Wednesday, April 4, 2012

The Clinch River Reactor Failure, Lessons Unlearned

It is my contention that the AEC made a terrible mistake by picking the Liquid Metal Fast Breeder Reactor over other breeder concepts. This mistake was compounded by a number of delusions held by the AEC management. By the late 1960's, "The AEC believed that the world uranium supply was very limited. This was very far from the case. In fact, Alvin Weinberg frequently noted that Manhattan Projects scientist had discovered that even at adverage crustal concentrations, more energy could be obtained from mined uranium than would be used to mine it. In addition a huge amount of recoverable uranium was disolved in sea water. Mining the sea for uranium, while more expensive than surface mining, obtained uranium. Sea water recovered uranium would not greatly increase the cost of electricity.

Thus the worry about the global uranium supply as a motive for building fast reactors was a collosal blunder. There was no need for the large amount of Pu-239 and problematic Pu-240 that the fast breeder would produce. A second question arose. What sort of reactors would use the fast breeder produced surplus Pu-239. If you produced more and more fast breeders, eventually you would arrive at the Sorcerer's Apprentice syndrom. Goethe wrote:

Go, I say,
Go on your way,
do not tarry,
water carry,
let it flow abundantly,
and prepare a bath for me.

Look, how to the bank he's running!
and now he has reached the river,
as quick as lightning,
once more water to deliver.
Look! The tub already
is almost filled up!
And now he is filling
every bowl and cup!

Stop! Stand still!
Heed my will!
I've enough
of the stuff!
I've forgotten - woe is me!
what the magic word may be.

At some point the breeder reactors begin producing too much plutonium. Breeders usually produce plutonium, and using plutonium as a fuel for thermal reactors carries some serious problems. The capture of a thermal neutron by a Pu-239 atom may lead to a fission rate as low as 65%. Plutonium is just not a very good fuel for thermal reactors. The Indians have decided to solve this problem by building fast breeders that breed both plutonium and U-233. The Indian fast breeder will produce only enough plutonium. U-233 is an ideal fuel for thermal resctors. This sort of solution never occurred to the AEC.

Another serious problem related to the form of fuel which the AEC chose was plutonium oxide (PuO2). This was mixed with uranium dioxide (UO2). The mixture was heated to over 2000 degrees, and turned into a ceramic. Unfortunately the chemical constituants of ceramices are difficult and expensive to recover.

Unfortunately the AEC also did not have even a preconceptual design and that made accurate cost estimates impossible. Without a preconceptual design, the exact details of the reactor parts were unknown, and without detailed information on the reactor parts, it was impossible to create reasonably accurate cost estimates. The AEC estimated the cost of a completed LMFBR. The original extimated cost of the Clinch River Reactor was $400 million. The last estimated cost in 1983 was $8 Billion.

A further flaw was the the amount of plutonium required to start a fast breeder, its cost and the plutonium yield of the fast breeder. I have no idea how much military grade plutonium cost, but the efforts of two major multi-reactor AEC facilities, Hanford and Savannah River, from World War II to the end of the cold war, seemed to have yielded 100 tons of military grade plutonium. Recovering ten tons of plutonium from LWR ceramic fuel has an estimated cost of $1 billion. Ten tons is enough to Power a LMFBR. Although the theoretical yield is 20% of the plutonium every year, yield estimates suggest that it takes 10 years of operation to produce enough Pu to start another LMFBR, although some reactors nay require as much as 20 years. An alternative to using Pu in the start charge is to use U-235 or U-233. Both produce fewer neutrons per neutron capture and thus would breed at a lower breeding ratio than a plutonium start charge would breed. Therefore starting a fast plutonium breeder would be either hugely expensive or lead to initially poor breeding performance.

I am writing here about classic LMFBRs, such as the Clinch River Reactor, and not the IFR. I do not know of any IFR pre-conceptual design that is capable of producing more than a 5% breeding gain, although IFR supporters assure me that pre-conceptual designs of IFRs capable of producing high breeding ratios exist in the minds of some retired scientists. Although I believe that these very intelligent and able people have some good ideas, I am not a mind reader, so I cannot tell if their ideas amount to a pre-conceptual plan. I must say that I believe in this possibility that some day the IFR will be built, but I am far from sure when, or how much it will eventually cost.

