Radiation monitoring in the residential environment; Time dependencies of air dose rate and Cs inventory

Yoshimura, Kazuya; Nakama, Shigeo; Fujiwara, Kenso

Journal of Radiation Protection and Research, 47(1), p.30 - 38, 2022/03

https://doi.org/10.14407/jrpr.2021.00199

PSTEP: Project for solar-terrestrial environment prediction

Kusano, Kanya*; Ichimoto, Kiyoshi*; Ishii, Mamoru*; Miyoshi, Yoshizumi*; Yoden, Shigeo*; Akiyoshi, Hideharu*; Asai, Ayumi*; Ebihara, Yusuke*; Fujiwara, Hitoshi*; Goto, Tadanori*; et al.

Earth, Planets and Space (Internet), 73(1), p.159_1 - 159_29, 2021/12

https://doi.org/10.1186/s40623-021-01486-1

The PSTEP is a nationwide research collaboration in Japan and was conducted from April 2015 to March 2020, supported by a Grant-in-Aid for Scientific Research on Innovative Areas from the Ministry of Education, Culture, Sports, Science and Technology of Japan. It has made a significant progress in space weather research and operational forecasts, publishing over 500 refereed journal papers and organizing four international symposiums, various workshops and seminars, and summer school for graduate students at Rikubetsu in 2017. This paper is a summary report of the PSTEP and describes the major research achievements it produced.

Temporal decrease in air dose rate in the sub-urban area affected by the Fukushima Dai-ichi Nuclear Power Plant accident during four years after decontamination works

Nakama, Shigeo; Yoshimura, Kazuya; Fujiwara, Kenso; Ishikawa, Hiroyasu; Iijima, Kazuki

Journal of Environmental Radioactivity, 208-209, p.106013_1 - 106013_8, 2019/11

https://doi.org/10.1016/j.jenvrad.2019.106013

Trends of air dose rate decrease after decontamination works and factors which affect them constitute essential information for radiation protection, such as prediction of external exposure to the public and implementation of measures to reduce such exposure. This study investigated the decrease of air dose rate (ambient dose rate at 1 m above the ground) at 163 points across sub-urban areas in the evacuation zone around the Fukushima Dai-ichi Nuclear Power Plant over the period of four years following the decontamination works carried out in November 2012. The air dose rate on the asphalt pavement decreased faster than on soil surfaces. In addition, air dose rates near the forest decreased at a slower pace than in open fields. These results suggest that the air dose rate in urbanized areas can decrease faster than in other types of land, even after decontamination. Based on comparisons with decrease rates obtained in other studies, the air dose rate tends to decrease faster outside the evacuation zone than inside it. The decrease in air dose rate after decontamination was slower than before decontamination. The contribution of the weathering effect and human activity was estimated to be about 80% and 20% of the ecological decrease rate, respectively.

Decrease in air dose rate after decontamination relating to difference in the ground surface properties

Nakama, Shigeo; Yoshimura, Kazuya; Fujiwara, Kenso; Ishikawa, Hiroyasu; Iijima, Kazuki

KEK Proceedings 2018-7, p.154 - 158, 2018/11

https://lib-extopc.kek.jp/preprints/PDF/2018/1825/1825007.pdf

Decrease in air dose rate in decontaminated area is essential information to estimate external exposure and to facilitate return of local residents, but the factors to control the decrease rate have not been cleared wholly. To clarify the effect of ground surface type (i.e. paved and soil surfaces) on the decrease in air dose rate at 1 m above the ground, surface dose rate at 1 cm above the ground and the air dose rate were monitored for four years since decontamination in 2011, and their decrease rates were compared relating to the ground surface type. Decrease in the air dose rate and the surface dose rate on the asphalt pavement showed faster rates than those on the soil surface. Ratio of decrease in the air dose rate and surface dose rate (decrease rate ratio) was distributed between 0.8 and 1.2 on open place not affected by surrounding environment. Therefore, decrease in the air dose rate was in agreement with the decrease of the surface dose rate, which is greatly affected by the ground surface. It became clear that the decrease rate constant of the air dose rate differs depending on the difference in the ground surface. Furthermore, it was also confirmed that the local soil erosion and sedimentation of the ground surface does not affect the decrease rate of the air dose rate.

