CFD Tools for Assessment of the Reactor Pressure Vessel Integrity in Pressure Thermal Shock Conditions: Thermalhydraulic Benchmark on the Validation Test Case UPTF

The Reactor Pressure Vessel (RPV) assessment and lifetime evaluation of the nuclear plants leads EDF and AREVA to use CFD tools for the demonstration of the Reactor Pressure Vessel (RPV) integrity. French PWR plants have been studied for a long time and so a large number of computations have been performed in three steps: System — CFD — Mechanical Analysis. This paper focuses on the CFD aspects and especially on the two different CFD tools imposed by the physical phenomena of the transient scenarii. Indeed, the results of the system code analysis (CATHARE computations) of the PTS transient induce two kinds of scenarii: single phase and two-phase flows in the cold leg. According to the approach considered, it was interesting to carry out a global benchmark with the different thermalhydraulic tools. In this frame, Code_Saturne and Star CD CFD tools used for single phase flow scenario configuration and NEPTUNE_CFD used for two phase flow configuration were confronted with UPTF (Upper Plenum Test Facility) experiment results in a single phase scenario. The choice to perform this benchmark on UPTF test case was retained because this integral test was very representative of the main physical phenomenon that is well suited for the validation of the CFD tools used to study the Pressurised Thermal Shock for the RPV integrity.