Tuesday, October 4, 2011

Graphite Free Core?

The Generation IV international forum describes itself as
a cooperative international endeavor organized to carry out the research and development (R&D) needed to establish the feasibility and performance capabilities of the next generation nuclear energy systems.

The Generation IV International Forum has thirteen Members which are signatories of its founding document, the GIF Charter. Argentina, Brazil, Canada, France, Japan, the Republic of Korea, the Republic of South Africa, the United Kingdom and the United States signed the GIF Charter in July 2001. Subsequently, it was signed by Switzerland in 2002, Euratom in 2003, and the People’s Republic of China and the Russian Federation, both in 2006.

The goals adopted by GIF provided the basis for identifying and selecting six nuclear energy systems for further development. The six selected systems employ a variety of reactor, energy conversion and fuel cycle technologies. Their designs feature thermal and fast neutron spectra, closed and open fuel cycles and a wide range of reactor sizes from very small to very large. Depending on their respective degrees of technical maturity, the Generation IV systems are expected to become available for commercial introduction in the period between 2015 and 2030 or beyond.
Molten Salt Nuclear technology is included in the Generation IV project and recently quite litterally the picture of the MSR in the web site has changed. What is going on here?

A recent brief EfT duscussion focuses on what is behind the crossing out of the graphite free core, but not why this is not a good idea. Lars notes
the French approach definitely avoids graphite and its waste flow. Leaves you with the challenge for startup though. Apparently the concerns about proliferation are much lower in France.
Concerns about the proliferation risks posed by LFTRs another thorium cycle MSRs are absurd, as another recent EfT discussion has demonstrated. In this discussion Lars notes,
LFTR is one of a very few technologies that have a serious chance to provide power to 9 billion people without serious damage to the environment. Along the way it can also chew up the existing transuranic waste. There are some big engineering challenges to solve. But so far as I can tell they are all solvable. The really big unknowns are: 1) can we get the cost below coal and 2) can we survive the politics.
The LFTR is not going to supply energy to nine billion people without a graphite core. Indeed a Graphite free core will require ten times as much fissionable material in its start up charge, and will leak neutrons like a sive. Leaking neutrons mean no thorium breeding. As Cyril R points out in the graphite free core discussion,
Graphite free core, what nonsense. Lots of graphite reflector in the French designs, and lots of graphite in the core and pebbles of the AHTR. Even Jaro's HW-MSR uses graphite tubes. Only no-graphite design we've seen is David's tube in tube, and that's fringe culture for the Gen IV VIPs.
It would appear that the conversation about MSR technology on EfT goes on at a much higher level of information than the conversation at the Generation IV forum. Thorium is not going to provide energy for 9 billion people without graphite cores.


Bill Young said...


If you want a low cost molten salt reactor to generate electricity for the masses, thorium with graphite moderation is the way to go.

If you want a molten salt reactor to destroy actinides, a fast reactor is the way to go. The French are working on a reactor to dispose of minor actinides.


Nathan2go said...

The obsession with fast reactor that is common with nuclear researchers is quite perplexing.

I suppose it is because for sustainable thermal reactors, the really important research needs have to do with cost-reducing the reprocessing (the Shippingport Light Water breeder experiment showed that the reactor worked fine, but the reprocessing was too expensive).

For solid fuel Uranium-cycle reactors with full recycle, thermal reactors have another problem that fast spectrums don't: the minor actinides buildup and create unwanted heat during reprocessing. Of course, the solutions are to add Thorium to the fuel (compensated by higher U enrichment) and/or switch to liquid fuel.

Lastly, we've lost interest in the 1960s reason for preferring a fast spectrum: to shorten doubling time. We now know that there is plenty of U in the world to start as many thermal spectrum reactors as we could want. And if they break even, or as with the DMSR, convert over 80%, then we can keep them fueled for a very long time without fuel prices going too high.

Gunnar Littmarck said...

It's easy to scare but difficult to create confidence.
See how German citizens still believe more in Stasis disinformation though it is 20 years old but backed up by, for example Greenpeace. Create confidence is difficult and takes time.
The fact that people take quick decisions on threats and slow on opportunities uses of all good sellers.
I always try to create confidence through education, the hard way.
Brian Wang has shown the right path, to obtain information for creating the shortest path to a global welfare, which is the requirement for peace and a global environment.

Yes We Can!

Anonymous said...

It's certainly possible to make efficient LFTRs without graphite. David LeBlanc's tube in shell reactor can do this.

But hostility towards graphite is unfair. It makes for very efficient LFTRs and is very safe. Nothing like Chernobyl with the positive void coefficients, we get inherently safe critical reactors with negative total coeffients, and have no water/steam in the core.

Graphite barely activates at all in the neutron flux, and is inert at environmental conditions such as in the sea, soil and air. So we can store this simply anywhere.

For a single fluid reactor, which is the simplest type of reactor that we can get operating the fastest, graphite is great. The only other way to make one would be the heavy-water MSR or the beryllium oxide MSR version of nuclear expert Jaro. Both attractive designs, but certainly no good reason to trash good old proven graphite cores.

By the way, I found out that the French design uses no graphite reflector, but does have a graphite blanket.

I don't know where the picture came from.


Anonymous said...

I have been thinking about the possibility of a dual spectrum fast/thermal reactor. Imagine a large graphite moderated reactor with a large hole down the centerline.

The central region would have an epithermal to fast spectrum which would tend to help flatten out the power distribution and help consume problematic actinides like Np 237. The graphite moderated annulus would reduce the fissile load, and reduce vessel damage from fast neutrons, compared to an all fast reactor.

It will take a good computer model to find the best geometry.

Bill Hannahan

Madalina said...

Hello Charles, I would like to invite you to join my Nuclear Safety Group on LinkedIn - it's a forum that has over 5000 members from all over the world. Here is the link: http://www.linkedin.com/groups?about=&gid=2170900&trk=anet_ug_grppro

And here are the links to its subgroups: http://nuclearsafety.info/discussion-forums/


Blog Archive

Some neat videos

Nuclear Advocacy Webring
Ring Owner: Nuclear is Our Future Site: Nuclear is Our Future
Free Site Ring from Bravenet Free Site Ring from Bravenet Free Site Ring from Bravenet Free Site Ring from Bravenet Free Site Ring from Bravenet
Get Your Free Web Ring
by Bravenet.com
Dr. Joe Bonometti speaking on thorium/LFTR technology at Georgia Tech David LeBlanc on LFTR/MSR technology Robert Hargraves on AIM High