Neutron Absorber Concept in Spent Fuel Casks Aiming at Improved Nuclear Safety and Better Economics

The recent increasing demand for better nuclear fuel utilization requires higher enriched uranium fuels which is a challenge for spent fuel handling facilities in all countries with nuclear power plants. The operation with higher enriched fuels leads to reduced reserves to legislative and safety limits of spent fuel transport and storage facilities. This study addresses the spent fuel solution with significantly increased nuclear safety and improved economics where a new concept of inseparable neutron absorber is introduced to achieve spent fuel reactivity decrease. Same or better criticality safety is achieved with significantly lower boron content in the cask basket. Alternatively, it is possible to reduce fuel assembly pitch with the same boron amount and subsequently decrease overall cask dimensions. Moreover, it is also feasible to reduce the subcritical multiplication of the neutron source, thus reducing the neutron dose in the vicinity of the cask. Efficiency of the new concept is demonstrated on criticality safety analysis of the GBC-32 spent fuel cask.