Fast Reactor Recycle Fuel Thermal Load

A series of calculations were performed modeling fast reactor core loadings for conversion ratios varying from 0 to 1 in 0.25 step increments to estimate the fuel thermal load from startup through five recycles. The heat loadings are expressed as a function of a future prototypical transportation cask thermal limit to provide an operational perspective. Since neither the physical characteristics nor dimensions of the fast reactor fuel are clearly defined at the present time, thermal power was selected as a measure to estimate the transportability with respect to current design technology The most significant conclusion is after approximately five years of cooling, the fast reactor spent fuel thermal loads are approximately equivalent to the initial heat load prior to irradiation. Therefore, transport casks for shipping fresh fuel should be designed to also accommodate the same fuel following irradiation and five years of cooling. Current design technology and transport regulations can be applied to encompass fast reactor recycle fuel; however, cask capacities will likely be lower than light water reactor spent nuclear fuel due to thermal and shielding requirements. Related observations include the heat load of the fuel, both when initially charged and 5 years following discharge, depends almost entirely upon the transuranic content; and the transuranic content of the discharge fuel is tightly linked to the TRU content of the initial fuel charge; being reduced by approximately one quarter each recycle. In general, thermal loads for fast reactor (FR) fresh and spent recycle fuel are an order of magnitude higher than high burnup LWR spent fuel, after both have been allowed to decay for 5 years.