A SURVEY OF THE EFFECTS OF NEUTRON IRRADIATION ON THE IMPACT AND OTHER MECHANICAL PROPERTIES OF PRESSURE VESSEL STEELS FOR THE SM-2 REACTOR

Abstract

Abstract: This technical report summarizes the data obtained in a recent literature survey conducted to determine the effects of neutron irradiation on the impact and other mechanical properties of both ferritic steels and austenitic stainless steels. The survey was primarily aimed at obtaining sufficient data on the behavior of pressure vessel steels at high integrated neutron flux levels in order that a reference material of construction could be selected for the SM-2 (APPR-1B) reactor vessel. Materials studied in this literature survey included carbon and low alloy steels such as: ASTM A-212B, ASTM A-201, ASTM A-301B (CR-Mo), ASTM A-106 (coarse and fine grained), ASTM A-285, ASTM A-302B (Mn-Mo), ASTM A-353, ASTM A-203 Grade D, E-7016 carbon steel weld metal, USS Carilloy T-1, HY-65 and HY-80. In addition, Types 304 and 347 stainless steels were also investigated as representative austenitic materials which might be used in pressure vessel construction. A careful evaluation was made of the irradiation induced changes in the mechanical properties of the above materials. The ferritic steels were evaluated primarily on the basis of increases in transition temperature due to irradiation and decreases in the amount of maximum energy absorbed prior to ductile failure. Factors such as industrial experience, changes in other mechanical properties and the susceptibility of these materials to temper embrittlement were also considered. Austenitic stainless steels were evaluated on the basis of post-irradiation and low temperature impact strength and on irradiation induced changes in other mechanical properties. Based on available data, it is concluded that austenitic stainless steels are capable of resisting harmful property damage at integrated neutron fluxes > 1 Mev of at least t to 2 x 10(21) nvt. However, with the application of special reactor operating procedures, ASTM A212B will be satisfactory at integrated neutron fluxes up to 5 x 10(19) nvt.