Nuclear Plant Feedwater Heater Life Cycle Optimization Through Comprehensive Condition Assessment Program

Many papers published over the last 25 years have strongly emphasized the need for an ongoing program of condition assessment through inspection and testing with subsequent failure cause analysis of feedwater heaters. Plants must be run more competitively; therefore, Utilities must try to decrease operation and maintenance costs, while optimizing overall plant efficiency. One recognized area that needs to be addressed in accomplishing this goal is the heat cycle. This paper specifically deals with the feedwater heating system. Utility engineers must monitor feedwater heater performance in order to recognize degradation, identify and mitigate failure mechanisms, and prevent in-service failures while optimizing availability. Periodic tube plugging without complete analysis of the degraded/failed areas resolves the immediate need for return to service; however, heater life will not be optimized. This paper is a direct follow-up to a previously published ASME paper that detailed the establishment of a comprehensive life cycle management program for feedwater heaters implemented at Peach Bottom Atomic Power Station (PBAPS). This particular paper reports the eventual results and benefits achieved through the continuance and perseverance of this program. This successful condition assessment case history included the following inspection, testing, and maintenance activities to ascertain reliable data in support of root cause analysis: • Removal of previously installed plugs. • Videoprobe inspection of failed areas. • Videoprobe inspections of the steam space. • Extraction of tube samples for further analysis. • Eddy current testing of selected tubes. • Evaluation of the condition of “insurance” plugged tubes for return to service. • Hydrostatic testing of selected tubes. • Repair plans based on the results of the above program. • Reviewing operating data to assess case history. • Monitor and continue the program over future planned unit outages. This paper concludes that no single method of inspection or testing should solely be relied upon in assessing actual conditions. It is a combination of evaluating all gathered data that affords the best chance in arresting problems and optimizing feedwater heater life. Problem heaters should be continuously monitored over time until the facts ultimately help to justify replacement.