Development of risk assessment code for dismantling of radioactive components in decommissioning stage of nuclear reactor facilities

Shimada, Taro; Sasagawa, Tsuyoshi; Miwa, Kazuji; Takai, Shizuka; Takeda, Seiji

Proceedings of International Conference on Environmental Remediation and Radioactive Waste Management (ICEM2023) (Internet), 7 Pages, 2023/10

https://doi.org/10.1115/ICEM2023-109848

Nuclear regulatory inspection should be performed on the basis of the risk information during the decommissioning phase of the nuclear power plant. However, it is difficult because the methodology for quantitatively assessing the radiation exposure risk during decommissioning activities has not been established. Therefore, a decommissioning risk assessment code, DecAssess-R, has been developed based on the decommissioning safety assessment code, DecAssess, which creates event trees from initiating events and evaluates the radiation risk resulting from public exposure dose for each accident sequence. The assessment took into account that mobile radioactive inventories that can be easily dispersed in the work area, such as radioactive dust accumulated in HEPA filters attached to a contamination control enclosure, will fluctuate with the progress of the decommissioning work. Initiating events were selected based on the investigation of accidents and malfunctions during dismantling, disassembly, and component replacement activities around the world, and event trees were created from the initiating events to indicate the progress scenario. The frequencies of occurrence were determined with reference to general industry data in addition to the above accidents and malfunctions, and the probabilities of event progression were determined with reference to failure data during the operation phase. The exposure risks during dismantling of components in the reference BWR were evaluated. As a result, the public exposure dose was maximum in case of fire during dismantling of reactor internals and fire spread to combustibles and filters, including radioactivity temporarily stored in the work area. The exposure risk was also maximum because the probability of occurrence of this accident sequence was greater than that of other scenarios.

Comprehensive exposure assessments from the viewpoint of health in a unique high natural background radiation area, Mamuju, Indonesia

Nugraha, E. D.*; Hosoda, Masahiro*; Kusdiana*; Untara*; Mellawati, J.*; Nurokhim*; Tamakuma, Yuki*; Ikram, A.*; Syaifudin, M.*; Yamada, Ryohei; et al.

Scientific Reports (Internet), 11(1), p.14578_1 - 14578_16, 2021/07

https://doi.org/10.1038/s41598-021-93983-2

Mamuju is one of the regions in Indonesia which retains natural conditions but has relatively high exposure to natural radiation. The goals of the present study were to characterize exposure of the entire Mamuju region as a high natural background radiation area (HNBRA) and to assess the existing exposure as a means for radiation protection of the public and the environment. A cross-sectional study method was used with cluster sampling areas by measuring all parameters that contribute to external and internal radiation exposures. It was determined that Mamuju was a unique HNBRA with the annual effective dose between 17 and 115 mSv, with an average of 32 mSv. The lifetime cumulative dose calculation suggested that Mamuju residents could receive as much as 2.2 Sv on average which is much higher than the average dose of atomic bomb survivors for which risks of cancer and non-cancer diseases are demonstrated. The study results are new scientific data allowing better understanding of health effects related to chronic low-dose-rate radiation exposure and they can be used as the main input in a future epidemiology study.

Preparedness and response for nuclear or radiological emergency as a designated public corporation

Okuno, Hiroshi; Okamoto, Akiko; Ebine, Noriya; Hayakawa, Tsuyoshi; Tanaka, Tadao

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 15 Pages, 2019/05

In the event of a nuclear or radiological emergency, the Japan Atomic Energy Agency (JAEA) as a designated public corporation assigned in the Disaster Countermeasures Basic Act of Japan undertakes a role to support the national government and local governments. This paper (1) illuminates the roles of the JAEA as a designated public corporation for preparedness and response to a nuclear or radiological emergency of nuclear facilities; (2) summarizes emergency response activities of the JAEA in accordance with its Disaster Management Operation Plan against the off-site radiological emergencies attributed to a loss of control of the Tokyo Electric Power Company (TEPCO)'s Fukushima Daiichi Nuclear Power Station that occurred in 2011; and (3) reports its activities in normal times especially participation in the drills organized by the national government and local governments in the light of the Basic Disaster Management Plan of Japan and Local Disaster Management Plans of prefectural governments, respectively.

Lessons learned in protection of the public for the accident at the Fukushima Daiichi Nuclear Power Plant

Callen, J.*; Homma, Toshimitsu

Health Physics, 112(6), p.550 - 559, 2017/06

https://doi.org/10.1097/HP.0000000000000666

What insights can the accident at the Fukushima Daiichi Nuclear Power Plant provide in the reality of decision making on actions to protect the public during a severe reactor and spent fuel pool emergency? In order to answer this question, and with the goal of limiting the consequences of any future emergencies at a nuclear power plant due to severe conditions, this article presents the main actions taken in response to the emergency in the form of a timeline. The focus of this paper are those insights concerning the progression of an accident due to severe conditions at a light water reactor nuclear power plant that must be understood in order to protect the public.

