Nuclear Criticality Safety Analysis for the Traveller PWR Fuel Shipping Package

The Traveller PWR fresh fuel shipping package represents a radical departure from conventional PWR fuel package designs. Two immediately noticeable features of the Traveller are that it carries a single fuel assembly instead of two as do other package designs, and that it has built-in moderator, which forms part of the flux-trap system. The criticality safety case shows that the Traveller satisfies both U.S. and IAEA licensing requirements, and demonstrates that the package remains acceptably subcritical under normal conditions and hypothetical accident conditions of transport. This paper looks at the modeling techniques that were used to analyze the several accident scenarios that were considered, including: o Lattice pitch expansion; o Lattice pitch expansion along the fuel assembly length; o Preferential flooding (selective flooding of different cavities); o Differential flooding (varying water levels inside different cavities); o Partial flooding (varying water density); o Axial rod displacement; o Sensitivity studies of variable foam densities and boron content in packaging; o Analysis for carrying loose rods in a rodbox; The criticality safety case for the Traveller proved to be a successful cooperative effort between ENUSA and Westinghouse.