Hitachi, Ltd.

Hitachi-ge Nuclear Energy, Ltd.

Other

Kurita Engineering Co., Ltd.

Hitachi Engineering Co., Ltd.

Makoto Nagase

Kazushige Ishida

Shunsuke Uchida

Motomasa Fuse

Katsumi Ohsumi

Hiroo Yoshikawa

Masanori Sakai

Makoto Hayashi

Tsuyoshi Itou

Hideyuki Hosokawa

Yoichi Wada

Yamato Asakura

Motohiro Aizawa

Naohito Uetake

Naoshi Usui

Kazumi Anazawa

Motoaki Sakashita

Tsuyoshi Ito

Tadashi Tamagawa

Toshio Sawa

Yukio Hirama

Masahiko Tachibana

Fumito Nakamura

Masao Endo

Motoaki Utamura

Hidefumi Ibe

Masaharu Sakagami

Masaaki Tsubaki

Shiro Takahashi

Katsuo Yokota

Fumihito Hirokawa

Masayoshi Kondoh

Kazuhiko Akamine

Satoshi Morisawa

Atsushi Watanabe

Tetsuya Matsui

Fuminobu Takahashi

Masahiro Koike

Renzo Takeda

Noriyuki Ohnaka

Hiroshi Kamimura

Yoshiyuki Takamori

Tsutomu Baba

Yasuko Aoki

Takashi Saito

Izumi Yamada

Haruo Fujimori

Kenji Yokose

Takaharu Fukuzaki

Kiyotomo Nakata

Masanori Takahashi

Yoshitaka Nishino

Satoshi Oouchi

Hidetoshi Karasawa

Kouichi Yamane

Youichi Wada

Nobuyuki Oota

Yamoto Asakura

Teruo Hara

Masao Endou

Mizuho Tsuyuki

Toru Kawasaki

Shintarou Yanagisawa

A noble metal injection apparatus is connected to a piping of a nuclear plant at the time of stop of the nuclear plant before start of the nuclear plant. In chemical decontamination, oxidation decontamination agent decomposition, and reduction decontamination on an inner surface of the pipe system are executed. After reduction decontamination, a part of an oxalic acid included in a reduction decontamination solution is decomposed and platinum is injected into the reduction decontamination solution of pH 3.5 or higher. When the platinum concentration becomes a preset concentration, a reduction agent is injected and the reduction decontamination solution including the platinum and reduction agent is brought into contact with the inner surface of the piping. The platinum is deposited on the inner surface of the piping. The injection of the platinum and reduction agent is stopped and the platinum and reduction agent are decomposed.

Method of depositing noble metal on structure member of nuclear plant

Both ends of a circulation pipe of a film formation apparatus are connected to a piping of a BWR plant. A chemical including chromium ions and formic acid is injected into a film formation solution flowing in the circulation pipe heated to a temperature within a range from 60&#xb0; C. to 100&#xb0; C. Furthermore, a chemical including iron (II) ions and formic acid, hydrogen peroxide, and hydrazine are injected into the circulation pipe. Due to the injection of these chemicals, a film formation solution of pH 7.0 including iron (II) ions, chromium ions, formic acid, hydrogen peroxide, and hydrazine is generated in the circulation pipe. This film formation solution includes hydrazine of, for example, 1000 ppm. The film formation solution is supplied to the piping, thus, a Fe&#x2014;CrOfilm (here, 0&#x3c;X&#x2266;0.1) is formed on the inner surface of the piping. The above method of forming the ferrite film on a structural member (for example, the piping) can be shortened time required to form the ferrite film.

[object Object]

A bath containing nickel ions and formic acid is injected into a film-forming aqueous solution flowing in a circulation pipe connected to feed water pipe made of carbon steel in a BWR plant. This film-forming aqueous solution is supplied into the feed water pipe through the circulation pipe, and then, a nickel metal film is formed on an inner surface of the feed water pipe. After the nickel metal film is formed, a film-forming aqueous solution containing iron (II) ions, formic acid, nickel ions, hydrogen peroxide, and hydrazine is supplied to the feed water pipe. A nickel ferrite film is formed on the surface of the nickel metal film in the feed water pipe. Then, the nickel ferrite film is come into contact with water containing dissolved-oxygen at 150&#xb0; C. or above to transform the nickel metal film into a nickel ferrite film. A thick nickel ferrite film is formed on the inner surface of the feed water pipe. Corrosion of the carbon steel member composing the plant can further reduce.

Suppression method for corrosion of carbon steel member

A bath containing nickel ions and formic acid is injected into a film-forming aqueous solution flowing in a circulation pipe connected to a feed water pipe made of carbon steel in a BWR plant. This solution is supplied into the pipe through the circulation pipe, and a nickel metal film is formed on an inner surface of the pipe. After the film is formed, a film-forming aqueous solution containing iron (II) ions, formic acid, nickel ions, hydrogen peroxide, and hydrazine is supplied to the pipe. A nickel ferrite film is formed on the surface of the nickel metal film in the pipe. The nickel ferrite film comes into contact with water containing dissolved oxygen at or above 150&#xb0; C. to transform the nickel metal film into a nickel ferrite film. A thick nickel ferrite film is formed on the inner surface of the feed water pipe.

