle can be commercialized, and the effort required seems unlikely while (or where) abundant uranium is available. In this respect, recent international moves to bring India into the ambit of international trade might result in the country ceasing to persist with the thorium cycle, as it now has ready access to traded uranium and conventional reactor designs."
This statement requires multiple answers:
1. The expression "much development" work is extremely ambiguous. ORNL researchers in the 1974 analyzed the developmental tasks required to for the development of a Molten Salt Thorium Breeder (ORNL-5018, Program Plan for the Development of Molten-Salt Breeder Reactors). The cost would have been somewhere around 2.5 billion 2009 dollars, to prototype stage. To date the United States has spent about $25 billion on the development of the Liquid Metal Fast Breeder Reactor without a product. Even if the development cost were several times higher that $2.5 billion, it would still be cheap, even in terms of what the United States spends researching renewables. A mini-Manhatten Project approach would vastly shorten the development time frame. With an investment of $15 billion, less than the United States spends on its space program every year, the United States could have a viable commercial LFRTR prototype in 5 years.
2. There is a strong motive for LFTR/TMSR development. Namely low cost rapid substitution of nuclear energy for fossil fuels. The LFTR is significantly simpler than the LWR, and it can be built with less materials, fewer parts and less labor. LFTRs that produce between 100 MWe and 400 MWe will be small and light enough to transport by truck, rail or barge. Factory ass production of LFTRs would greatly increase labor productivity. Because of its small size, and high level of safety, LFTR site construction would be less expensive. Thus dramatic savings in nuclear construction costs could be realized by switching from LWR to LFTR technology. Finally factory production would dramatically increase the scaleability of nuclear power, making the replacement of 80% of fossil fuel energy sources by 2050
3 Indian efforts to develop the thorium cycle are likely to presist for some time for several reasons:
A.The international imbargo on uranium sals to India, will not be forgotten quickly, and a determination to make India independent of international uranium sources will remain fixed for some time to come.
B. India has at least a low cost thousand year fuel supply in surface thorium deposits, that beg to be used.
Dr. Dittmar thus has suggested views that are supportive of the case for thorium generally, and offers indirectly for the Liquid Fluoride Thorium Reactor. The major problems for thorium breeding molten salt reactors, which Dittmar notes have more to do with the current scale of development, than development difficulties. A much larger development effort, could vastly shorten development time.
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I read Dr. Dittmar's lengthy posting on "The Oil Drum". The tome is full of fear and a negative, "Can't-Do" attitude. His arguments have a number of weak points.
Early in the posting, Dr. Dittmar makes of point of stating what a wonderful material U233 is for making nuclear weapons. But then later on, he states that is a poor material for solid fuel reactors since is so hard to handle, especially so with the U232 contamination. I have a hard time understanding why anyone would want to try to make a weapon with U233 when doing it with U235 is so much easier (easier to obtain, much easier to handle).
He goes on to discuss the dangers of low level radiation, justifying his position of its danger from the stance taken by the regulatory bodies of many countries - lowest possible exposure. While this may be the regulatory standard, I think there is good evidence to suggest that such stringent regulation ends up costing lives as safe nuclear energy is made unnecessarily expensive and its progress impeded.
The arguments against Gen IV reactors is something like this: "Little progress has been made on Gen IV reactors in the last 10 years due to lack of funding, therefore they can't be done."
What has been lacking is sufficient incentive to focus our collective minds on the issue. Conventional fossil and nuclear energy have been plentiful enough that we have had the luxury of doing little to develop advanced sources. If fossil fuels become scare and expensive, I believe would would see major progress in short order. I wish things did not have to work this way, but it seems to be human nature.
Don. I did not say that I regarded Dr. Dittmar's pos ta realistic assessment of the nuclear power. My point here is to note that that his arguments are largely consistent supportive of LFTR development. Some of the points he attempts to make are absurd. For example, the arguments that past Liquid Sodium reactors were not true fast breeders. Even if true, there is little doubt that LMFBRs work.
"My point here is to note that that his arguments are largely consistent supportive of LFTR development."
Just don't expect Dittmar to see it that way!
