Using ‘Component Multiplication’ in Monk to Reduce Pessimism in the Dose Rate Assessment for Water-Filled (Ullaged) Transport Packages

Abstract

AbstractThe external dose rates from spent fuel packages consist of gamma ray and neutron components. The source of gamma rays is from fission products and actinides in the spent fuel and from activation products in structural components of the fuel element. Neutrons originate from spontaneous fission in actinides (for example from curium isotopes) within the spent fuel and from (alpha, n) reactions in oxide fuel. However, a significant number of neutrons are produced due to further fission within the fuel. This is known as neutron enhancement or multiplication (M). To treat the effects of enhancement, the neutron source may be scaled within the dose rate calculation. In a wet package, it has been customary to determine keffective (keff) for a completely water-filled package or a package with a defined water level (for the horizontal transport condition). The irradiation of the fuel is normally taken into account in calculating keff for this purpose. The neutron enhancement is then obtained by calculating...