Regulatory Review Of The CANDU® Fuel Modification Program in Canada

Abstract

Aging of CANDU® nuclear power plants affects various safety margins of the plants. For certain design basis accidents in safety analysis, margin to fuel sheath dryout is one of the safety margins that have been detrimentally affected, leading to a reduced margin to dryout with time. If no proactive actions were taken, the plants would have to de-rate their operations at earlier times. To delay the de-rating, the nuclear Industry has taken multi-initiatives to restore, or partially restore the safety margins that have been erodeddue to plant aging. One of the initiatives is modification/re-optimization of the current fuel design, in order to improve the fuel thermalhydraulic performance, i.e., postpone fuel sheath dryout, thereby offset partially the erosion of margin to fuel sheath dryout. Several Canadian utilities have already proceeded with the fuel modification program and requested approval of the Canadian Nuclear Safety Commission (CNSC) to load the modified fuel into their reactors. This paper summarizes the CNSC requirements, the review processes, the current status, and the technical challenges associated with licensing review of the fuel modification in Canada.