Bill, I don'r, What I am doing amounts to using the Devil's argument against himself. Arguing if what the Devil says is true, he has really offered support for my case.
Actually, there is a real problem with breeder reactors hidden within that description. Where a more conventional reactor has a good neutron economy available, taking one neutron to release on average slightly more than two from fission, a breeder (whether thorium or uranium) needs two neutrons going in to get that going out - one to breed earlier, and then one to fission later. It is indeed tricky to stay above break even with just that going on, what with unavoidable losses to poisons, control rods and the outside world.
However, there is something that helps. Beryllium is a neutron multiplier, if it gets hit with fast neutrons; each fast neutron will release two slower neutrons. With that, everything gets more realistic. But I have never seen this brought out in discussions, so I think break even issues should be addressed better. For instance, this suggests to me that thorium breeders ought not to use separate moderators but instead rely on beryllium in the molten salts to do it (so it can capture proportionally more fast neutrons it can multiply), or be run as fast breeders with a beryllium based intermediate blanket before an outer breeding blanket (whether thorium or uranium based).
As I say, I have not seen this covered.
I supposed it is a good thing that Dr. Dittmar's criticism of nuclear power didn't land any punches on the Liquid Fluoride Thorium Reactor or LFTR (it is quite a promising technology); however, his criticism of other reactors was not supported by the data in his essay.
He unsuccessfully attempts to renew an outdated argument against nuclear power that since there is only enough uranium in the world for a few decades of nuclear energy (because breeder don’t work), why bother?
His primary flaw is that he overlooks the concepts of the near-breeder and the break-even breeder. During WWII, it was widely believed that since uranium was quite rare, a breeder reactor needed to breed much more fissile material than it consumed in order to allow nuclear energy to meet all humanity’s energy needs. We now know that cheap uranium is plentiful (more so than natural gas and petroleum on a Light Water Reactor or LWR basis); and expensive uranium is extremely plentiful. Hence a near-breeder (several types have been studied), that for example uses 1/3 of the uranium ore compared to a LWR could cost effectively generate more energy from the world’s uranium than is contained in all of the coal, oil, and natural gas in the world.
A break-even breeder (one that has a breeding gain of 0.00, to use Dittmar’s disparaging terminology, such as the Shippingport Light Water Breeder and several recent LMFBRs), once started, would generate the same amount of fissile fuel it used, and so would never run out of fuel (for a billion years!). He ignores the advantage that these reactors would have: once started, no fissile material would ever leave or enter the power plant (assuming on-site reprocessing, such as was proposed for the USA’s IFR breeder). The challenge, as Dittmar points out, is that breeders typically require much more fuel for startup than LWRs (the exception being LFTRs). This puts them at a cost disadvantage compared to LWRs, but probably not compared to renewable energy systems with energy storage.
As to whether we could produce enough fissile material to startup a fleet of breeders large enough to supply all of our needs, it should be remembered that each LWR, during its 60 year lifetime, can produce enough “waste” to startup between one and two Liquid Metal Fast Breeder Reactors or LMFBRs with the same power. So the answer seems to be yes (this is of course greatly helped by efficiency and conservation!).
The important conclusion that I draw from studying the LMFBR is it would be a great disservice to our descendants to permanently dispose of our nuclear “waste” before it is conclusively determined whether they will need it for their breeder reactors (remember that nuclear “waste” becomes less hazardous and therefore more economical to utilize with the passage of time). Only the future will tell whether the LMFBR or LFTR will come to dominate.
The original MSRE salt contained flourine, lithium and beryllium but, by the sounds of what you said, PML, moderated its spectrum too severely to be able to use Be's neutron multiplication.
When people refer to 'running out of uranium' they completely ignore past experience with mineral resources. There are never more than 30-40 years of proven reserves of anything. That was true of copper 100 years ago and is STILL true. The reason is that when you start to run out you look for more, with better technology. It can't be guaranteed, but it should be pointed out that in an historical sense, we haven't even begun to look for uranium. Why would it be any different than any other mineral resource? I read an article not long ago that there appeared to be large deposits in Greenland. The point is that we don't know how much uranium is out there, but the best 'guess' is that there is a lot.
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