Abstract: A member adapted for use under a stress in an atmosphere of a temperature below the creep temperature and made from an Ni base alloy having a high resistance to stress corrosion cracking. The Ni alloy consists essentially of, by weight, 15 to 25% of Cr, 1 to 8% of Mo, 0.4 to 2% of Al, 0.7 to 3% of Ti, 0.7 to 4.5% of Nb and the balance Ni, and has an austenite matrix in which precipitated is at least one of .gamma.' phase and .gamma." phase. The member can suitably used as parts which are subjected to pure water in nuclear reactor.

Abstract: In a boiling water-type, nuclear power plant, deposition of radioactive substances on the surfaces of out-of-core components in the primary cooling water system in the nuclear power plant is suppressed by injecting an alkaline element into reactor water in the presence of more than an amount of the oxygen formed by nuclear fission of the reactor water and dissolved in the reactor water, particularly without hydrogen gas injection, during the nuclear heatup operation period of a boiling water type, nuclear power plant and circulating the injected alkaline element through the primary cooling water system of a nuclear reactor, thereby forming an oxide film on the surfaces of out-of-core components in the primary cooling water system of the nuclear reactor. Exposure of plant personnel to radioactivity can be reduced thereby. The present boiling water-type, nuclear power plant is provided with a means for forming such oxide film.

Abstract: The primary cooling water in a primary cooling water recirculation path of a nuclear power plant is heated and recirculated in the presence of beryllium, and a film of nickel ferrite and/or cobalt ferrite is formed on the surface of pipings and various apparatus and devices connecting with the primary cooling water. The beryllium is injected in the form of beryllium ion into the primary cooling water, or is disposed in the form of beryllium or beryllium-containing alloy in the piping and/or the various apparatus and devices.

Abstract: A cleaning fluid such as a chemical decontamination solution originally containing one or more cleaning or decontamination reagents in low concentrations and deteriorated after a cleaning or decontamination treatment step by containing metal oxides therein can be regenerated by introducing such a deteriorated cleaning fluid into an electrolytic cell, passing a direct current through said cleaning fluid between two electrodes, and removing said metal oxides by depositing dissolved metal ions on the cathode as metals from the cleaning fluid.

Abstract: In-pile parts for a nuclear reactor made of alloy consisting essentially of by weight 0.01-0.2% C, 10-21% Cr, 1-4% Ti, 0.3-2% Nb, 0.1-2% Al and the balance Ni wherein Ti content being higher than Nb content, said alloy having the microstructure of chromium carbides precipitated in the grain boundaries and a .gamma.' phase precipitated in the grains with the matrix thereof being austenite in microstructure.

Abstract: A butt welded tubular structure composed of tubular members of austenite stainless steel including a restraining member providing a cover to the entire outer circumferential surfaces of a welded joint and heat affected zones of the tubular members, the restraining member being formed of a metal or alloy of lower stress corrosion cracking sensitivity than the material of the tubular members and joined at the entire surfaces of opposite end portions thereof to the tubular members by welding, although the restraining member is not joined to the tubular members at portions of the restraining member corresponding to the welded joint and heat affected zones of the tubular members.