ThO2-UO2 annular pins for high burnup fuels

The main purpose of this work is to investigate the use of annular fuel pin s (particularly pins containing thorium dioxide) for high burnup fuel. The following parameters were evaluated and compared between postulated mixed t horium-uranium dioxide standard and annular (9% void fraction) type fuel as semblies, as a function of burnup: the infinite multiplication factor, the uranium and plutonium isotopic compositions, the fuel temperature coefficie nt of reactivity and the conversion ratio. We used the SCALE-4.3 code syste m. The calculation method consisted in obtaining actinide and fission produ ct number densities as functions of assembly burnup, by means of a 1-D tran sport calculation combined with a 0-D burnup calculation. These number dens ities were then used in a 3-D Monte Carlo code for obtaining k(infinity) fr om two-dimensional-symmetry "snapshots". (C) 2000 Elsevier Science Ltd. All rights reserved.