PSI - Issue 60

Rahul Mittal et al. / Procedia Structural Integrity 60 (2024) 535–540 Rahul Mittal/ StructuralIntegrity Procedia 00 (2019) 000 – 000

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Fig. 4. Performance of Hydraulic Snubbers in Indian PHWRs (a) Drag force; (b) Locking Acceleration

6. Conclusion  Snubbers are being used in nuclear system in Indian PHWRs to restrain the piping/equipment during dynamic events. Location and load capacity/rating of snubbers on piping/equipment are finalized using detailed Finite Element analysis of the Primary Heat Transport system. Continuous efforts have been made to minimize the numbers of snubbers used in Indian PHWR units starting from older 220 MWe to the latest 700 MWe PHWR units.  As a part of ISI program, periodic functional testing and inspection of snubbers is being carried out to monitor any degradation in performance parameters of the snubbers. Degradation in performance of mechanical snubbers such as higher drag force, deviation in locking characteristics etc. have been observed in some of the older PHWR units. As a part of life management of snubbers in older PHWR units, mechanical snubbers are being replaced with hydraulic snubbers, which are more reliable compared to the mechanical snubbers.  Apart from carrying out regular ISI of snubbers, provisions are made for online monitoring of the health of snubbers. This system comprises of instrumentation for prompt indication in case of any malfunction of snubber. This ensures proper snubber functioning during plant operation. Acknowledgements Authors hereby acknowledge and sincerely thank the operating PHWR units of Nuclear Power Corporation of India Ltd. (NPCIL) namely NAPS-1&2, KAPS-1&2, RAPS-3 to 6, KGS-1 to 4 and TAPS-3&4 for carrying out functional testing of snubbers and compiling the inspection results during ISI campaigns. References 1. NUREG/CR-5870, PNL-8051, RV, R9, Results of LWR Snubber Ageing Research 2. NUREG/CR-5386, PNL-6911, RM, R9, Basis for Snubber ageing research: Nuclear Plant Aging Research Program 3. NUREG/CR-4279, PNL-5479 Vol-1, RM, RV, Aging and Service Wear of hydraulic and mechanical snubbers used on safety related piping and components of nuclear power plants. 4. ASME B&PVC Section III Div. 1 Subsection NB Rules for Construction of Nuclear Facility Class 1 Components, 2021 edition 5. ASME B&PVC Section XI Rules for In-service Inspection of Nuclear Power Plant Components, 2021 edition 6. ASME QME-1, Qualification of Active Mechanical Equipment Used in Nuclear Facilities 2021 edition 7. AERB Safety Guide AERB/NPP/SG/O-2 In-Service Inspection of Nuclear Power Plants, March 2004 8. ISI Manual for various operating Nuclear Power Plants