As of an example of ageing assessment of CANDU CSSCs, detail procedure and methodology applied to the ageing assessment of fuel channel are presented. Although ageing status depends on the design condition and O&M history of each plant, fuel channel is usually the most highlighted component in aged CANDU plants in terms of safety, integrity, performance, and maintenance [5]. To assess ageing of fuel channel they reviewed lots of plan information and evaluated its ageing in respect to the degradation mechanisms.

A. II.4.1. DESIGN REQUIREMENTS

Design requirements and performance expectations/criteria of components along with degradation allowances covering the service life of the pressure tube are reviewed first. This includes design temperature and pressure, design mechanical loads, pressure tube initial dimensions, corrosion and wear allowances, pressure tube deformation allowances, fracture toughness, pressure tube material, end fitting material, etc. Design documents such as FSAR, design manual, technical specification are reviewed to understand the design requirements. The fuel channel assemblies are designed to satisfy its intended functional requirements for 210,000 effective full power hours (EFPH) of CANDU6 reactor operation (i. e., 30 years at a capacity factor of 80%). Table A. II.2 shows the allowance of corrosion/wear and deformation of a pressure tube.