Hitachi, Ltd.

Babcock-hitachi Kabushiki Kaisha

Hitachi Metals, Ltd.

Hitachi Kyowa Kogyo Co., Ltd.

Shigeo Hattori

Takahiko Kato

Yasuhisa Aono

Koichi Kurosawa

Junya Kaneda

Hideyo Kodama

Takenori Shindo

Masanori Sakai

Akira Yoshinari

Masahiko Arai

Isao Masaoka

Noriyuki Ohnaka

Yasuo Kondo

Hideyo Saito

Hisao Itow

Takayuki Numata

Yasuhiko Mori

Asao Nishimura

Hideo Miura

Tetsuya Nagata

Ryoichi Sasaki

Katsumi Mabuchi

Rikizo Watanabe

Kunio Enomoto

Takuya Takahashi

Tasuku Shimizu

Ren Morinaka

Jiro Kuniya

Masahiro Otaka

Eisaku Hayashi

Shinji Sakata

Toshimi Matsumoto

Masakiyo Izumiya

Hiroshi Yamauchi

Kiyotomo Nakata

Shigeki Kasahara

Kiyoshi Yamauchi

Kazuo Amano

Kasunori Sato

Shigeki Ono

In order to provide an austenitic single crystal stainless steel having preferable stress corrosion cracking resistance, strength, and irradiation induced embrittlement resistance so as to extend the life of a nuclear reactor core structure, which is used under a high radiation dose environment, a method is employed, which comprises the steps of homogeneously dispersing carbides into a parent phase of the austenitic single crystal stainless steel by a two step solution heat treatment, and subsequently effecting an ageing heat treatment after rapid cooling for precipitating fine carbides. Austenitic single crystal stainless steel having preferable stress corrosion cracking resistance, strength, and irradiation induced embrittlement resistance can be provided, and the life of nuclear reactor core structure, which is used under a high radiation dose environment, can be extended.

Precipitation hardening type single crystal austenitic steel, and usage

Precipitation hardening type single crystal austenitic steel

A method of performing thermal working to metal material containing helium, which comprises the steps of previously feeding current through a thermally working portion of the metal material containing helium to thereby reduce a helium content in the portion without melting the portion and then heating and melting the portion to improve the defects of the metal structure of the metal material containing helium. As a result, the improvement and removal of defects of the metal structure can be achieved by reducing a helium content in the thermally working portion of the metal material.

Thermal working method of metal material containing helium and thermal

A system of preventive maintenance for plant component parts correlates parameters for determining the transition probability distribution of degradation phenomena, selects an arbitrary influencing factor with respect to each of various influencing factors of the degradation phenomena, selects one of the parameters for the transition probability distribution as a first function, and sets the transition probability distribution when the variables of various influencing factors are reference degree values of a reference system. The system computes a ratio between the first function and the parameter value in the reference system to give a function of the subdivided index of degradation of the influencing factor, multiplies the subdivided index of degradation of various influencing factors by a unit conversion and a coefficient for reliability.

Maintenance systems for degradation of plant component parts

Low temperature water in a low temperature water tank 12 installed outside a reactor pressure vessel 9 is pumped by a high pressure pump 15 and supplied through a conductor 17 under pressure. The supplied water is ejected, as a stream of cold water jet 8, from a nozzle 14 connected to the conductor 17 and introduced into the reactor pressure vessel 9 by a driving mechanism. The stream of cold water jet 8 ejected from the nozzle 14 is directed to impinge against a predetermined position of a core shroud 13 in reactor water 11 filled in the reactor pressure vessel 9 and being at temperature higher than the low temperature water. Then, while continuing to eject the cold water jet 8 from the nozzle 14, the nozzle 14 is moved away from the predetermined position, or the ejection of the cold water jet 8 from the nozzle 14 is stopped, allowing the predetermined position to be heated again with the temperature of the reactor water 11. A thermal shock is thereby applied to the predetermined position for improvement in residual stress of the core shroud 13.

Residual stress improving method for members in reactor pressure vessel

A corrosion degree measuring method capable of field measurement for intergranular corrosion, particularly the sensitization degree, of the plant's structural materials in a narrow space. The metal electrode made of a material being measured and the counter electrode to the metal electrode are immersed in an electrolytic solution. A voltage is applied to the metal electrode in the anodic direction so as to raise the potential of the metal electrode up to the passive state potential and to keep the metal electrode at the passive state potential. The passive state potential is used as a reference potential, and a pulse-like potential signal is applied to the metal electrode in the cathodic direction. At the time of the application of the pulse potential signal, a current between the metal electrode and the counter electrode is measured, and the corrosion degree of the material being measured is determined from the intensity of the current.

Method and apparatus for measuring degree of corrosion of metal materials

A method and system for electrochemically measuring the sensitization to stress corrosion cracking of small pipes of plant structural members in a very short period of time. A micro electrochemical cell for measuring the sensitization is movably disposed within a BWR plant ICM housing or an instrumentation pipe. An electrochemical instrumentation system for performing the electrochemical potential variation such as pulse voltammetry and a remote control system for remotely controlling the electrochemical cell are provided.

Method and apparatus for measuring sensitization of structural members

A part of an ICM housing including a portion to be repaired, welded to a wall of a reactor pressure vessel in operation, is cut and removed and a new ICM housing half is welded to the remaining part of the ICM housing to form a new ICM housing. The new ICM housing is provided at the welding portion thereof with a molten metal layer containing 4 wt % or more .delta. ferrite. A sleeve made of stainless steel is located at the welding portion of an inner peripheral surface of the new ICM housing made so as to be molten by a TIG welding machine to form the molten metal layer, with the molten metal layer preventing stress corrosion cracking of the new ICM housing.

Method and structure for repairing an elongated metal hollow member

An ICM housing welded to a wall of a reactor pressure vessel in operation is provided with a molten metal layer containing 4 wt. % or more .delta. ferrite at a portion of an inner peripheral surface thereof which corresponds to a weld. A sleeve made of stainless steel is located at the competent portion of the inner peripheral surface of the ICM housing stainless steel so as to be molten by means of a TIG welding machine to form the molten metal layer. The molten metal layer prevents stress corrosion cracking of the ICM housing.

Method and structure for preventive maintaining an elongated metal

An austenitic steel excellent in resistance to neutron irradiation embrittlement which contains, by weight, not more than 0.03% carbon, not more than 1% silicon, 5 to 25% manganese, 15 to 26% chromium, and 10 to 20% nickel, the ratio of atomic volume of chromium to the average atomic volume of matrix of the steel being from 0.900 to 1.030. It is possible to add to the austenitic steel, besides the above-mentioned alloying elements, at least one element selected from the group consisting of niobium, titanium, zirconium, tantalum and vanadium which are effective in corrosion resistance and irradiation embrittlement under neutron irradiation in total amounts of not more than 1.0%. At least one of components composing the inside of a nuclear reactor or nuclear fusion reactor is made of the austenitic steel.

Austenitic steel excellent in resistance to neutron irradiation

A method and apparatus for inspecting the change in a water quality in terms of the change in a corrosion rate by detecting the capacity change between opposed electrodes due to the corrosion of electrode surfaces. As a result, the water quality can be continuously monitored over a long time while leaving the electrodes in the water to be inspected. Thus, the method and apparatus are suited for controlling the water quality especially in an atomic reactor vessel.

Water quality inspection method and apparatus therefor

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.

Member made of nickel base alloy having high resistance to stress

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.

In-pile parts for nuclear reactor and method of heat treatment therefor

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Ibaraki, Japan

Shigeo Hattori