Evaluation of application effect of the integrated safeguards approach for MOX fuel fabrication facilities from the operator's viewpoint

Ninagawa, Junichi; Asano, Takashi; Nagatani, Taketeru; Nakajima, Shinji; Nomi, Takayoshi; Fujiwara, Shigeo

Proceedings of INMM 52nd Annual Meeting (CD-ROM), 8 Pages, 2011/07

Japan was transferred to the Integrated Safeguards (IS) scheme in September 2004. The IS approach for JNC-1 site, including PFPF, was developed to improve the efficiency of safeguards while maintaining the effectiveness and has been implemented since August 2008. JAEA has evaluated the validity of the IS approach for PFPF based on the historical performance over about three-year period. As the result of evaluation, JAEA confirmed the improvement of efficiency of inspection activities and the reduction of the impact of inspection activities on plant operation. On the other hand, the IAEA has also evaluated the validity of IS approach and considered to modify based on the result of its evaluation. In order to maintain or improve the validity of the IS approach, JAEA thinks that it will be necessary to work very closely and honestly with the inspectorate to address this modification process.

Development of monitoring system for land transport conditions of nuclear materials

Yamamoto, Kiyoaki; Yuasa, Wataru; Uchida, Shinichi; Inose, Shoichi; Fujiwara, Shigeo

Proceedings of 16th International Symposium on the Packaging and Transport of Radioactive Materials (PATRAM 2010) (CD-ROM), 6 Pages, 2010/10

It is very important to monitor land transport conditions continually in order to implement the safe and smooth transport of nuclear materials, especially to quickly obtain the accurate visual information and carry out emergency response swiftly and properly in the event of transport accident. Plutonium Fuel Development Center of JAEA developed the system for real-time monitoring of transport conditions of nuclear materials. The location information from GPS is transmitted to ground station from transport monitoring equipment installed on vehicle of convoy via the satellite, and transmitted to the TransportControlCenter (TCC) periodically through telephone line. The location information from GPS is also directly transmitted to ground station from transport monitoring equipment by ground wave and transmitted to TCC through telephone line. In both cases, location information is shown on a monitoring panel in TCC. Image monitoring system is one for transmitting motion picture taken by cameras equipped on the roof of vehicle of convoy to TCC through ground wave and showing it on a monitoring panel in TCC. It is also possible to transmit image to TCC with this system, which is taken by the portable camera for emergency response. The camera is taken out of transport monitoring equipment, installed on the proper place, and remotely controlled from TCC. For the development of transport conditions monitoring system, following requirements were considered taking into account the use in emergency response and long-term transport, -Compactness to fit limited space on the vehicles -Applicability for conditions in vibration and temperature change anticipated in transport operation. -Long-term stability and redundancy of power supply The developed system is very useful not only for monitoring normal transport conditions but also for planning emergency response program because it can transmit accurate visual information to TCC in the event of transport accident.

Development of integrated safeguards approach for JNC-1 site from the operator's viewpoint

Asano, Takashi; Fujiwara, Shigeo; Takahashi, Saburo; Nagatani, Taketeru; Fukuhara, Junichi; Kodani, Yoshiki; Kimura, Takashi; Miura, Yasushi

Proceedings of INMM 50th Annual Meeting (CD-ROM), 10 Pages, 2009/00

JAEA commenced to consider the integrated safeguards (IS) approach for JNC-1 site as the new concept of safeguards for further reduction of influence of facility operation by the safeguards activity. On the other hand, the board of governors of IAEA led the broader conclusion to Japan on June 2004 and safeguards implementation in Japan was transferred to the IS scheme in September 2004. IAEA aimed to improve efficiency of safeguards implementation for the plutonium handling facility by optimization of use of advanced safeguards systems and new safeguards regime without reduction of effectiveness of safeguards. The IS approach for JNC-1 site was developed and implemented on August 2008 after many discussions among IAEA, Japan Safeguards Office (JSGO) and JAEA. This paper shows contributions by JAEA to development of this approach from the operator's view point and influence to the operator by implementation of IS approach.

