Manufacturing and material properties of forgings for the reactor pressure vessel of the high temperature engineering test reactor

For the reactor pressure vessel (RPV) of the high temperature engineering test reactor (HTTR) which has been developed by the Japan Atomic Energy Research Institute (JAERI), 2.25Cr-1Mo steel is used for the first time in the world for a nuclear reactor pressure vessel. The RPV is 13.2 m in height and 5.5 m in internal diameter. Operation temperature is about 400°C and the internal pressure is 4 MPa. A material confirmation test has been carried out to demonstrate good applicability of forged low Si 2.25Cr-1Mo steel to the RPV of the HTTR. Recently, Japan Steel Works has succeeded in manufacturing large size ring forgings and a large size forged cover dome integrated with nozzles for the stand pipe for the RPV. This paper describes the results of the material confirmation test as well as the manufacturing and material properties of the large forged cover dome integrated with nozzles for the stand pipe.