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As a recently results of the irradiation test, it has been found that the brittleductile transition temperature shifts to higher temperature for the structural steels when these are irradiated. Therefore, the problem of the brittle fracture of the reactor pressure vessel is now emphasized from the standpoint of the safety of reactor operation.This paper describes the theoretical and experimental studies on the neutron irradiation brittleness both in Japan and other countries. The paper also points out the some problems encountered in the irradiation tests.

The First International Conference on Structural Mechanics in Reactor Technology was held in Berlin, Germany, 20-24 September 1971. The purpose of the Conference was to bring together engineers and scientists actively engaged in structural mechanics problems in the field of reactor technology to meet with fundamentalists in the general field of engieering mechanics and to present and discuss applied and fundamental papers on structural mechanics problems in reactor technalogy.The Conference was organized by the Bundesanstalt fOr MaterialprOfung (BAM), Berlin and Commission of the European Communities, Brussel, in collaboration with cooperating establishments and sponsoring societies. About 800 participants attended and some 340 papers were presented. These were classified into twelve divisions.A: Opening Session, B: Power Reactor Development and Structural Mechanics, C: Fuel and Cladding, D: Fuel Elements, E: Shock and Vibration Analysis of Reactor Components, F: Structural Analysis of Core Support and Coolant Circuit Structures, G: Steel Pressure Vessels, H: Prestressed Concrete Pressure Vessels, J: Analysis of Shell Structures, Containment, K: Seismic Response Analysis of Nuclear Power Plant Systems, L: Thermal and Mechanical Analysis, M: Design, Reliability Methods.

A summary is given of topics appearing in papers and discussions presented at the 2nd International Conference on Structural Mechanics in Reactor Technology (SMiRT) held in Berlin, at the Post-Conference Meeting on Computational Aspects of the Finite Element Method held in Stuttgart, and at the 2nd International Conference on Pressure Vessel Technology (PVT) held in San Antonio.The review also covers a discussion meeting on containment design aimed at resistance against air craft crashes and explosions held at the Institut Reaktorsicherheit (IRS) and other pertinert information from several organizations.

A finite element method is presented, which deals with structures subjected to both high temperatures and neutron irradiation. The material effects discussed in this paper include the usual thermo-elastoplastic effects, thermal and irradiation-induced creep and swelling due to the fast neutron fluence. Heat conduction equations and equilibrium equations are derived by assuming a specific form of free energy together with the thermodynamic laws, von Mises yield criteria and the associated flow rule. To demonstrate the effectiveness of the present formulation, the transient creep analysis of a three-dimensional solid subjected to creep effect is presented.