Performance of Thorium Fuel Cycles in the Pebble-Bed Reactor

For the pebble-bed high-temperature reactor, a wide choice is available for the design of the fuel elements and for the reactor fueling scheme. This flexibility has been utilized for the conception of different possibilities for the closure of the thorium fuel cycle. The easiest scheme is mixed-oxide recycling with repeated recycling of ²³⁶U. Loading recycle fuel into separate elements without thorium reduces the uranium ore demand by 13%. Entire separation of the feed and breed circuits brings another reduction of 5%. Furthermore, the feed-breed cycle allows the production of ²³³U for the near-breeder variant. This variant achieves a conversion ratio of 0.97, and it represents a possible choice for efficient protection of uranium ore resources. Within the span of uncertainties in the cost assumptions, fuel cycle costs are found to be comparable for all considered cycles, including the near-breeder.