Abstract: A multistage rolling mill includes: four columns 12a, 12b, 12c, and 12d linking, in an up-down direction, four corners of each of an upper mill housing 8, a lower mill housing 9, and a base mill housing 10; a press-down section that is provided on an upper side of the four columns 12a, 12b, 12c, and 12d in a vertical direction and that is capable of raising and lowering the upper mill housing 8; and a lower mill housing spacer that is provided between the lower mill housing 9 and the base mill housing 10 and that adjusts the position of the lower mill housing 9 in the vertical direction. With this configuration, a compact multistage rolling mill with a smaller installation space than a conventional cluster-type rolling mill is provided.

Abstract: Within a housing, divided backing bearing assembled shafts are each moved on any one of a housing bore upper surface 8a constituting the housing, spray frame upper surfaces 9, and rails 13, 19, and 20 of a changing carriage 12 by a sliding apparatuses, and outside the housing, the divided backing bearing assembled shafts are extracted from within the housing or inserted into the housing by being moved on the rails 13, 19, and 20 of the changing carriage 12 by sliding apparatuses. There are thus provided a rolling mill that makes changing of divided backing bearing assembled shafts in the rolling mill easier than conventional, and a method of changing the divided backing bearing assembled shafts in the rolling mill.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: [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.

Abstract: In a chemical decontamination method and a chemical decontaminating system for chemically decontaminating radioactive nuclides from a metallic material surface contaminated by the radioactive nuclides, the method comprise the processes of reductively decontaminating using a reductive decontaminating agent containing at least two kinds of components; and then decomposing the reductive decontaminating agent using a decomposing apparatus for decomposing at least two kinds of chemical substances in the reductive decontaminating agent.

Abstract: 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.