The management plan for the LMFBR was another huge mistake. The management of the Clinch River Reactor should have been turned over to Argonne National Labatory, which had very considerable experience with designing liquid metal cooled reactors. Argonne was kept out of the loop and the management of the Clinch River Reactor appears to have been clueless. They spent $1 billion of taxpayer money before the project was shutdown, and had very little to show for it.

The failure of the Clinch River Reactor provides us with a precautionary message. Many mistakes were made from the get go, but the people who should have been aware of them, appearantly did not think things through. The same disasterous mistake is being made today by the advocates of renewable energy.

In the late 1960s, the AEC mistakenly believed that the recoverable uranium supply was far more limited than was in fact the case. Overlooking numerous problems, the AEC chose to put all of its future eggs into a deeply flawed breeder reactor project, the Clinch River Breeder Reactor. This reactor project proved to be an expensive failure. Unfortunately the lessons that should have been learned from the Clinch River Reactor were ignored and the same sort of mistakes are being committed in new energy programs.


Anonymous said...

It is not extremely difficult to change the breeding ratio of a fast breeder. I contend that generating too much plutonium would never occur unless there was a major upset in a planned expansion of nuclear power.

For example, we might envision a plan to expand to N gigawatts of sustainable nuclear energy. We would begin by building breeders that would establish the stock of fissile material necessary for these start ups, but eventually we would have a sufficient source of fissile material for the planned reactors and we would start building lower BR/CR reactors. Once we reach the desired capacity, we convert the breeders into break-even designs or otherwise balance the fissile production with consumption. It's not as trivial as flipping a switch, but it's doable with an extended outage.

I think your other points about the CRBR management and the underestimation of the uranium resource are valid.

Charles Barton said...

The temptation to over breed comes from the value of plutonium. It id extreemly valuable, as I have indicated. The price, of course will eventually drop woth over breedlng. But if it drops to far the economics of fast breeder reactors may not work. I intend to look more at the economics of fast breeders in comming posts.

Nathan2go said...

The book "Plentiful Energy" has a funny story about oxide fuel for fast breeders. At Argonne labs they started out with metal fuel (it's safer and leads to better breeding). But they found that metal fuel swelled a lot during irradiation (and would break the cladding, even at low burn-up). The Clinch River team assumed that they had to switch to a fuel that swelled less (oxide). The IFR guys were smart enough to realize that they could simply leave more space in the cladding for swelling, problem solved.

Sadly, even the IFR team was not smart enough to realize the value of breeding U233 (diluted with U238). Much nuclear opposition is driven by fear, and having power plants sell excess LEU is much less scary than selling Pu (especially when bred fuel is transported off-site).

LFTRs to Power the Planet said...

I was hugely impressed by retired personnel from Argonne Lab, recently speaking with incredulity about the USA turning away from the solution to future energy needs and closing down EBR-II.

".....Doesn't the Country realise what they're losing here?....":

Charles Barton said...

LFTRs, I do not believe that the IFR offers as much as the MSR/LFTR. Nore is a high breeding ratio IFR as well developed as the LFTR, for which several designs emerged from ORNL in the 1960's and 1970's.

Engineer-Poet said...

Fast-spectrum reactors like the IFR offer two things the LFTR does not:

1.  A way to completely burn the stocks of actinides from LWRs, as well as any excess Np and Pu-238 from thorium breeders.

2.  A way to make use of the half-million tons of uranium already in storage in the USA alone.

GE's S-PRISM solved the "over-breeding problem", if it is a problem.  It has a configuration with axial reflectors and a breeding ratio of 1.05, and a configuration with axial breeding blankets and a breeding ratio of 1.22.  If you want sub-unity breeding, replace the breeding blanket with a leaky reflector inside a neutron absorber.

IMO we need to build both thorium-thermal and uranium-fast reactors, because they each can do jobs that the other cannot.


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