Impact of degraded cooling water system performance upon power plant operations

A number of recent events have focused attention on the performance of cooling water systems at power plants. In various region of the country, the unusual weather and temperatures occurring during the past several summers have led to abnormally high ultimate heat sink temperatures. In addition, the industry is addressing the effect of component aging upon cooling water system performance. The Nuclear Regulatory Commission (NRC) has issued generic letter 89-13, which summarizes their concerns regarding performance degradation of cooling water systems. As a result of the meteorological phenomenon and to identify potential system degradation, equipment reviews and analyses of cooling water systems and serviced components are necessary. These efforts determine if any degraded system or equipment performance exists and the consequential affect on the serviced components. This paper reviews the factors leading to service water system degradation, the methods to quantify reduced system capability, and the evaluation of component performance with reduced cooling water systems flow or increased cooling water temperature