FUELLING STUDY OF A CANDU REACTOR USING FUEL CONTAINING BURNABLE NEUTRON ABSORBERS

Abstract

A fuelling study for a CANDU reactor was conducted using 37-element natural uranium (NU) fuel, augmented with burnable neutron absorbers to mitigate the effects of fuelling transients and improve power compliance margin during refuelling. The burnable absorbers of interest include Gd2O3 and Eu2O3. Various quantities of the two neutron absorbers are considered, and they are added homogeneously to the CANLUB coating of fuel bundles. The study was conducted to demonstrate the gain in operating margins of CANDU reactors incurred by implementing the neutron absorber containing fuel design. The computer code Reactor Fuelling Simulation Program (RFSP) developed by the Canadian Nuclear Laboratories (CNL), previously Atomic Energy Canada Limited (AECL), was utilized to simulate the fuelling of the 480 channels, with each channel containing 13 fuel bundles. This is one of the CANDU reactor designs used in Ontario. Simulations were conducted for the 37-element NU fuel bundle design, with and without the neutron absorber modification to demonstrate the relative gain in margin incurred by the addition of burnable absorbers. Fuel safety and performance are always important topics of consideration for nuclear utilities and regulatory bodies. The results of this study present improvements in the operating margin and the economy of neutrons for the considered CANDU reactor at the expense of a reasonably simple change to the fuel design.