Inspection of radioactive waste packages stored in the Waste Storage Facility L; Planning and trial operation

Kawahara, Takahiro; Suda, Shoya; Fujikura, Toshiki; Masai, Seita; Omori, Kanako; Mori, Masakazu; Kurosawa, Tsuyoshi; Ishihara, Keisuke; Hoshi, Akiko; Yokobori, Tomohiko

JAEA-Technology 2023-020, 36 Pages, 2023/12

JAEA-Technology-2023-020.pdf:2.79MB

We have been storing drums containing radioactive waste (radioactive waste packages) at waste storage facilities. We have been managing radioactive waste packages along traditional safety regulations. However, over 40 years has passed from a part of them were brought in pit-type waste storage facility L. Most of them are carbon steel 200 L drums, and surface of them are corroded. For better safety management, we started to take drums out from the pit and inspect them in FY 2019. After each inspection, we repair them or remove the contents of the drum and refill new drums if necessary. In this report, we will introduce the planning, the review of the plan, and the trial operation of this project.

Rearrangement works of unbalanced waste packages by influence of the Great East Japan Earthquake

Ishihara, Keisuke; Kanazawa, Shingo; Kozawa, Masachiyo; Mori, Masakazu; Kawahara, Takahiro

JAEA-Technology 2017-002, 27 Pages, 2017/03

JAEA-Technology-2017-002.pdf:21.88MB

At radioactive waste management facilities in the Nuclear Science Research Institute, solid radioactive wastes are stored by using containers such as 200L drums and pallets to tier containers in 2 to 4 stacks in the height direction in waste storage facilities (Waste Storage Facility No.1, Waste Storage Facility No.2 and Waste Size Reduction and Storage Facility). On March 11, 2011, the Great East Japan Earthquake was happened, and some waste packages dropped from their pallets and large number of waste packages moved from their original position and inclined due to the influence of the earthquake in the waste storage facilities. There was no experience of rearrangement works to set those dropped and unbalanced waste packages in their original position and it was necessary to prepare detailed work procedures and progress for this task to prevent the occurrence of industrial accidents. Therefore, we prepared detailed work manual and repeatedly carried out mock-up test. And then, we started rearrangement work from April 2011 after confirmation of workers skill and adequacy of the work manual. Finally, all rearrangement works for stored waste packages took about four and half years and were completed in September 2015 without any accident and shutdown of storage function. This report summarizes the countermeasures to reduce exposure doses of workers and to prevent the occurrence of industrial accidents during the rearrangement works.

Replacement of upper core structure in experimental fast reactor Joyo, 1; Existing damaged upper core structure jack-up test

Ito, Hiromichi; Suzuki, Nobuhiro; Kobayashi, Tetsuhiko; Kawahara, Hirotaka; Nagai, Akinori; Sakao, Ryuta*; Murata, Chotaro*; Tanaka, Junya*; Matsusaka, Yasunori*; Tatsuno, Takahiro*

Proceedings of 2015 International Congress on Advances in Nuclear Power Plants (ICAPP 2015) (CD-ROM), p.1058 - 1067, 2015/05

In the experimental fast reactor Joyo (Sodium-cooled Fast Reactor (SFR)), it was confirmed that the top of the irradiation test sub-assembly had bent onto the in-vessel storage rack as an obstacle and had damaged the upper core structure (UCS). There is a risk of deformation of the UCS and guide sleeve (GS) caused by interference between them unless inclination is controlled precisely. To mitigate the risk, special jack-up equipment for applying three-point suspension was developed. The existing damaged UCS (ed-UCS) jack-up test using the jack-up equipment was conducted on May 7, 2014. As a result of this test, it was confirmed that the ed-UCS could be successfully jacked-up to 1000 mm without consequent overload. The experience and knowledge gained in the ed-UCS jack-up test provides valuable insights and prospects not only for UCS replacement but also for further improving and verifying repair techniques in SFRs.

Negative-U system of carbon vacancy in 4H-SiC

Son, N. T.*; Trinh, X. T.*; Lvile, L. S.*; Svensson, B. G.*; Kawahara, Kotaro*; Suda, Jun*; Kimoto, Tsunenobu*; Umeda, Takahide*; Isoya, Junichi*; Makino, Takahiro; et al.

Physical Review Letters, 109(18), p.187603_1 - 187603_5, 2012/11

https://doi.org/10.1103/PhysRevLett.109.187603

Inspection and repair techniques in reactor vessel of sodium cooled fast reactor, 9-3; Replacement of UCS

Ota, Katsu; Ito, Hiromichi; Ushiki, Hiroshi; Yoshihara, Shizuya; Tobita, Shigeharu; Kawahara, Hirotaka; Hara, Masahide*; Okazaki, Hiroyoshi*; Tanaka, Junya*; Tatsuno, Takahiro*

no journal, , 

no abstracts in English