Service water system management: Solving problems at reduced costs

Recent advances in corrosion-resistant materials, equipment design, cleaning, refurbishment, chemical treatment, and in situ monitoring offer improved raw water piping system reliability, performance, and availability. However, large-scale raw water corrosion mitigation can cost in excess of $50 million per unit to implement, Additional expense due to plant down time can also be incurred. Recent design evaluations to assess the corrosion effects in the service water systems at several nuclear generating units baselined the condition of the systems, estimated their remaining service life, and helped develop remediation programs for ensuring their long-term safety, reliability, and availability. The corrosion assessments identified a variety of condition ranging from minor flow reduction to aggressive through-wall leakage. The solutions recommended to address these conditions are as varied as the problems themselves and incorporate the latest innovations in engineering and corrosion mitigation technology. The use of new technology limited the invasiveness of the solutions and reduced the life-cycle cost of the programs. Surveys conducted to evaluate the effectiveness, potential pitfalls, and track records of these technologies provide a benchmark for evaluating their constructibility, cost, and performance in controlling long-term service water corrosion. Although the final cost depends to a large degree on the effectiveness of interim actions and the long-term system performance, the mitigation techniques are expected to provide a potential cost savings of 50% to 75% when compared with older technologies and reactive mitigation. This paper summarizes the technical safety, and economic considerations that were used in developing the long-term corrosion management program for one of these units