급수승압펌프 전단 스트레이너 구조 변경을 통한 운전성능 향상에 관한 연구

Abstract

The main feedwater system of nuclear power plants(NPPs) supplies the feedwater to two steam generators at the rated temperature, pressure and flow rate from the deaerator storage tank. Two motor-driven feedwater booster pumps and two turbine-driven main feedwater pumps play an important role in supplying the rated feedwater flow to the steam generator during normal power operation, and are a key system for safe operation of the NPPs. During normal operation, the strainer is installed at the front of the feedwater booster pump. Its function is to prevent the tubes of high-pressure heater, low-pressure heater, and steam generator from being damaged by the influx of foreign material. However, since the strainer is vulnerable to reverse differential pressure, it may be damaged when the inverse flow path is formed during the operation and maintenance. This can lead to the inflow of foreign materials and the loss of the integrity of the system and components. As a result, damaged foreign materials are introduced into the system, making it difficult to secure integrity of the system and facilities. Recently, thus, improvement in the design of strainer has been attempted. This study performed the analyses to confirm the adequacy of design improvement in terms of structural integrity and system stability. In order to evaluate the adequacy of the design improvement of strainer, the pressure difference between the inlet and outlet of the newly designed strainer was analyzed under normal and design flow conditions with assumptions of 0% and 50% clogging. The stresses of the strainer by pressure difference were calculated, and the structural integrity of the strainer was confirmed for different operating conditions. Also, the effect of strainer on the total head and NPSH(Net Positive Suction Head) of the pump and on the stresses in the piping system were evaluated. From the results of analyses, it was concluded that the design improvement of strainer has no negative effect on the structural integrity and system stability under normal and transient conditions. Thus it was expected that design improvement of strainer would contribute greatly to the safety operation of the NPPs.