Tendency of raw materials for atomic energy industries

Recently, the location of nuclear power plants has become difficult, and in this connection, the tendency toward large capacity plants is conspicuous. Reflecting this situation, the structural materials used are changing gradually. In this paper, the changes in the kinds of steels and the properties required are discussed on the materials for pressure vessels and containment vessels of light water reactors, and the results of the tests carried out in Kawasaki Steel Corp. are reported. The steel materials used for reactor pressure vessels at present in Japan are JIS G 3120, grade 2, SQV 2A steel plates and JIS G 3212, SFVV 3 steel forgings, which were instituted on the basis of the steels used in U.S.A. These steel materials were improved especially in their toughness when their thickness is increased. The requirements for the pressure vessel materials are the quality of high degree and its assurance, the prevention of unstable break, the suppression of the embrittlement due to neutron irradiation, and the increase of unit material weight. The manufacturing processes for the steel plates and forgings are shown, as the trial manufacture and the tests for confirming their properties have been carried out recently. As for the test results, chemical composition, internal condition, mechanical properties, low temperature toughness, rupture toughness and fatigue characteristics are reported. SPV 50 high strength steel and prestressed concrete for containment vessels are also described. (Kako, I.)