Hitachi, Ltd.

Other

Kurita Engineering Co., Ltd.

Naohito Uetake

Makoto Nagase

Yamato Asakura

Hiroo Yoshikawa

Kazushige Ishida

Katsumi Ohsumi

Kazumi Anazawa

Tadashi Tamagawa

Tetsuo Fukasawa

Fumito Nakamura

Masayoshi Kondoh

Fumio Kawamura

Shunsuke Uchida

Toshio Sawa

Kouichi Yamane

Makoto Kikuchi

Kenichi Ito

Shin Tamata

Renzo Takeda

Kiyomi Funabashi

Hideo Yusa

Hideyuki Hosokawa

Noriyuki Ohnaka

Motohiro Aizawa

Yoshiyuki Takamori

Akira Maru

Yoshihiro Ozawa

Kazuhiko Akamine

Akira Ichimura

Masaharu Ohtsuka

Haruo Hasimoto

Hajime Iba

Ietsugu Sekine

Teruo Hara

In a chemical decontamination method of chemically decontaminating radioactive nuclides from a metallic material, oxalic acid and hydrazine are injected as a reductive decontaminating agent into water that is in contact with the metallic material. Injection of the hydrazine is stopped after a cation resin arranged in a circulation line connected to the metallic material breaks, and at least the oxalic acid and the hydrazine in the reductive decontaminating agent are decomposed using a decomposing catalyst.

Method of chemical decontamination and system therefor

In a chemical decontamination apparatus, a catalyst decomposition column in an upstream side of an ion exchange resin column and a hydrogen peroxide injection apparatus in a further upstream side, reduce the amount of waste products caused by a chemical decontaminating agent where a mixed decontaminating agent for a composition trapped in a cation resin column and for a composition trapped in an anion exchange resin are used for the chemical decontaminating agent, selectively decompose the composition trapped in the cation resin column in an inlet side of a cleaning apparatus when radioactive nuclides in the decontaminating agent are cleansed using the cation resin column during decontamination, and decompose both compositions after completion of the decontamination. The chemical decontamination thus selectively decomposes the chemical decontaminating agent, which is a component of the load to the cation resin column.

Apparatus for chemical decontamination

To suppress a decrease of thickness due to corrosion of structural members and to achieve a removal of radionuclides with good efficiency in a nuclear power plant, oxidation decontamination is first conducted. An aqueous potassium permanganate solution is supplied from a circulation line to a reactor pressure vessel, which is a stainless steel structural member, and a reactor water cleanup system piping and a drain piping, which are carbon steel structural members. These structural members are oxidation-decontaminated by the action of potassium permanganate. Then the above-mentioned structural members are reduction-decontaminated by using an aqueous oxalic acid solution. The aqueous oxalic acid solution contains hydrazine.

Method of chemical decontamination

Processes of reductive decontamination using an agent containing at least two kinds of components, and then decomposing the agent using an apparatus for decomposing at least two kinds of chemical substances in the agent, are employed in chemical decontamination. A catalyst decomposition column in an upstream side of an ion exchange resin column and a hydrogen peroxide injection apparatus in a further upstream side, reduce the amount of waste products caused by a chemical decontaminating agent where a mixed decontaminating agent for a composition trapped in a cation resin column and for a composition trapped in an anion exchange resin are used for the chemical decontaminating agent, selectively decompose the composition trapped in the cation resin column in an inlet side of a cleaning apparatus when radioactive nuclides in the decontaminating agent are cleansed using the cation resin column during decontamination, and decompose both compositions after completion of the decontamination. The chemical decontamination thus selectively decomposes the chemical decontaminating agent, which is a component of the load to the cation resin column. The chemical decontamination moderates corrosion of material by using a chemical decontaminating agent decomposing apparatus capable of decomposing the components trapped by the cation exchange resin and components trapped by an anion exchange resin at the same time.

