Analysis of Fouling Resistance in Safety-Related Heat Exchangers

As a part of nuclear safety activities, developed countries have performed Periodic Safety Review (PSR) to verify and improve the safety of operating Nuclear Power Plants (NPPs). In 1999, it was decided by the Korean Atomic Energy Safety Committee to adopt the PSR program. PSR is officially legislated in 2001 as a 10-year-basis safety evaluation process. Since the first tentative application of PSR for Gori Unit 1 in 2000, it is now progressing well. Generally PSR assesses the cumulative effects of plant ageing and plant modifications, operating experience, technical developments and site aspects. The reviews include an assessment of plant design and operation against current safety standards and practices. After reviewing activities, safety is enhanced by implementing the corrective actions and/or safety improvements. When a PSR was performed in Gori Units 3-4, several safety-related heat exchangers in the Reactor Coolant System (RCS) such as a letdown heat exchanger were pointed out as the components necessitating a corrective action which is the analysis of fouling resistance. The fouling resistance is used as an important parameter to evaluate the safety as well as the economics of heat exchangers. However it is difficult to develop a credible analysis procedure due to considerable discrepancy between normal operating conditions and design conditions. This issue was identified while we were conducting a study in KNICS (Korea Nuclear I and C System) R and D program. We might be able to guess other NPPs in Korea are likely to have the same issue. This paper involves the characteristics of the safety related heat exchangers and the methodology to develop the analysis procedure