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Sr (
Sr) from port of Fukushima Daiichi Nuclear Power Plant; Analysis of the temporal variation from the accident to March 2022 and evaluation of its impact on Fukushima coast and offshore areasMachida, Masahiko; Iwata, Ayako; Yamada, Susumu; Otosaka, Shigeyoshi*; Kobayashi, Takuya; Funasaka, Hideyuki*; Morita, Takami*
Nihon Genshiryoku Gakkai Wabun Rombunshi (Internet), 22(4), p.119 - 139, 2023/11
We estimate monthly discharged inventory of Sr from port of Fukushima Daiichi Nuclear Power Plant (1F) from Jun. 2013 to Mar. 2022 by using the Voronoi tessellation method inside the port, following the monitoring of Sr sea water radioactivity concentration inside the port. The results suggest that the closure of sea side impermeable wall is the most effective for the reduction of discharged one. In addition, the results roughly reveal the monthly discharged inventory required to observe visible enhancement of the sea radioactivity concentration from the background level in each area. Such outcome is significant for considering environmental impacts on the planned future releasing of the treated water accumulated in 1F site.
Machida, Masahiko; Iwata, Ayako; Yamada, Susumu; Otosaka, Shigeyoshi*; Kobayashi, Takuya; Funasaka, Hideyuki*; Morita, Takami*
Journal of Nuclear Science and Technology, 60(3), p.258 - 276, 2023/03
Times Cited Count：1 Percentile：31.61(Nuclear Science & Technology)We estimate monthly discharge inventory of tritium from the port of Fukushima Dai-ichi Nuclear Power Plant (1F) from Jun. 2013 to Mar. 2020 using the Voronoi tessellation scheme, following the tritium monitoring results inside the port started in Jun. 2013. As for the missing period from the first month of 1F accident, Apr. 2011 to May 2013, we calculate the tritium discharge inventory by utilizing the concentration ratio of tritium to 
Cs in stagnant contaminant water during the initial direct run-off period until Jun. 2011 and the discharge inventory correlation between tritium and Cs for the next-unknown continuous-discharge period from Jul. 2011 to May 2013. From all the estimated results over 9 years, we find that the monthly discharge inventory sharply dropped immediately after closing the seaside impermeable wall in Oct. 2015 and consequently coincided well with the sum of input inventories of drainage water and subdrain etc. purified water into the port. By comparing the above estimated results with those in the normal operation period before the accident, we point out that the discharge inventory from 1F port after the accident is not so large. Even the estimation value for the accident year 2011 is found to be comparable to the maximum of operating pressurized water reactors releasing relatively large inventories in the order. At the national level, the total domestic release inventory in Japan significantly decreased after the accident owing to the operational shutdown of most plants. Furthermore, the total Japanese discharge inventory including 1F are found to be minor compared with those of nuclear reprocessing plants and heavy-water reactors on a worldwide level. From the above results, we suggest that various scenarios can be openly discussed regarding the management of tritium stored inside 1F with the help of the present estimated data and its comparison with the past discharge inventory as well as those of other nuclear facilities.
Machida, Masahiko; Iwata, Ayako; Yamada, Susumu; Otosaka, Shigeyoshi*; Kobayashi, Takuya; Funasaka, Hideyuki*; Morita, Takami*
Nihon Genshiryoku Gakkai Wabun Rombunshi (Internet), 22(1), p.12 - 24, 2023/01
We estimate inventory of tritium in two sea areas corresponding to coastal and offshore ones around Fukushima Daiichi Nuclear Power Plant (1F) based on the measurement results of sea-water tritium concentration monitored constantly from 2013 to Jan. 2021 by using Voronoi tessellation scheme. The obtained results show that the offshore area inventory and its temporal variation amount correspond to approximately 1/5 and 1/40 of that of the treated-water accumulated inside 1F, respectively. These results just suggest that the presence of tritium already included in sea-water as the background is non negligible in evaluating the environmental impact by releasing the accumulated treated-water into the sea region. We also estimate the offshore area inventory before 1F accident and find that it had exceeded over 1F stored inventory over about 30 years from 1960s to 1980s with approximately 4 times larger in the peak decade, 1960s. This fact means that we had already experienced more contaminated situation over 30 years in the past compared to the conservative case appeared by just releasing whole the present 1F inventory. Here, it should be also emphasized that the past contaminated situation was shared by the entire world. We further extend the estimation region into a wider region including an offshore area from Miyagi to Chiba prefectures and find that the area average inventory is now comparable to a half of the present 1F one. Finally, we estimate internal dose per year via ingesting fishes caught inside the area when 1F inventory is just added inside the area and kept for a year. The result indicates that it approximately corresponds to 1.0
of the dose from natural radiation sources. From these estimation results, it is found that all the tritium inventory stored inside 1F never contribute to significant dose increment even when it is instantly released into the area.
