Criticality safety determination of spent fuel storage vault

Effective multiplication factor has been calculated for one PWR fresh fuel assembly immersed in a spent fuel storage vault on the basis of the neutron transport theory. A numerical calculation has been carried out by means of Sn approximation. The method employed in this study is that the energy domain is broken into 16 groups, the angular variable is divided into four discrete direction, i.e., S4, and the spatial variable which is divided into fine meshes at the interface between different materials is discretized into 27 mesh points. The calculated Ksub(eff) value of 0.6145 seems to be far smaller in comparison with the value obtained by other author for an infinite array of fuel assemblies. (author)