Design and qualification of Jules Horowitz Reactor Control Rod Drive Mechanisms

The Jules Horowitz Reactor Control Rod Drive Mechanisms (CRDMs) are subject to stringent requirements such as: safety, operation, environment and geometry. Therefore the development of two different types of CRDMs demanded a huge effort in terms of design and qualification. AREVA TA successfully led the project to meet the specifications. A major milestone, the drop times of the rods qualification, has recently been achieved. The 27 control rods located in the center of the fuel assemblies are actuated by 27 CRDMs from 2 types ensuring respectively the emergency shutdown response time and the control of the reactor and maintain at shutdown. Specific design features have been developed and qualified to address the following very challenging issues: the short passive drop time of the control rods despite the significant countercurrent flow, the leak tightness at the pool interface, 2 lines of defense against the neutron absorber ejection, narrow space, high reliability. The paper presents the context, the requirements, the design features and the development and qualification process of the 2 CRDM types. The paper details: - JHR mechanisms general design features by means of functional diagrams and CAD pictures focusing on: • The different sub-assemblies and how they are loaded in the reactor; • The 2 different ways to prevent absorber ejection under upwards flow; • The implemented features to prevent vibration under high velocity flows; • The 2 diverse CRDMS designs actuating respectively the safety rods and the other control rods; • The main qualification tests that are being led on an ASA and an APAC prototype mechanism with a specific hydraulic loop. (author)