Removal of spent fuel sheared powder for decommissioning of Main Plant

Nishino, Saki; Okada, Jumpei; Watanabe, Kazuki; Furuuchi, Yuta; Yokota, Satoru; Yada, Yuji; Kusaka, Shota; Morokado, Shiori; Nakamura, Yoshinobu

JAEA-Technology 2023-011, 39 Pages, 2023/06

JAEA-Technology-2023-011.pdf:2.51MB

Tokai Reprocessing Plant (TRP) which shifted to decommissioning phase in 2014 had nuclear fuel materials such as the spent fuel sheared powder, the diluted plutonium solution and the uranium solution in a part of the reprocessing main equipment because TRP intended to resume reprocessing operations when it suspended the operations in 2007. Therefore, we have planned to remove these nuclear materials in sequence as Flush-out before beginning the decommissioning, and conducted removal of the spent fuel sheared powder as the first stage. The spent fuel sheared powder that had accumulated in the cell of the Main Plant (MP) as a result of the spent fuel shearing process was recovered from the cell floor, the shearing machine and the distributor between April 2016 and April 2017 as part of maintenance. Removing the recovered spent fuel sheared powder was conducted between June 2022 and September 2022. In this work, the recovered powder was dissolved in nitric acid at the dissolver in a small amount in order to remove it safely and early, and the dissolved solution was sent to the highly radioactive waste storage tanks without separating uranium and plutonium. Then, the dissolved solution transfer route was rinsed with nitric acid and water. Although about 15 years had passed since previous process operations, the removing work was successfully completed without any equipment failure because of the organization of a system that combines veterans experienced the operation with young workers, careful equipment inspections, and worker education and training. Removing this powder was conducted after revising the decommissioning project and obtaining approval from the Nuclear Regulation Authority owing to operating a part of process equipment.

Clean-up activity of spent fuel powder (UO powder) in mechanical treatment cell at Tokai Reprocessing Plant

Furuuchi, Yuta; Sato, Shinji; Yatabe, Hitoshi; Yokota, Satoru; Yamada, Takashi; Yahagi, Fumio; Terunuma, Hirotaka; Tokoro, Takeshi; Takahashi, Akihiro; Iijima, Shizuka; et al.

no journal, , 

Clean-up activity of spent fuel powder (UO powder) 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.

Rationalization of maintenance at the Krypton Recovery Development Facility by adding nitrogen replacement equipment and removing liquid nitrogen storage tank

Furuuchi, Yuta; Okada, Jumpei; Kimura, Norimichi*; Watanabe, Kazuki; Hayashi, Yoshitsugu*; Hirayama, Yusuke*; Tashiro, Yoshiyuki*; Uchida, Naoki

no journal, , 

At Krypton Recovery Development Facility in Tokai Reprocessing Plant (TRP), the nitrogen gas, which was supplied from the liquid nitrogen tank, was used instead of compressed air to manage the enclosure function of the facility during the compressor was broken. It was necessary to remove the liquid nitrogen tank possible because it had the possibility of being tsunami debris which affect significant impact on the other TRP facility. Before the tank removal, the automatic switching function was attached to the air compressors as nitrogen replacement equipment. This function switches the starting and stopping the compressors, opening and closing valves after detection of equipment failure. When attaching this function, additional equipment was minimized by utilizing existing equipment. Then, the liquid nitrogen tank was dismantled after transporting outside TRP. These works eliminated the cost of purchasing liquid nitrogen and inspections of the equipment.