Research on Martensitic Stainless Steel Used on the Latch Housing of European Pressurized Reactor (EPR) Control Rod Drive Mechanism (CRDM)

Abstract

As one of the most important equipment for reactivity control, Control Rod Drive Mechanism (CRDM), which is widely used in Pressurized Water Reactor (PWR) nuclear power plant, has a series of important security functions. As part of the reactor pressure boundary, materials for European Pressurized Reactor (EPR) CRDM pressure housing needs to have relatively high strength and sufficient toughness (i.e., appropriate yield ratio). As an important part of the magnetic circuit, martensitic stainless steel used for latch housing (a part of pressure housing) needs to have good magnetic properties. It is difficult for the yield ratio and the magnetic properties of the materials to meet the specification requirements simultaneously. Based on the design specification, this research refers to the relevant international manufacturing experience and combines the current manufacture with engineering practice. The manufacturing process and key parameters of the material for latching housing of CRDM are established. The martensitic stainless steel which meets the design requirements has been successfully prepared. The comprehensive properties (e.g. yield ratio and magnetic properties) of the material are improved as well. The performance indicators have reached international advanced level. The successful development of the martensitic steel for EPR CRDM latch housing provides strong technical support for the construction of nuclear power projects at home and abroad.