The paper deals with the analysis of the performance of a primary pipe of a typical PWR subjected to ageing mechanisms. To the aim an inverse space marching method is applied. From reconstructed temperature it is possible to determine . temperature values at surfaces that are difficult to reach and inspect. | Progress in Nuclear Energy 131 2021 103573 Contents lists available at ScienceDirect Progress in Nuclear Energy journal homepage http locate pnucene Preliminary study of the effects of ageing on the long-term performance of NPP pipe Salvatore Angelo Cancemi Rosa Lo Frano DICI-Universit a di Pisa Pisa Italy A R T I C L E I N F O A B S T R A C T Keywords Most of today s operating nuclear plants are facing long-term operation LTO issues caused by the time Safety degradation and or deterioration suffered by the system structure and components SSCs . These phenomena Inverse method are known as ageing and are responsible for the change of material properties and in turn may affect the Long-term operation structural integrity of plant SSCs. Ageing Thermal loads The paper deals with the analysis of the performance of a primary pipe of a typical PWR subjected to ageing Maintenance mechanisms. To the aim an inverse space marching method is applied. From reconstructed temperature it is possible to determine . temperature values at surfaces that are difficult to reach and inspect. Accordingly based on the thermal gradient across the pipe wall the residual thickness of the pipe may be determined and used for structural capacity verification. Analytical and numerical thermo-mechanical analyses are performed considering several thinning rates. The effects of both homogeneous and heterogeneous thinning are also investigated. The results suggest that an excessive general or local thinning may affect the strength capacity of pipe. The performance of the pipeline confirms the possibility of the life extension if the thinning rate is kept below mm year even when the plant operating conditions are outside the prescribed operating limits. defined determined. Fig. 1 shows the decrease of the safety margin as a 1. Introduction function of the time analysing it it is clear how important it is to guarantee a minimum safety level whatever the events that could occur.
