Neutron shielding problems in the shipping of high burnup thermal reactor fuel

AbstractAn evaluation of the radiation from higher exposure light water reactor fuel that is of significance in shipping container design has been made. Because these fuels contain significant quantities of transplutonium nuclides, it has been established that the neutron emission rate and the associated biological dose rate are of large enough magnitude to require special consideration in the shielding design. This analysis is based on experimental determination of heavy element nuclide concentrations in both PWR and BWR fuels and the use of ANISN-type shielding calculations. The results indicate that a conventional cask would not have sufficient neutron shielding capability to permit shipment of spent fuel with exposures in excess of ∼22 000 MWd/MT. Hence, a new generation of shipping casks with specific provisions for neutron shielding is required.