Primary coolant pH for control of CANDU plant aging

Plant aging can be defined as any degradation with time of system performance which increases the operator's difficulty in maintaining operation within design specification. Degradation can be a physical change in a component beyond the design value, e.g. surface roughness, or a change in operating conditions, e.g. RIHT rise. This paper focuses on the corrosion of the carbon steel piping in the CANDU primary circuit and the aging issues that arise. In one approach, a small reduction in the coolant pH has been recommended to operating plants which will slow those aging issues driven by dissolved iron transport around the primary circuit. In addition, chemical decontamination of the entire HTS is suggested to restore primary circuit surfaces to near-original conditions. (author)