Void Reactivity Studies for the ATUCHA-II PHWR Reactor - Preliminary Design of a Lower Void Reactivity Fuel

Abstract

Atucha-II is a 745 MWe (2160 MWt) nuclear station, D₂O moderated and cooled, of German (Siemens) pressure-vessel design, located in Argentina. It has 451 vertical coolant channels in an hexagonal lattice with a lattice pitch of 27.2 cm and the fuel assemblies (FA) are clusters of 37 natural UO₂ rods with an active length of 530 cm. The coolant void reactivity (CVR) is positive and approximately 10.5 mk for equilibrium burnup fuel. This paper presents a preliminary design of a lower void reactivity fuel for Atucha-2, using slightly enriched uranium except for the central rod which has NU and dysprosium. It also presents some CVR cell comparisons between WIMS-D5 and MCNP5 and CVR core comparisons between WIMS-D5 / DRAGON / PUMA with MCNP5, which show quite good agreement.