A formic acid aqueous solution that contains Fe (II) ions is produced by dissolving metal iron in a formic acid aqueous solution. Nitrogen is supplied from a nitrogen supply device to a chemical liquid tank and then discharged from a discharge line to reduce the dissolved oxygen concentration in the aqueous solution. The chemical liquid tank is filled with the formic acid aqueous solution sealed with nitrogen, and is transferred from a factory to a nuclear reactor building designated as radiation-controlled areas. Inside the nuclear reactor building, the chemical liquid tank is installed in a film deposition apparatus connected to a reactor water recirculation pipeline. The formic acid aqueous is supplied from the chemical liquid tank to the inside of the reactor water recirculation pipeline, and then a ferrite film is formed on the inner surface of the reactor water recirculation pipeline.

Method of suppressing deposition of radioactive isotope

A method of suppressing deposition of radionuclides on components of a nuclear power plant comprises forming a ferrite film by contacting a first chemical including iron (II) ions, a second chemical for oxidizing the iron (II) ions to iron (III) ions, and a third chemical for adjusting the pH of a processing solution containing a mixture of the first and second chemicals to be 5.5 to 9.0 with the metal member surface in a time period from a finishing stage in decontamination step of removing contaminants formed on the surface of metal member composing the nuclear power plant, and suppressing deposition of radionuclides on the metal member by the ferrite film.

Suppression method of radionuclide deposition on reactor component of nuclear power plant

A formic acid aqueous solution that contains Fe (II) ions is produced by dissolving metal iron in a formic acid aqueous solution. Nitrogen is supplied from a nitrogen supply device to a chemical liquid tank and then discharged from a discharge line to reduce the dissolved oxygen concentration in the aqueous solution. The chemical liquid tank is filled with the formic acid aqueous solution sealed with nitrogen, and transferred from a factory to a nuclear reactor building designated as radiation-controlled areas. Inside the nuclear reactor building, the chemical liquid tank is installed in a film deposition apparatus connected to a reactor water recirculation pipeline. The formic acid aqueous is supplied from the chemical liquid tank to the inside of the reactor water recirculation pipeline, and then a ferrite film is formed on the inner surface of the reactor water recirculation pipeline.

The object of this invention is to provide a method for mitigating a stress corrosion cracking of reactor structural material which makes it possible to suppress the rise in the main steam line dose rate without secondary effects such as a rise in the concentration of radioactive cobalt-60, etc. in the reactor water. Hydrogen and a reductive nitrogen compound containing nitrogen having a negative oxidation number (for example, hydrazine) are injected into the core water of boiling water nuclear power plant. By injecting the reductive nitrogen compound containing nitrogen having a negative oxidation number into the core water, the stress corrosion cracking of structural material of reactor can be mitigated without side reactions such as a rise in the concentration of cobalt-60, etc.

Method of stress corrosion cracking mitigation for nuclear power plant structural materials

A natural circulation boiling water reactor provides to a chimney with a plurality of tubes. That is to say, each of the plurality of tubes partitions the coolant flow path above a core. Thus, unlike the conventional natural circulation boiling water reactor providing the flow path partition wall grid in which the plate members are made integral by welding and coolant flow paths are partitioned, the chimney of the natural circulation boiling water reactor can reduce the number of welded portions because the edges of the four corners of each flow path do not need to be welded. The natural circulation boiling water reactor can avoid removal as a single unit, as in the case of the flow path partition wall grid in the conventional natural circulation boiling water reactor, by detaching each tube. The chimney can be easily detached from the reactor pressure vessel.

Natural circulation boiling water reactor and handling method thereof

Suppression method of radionuclide deposition on reactor component of nuclear power plant and ferrite film formation apparatus

Method of stress corrosion cracking mitigating for nuclear power plant structural materials

It is an object of the present invention to efficiently suppress radionuclide deposition on a reactor component of nuclear power plant. Radionuclide deposition on the surface of a metallic reactor component of nuclear power plant is suppressed by forming a ferrite film on the component, wherein the film is formed, after decontamination for removing radionuclides contaminants from the component surface is completed and before the plant is started up, by contacting a treatment solution which mixes a first agent containing the iron (II) ions, a second agent for oxidizing the iron (II) ions into the iron (III) ions and a third agent for adjusting pH level of a solution to 5.5 to 9.0 in this order with the reactor component surface.

A handling method for a natural circulation boiling water reactor having a chimney having cylindrical chimney shell disposed above a core in a reactor pressure vessel, a plurality of square tubes disposed in the chimney shell, and a grid support plate with grid holes supporting and in communication with a lower end portion of the square tubes so that adjacent square tubes are disposed at an interval which exceeds the width of one square tube between them. The method includes steps shifting predetermined ones of the square tubes to the interval between the square tubes, and performing maintenance and inspection of members around a core via the grid holes which appear at positions from which the predetermined square tubes are taken out due to the shift of the predetermined square tubes.

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Mito, Japan

Makoto Nagase