Hitachi, Ltd.

Hitachi Engineering Co., Ltd.

Michiyoshi Yamamoto

Takahiko Kato

Yasuhisa Aono

Katsumi Ohsumi

Akira Yoshinari

Hideyo Kodama

Masakiyo Izumiya

Kiyotomo Nakata

Hisashi Sato

Shigeki Kasahara

Shizuka Shimanuki

Shinji Mitani

Shinzoo Ikeda

Yoshie Takashima

Hiroo Igarashi

Shizuo Matushita

Hideya Anzai

A method and an apparatus for estimating the remaining service life of an object by measuring the physical quantity of a sample and which are applicable to a nuclear reactor. A plurality of model samples are experimentally prepared by preliminarily disposing a material having substantially the same composition as the object to be subjected to the estimation in an environment substantially the same as the object and measuring the physical quantities of the model samples in relation with exposure times. From this experiment, a relationship between the exposure time and the physical quantity under such an environment is obtained. Further, a critical exposure time which will cause an unstable fracture of a material of an actual sample, which is made of a material substantially the same as the object and placed in substantially the same environment as the object, is preliminarily obtained from the relationship between the exposure time and the physical quantity for the model samples. The physical quantity of the actual sample is then measured. Subsequently, an actual exposure time corresponding to the physical quantity of the actual sample is obtained by using the relationship between the physical quantity and the exposure time. Thereafter, a difference between the critical exposure time and the actual exposure time is calculated to obtain a remaining service life of the object.

Method of and apparatus for estimating remaining service life of

An austenitic steel comprising Ni of 9-30%, Cr of 10-23%, and Fe of at least 45%, is characterized in comprising enough Cr and Ni to form whole austenitic structure in the equilibrium diagram at 700.degree. C., having austenitic phase at room temperature, and the austenitic phase is a single crystal, and has superior resistance against stress. The austenitic steel preferably comprises C.ltoreq.0.1%, Si.ltoreq.1%, Mn.ltoreq.2%, Ni 9-15%, Cr 16-18.5%, and at least one of elements selected from the group of Mo 1-3%, Ti 0.05-1%, and Nb 0.1-1.5%. The alloy is useful as a material for members of a reactor core of a nuclear reactor.

Fe-base austenitic steel having single crystalline austenitic phase,

Control rods are inserted into the core of a nuclear reactor in operation to shut down the reactor output. Before completion of entire control rod insertion, a high-temperature coolant flowing in piping for a reactor water clean-up system is sprayed into the space in the upper portion of the reactor vessel. As the space is under negative pressure, oxygen existing in the water droplets of the sprayed coolant is separated. After completion of entire control rod insertion, a residual heat removal system is operated. The spraying operation is discontinued and a low-temperature coolant cooled by a heat exchanger in the residual heat removal system is sprayed into said space. The coolant sprayed by said first spraying operation is not cooled by the heat exchanger in said residual heat removal system.

Nuclear reactor degassing method and degassing system

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Hitachi, Japan

Michiyoshi Yamamoto