The present work deals with the development of a detailed Finite Element (FE) model of the Atucha II Nuclear Power Plant (NPP) Reactor Pressure Vessel (RPV) for Pressurized Thermal Shock (PTS) analysis. This model simulates both the base and the cladding metal, the Cold Legs (CL), the Hot Legs (HL), the emergency systems penetrations with the corresponding nozzles. A complete RPV FE model is needed for the calculation of the stresses in the undamaged structure to be used as input for the calculation of the stress intensity factor KI by means of the “weight function” method. This is one step of the methodology developed at University of Pisa (UNIPI) for the deterministic analysis of PTS scenarios. Such methodology is based on the use of a chain of codes and starts with the thermal hydraulic analysis of the NPP with a system code (such as Relap5, Cathare2, etc.) for a selected transient scenario. The goal of this step is to estimate the cooling load induced on the internal RPV wall surface by the Emergency Core Coolant (ECC) injection, and provide boundary conditions for the next step. The region of interest is represented by the welding lines in the down-comer region. The next step consists of the 3D analysis of the down-comer flow and of the temperature field in the RPV wall, using a CFD code with Conjugate Heat Transfer (CHT) capabilities. Once the pressure of the system and the temperature in the RPV wall is known, a stress analysis can be performed by means of a Finite Element (FE) structural mechanics code. The last step of the methodology is the Fracture Mechanics (FM) analysis using weight functions, to calculate the stress intensity KI factor at crack tip to be compared with the critical stress intensity factor KIc.
Development of a Finite Element Model of ATUCHA II NPP Reactor Pressure Vessel for Pressurized Thermal Shock Analysis
D'AURIA, FRANCESCO SAVERIO
2008-01-01
Abstract
The present work deals with the development of a detailed Finite Element (FE) model of the Atucha II Nuclear Power Plant (NPP) Reactor Pressure Vessel (RPV) for Pressurized Thermal Shock (PTS) analysis. This model simulates both the base and the cladding metal, the Cold Legs (CL), the Hot Legs (HL), the emergency systems penetrations with the corresponding nozzles. A complete RPV FE model is needed for the calculation of the stresses in the undamaged structure to be used as input for the calculation of the stress intensity factor KI by means of the “weight function” method. This is one step of the methodology developed at University of Pisa (UNIPI) for the deterministic analysis of PTS scenarios. Such methodology is based on the use of a chain of codes and starts with the thermal hydraulic analysis of the NPP with a system code (such as Relap5, Cathare2, etc.) for a selected transient scenario. The goal of this step is to estimate the cooling load induced on the internal RPV wall surface by the Emergency Core Coolant (ECC) injection, and provide boundary conditions for the next step. The region of interest is represented by the welding lines in the down-comer region. The next step consists of the 3D analysis of the down-comer flow and of the temperature field in the RPV wall, using a CFD code with Conjugate Heat Transfer (CHT) capabilities. Once the pressure of the system and the temperature in the RPV wall is known, a stress analysis can be performed by means of a Finite Element (FE) structural mechanics code. The last step of the methodology is the Fracture Mechanics (FM) analysis using weight functions, to calculate the stress intensity KI factor at crack tip to be compared with the critical stress intensity factor KIc.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
