Regulatory Perspectives on Fitness for Service Assessments of CANDU Pressure Boundary Components

Abstract

Major pressure boundary components such as pressure tubes, feeder pipes and steam generators at some Canadian CANDU nuclear power plants are entering periods of extended operation beyond their initially assumed operating life. The Canadian Nuclear Safety Commission (CNSC) has approved their long term operations based on the assurance of fitness for service of those components which was composed of condition assessments and aging management programs carried out and implemented by the Canadian licensees. The condition assessments were conducted to demonstrate that components would be within their design basis for the period of intended long term operation and the aging management program was implemented to ensure that the conditions of the components would be maintained as evaluated in the condition assessments and to monitor if new degradation mechanisms would become active. This paper presents the CNSC regulatory practice adopted in the course of technical reviews of fitness for service assessments of major pressure boundary components conducted by Canadian nuclear licensees to demonstrate the safe long term operation of major components can be achieved.