Abstract
The present paper describes the main features and an application to a real Nuclear Power Plant (NPP) of an Integrated Software Environment (in the following referred to as “platform”) developed at University of Pisa (UNIPI) to perform Pressurized Thermal Shock (PTS) analysis. The platform is written in Java for the portability and it implements all the steps foreseen in the methodology developed at UNIPI for the deterministic analysis of PTS scenarios. The methodology starts with the thermal hydraulic analysis of the NPP with a system code (such as Relap5‐3D and Cathare2), during a selected transient scenario. The results so obtained are then processed to provide boundary conditions for the next step, that is, a CFD calculation. Once the system pressure and the RPV wall temperature are known, the stresses inside the RPV wall can be calculated by mean a Finite Element (FE) code. The last step of the methodology is the Fracture Mechanics (FM) analysis, using weight functions, aimed at evaluating the stress intensity factor (KI) at crack tip to be compared with the critical stress intensity factor KIc. The platform automates all these steps foreseen in the methodology once the user specifies a number of boundary conditions at the beginning of the simulation.
Highlights
The RPV has long been considered one of the most reliable components in Pressurized Water Reactors (PWRs)
The present paper describes the main features and an application to a real Nuclear Power Plant (NPP) of an Integrated Software Environment developed at University of Pisa (UNIPI) to perform Pressurized Thermal Shock (PTS) analysis
The main initiating PTS events identified in the literature are Small Break Loss of Coolant Accident (SBLOCA), Main Steam Line Break (MSLB), Loss of Main Feed Water (LOFW), Steam Generator Tube Rupture (SGTR), and Loss Of Heat Sink (LOHS)
Summary
The RPV has long been considered one of the most reliable components in Pressurized Water Reactors (PWRs). Nowadays a general target for the countries that produce nuclear energy is to extend the operation life of existing plants. From this point of view, the RPV is one of the major components that may limit the useful life of the nuclear power plant. Severe loading conditions are produced during a Pressurized Thermal Shock (PTS) scenario, in which an over cooling in a limited region of the RPV internal surface may induce strong thermal stresses, while the internal pressure being maintained at high thermal level or the system being repressurized during the transient.
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