Techniques of the snubber testing in a nuclear power plant

The performance of PSI/ISI is one of the important inspections which improve the safety, reliability and operability of nuclear power plant. Therefore, KAERI has performed the inspections for the safety-related piping systems, pressure vessel and support components of NPP by the NDT methods in accordance with the related technical codes and standards. ASME Sec.XI of 1989 requires to perform the visual inspection and functional test of snubbers in accordance with ASME/ANSI OM-Part 4 additionally. Especially, the inspection and functional test of heavy duty hydraulic snubbers attached to the steam generator and RC pump have also been added. The main role of snubbers protects the piping system and pressure vessel from the transient events such as water hammer and earthquake during operation. Throughout the analysis of the status of snubbers in NPP, the snubber failure cases in domestic and foreign countries, the requirements and technical standards of the inspection and test, problems of snubbers in NPP, and snubber reduction program, this report requires to follow the technical codes and standards for the inspection and functional test of snubbers now being insufficient in Korean NPP. As a following action, the safety verification analysis for the reliability of piping systems and components of NPP due to snubber failure causes will be studied, and also the snubber reduction program of NPP will simplify the control and maintenance of the expensive snubbers. The objective of this report is to provide the problems of snubber in Korean NPP and contribute to the integrity assurance of the piping systems and components by the inspection and test of snubbers. 17 figs., 9 tabs., 19 refs. (Author)