Kabushiki Kaisha Toshiba

Masami Enda

Yutaka Hasegawa

Seiji Yamamoto

Hitoshi Sakai

Yumi Yaita

Ichiro Inami

Takeshi Kanasaki

Mitsuyoshi Sato

Reiko Fujita

Toshihiro Yoshii

Nagayoshi Ichikawa

Hideaki Heki

Osamu Sasaki

Norihisa Saito

Masayuki Kaneda

Yutaka Uruma

Hiromi Aoi

Yoshinari Takamatsu

Katsumi Hosaka

Tetsuo Morisue

Satoshi Hiraragi

Jiro Sakurai

A chemical decontamination apparatus of the present invention chemically dissolves radioactive substance-containing oxide films formed or adhering on the surface of a decontamination object by using ozone water to conduct decontamination. The chemical decontamination apparatus includes an ozone generating unit for generating ozone gas, an ozone supplying device for supplying the generated ozone gas to an ozone supplying unit in water, and a sintered metal elementwhich is disposed in the ozone supplying unit and to which ozone gas is supplied from the ozone supplying device. The ozone gas supplied to a sintered metal element interior from the ozone supplying device is allowed to flow out of the element into water so as to generate ozone water.

Chemical decontamination apparatus and decontamination method therein

A system for chemically decontaminating radioactive material.

System and method for chemical decontamination of radioactive material

Chemical decontamination method of dissolving oxide film adhered to contaminated component including, preparing decontamination solution in which ozone is dissolved and oxidation additive agent, which suppresses corrosion of metal base of the contaminated component, is added, and applying the decontamination solution to the contaminated component, thereby to remove the oxide film by oxidation.

Method for treating a chemical decontamination solution

A method for chemically decontaminating radioactive material. The method includes reducing-dissolving step for setting surface of radioactive material in contact with reducing decontamination liquid including mono-carboxylic acid and di-carboxylic acid as dissolvent; and oxidizing-dissolving step for setting the surface of the radioactive material in contact with oxidizing decontamination liquid including oxidizer. The method may include repeated pairs of steps, each pair including the reducing-dissolving step and the oxidizing-dissolving step. The mono-carboxylic acid may include formic acid, and the di-carboxylic acid includes oxalic acid. The oxidizer may be ozone, permanganic acid or permanganate.

Ozone gas having a high ozone concentration is generated by a solid electrolyte electrolytic process. An ozone solution is prepared by injecting the ozone gas into an acidic solution of pH 6 or below. The ozone solution heated at a temperature in the range of 50&#xb0; to 90&#xb0; C. is supplied to a contaminated object to oxidize and dissolve a chromium oxide film by an oxidizing dissolving process. The ozone solution used in the oxidizing dissolving process is irradiated with ultraviolet rays to decompose ozone contained in the ozone solution, the ozone solution is passed through an ion-exchange resin to remove ions contained in the ozone solution. An oxalic acid solution is supplied to the contaminated object to dissolve an iron oxide film by a reductive dissolving process. Oxalic acid remaining in the oxalic acid solution after the reductive dissolving process is decomposed by injecting ozone into the oxalic acid solution and irradiating the oxalic acid solution with ultraviolet rays, and ions contained in the oxalic acid solution is removed by an ion-exchange resin.

Method of chemically decontaminating components of radioactive material handling facility and system for carrying out the same

Ozone gas having a high ozone concentration is generated by a solid electrolyte electrolytic process. An ozone solution is prepared by injecting the ozone gas into an acidic solution of pH 6 or below. The ozone solution heated at a temperature in the range of 50&deg; to 90&deg; C. is supplied to a contaminated object to oxidize and dissolve a chromium oxide film by an oxidizing dissolving process. The ozone solution used in the oxidizing dissolving process is irradiated with ultraviolet rays to decompose ozone contained in the ozone solution, the ozone solution is passed through an ion-exchange resin to remove ions contained in the ozone solution. An oxalic acid solution is supplied to the contaminated object to dissolve an iron oxide film by a reductive dissolving process. Oxalic acid remaining in the oxalic acid solution after the reduction dissolving process is decomposed by injecting ozone into the oxalic acid solution and irradiating the oxalic acid solution with ultraviolet rays, and ions contained in the oxalic acid solution is removed by an ion-exchange resin.

