Evaluation on activation activity of radioactive materials remaining in JMTR Reactor Facility

Nagata, Hiroshi; Otsuka, Kaoru; Omori, Takazumi; Ide, Hiroshi

JAEA-Technology 2022-017, 113 Pages, 2022/08

JAEA-Technology-2022-017.pdf:6.17MB

Japan Materials Testing Reactor (JMTR) was decided as a one of decommission facilities in April 2017. The activation activity of radioactive materials remaining in the reactor facility was evaluated in order to submit the decommissioning plan to the Nuclear Regulation Authority. Total activation activity was 9.310 Bq after the permanent shutdown of reactor, 2.710 Bq after 21 years, 1.010 Bq after 40 years and 2.410 Bq after 100 years. The structure with high activation activity was the core structural materials in JMTR such as beryllium frame, aluminum reflector, etc., and the material was stainless steel, beryllium, etc. The ratio of nuclides to the total amount of activated radioactivity was highest in H-3 until about 40 years after the reactor shutdown, and then in Ni-63. For reference, the radioactivity level was classified based on the results of the obtained radioactivity concentration. The ratio of the weight of each radioactivity level to the total weight was 0.3-0.4% (10-13t) for L1, 0.0-0.4% (0-14t) for L2, 1.0-1.2% (32-39t) for L3 and 98.0-98.7% (about 3200t) for CL until 100 years after the reactor shutdown. It was found that those classified as CL account for more than 90% of the total. When treating and disposing of radioactive waste, evaluation will be carried out based on appropriate methods, including evaluation results of secondary pollutants.

Evaluation on activation activity of reactor in JRR-2 applied 3 dimensional model to neutron flux calculation

Kishimoto, Katsumi; Arigane, Kenji*

JAERI-Tech 2005-016, 83 Pages, 2005/03

JAERI-Tech-2005-016.pdf:10.52MB

Revaluation to activation activity of reactor evaluated at the notification of dismantling submitted in 1997 was carried out in JRR-2 where decommissioning was advanced now. In the revaluation, estimation accuracy on neutron streaming at various horizontal experimental tubes was improved by applying 3 dimensional model to neutron transport calculation that had been carried out by 2 dimensional model, and calculating with TORT. As the result, excessive overestimations on horizontal experimental tubes and biological shield that had greatly contributed to total activation activity in evaluation at the notification of dismantling was revised, sum of their activation activities in the revaluation decreased to 1/18(case after 1 year from the permanent shutdown of reactor) of evaluation at the notification of dismantling, and the structural materials that had large activation activity were changed. By the above, it was shown that introducing 3 dimensional model was effective in evaluation on activation activity of the research reactor that had a lot of various experimental tubes.

JRR-2 decommissioning activity, 1

Nakano, Masahiro; Arigane, Kenji; Okawa, Hiroshi; Suzuki, Takeshi; Kishimoto, Katsumi; Terunuma, Akihiro; Yano, Masaaki; Sakuraba, Naotoshi; Oba, Nagamitsu

JAERI-Tech 2003-072, 92 Pages, 2003/08

JAERI-Tech-2003-072.pdf:6.99MB

The decommissioning plan of the Japan Research reactor No2(JRR-2), decommissioning activities until the first half of phase-3, radioactive wastes and exposure dose of workers are described in this report. Since the first criticality in October 1960, JRR-2 had been operated about 36 years for various experiments. However, JRR-2 was permanent shutdown in December 1996 based on JAERI's long term plan, and the decommissioning of the JRR-2 was started in August 1997. Decommissioning of the JRR-2 was planed for 11 years from 1997 to 2007 and the program was divided into 4 phases. The decommissioning activities of the phase-1, phase-2 and the first half of phase-3 had already completed as planned in March 1998, February 2000, March 2002, respectively. The decommissioning activities of the later half of Phase-3 (dismantling of the reactor cooling systems) are carrying out at present time with planed 2002 and 2003 fiscal years.

Annual report of Department of Research Reactor 2001; April 1, 2001 - March 31, 2002

Department of Research Reactor

JAERI-Review 2002-033, 215 Pages, 2002/12

JAERI-Review-2002-033.pdf:16.19MB

no abstracts in English

Study on residual radioactive inventory estimation in reactor decommissioning program (Contract research)

Sukegawa, Takenori; Hatakeyama, Mutsuo; Yanagihara, Satoshi

JAERI-Tech 2001-058, 81 Pages, 2001/09

JAERI-Tech-2001-058.pdf:5.98MB

In general, neutron transport and activation calculation codes are used for residual radioactive inventory estimation; however, it is essential to verify calculations by measurement results because of geometrical complexity of the reactor and so on. The comparison between measured and calculated radioactivity in the JPDR core components showed a relatively good agreement (factor of 2), and it was cleared that water content and weight ratio of steel bars to concrete materials significantly influenced the neutron flux distribution in the biological shield (factor of 2-10 error). The measured radioactivity inside of the reactor pressure vessel wall and at the inner part of the biological shield was compared in detail with the calculations to verify the methodology applied to calculations of radioisotope production. Then it was found that the radioactive inventory could be estimated accurately with combination of calculations and measurement of radioactivity in samples and dose rate distribution for planning of dismantling activities.

Evaluation of methodology on radioactive inventory estimation in the Japan power demonstration reactor decommissioning program

Sukegawa, Takenori; Hatakeyama, Mutsuo; Yanagihara, Satoshi

Journal of Nuclear Science and Technology, 37(Suppl.1), p.367 - 371, 2000/03

https://doi.org/10.1080/00223131.2000.10874908

no abstracts in English

Design concept of disposal systems for highly activated waste

Okoshi, Minoru; Abe, Masayoshi; Yoshimori, Michiro; Sakai, Akihiro

Proc. of Waste Management'98 (CD-ROM), 5 Pages, 1998/00

no abstracts in English

The Japan power demonstration reactor dismantling project; Radiation control

;

Dekomisshoningu Giho, 0(15), p.24 - 34, 1996/12

http://www.randec.or.jp/publish/documents/gihou/Decommissioning%20gihou_15.pdf

no abstracts in English

Contamination control, clearing and radiation monitoring in nuclear research facilities

Ikezawa, Yoshio

Saikin No Kenkyu Shisetsu, 0, p.304 - 311, 1995/00

no abstracts in English

Development of code system for management of reactor decommissioning(COSMARD), I; Description of project management data calculation facility and its user guide

Yanagihara, Satoshi;

JAERI-M 94-005, 61 Pages, 1994/02

JAERI-M-94-005.pdf:1.84MB

no abstracts in English