Study on criticality safety control of fuel debris for validation of methodology applied to the safety regulation

Suyama, Kenya; Ueki, Taro; Gunji, Satoshi; Watanabe, Tomoaki; Araki, Shohei; Fukuda, Kodai; Yamane, Yuichi; Izawa, Kazuhiko; Nagaya, Yasunobu; Kikuchi, Takeo; et al.

Proceedings of 12th International Conference on Nuclear Criticality Safety (ICNC2023) (Internet), 6 Pages, 2023/10

To remove and store safely the fuel debris generated by the severe accident of the Fukushima Daiichi Nuclear Power Station in 2011 is one of the most important and challenging topics for decommissioning of the damaged reactors in Fukushima. To validate the adopted method for the evaluation of criticality safety control of the fuel debris through comparison with the experimental data obtained by the criticality experiments, the Nuclear Regulation Authority (NRA) of Japan funds a research and development project which was entrusted to the Nuclear Safety Research Center (NSRC) of Japan Atomic Energy Agency (JAEA) from 2014. In this project, JAEA has been conducting such activities as i) comprehensive computation of the criticality characteristics of the fuel debris and making database (criticality map of the fuel debris), ii) development of new continuous energy Monte Carlo code, iii) evaluation of criticality accident and iv) modification of the critical assembly STACY for the experiments for validation of criticality safety control methodology. After the last ICNC2019, the project has the substantial progress in the modification of STACY which will start officially operation from May 2024 and the development of the Monte Carlo Code "Solomon" suitable for the criticality calculation for materials having spatially random distribution complies with the power spectrum. We present the whole picture of this research and development project and status of each technical topics in the session.

Long term treatment of waste TBP/n-dodecane with steam reforming system

Sone, Tomoyuki; Nakagawa, Akinori; Koyama, Hayato; Gunji, Kiyoshi; Nonaka, Kazuharu; Sasaki, Toshiki; Tashiro, Kiyoshi; Yamashita, Toshiyuki

JAEA-Technology 2009-023, 33 Pages, 2009/06

JAEA-Technology-2009-023.pdf:8.11MB

Steam reforming (SR) method consists of the gasification process in which organics are vaporized and decomposed with superheated steam and the oxidation process in which vaporized organics are decomposed by oxidizing reaction with heated air. 2,500L of waste TBP/n-dodecane contaminated with uranium was treated using the demonstration scale steam reforming system to examine the performance of the system. Results obtained in this study show that the temperature in the SR system was controlled under the self-regulation temperature, the concentration of CO and NOx in the off-gas were controlled less than 100ppm and 250ppm respectively, the distribution ratio of uranium to off-gas treatment system was under 0.12% and the gasification ratio of waste TBP was more than 99%. This long-term waste treatment test has demonstrated that the SR system can safely and effectively reduce the volume of the waste.

Progress of environmental sampling program at Japan Atomic Energy Research Institute

Nishimura, Hideo; Magara, Masaaki; Hanzawa, Yukiko; Esaka, Fumitaka; Takahashi, Tsukasa; Gunji, Katsubumi; Miyamoto, Yutaka; Yasuda, Kenichiro; Tsuruta, Yasuhiro; Tsuda, Shinji; et al.

Heisei 11-Nendo Hosho Sochi Semina Koenroku Tekisuto, p.95 - 107, 2000/01

no abstracts in English

Program to develop analytical techniques for ultra trace amounts of nuclear materials in environmental samples

Hanzawa, Yukiko; Magara, Masaaki; Esaka, Fumitaka; Watanabe, Kazuo; Usuda, Shigekazu; Gunji, Katsubumi; Yasuda, Kenichiro; Takahashi, Tsukasa; Nishimura, Hideo; Adachi, Takeo; et al.

Proceedings of the Institute of Nuclear Materials Management 40th Annual Meeting (CD-ROM), 7 Pages, 1999/00

no abstracts in English

The Operational and maintenance experience of the fuel handling facility of "JOYO" (5)

Sekiguchi, Mineo*; *; *; *; *; *; *

PNC TN9410 87-124, 392 Pages, 1987/09

PNC-TN9410-87-124.pdf:11.38MB

The fuel handling facility was set up in oct. 1974. The operational tests were done in three phases successively, first in air, then in argone gas and finally under sodium at 250C. Initial fuel loading for criticality of "Joyo" started in March 1977 and the criticality was achieved in April. After this, lower power test, power up test for 50 MW, 50 MW cycle operations, power up test for 75 MW, and 75 MW cycle operations followed till Dec. 1981. After the core conversion from the Breeding Core (MK-I Core) to the Irradiation Core (MK-II Core), 100 MW power achieved in March 1983 and the 100 MW cycle operation is going well now. In the meanwhile, the fuel handling facility transfered about 600 core assemblies and were checked five times as the regular inspection. This report reviews the experiences of operation and maintenance of the fuel handling facility from Jan. 1983 to Dec. 1985.

MK-II Core conversion activities result in the experimental fast reactor "Joyo""

*; *; *; *; *; *; *

PNC TN941 83-27VOL1, 827 Pages, 1983/02

PNC-TN941-83-27VOL1.pdf:25.12MB

In the Experimental Fast Reactor "Joyo", Core Conversion from the Breeding Core (MK-I Core) to the Irradiation Core (MK-II Core) was begun in January 1982. Core Conversion required the refueling of 290 core elements, reconstruction of the control rod drive mechanism, and change-out of both the upper guide tube and lower guide tube of the control rods. The schedule for these activities was planned carefully to achieve 100MWt power in March 1983. Joyo achieved MK-II core initial criticality on November 22, 1982, on schedule and immediately began core characterzation. As the result of the Core Conversion activities, we handled many core elements, twice as many as before this core conversion, and in so doing obtained many kinds of experience and data for maintenance and operation of the refueling system. This report describes the considerable pre-conversion activities and planning, and the accomplishments and results of these Core Conversion activities.