Estimation of mechanical properties of irradiated nuclear pressure vessel steel by use of subsized CT specimen and small punch specimen

Abstract

This paper reports on the 2-1/4 Cr-1M{sub 0} steel that has been selected as the material for the reactor pressure vessel (RPV) of a multipurpose experimental high temperature gas cooled reactor designed by JAERI. The 2-1/4 Cr-1M{sub 0} steel has successful records for high temperature pressure vessels in the petrochemical industries and the ASME Code Case authorizes the use of the steel in these pressure vessels. However, the steel has not been used to nuclear reactor pressure vessels so far. Since the material in the so-called belt line region of the nuclear pressure vessels undergo changes in toughness and strength due to neutron irradiation, it is quite urgent to collect the fracture toughness and strength data of the irradiated steel for the evaluation of the structural intergravity of the reactor pressure vessel of high radiation resistance. In order to study irradiation damage of 2-1/4 Cr-1M{sub 0} steel, small specimens are required because of the severe limitations on specimen size in irradiated-material testing facilities (e.g. the limited space available for testing in nuclear reactors and the narrow damage zone produced by charged particle accelerators). In order to obtain more information about fracture properties of the 2-1/4 Cr- 1M{sub 0} steel frommore » specimens, a subsized compact tensile (CT) specimen, a small punch (SP) specimen and tensile specimen of the irradiated 2-1/4 Cr-1M{sub 0} steel were used to provide radiation effects on fracture toughness, yield strength and ultimate strength. The small punch test, which has been developed recently provides information of the yield and ultimate strength as well as fracture toughness. This report describes the behavior of the neutron irradiation embrittlement of the nuclear reactor pressure vessel steel 2-1/4 Cr-1M{sub 0} by use of new testing approach - subsized specimen techniques.« less