Design and fabrication of HTTR reactor pressure vessel

The High Temperature Engineering Test Reactor (HTTR) is under construction at the Oarai Research Establishment, JAERI and planned to be critical at the end of 1997. The HTTR is a High Temperature Gas-cooled Reactors (HTGRs) with thermal output of 30MW, inlet coolant temperature of 395degC, and outlet coolant temperature of 850degC at rated operation and 950degC at high temperature test operation. 2.25Cr-1Mo steel is chosen for the reactor pressure vessel of the HTTR because its temperature reaches about 400degC at normal operation. 2.25Cr-1Mo steel has higher creep rupture strength than Mn-Mo steel used for the reactor pressure vessels of Light Water Reactors (LWRs). For the components of the HTTR reactor pressure vessel subjected to low temperatures where creep deformation is negligible, a design guideline based on Japanese structural design standard for LWRs 'Technical standards for LWR power plant components-Ministry of International Trade and Industry Standard No.501' is utilized. On the other hand, design of the components for high temperature application, where creep behavior dominates, is conducted under newly determined high temperature structural design guideline and design material data. The fabrication of the HTTR reactor pressure vessel took about 23 months. It was installed in a reactor containment vessel in August, 1994. After core components had been installed in the reactor pressure vessel, pressure test of the primary and secondary cooling system including the reactor pressure vessel was performed and successfully ended in March, 1996. This paper reports issues of the HTTR reactor pressure vessel such as structure, material, stress analysis, fabrication, examination and testing. (author)