The Remote transmission test of the GUAM measurement data by the wireless LAN

Asano, Takashi; Fujiwara, Shigeo; Takahashi, Saburo; Nemoto, Tadayuki*; Sato, Takashi*; Kuniyasu, Kazufusa*; Hiruta, Kazuhiko*

Kaku Busshitsu Kanri Gakkai (INMM) Nihon Shibu Dai-28-Kai Nenji Taikai Rombunshu (CD-ROM), 11 Pages, 2007/00

JAEA has developed and demonstrated the Remote Monitoring (RM) technology on the safeguards equipment at the storage area in PFPF to improve the efficiency of the inspection activity. JAEA is considering the expansion of the RM technology to the safeguards equipment in the process area to improve the efficiency of the inspection activity under the integrated safeguards. JAEA considers that the cabling cost and work in the facility will be reduced to apply the wireless LAN to the RM technology. JAEA performed the confirmatory testing of the performance of the Glove box Unattended Assay and Monitoring system (GUAM) and the remote transmission of the GUAM measurement data by the wireless LAN in cooperation with Japan Nuclear Fuel Limited. In this test, JAEA confirmed it's possible to establish the wireless LAN networking in the process area. This paper reports the applicability of the wireless LAN to the RM technology based on the results of the confirmatory testing.

The Future Plan and Effects of the Remote Monitoring System in PFPF

Ninagawa, Junichi; Takahashi, Saburo; Fujiwara, Shigeo; Asano, Takashi

45th Annual Meeting of the Institute of Nuclear Ma, 0 Pages, 2004/00

JNC has developed a Remote Monitoring System (RMS) for unattended mode NDA in corporation with Los Alamos National Laboratory (LANL) under a JNC/DOE safeguards cooperation agreement. The purpose of this development is to improve the efficiency of safeguards activities for both the operator and the inspectors, and to improve transparency of nuclear material management. As a result of the field trials, technical problems of the RMS have been mostly resolved. Therefore, the JNC is evaluating how the RMS may contribute to the efficiency of safeguards activities by step-by-step implementation of RMS to PFPF in near future. Extending the RMS into not only storage areas, but also fuel fabrication process areas, has the possibility of reduction of actual visits to the facility. There is also the possibility of reduction of impact on facility operations. This paper describes the plans of JNC and LANL for applying RMS at PFPF.

Experience and achievement on safeguards by design for Plutonium Fuel Production Facility (PFPF)

Ninagawa, Junichi; Nagatani, Taketeru; Asano, Takashi; Fujiwara, Shigeo

no journal, , 

Fully automated MOX fuel fabrication process was positively introduced at the PFPF to improve fuel production capability and to reduce personal radiation exposure which is caused by handling of large amount of plutonium. From the viewpoint of safeguards, some disadvantages were supposed by introduction of the automated process (e.g. difficulty of access to the nuclear material, etc.). Therefore, JAEA developed a concept of the safeguards approach for the PFPF so as to obtain compatibility of safeguards with facility operation from the early stage of design phase, and developed advance safeguards systems based on this results. Thus, efficiency and effectiveness of safeguards were improved with the minimum impact on the facility operation. Furthermore, these efforts contributed to the development of the Integrated Safeguards approach implemented to JNC-1 site on August 1st 2008. This paper shows experience and achievement on "safeguards by design" for the PFPF.