Annual report of Nuclear Emergency Assistance and Training Center (April 1, 2014 - March 31, 2015)

Nuclear Emergency Assistance and Training Center

JAEA-Review 2016-005, 55 Pages, 2016/05

JAEA-Review-2016-005.pdf:3.61MB

The Japan Atomic Energy Agency, JAEA, is a designated public institution under the Disaster Countermeasures Basic Act and under the Armed Attack Situations Response Act. Based on these Acts, the JAEA has the responsibility of providing technical support to the national government and/or local governments in case of nuclear and/or radiological incidents. In order to fulfill the tasks as the designated public institution, the JAEA has established the Emergency Action Plan and the Civil Protection Action Plan. In case of a nuclear/radiological emergency, the Nuclear Emergency Assistance and Training Center (NEAT) dispatches specialists of JAEA, supplies the national government and local governments with emergency equipment and materials, and gives them technical advice and information. In normal time, NEAT provides various exercises and training courses concerning nuclear preparedness and response to emergency responders including the national and local government officers, in addition to the JAEA staff members. The NEAT also researches nuclear emergency preparedness and response, and cooperates with international organizations on the above research theme. In the FY2014, the NEAT accomplished the following tasks: (1) Technical support activities as a designated public institution in cooperation with the national and local governments, (2) Human resource development, exercise and training of nuclear emergency responders for the national and local governments, (3) Researches on nuclear emergency preparedness and response, and release to the public as useful information, (4) Technical contributions to Asian countries on nuclear emergency preparedness and response in collaboration with the international organizations.

ICRP Publication 116 "Conversion Coefficients for Radiological Protection Quantities for External Radiation Exposures"; Summary

Endo, Akira

Isotope News, (736), p.34 - 37, 2015/08

http://www.jrias.or.jp/books/pdf/201508_TRACER_ENDO.pdf

Japanese translation of ICRP Publication 116 entitled "Conversion Coefficients for Radiological Protection Quantities for External Radiation Exposures" was published by the Japan Radioisotope Association in March 2015. The book gives fluence to dose conversion coefficients for both effective dose and organ absorbed doses for various types of external exposures, consistent with the 2007 Recommendations of the ICRP. A complete set of conversion coefficients is provided in an accompanying CD in ASCII format and Microsoft Excel software. This article overviews ICRP Publication 116 and its impact to practice of radiation protection.

Periodical public opinion survey on nuclear energy; Inhabitants living Tokyo metropolitan area

Shinoda, Yoshihiko; Tsuchida, Shoji*; Kimura, Hiroshi*

Nihon Genshiryoku Gakkai Wabun Rombunshi, 13(3), p.94 - 112, 2014/09

https://doi.org/10.3327/taesj.J13.018

Fukushima Daiichi Nuclear Power Plant accident (Fukushima accident) has brought about a great change in many people's perceptions about nuclear power plant safety. When discussing future energy options for Japan, it is important to have a full grasp of the attitude of a large number of people towards nuclear energy. The Atomic Energy Society of Japan has conducted annual questionnaire survey of 500 adults who live within 30 kilometers of Tokyo Station. The aim of this survey is to assess trends in public attitude towards nuclear energy. The authors that designed the questionnaire entries of this survey have been managing questionnaire data as members of the Data Management Working Group under the Social and Environmental Division of the Atomic Energy Society of Japan. We confirmed the change in public attitude towards nuclear energy through this periodical survey after the Fukushima accident. In particular, public concerns about the use of nuclear energy increased after the Fukushima accident, and many people have raised doubts over the use of nuclear energy in the future.

Proceedings of 3rd International Symposium on Radiation Education, ISRE 04; August 23-26, 2004, Nagasaki Brick Hall, Nagasaki, Japan

Office of Planning

JAERI-Conf 2005-001, 620 Pages, 2005/03

JAERI-Conf-2005-001-1.pdf:62.9MB
JAERI-Conf-2005-001-2.pdf:47.33MB

The Third International Symposium on Radiation Education was held on August 23-26, 2004 at Nagasaki, Japan. The fundamental knowledge of radiation and related nuclear matters should be properly communicated to students and general public. The symposium has been devoted to developing an effective method of radiation education. To remove unnecessary fears for radiation and to utilize radiation and nuclear energy to contribute to the human welfare, the spirit of radiation education was first announced internationally in 1998 at Hayama, Japan, and then confirmed in 2002 at Debrecen, Hungary, and now was reassured in August 2004 at Nagasaki. The symposium consisted of 5 sessions with 77 submitted papers, and involved 141 participants from 13 countries.

Towards to realize a quake-proof information control and management system for nuclear power plant

Nakajima, Norihiro; Kimura, Hideo; Higuchi, Kenji; Aoyagi, Tetsuo; Suzuki, Yoshio; Hirayama, Toshio; Yagawa, Genki

Dai-23-Kai Nihon Shimyureshon Gakkai Taikai Happyo Rombunshu, p.117 - 120, 2004/06

The pablic acceptance of nuclear power plants operations requests information of status for the safety and ease. Previous technology in computational scinece is generarlly carried out the analysis as an uniform structure, although the plants are assembled by thousand of parts. The proposed approach is to develope assembled structural analysis and fluid/heat analyis in assembled structures under the natural and actual environmnet such as daily operation, small quakeing which does not induce shut down procedure, and so on.

Dose evaluation with ICRP Publication 60 at postulated accidents of NSRR, 2003

Kashima, Yoichi; Taki, Mitsumasa; Kikuchi, Masamitsu; Sasajima, Hideo; Nakamura, Takehiko

JAERI-Tech 2003-088, 100 Pages, 2003/12

JAERI-Tech-2003-088.pdf:5.55MB

A new experiment plan is in progress to perform pulse-irradiation experiments at the NSRR with irradiated fuel rods in the high temperature and high pressure capsules. This report describes the results of the public dose evaluation for the design basis accident and postulated accidents with the models that follow the ICRP Publication 60. It was confirmed that the results met the criteria for safety design and siting with ample margins.