Water Loss in Fast Project Interim Fuel Storage Rack

摘要

Water loss calculations for the concrete FAST interim fuel storage rack were performed at the request of Exxon Nuclear. Because water in concrete, whether chemically combined or in a free state, is a critical component for neutron attenuation and radiation shielding, loss of water within a concrete structure designed to contain various forms of nuclear material could present a criticality problem within the structure. Although a definitive optimum water content has not been presented at this time, it appears that 4 weight % is a minimum content for efficient attenuation. Although other elements in concrete contribute to neutron attenuation, hydrogen with its large cross section is the dominant attenuating element. The results of calculations indicate that the present design of the fuel rack is inadequate for the proposed total fluence and that the minimum safe water content would be reached within one year's operation. (ERA citation 05:024092)