Experimental Characterization of Hydraulics in EPR™ Control Rod Guide Assembly: EDF and AREVA Complementary Approaches

Abstract

The new EPR™ Evolutionary high-Power nuclear Reactor is based on the best design concepts of French and German experiences over the past thirty years in power plant design construction and operation. In the framework of detailed engineering phase of plant construction in Finland (Olkiluoto 3) and in France (Flamanville 3), various investigations were led to improve the knowledge of hydraulics in innovative Reactor Pressure Vessel internals. A specific attention has been paid to hydraulics in Control Rod Guide Assembly (CRGA), which is an innovative component derived from the KONVOI design but adapted to the EPR™ design. In order to assess the hydraulic behavior of the EPR™ CRGA, a complementary experimental approach was developed by EDF and AREVA. Two mock-ups, representative of the full-scale EPR™ Control Rod Guide Assembly, were designed: MAGALY mock-up using real prototype of CRGA within AREVA’s engineering teams and PHACETIE mock-up at same scale but dedicated to a more analytic approach designed by EDF. The aim of the paper is to present the tests performed on two mock-ups to characterize the hydraulic behavior of this innovative EPR™ CRGA. At first, a comparison of the two mock-ups was done. The benchmark showed that the two mock-ups feature similar hydraulic behavior. The head losses evaluated along the experimental devices are practically identical. Moreover, the results showed that the global hydraulic forces applied to the Rod Cluster Control Assembly (RCCA) just up to the Upper Core Plate (UCP) are in a very good agreement. The good comparison between the two mock-ups strengthens the hydraulic characterization methods of the hydraulics in EPR™ CRGA. Specific studies were also led on the two mock-ups. The MAGALY mock-up was used to characterize the impact of the EPR™ operating conditions on the CRGA hydraulics behavior and especially on the vibrations and the drag forces applied to RCCA. Complementary measurements by using Laser Velocimetry techniques (PIV and LDV) were carried out on the PHACETIE mock-up allowing an evaluation of the velocity field inside the CRGA. The results obtained thanks to the two mock-ups allowed AREVA and EDF to have a good knowledge of the hydraulics behavior in the EPR™ CRGA. In a next step, further studies will be performed in order to deepen the knowledge of the vibratory behavior of the RCCA and the control rod drop time.