ThO_2--UO_2 annular pins for high burnup fuels

摘要

The main purpose of this work is to investigate the use of annular fuel pins (particularly pins containing thorium dioxide) for high burnup fuel. The following parameters were evaluated and compared between postulated mixed thorium uranium dioxide standard and annular (9/100 void traction) type fuel assemblies, as a function of burnup: the infinite multiplication factor. the uranium and plutonium isotopic compositions, the fuel temperature coefficient of reactivity and the conversion ratio. We used the SCALE-4.3 code system. The calculation method consisted in obtaining actinide and fission product number densities as functions of assembly burnup, by means of a l --D transport calculation combined with a 0--D burnup calculation. These number densities were then used in a 3-D Monte Carlo code for obtaining k.x from two-dimensional-symmetry "snapshots".