The Modification of Fuelling Frequency and the Use of Burnable Absorbers in CANDU Reactors

Abstract

As CANDU reactors age, operational margins have narrowed. Power ripples that result from the insertion of fresh fuel constantly challenge the limit of these boundaries. To address the situation, this study has altered the conventional fuelling scheme in an iterative fashion, with the addition of 8 bundle shift rings to reduce the fuelling frequency, and thus the demand on fuelling machines. Both NU and NU laced with BNAs were considered. Results indicated that both the absolute maximum channel power and LZC fill fractions were reduced when 150 mg of Gd₂O₃ was added to NU fuel; these findings were unanimous for the various fuelling schemes considered.