An insulating shield plate (1) divides a room of an electrolysis bath (2) into an anode chamber (13) and a cathode chamber (14). An anode (5) is disposed in the anode chamber (13), and a cathode (6), metallic waste (7) and heater (4) are disposed in the cathode chamber (14). An electrolyte (3) stored in the electrolysis bath (2) flows in a circulation path from a circulating pump (10) through a circulating line (12) and filter (11) to return the electrolysis bath (2). An exhaust gas processing device 9 is connected to the electrolysis bath (2). When a voltage is supplied to the anode (5) and cathode (6), a surface of the metallic waste (7) is charged in a positive polar to dissolve a base metal of the metallic waste (7). Further, a cylindrical anode (33) is arranged in an electrolyte (32) in an electrolysis bath (31), and a cylindrical metal (34) as a metallic waste is arranged in the cylindrical anode (33). After a bar-shape cathode (35) is arranged in the cylindrical metal (34), a DC voltage is supplied to the cylindrical anode (33) and the bar-shape cathode (35). At this time, the system may be constructed in that oxygen occurs by charging in a positive polarity an inner surface of the cylindrical metal (34) and the base metal of the cylindrical shape is dissolved.

Apparatus and method for electrochemical decontamination of radioactive

An insulating shield plate (1) divides a room of an electrolysis bath (2) into an anode chamber (13) and a cathode chamber (14). An anode (5) is disposed in the anode chamber (13), and a cathode (6), metallic waste (7) and heater (4) are disposed in the cathode chamber (14). An electrolyte (3) stored in the electrolysis bath (2) flows in a circulation path from a circulating pump (10) through a circulating line (12) and filter (11) to return the electrolysis bath (2). An exhaust gas processing device 9 is connected to the electrolysis bath (2). When a voltage is supplied to the anode (5) and cathode (6), a surface of the metallic waste (7) is charged in a positive polarity to dissolve a base metal of the metallic waste (7). Further, a cylindrical anode (33) is arranged in an electrolyte (32) in an electrolysis bath (31), and a cylindrical metal (34) as a metallic waste is arranged in the cylindrical anode (33). After a bar-shaped cathode (35) is arranged in the cylindrical metal (34), a DC voltage is supplied to the cylindrical anode (33) and the bar-shaped cathode (35). At this time, the system may be constructed in that oxygen occurs by charging in a positive polarity in an inner surface of the cylindrical metal (34) and the base metal of the cylindrical shape is dissolved.

Apparatus for electrochemical decontamination of radioactive metallic

A decontaminating liquid capable of removing a radioactive substance adhering to or deposited in a metal waste is produced by a method which comprises immersing an anode made of a metal or a metal oxide having a high oxygen overvoltage equal to or higher than the oxygen overvoltage of platinum and a cathode made of a metal or a metal oxide having a low hydrogen overvoltage equal to or lower than the hydrogen overvoltage of platinum in an acidic solution having dissolved therein a metal ion in a low-oxidation state and causing passage of an electric current between the two electrodes thereby giving rise to a metal ion in a high-oxidation state.

Method for production of decontaminating liquid

The invention resides in an apparatus for the decontamination of radioactivated metallic waste by the electrolytic oxidation-reduction with an aqueous nitric acid solution containing trivalent cerium ions, i.e. the step of converting the trivalent cerium ions into tetravalent cerium ions through electrolytic oxidation and the step of dissolving the surface layer of the radioactivated metallic waste by oxidizing it with the electrolytic solution now vested with the oxidative power of the freshly produced tetravalent cerium ions and, at the same time, effecting regeneration of the tetravalent cerium ions. The main objects of this invention are to provide a high decontamination efficiency and suppression of the amount of secondary waste to be generated to the minimum by the apparatus which is capable of thoroughly dissolving the surface layer of the object under treatment without reference to size and shapes, the very factors that prevent the conventional methods of decontamination from fulfilling their functions indiscriminately, thereby lowering the level of radioactivity to a point where the object will be handled as safely as ordinary industrial waste.

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Kanagawa-ken, Japan

Masami Enda