A reactor water clean-up system is provided with a first filter demineralizer having a filter resin containing an alkali substance and a second filter demineralizer with a filter resin not containing an alkali substance. The reactor water is supplied to the first filter demineralizer during the term from the starting operation of the preoperating test of the nuclear reactor and of each fuel cycle to 2000 EFPH. The alkali substance contained in the filter resin is guided into the nuclear reactor to change the pH of the reactor water in the nuclear reactor to the weak alkali side. The Cr quantity which is taken in the oxide film of the fuel cladding tube surface is reduced. After 2000 EFPH from the starting operation, the supply of the reactor water to the first filter demineralizer is stopped, and then, the reactor water is supplied to the second filter demineralizer.

Boiling water reactor and its operating method

In a nuclear fuel rod having a zirconium liner and a method of manufacturing the same, the outer surface of a zircaloy cladding tube in which fuel pellets are filled has an oxide film having fine irregularities of which the pitch is 1 .mu.m or less. The fine irregularities are formed by oxidizing the surface in high temperature steam or polishing the surface of the cladding tube. The surface of the fuel rod can effectively trap radioactive substances in the reactor water.

Nuclear fuel rod and method of manufacturing the same

In reactor water control for a BWR power plant during an operation cycle after loading new fuel rods in the BWR power plant, an operation is performed which accelerates deposition of crud on the fuel rods until the deposition amount of the crud on the fuel rods reaches a predetermined target value within the operation cycle concerned. After the deposition amount of the crud has reached the predetermined target value, the crud deposition accelerating operation is terminated, whereby even when loading new fuel rods such as Zr liner type fuel rods having a surface on which metal ion deposition has been difficult, radioactivity in the reactor water is efficiently reduced.

Reactor water control method in BWR power plant, BWR power plant having

A water quality control method for a nuclear power plant comprising the steps of maintaining the iron concentration in the feed water below 0.05 ppb by increasing iron removing rate at a condensed water purifying loop, shifting the pH of the reactor water below a pH of 6.8 determined at a room temperature by injecting carbon dioxide gas in the primary cooling system and further optionally reducing the dissolved oxygen concentration in the reactor water below 20 ppb by injecting hydrogen gas into the primary cooling system, whereby .sup.60 Co ion concentration in the primary cooling system is maintained low for a long interval.

Water quality control method and device for nuclear power plant, and

An object of the present invention is to provide a method and a nuclear plant capable of preventing deposition and activation of crud to a nuclear fuel rod and decreasing the radioactivity level in reactor water. Metal ions solely having a low deposition rate coefficient are made to coexist to prevent or decrease deposition of radioactive corrosion products to the nuclear fuel rod. A method and a nuclear plant capable of preventing deposition and activation of crud to the nuclear fuel rod and decreasing the radioactivity level in reactor water can be provided.

Method of operating BWR plant, BWR plant and metal element injecting

Cations and anions contained as impurities in a spent organic solvent can be removed by an alkaline aqueous solution passing through inside of hydrophobic porous membrane such as hollow fibers for capturing anions and by an acidic aqueous solution passing through inside of hydrophobic porous membrane such as hollow fibers for capturing cations at the same time so as to regenerate the organic solvent. An apparatus suitable for removing cations and anions simultaneously from the spent organic solvent is also provided.

Process and apparatus for regenerating spent reprocessing extraction

Method for solidifying radioactive waste

YThis invention concerns solidification products capable of immobilizing radioactive wastes containing water soluble solid components stably for a long period of time, as well as a process for producing the same, in which radioactive wastes are immobilized with an alkaline earth metal silicate compound and the alkaline earth metal silicate compound intakes the water content in the solidifying agent as the bound water to or a hydrate. High temperature and high humidity condition has been found to be necessary upon curing in order to take the water content as the bound water. This invention can provide solidified wastes with less development of detects such as open pores or cracks.

Solidified radioactive wastes and process for producing the same

A solid radioactive waste can be solidified by a process comprising packing a solid radioactive waste in a container, adding to the container an aqueous solution comprising an alkali silicate, a hardening agent and a fluidity-improving agent for the aqueous solution and conducting the solidification of the alkali silicate, the resulting solidified radioactive waste being excellent in weather resistance, showing no cracks and having sufficient strength.

Process for solidifying radioactive waste

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Hitachinaka, Japan

Naohito Uetake