[beefman]

'It can burn any fuel' is just code for 'we have no real core design yet'. But it doesn't matter, because no nuclear fuel is significantly better than any other, and they're all thousands of times better than alternatives.

Thorium is always used in mixed cores. An accelerator-driven thorium reactor will contain uranium from breeding even if no uranium is ever loaded into it.

[jddw]

There are core designs for low enriched uranium loading, mixed thorium loading, and spent fuel loadings. Have to make sure a fuel design works before it's claimed to work.

[beefman]

With 12 years of burnup? I've been having trouble getting burnup codes to handle thorium. What are you using? Apparently I should be using Serpent.

But anyway, 12 years is too long, even if it's feasible. Something like 4 years should be better, due to the learning curve on these. For instance, think of a reactor in the field as a ship on a long trip while technology at home continues to improve

http://en.wikipedia.org/wiki/Wait_Calculation

Edit: The lower the enrichment, and the lower the excess reactivity, the better.