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.