Hitachi, Ltd.

Babcock-hitachi Kabushiki Kaisha

Hitachi-ge Nuclear Energy, Ltd.

Hitachi Kyowa Kogyo Co., Ltd.

Hideyo Saito

Koichi Kurosawa

Makoto Hayashi

Kunio Enomoto

Masahiro Otaka

Shigeo Hattori

Yasumasa Tamai

Takayuki Numata

Hiroshi Tsujimura

Takenori Shindo

Motoya Ito

Satoshi Kanno

Shinji Sakata

Takashi Saito

Keiichi Uraki

Kunio Hasegawa

Kouji Shiina

Shiro Takahashi

Masahiro Kobayashi

Yoshinori Karatsu

Masahito Mochizuki

Tadakazu Oguri

Hiroaki Asakura

Shoji Hayashi

Minoru Masuda

Kenichi Nihei

In implementing an induction heating stress improvement (IHSI) method in a nuclear plant, cooling characteristic with respect to the inner surface of piping is improved by appropriate structure/layout of nozzles, and further, the cooling effect when applying IHSI to a real machine is verified by installing a thermometer, as well as air in the portion subjected to IHSI is removed by heating the piping prior to the execution of IHSI.

Induction heating stress improvement

A method of maintaining the housing of a reactor pressure vessel having: a reactor pressure vessel into which cooling water is introduced; a cylindrical housing which penetrates an end bracket of the reactor pressure vessel; and a circumferential weld for securing the intermediate portion of the housing to the reactor pressure vessel by welding, the method of maintaining a housing of a reactor pressure vessel comprising the steps of: remaining the cooling water in the reactor pressure vessel; preventing leakage of the cooling water in the reactor pressure vessel through the housing by sealing the housing; making the inside portion of the housing lower than the seal to be a hollow space of a gas atmosphere; heating a heat affected zone due to welding by using a heating device inserted into the hollow space from a lower portion so as to compressive-yield the inner surface of the housing in the heat affected portion upper than the circumferential weld and tensile-yield the outer surface; and cooling heated portion inside of the housing, which has been yielded, so as to tensile-yield the inner surface of the housing by using a cooling device inserted into the housing from a lower portion, whereby compressive stress is allowed to remain in the tensile-yielded portion.

Method of maintaining housing of reactor pressure vessel and heat

A water jet peening method in which a pressurized water jet flow containing cavities is jetted through a nozzle having a velocity increasing orifice portion and a horn-like jetting hole formed continuously with the velocity increasing orifice portion to impinge against a surface of a metallic material immersed in water and to cause the cavities to collapse at the surface of the metallic member, and a tensile plastic deformation is caused in a surface layer of the metallic material by a local high pressure generated by the impingement and the collapse so that a residual tensile stress in the surface of the metallic member is reduced. In this method, the nozzle is vibrated so that vibration-induced cavities are formed in the vicinity of a nozzle wall surface, and the vibration-induced cavities are caused to impinge against the surface of the metallic member by the pressurized water jet flow containing cavities. It is thereby possible to promote the generation of cavities even in a case where pure water existing in a nuclear reactor and scant of nuclei from which cavities will be generated is used in peening of an internal structual member of the reactor.

Method of and apparatus for water-jet peening

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

The susceptibility of austenitic stainless steel is tested by inputting a highly magnified image of the polished and etched steel surface through a microscope, a CCD camera and an input device into an image processor. The image processor is set up to identify grain boundary locations in the image, take width measurements across the grain boundaries, based on luminance distribution, and calculate average and maximum values for the measured widths. These calculated measured values are compared with experimentally-determined reference values -1 to 1.5 .mu.m for mean width and 2 to 3 .mu.m for maximum width - and a susceptibility status determined accordingly. The status can then be output using a display e.g. screen or printer.

Method and apparatus for detecting stainless steel sensitization

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

A method for improving a property of a weld of an austenitic stainless steel which is a part of a structure being brought into contact with a corrosive fluid at a region having been affected by welding heat on both of opposed surfaces, comprising the steps of: cooling said thermally affected region on one of said opposed surfaces; and simultaneously with said cooling step, applying a melting treatment to the other surface, thereby changing the melting treatment portion into a micro structure that contains delta (.delta.) ferrite and is superior in corrosion resistance property. The latter surface is improved in high tensile stress generated by the welding work. Namely, its stress is reduced. The melting heat for said melting treatment is obtained by application of high density energy.

Method for improving property of weld of austenitic stainless steel

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Hitachi, Japan

Hideyo Saito