Deformation and recrystallization mechanisms are worthy of a note as the controls in properties of metallic materials. In this study, deformation and recrystallization of aluminum single crystal were in-situ observed using synchrotron X-rays, and the recrystallization behavior was obtained. The specimen was deformed with plastic strain of 8 %, and was heated at 753 K. after 6 minutes from heating, the diffraction from subgrains were appeared in the diffraction pattern of the initial crystal. The subgrains c...
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In-situ Observation during Deformation and Recrystallization of Aluminum Single Crystal using Synchrotron Radiation

In order to ensure the long-term safety of the vitrified radioactive waste, the relationship between number of stirring and characteristics of material strength after melting the raw material glass and simulated vitrified radioactive waste were investigated by synchrotron radiation X-rays. As a result, it was clarified that the internal defects in simulated vitrified radioactive waste increased and the material strength of simulated vitrified radioactive waste was suitable as increasing the number of stirri...
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Evaluation of Material Strength for Soundness of Vitrified Radioactive Waste using Synchrotron Radiation X-rays

The high level radioactive liquid waste is analyzed for the vitrification process control and the vitrified waste quality in the hot cell of Tokai Vitrification Facility, Tokai Reprocessing Plant. There are 8 Master-slave manipulators, 7 lighting equipment, an electronic balance, and an inductively coupled plasma-optical emission spectrometer used for remote operation, securing visibility, total oxide analysis, and elemental analysis in the analytical hot cell. These equipment and analytical apparatus must ...
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Remote maintenance technologies of equipment and analyzing apparatus in hot cell of Tokai Vitrification Facility, Tokai Reprocessing Plant

In order to confine radioactive materials inside the building, buildings, hot-cells and vessels are maintained at a lower air pressure than the atmospheric environment in Tokai Reprocessing Plant. For this purpose, air exhausters are continuously operated. However, during the periodic maintenance of the electric substation in September 2011, the incident in which the vessel ventilation including the spare machine of the highly radioactive liquid waste storage tank have not been started. In this paper, the c...
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Improving the safety of the power supply system by separating the power supply circuit for control in the power distribution board in Tokai reprocessing plant

Highly active liquid waste, which is generated by the reprocessing of spent nuclear fuel, is stored in storage tank of Tokai Reprocessing Plant until it is vitrified. The waste solution in the tank is periodically agitated to avoid the precipitation of insoluble residues during the storage. Three way valves and ball valves have been located at the tank for agitation. Radiation dose rate at the valve location is high and operator’s radiation exposure become a problem. Therefore, measures to reduce radiation ...
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Dose reduction measure in exchange work of valves used for agitation of highly active liquid waste in storage tank

Tokai Reprocessing plant (TRP), which temporarily suspended the reprocessing of spent fuel in 2007, moved to decommissioning in 2018 without restarting operations. Under the decommissioning situation, the high- level radioactive liquid waste generated in the past reprocessing operation is the highest potential risk in TRP. These high-level radioactive liquid wastes are stored in High Active Liquid Waste Storage Facility (HAW) and sequentially Vitrified in Tokai Vitrification Facility (TVF). The serious acci...
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Application of Probability Risk Assessment in TRP and its capability to Maintenance Planning

Low level liquid waste generated from reprocessing of spent nuclear fuel in the Tokai Reprocessing Plant solidified with bitumen from 1982 to 1997. About 30,000 of bituminized wastes were produced, and have stored in the storage facility. Recently, the leakage phenomenon due to the corrosion of bituminized waste drum occurred in the other nuclear facility. Based on the malfunction event, we have advanced the development of remote observation device for grasping soundness of the bituminized waste drums store...
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Development of a remote observation device for radioactive waste drum in the Tokai Reprocessing Plant

Tokai Reprocessing Plant (TRP) is implementing its decommissioning activities based on the decommissioning plan approved by Nuclear Regulation Authority (NRA). In the decommissioning, safety countermeasure against earthquakes and tsunamis is a top priority matter, especially for High Active liquid Waste facility (HAW) and Tokai Vitrification Facility (TVF), which handle highly radioactive liquid waste with high safety risks. This study focuses on the immediate tsunami countermeasures among the other safety ...
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Evaluation of Tsunami debris impact on Tokai Reprocessing Plant

Clean-up activity of spent fuel powder (UO2 powder etc.) in mechanical treatment cell was performed for the purpose of the preparation of decommissioning at TRP.For the clean-up activity, we selected an inexpensive vacuum cleaner and made tools, that was improved taking into account of use by means of a crane or a manipulator in the high dose cell, and applied it after a mock-up test.We report our experience and knowledge provided through this clean-up activity....
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Clean-up activity of spent fuel powder (UO2 powder) in mechanical treatment cell at Tokai reprocessing plant

High active liquid waste (HAW) of about 340 m3 is stored in the HAW tanks at the Tokai Reprocessing Plant. However there is no effective observation method inside the cell installing the HAW tank because of its high dose rate. This time, by utilizing the existing guide rail, design and manufacture of the new device for observation, optimization of the device by mockup, inside the cell observation and dose rate distribution measurement inside the cell were conducted. As the result, we were succeeded in obser...
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Approaches for observation inside the cell storing HAW tank at TRP