Mitigation of End Flux Peaking in CANDU Fuel Bundles using Neutron Absorbers

Abstract

The end-flux peaking (EFP) is a phenomenon where a region of elevated neutron flux occurs at the end regions between two adjoining fuel bundles in CANDU reactors. These peaks of high neutron flux lead to an increase in fission rate and therefore greater heat generation in the end regions. This increase in heat generation is of particular concern during accident conditions. It is known that addition of neutron absorbers into fuel bundles can help mitigate EFP, yet their implementation in CANDU reactors using natural-uranium fuel has not been pursued. Monte Carlo N-Particle code (MCNP) 6.1 was used to simulate the addition of a small amount of neutron absorbers strategically at the bundle ends. The model includes two half bundles with a single end region, with varying amounts of Eu₂O₃ within the last two pellets. This paper will present some preliminary results collected thus far.