ON-BOARD EXPERIMENT AND ANALYSIS OF DOSE RATE DISTRIBUTIONS IN A SPENT FUEL SHIPPING VESSEL

An on-board experiment was carried out in a spent fuel shlpping vessel, the Pacific Swan, in whlch 13 casks of the TN-12A and Excellox 3 type were loaded in five holds, and neutron and gamma ray dose rates were measured on the hatch covers of the holds. Before shipping, dose rates were also measured on the cask surfaces one by one for the purpose of eliminating radiation from other casks. The Monte Carlo coupling technique was successfully employed to analyse the measured neutron dose rate distributions in the vessel. As a result of this study, the Monte Carlo coupling code system, MORSE..CG/CASK-VESSEL, on whlch the MORSE..CG was based, was established. The agreement between the measured and the calculated neutron dose rates on the TN-12A cask surface was satisfactory. The calculated neutron dose rates agreed with the measured values within a factor of 1.5 on the Hold 3 hatch cover but to within a factor of 2 on the Hold 5 cover in whlch a concrete shield was fixed.