Off to Russia

I just started reading “The Rise of Nuclear Fear” by Spencer Weart. Already I found out that it started thousands or millions of years ago with the fear of witches, jins, etc.

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I hope that your trip to Russia is productive.

Meanwhile, I suggest that people visit the following web site and post appropriate comments:

http://2greenenergy.com/

I’ve posted comments on the following page of the website, using FRE as my ID:

http://2greenenergy.com/another-nuclear-power-plant/22020/

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SteveK9,

Thanks for the additional information and the link. I’m glad that you made a post to the web page to which I provided the link; perhaps others will also.

However, I do question one thing in the linked-to article. According to the article, our present nuclear technology makes use of only the U235. It was my understanding that some of the U238 is transmuted to plutonium and that most of the plutonium is then fissioned. If my understanding is correct, then our present reactors actually do some limited breeding.

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Frank: I’m a scientist but there are people on this site much more knowledgeable than I am. From what I have read we do get some limited breeding in a PWR. So, with natural U at 0.7% U235, we get a good portion of that in the enrichment to ~5% U235 for fuel (and throw away some), then we get some addtional energy from Pu production from U238 and overall obtain about 1% of the energy in the original U compared to fissioning it all.

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The Breakthrough Institute also has some articles suggesting offsets are illusory and by implication fraudulent. Could be why we are supposed to spend billions on them as a nation if we are not on-track with emissions by 2015.

I haven’t done the numbers but I think we could make some reasonably priced jet fuel from coal and gas if we didn’t also burn those fuels in power stations. That’s for an overall 80% emissions cut not 100%. Bullet trains travelling at 350 kph powered by electricity might replace some air travel with the slight problem of underwater tunnels any further than the English Channel.

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@George
Based on my recollection of a presentation by Eric Loewen a year or two ago at my university, the GE plan is to build the fast reactor first and demonstrate the economics of that technology, *then* build the fuel cycle support facilities.

This understanding seems consistent with GE’s activities in the UK. http://www.independent.co.uk/news/science/plans-to-build-a-nuclear-fast-reactor-at-sellafield-come-a-step-closer-7608840.html

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Cyril R:

On another thread, having promoted the virtues of lead cooled fast reactors, you went on to suggest that uranium/thorium hybrid fuel for SFRs would offer anti proliferation advantages.

I would appreciate more information as I set great store on your opinions. I think this may be the appropriate thread to make this approach because, in part, I’m seeking information on pyroprocessing.

First, lead.
I had understood that lead bismuth was generally preferred to lead because of lower material damage. However, I have also read that you can only expect to get isobreeding from a lead/bismuth fast reactor and need sodium cooling for true breeding (without understanding why this should be so).

Have the corrosion problems of pure lead coolants been overcome?
If so,could one expect lead to be equivalent to sodium with respect to breeding ratios?

Second, hybrid fuels and pyroprocessing.
Suppose one wished to use RG Plutonium as fissile and uranium/thorium as fertile, what would be the composition of the fuel elements? Would one operate a core and blanket for maximum breeding with both uranium and thorium in the blanket for proliferation resistance and plutonium and uranium in the core? Alternatively, what would happen in terms of breeding if one used homogeneous fuel assemblies of mixed metals and no blanket? What would be the reprocessing implications of either approach? Would thorium go to the cathode along with other heavy metals? Would thorium get there together with (other) actinides (I’m not sure whether thorium is classed as an actinide) or sequentially? If the latter, what would be the proliferation implications?

i hope you can bear with me. I’m aware that a little learning is a dangerous thing and can understand, therefore, that these questions may be irritating.

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Douglas Wise:

Lead bismuth eutectic is more corrosive than pure lead. That is because, even though the temperature can be lowered with the lower melting point of lead-bismuth eutectic, bismuth dissolves more metals much more strongly. That then results in dissolution-deposition in hotter/colder parts which is what causes the corrosion. Also bismuth is surprisingly rare for large scale application in fast reactors, and produces a couple orders of magnitude more polonium. So for a large reactor, where dealing with freezing is easier, pure lead is preferred. The corrosion issues are very easy to overcome; you weld overlay ordinary high temp high strength steels with a metal that is noble in lead, eg molybdenum or niobium. Corrosion on these two metals by lead is zero. Nothing special here; today’s PWRs all do this. They use cheap strong low and high temperature steels for the pressure vessel etc. and then line it with stainless steel on all water contacting internal parts.

Re the breeding of different metal coolants. Sodium, lead, and lead bismuth can all breed just fine in fast spectrum. Lead is actually a bit better in the neutronics than sodium. For example its neutron slowing and absorption is less and boiling point much higher than sodium, this results in no issues with void reactivity. Because of this lead allows a wider spectrum, either faster or slower than a sodium reactor. Going faster means better breeding than with sodium. But it also means a higher fissile startup is required.

Re the core configuration. It depends on your priorities. If blankets are allowed from the proliferation angle and you don’t mind producing less power (blankets produce less power than the seed region) then you want to use blankets. If you are worried about proliferation (but you wouldn’t really with a hybrid Th232-U238 cycle) and/or want to maximise core power for a given core size (important economical consideration!) the you use homogeneous fuel elements. Those elements would then contain Pu, Th232 and U238 all together. In terms of breeding and fissile startup, it favors blankets especially for smaller cores (these leak more neutrons due to their higher surface area to volume). My own preference is for a larger core with homogeneous fuel elements, moderate to high burnup, but use a thick layer of lead around the core for reflecting leaked neutrons. Keep it simple.

Re the reprocessing. Thorium is quite predictable. It will follow the rare earths and plutonium. But you can recover it by simple distilling of the chloride salt; ThCl4 comes at at acceptable temperatures. Alternatively you can use distillation of the metals directly, that is something I’m preferring if it is possible (because all the actinides including fertile always stay together homogeneously and it is chemically very simple).

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