The Current Status of CANDU Steam Generators

This paper analyzes world steam generator (SG) operational experience (OPEX), research and development (R&D) for operational CANDU SGs. Emphasis is placed on design configuration, materials, and chemistry. SG OPEX from various databases is recounted to identify performance trends, active degradation mechanisms and common failure modes. A summary of CANDU and pressurized water reactor (PWR) SG OPEX including tube plugging statistics by material and degradation mechanism is provided. A discussion of ongoing SG-related research initiatives is also included. It was found that SGs with Monel-400 tubing and carbon steel tube support would perform well if properly maintained although Incoloy-800 tubing and stainless steel tube support is the current preferred design for CANDU, regarding Inconel-600 as an interim solution. All volatile treatment has also been adopted as the preferred SG chemistry for the CANDU fleet. Lessons learned from OPEX are highlighted and further international collaboration on the study of plant ageing, SG integrity, and nuclear safety is encouraged.