Thorium vehicle will run 100 years on 8 grams of fuel

[PamW]

29. Reactor Physics 101

johnd83,

Boron is added to the water in a PWR as a chemical "shim". It is used to adjust for the reactivity swing between a freshly fueled cored, and a core that has been burned for some time.

Water isn't the problem; there's plenty of water to moderate neutrons. However, if the core is melted then that water is "contaminated" with U-238 which is the resonance absorber. It's elementary Reactor Physics 101 to show that for a homogenous mixture of reactor fuel, water, and control material that it is IMPOSSIBLE to have a sustained criticality.

For the fuel enrichments used in reactors; you HAVE to have the water moderator to be FREE of U-238 in order to get a criticality. A melted core will have the water contaminated with melted U-238 containing material.

I understand the design of a liquid fuel reactor, and as I mentioned several posts ago; if you have liquid fuel, one can have continuous online removal of fission products to mitigate decay heat. However, that works for BOTH thorium and uranium fuel.

I don't believe you have any impressive credentials until you realize that it's NOT the thorium fuel that results in mitigated decay heat; it is the use of liquid fuel along with continuous online removal of fission products that mitigates decay heat, and that scheme can be used for uranium fuel just as well as thorium.

PamW