Machida, Masahiko; Iwata, Ayako; Yamada, Susumu; Otosaka, Shigeyoshi*; Kobayashi, Takuya; Funasaka, Hideyuki*; Morita, Takami*
Nihon Genshiryoku Gakkai Wabun Rombunshi, 21(1), p.33 - 49, 2022/03
We estimate monthly discharge inventory of tritium from the port of Fukushima Daiichi Nuclear Power Plant (1F) from Jun 2013 to Mar 2020 by using the Voronoi tessellation scheme, following that the tritium monitoring inside the port has started since Jun 2013. As for the missing period from the initial month, Apr 2011 to May 2013, we calculate it by utilizing the concentration ratio of tritium to that of Cs in stagnant contaminant water during the initial direct discharged period to Jun 2011 and the discharge inventory correlation between tritium and Cs for the next-unknown continuously-discharged period up to May 2013. From the all- estimated results over 9 years, we find that the monthly discharge inventory sharply dropped just after closing the sea-side impermeable sea-wall in Oct. 2015 and subsequently coincided well with the sum of those of drainage and subdrain. By comparing the estimated results with those in the normal operation period before the accident, we point out that the discharge inventory from 1F port is not so large compared to those during the normal operation. Even the estimated one in year 2011 is found to be comparable to the maximum of operating pressurized water reactors discharging relatively large inventory in the order. In the nation level, the whole Japan domestic discharge inventory significantly decreased after the accident due to operation shutdown of most plants. Furthermore, 1F and even Japanese total discharge inventory are found to be entirely minor when comparing those of nuclear reprocessing plants and heavy-water reactors in world-wide level. From the above, we suggest that various scenarios can be openly discussed on the management in tritium stored inside 1F with help of the present estimated data and its comparison with the past discharge inventory.
Machida, Masahiko; Yamada, Susumu; Iwata, Ayako; Otosaka, Shigeyoshi; Kobayashi, Takuya; Watanabe, Masahisa; Funasaka, Hideyuki; Morita, Takami*
Journal of Nuclear Science and Technology, 57(8), p.939 - 950, 2020/08
Times Cited Count：9 Percentile：71.58(Nuclear Science & Technology)After direct discharges of highly contaminated water of the Fukushima Daiichi Nuclear Power Plant (1F) from April to May 2011, Kanda suggested that relatively small amounts of run-off of radionuclides from the 1F port into the Fukushima coastal region subsequently continued by his estimation method. However, the estimation period was limited to up to September 2012. Therefore, this paper estimates the discharge inventory up to June 2018. In the missing period, the Japanese government and Tokyo Electric Power Company Holdings have continued efforts to stop the discharge, and consequently, the radionuclide concentration in seawater inside the 1F port has gradually diminished. We show the monthly discharge inventory of Cs up to June 2018 by two methods, i.e., Kanda method partially improved by the authors and a more sophisticated method using Voronoi tessellation reflecting the increase in the number of monitoring points inside the 1 F port. The results show that the former always yields overestimated results compared with the latter, but the ratio of the former to the latter is less than one order of magnitude. Using these results, we evaluate the impact of the discharge inventory from the 1F port into the coastal area and radiation dose upon fish ingestion.
Machida, Masahiko; Yamada, Susumu; Iwata, Ayako; Otosaka, Shigeyoshi; Kobayashi, Takuya; Watanabe, Masahisa; Funasaka, Hideyuki; Morita, Takami*
Nihon Genshiryoku Gakkai Wabun Rombunshi, 18(4), p.226 - 236, 2019/12
After direct discharges of highly-contaminated water from Unit 2 and 3 in Fukushima Daiichi Nuclear Power Plant (1F) in April to May 2011, Kanda suggested that relatively small run-off of radionuclides from 1F port into Fukushima coastal region has subsequently continued by using his estimation scheme. However, the estimation period was limited until September 2012, and there has been no report on the issue since the work. Therefore, this paper focuses on discharge inventory from 1F port until June 2018. In the missing period, the central government and Tokyo Electric Power Company Holdings have done continuous efforts to stop the discharge, and consequently sea water concentration inside 1F port has diminished gradually. We show monthly discharge inventory of Cs-137 until June 2018 by two schemes, i.e., Kanda's scheme partially improved by authors and more sophisticated one using Voronoi tessellation reflecting the increment of the number of monitoring points inside 1F port. The results show that the former always presents overestimated results compared to the latter but the ratio of former to latter is less than one order. Based on these results, we evaluate impact of discharge inventory from 1F port into the coastal area and radiation does via fish digestion.
Sasaki, Toshiki; Kaminishi, Shuji*; Miyamoto, Yasuaki; Funasaka, Hideyuki
Materials Research Society Symposium Proceedings, Vol.1518, p.257 - 268, 2013/10
The Fukushima Daiichi Nuclear Power Station accident and restoration works have produced significant volume of radioactive waste. The waste has very different characteristics from usual radioactive waste produced in nuclear power stations and it requires extensive research and development for management of the waste. R&D works such as radionuclide analysis of the waste, hydrogen generation/diffusion analysis of a storage vessel, corrosion evaluation of storage vessels, etc. have been performed for characterization and safe storage of the waste. The detailed R&D plan for processing and disposal waste will be established by the end of FY2012.
Nagata, Takashi; Ichimiya, Masakazu; Funasaka, Hideyuki; Mizuta, Shunji; Nagura, Fuminori
Nihon Genshiryoku Gakkai-Shi ATOMO
, 51(4), p.234 - 238, 2009/04
no abstracts in English
Funasaka, Hideyuki; Nakamura, Hirofumi; Namekawa, Takashi
Proceedings of 16th Pacific Basin Nuclear Conference (PBNC-16) (CD-ROM), 6 Pages, 2008/10
On the FaCT project in Japan, six development issues for the advanced aqueous reprocessing system are identified. Crystallization is the one of the major technologies to recover a large amount of uranium from the dissolver solution. The residual solution is loaded to the extraction process for U, Pu and Np co-recovery. Raffinate solution from the extraction process contains FP and MA, where MA is extracted by chromatography. These processes are expected to be more efficient in costs, wastes management, and the plutonium proliferation. As for the fuel fabrication technology, six development issues are identified. The source powder preparation technology of the conversion and granulation process is the most essential for the simplified pelletizing method technology. Remote operation and remote maintenance technique is essential to handle the low decontaminated TRU fuel in a hot cell. Current development status and plan of this integrated system until around 2015 is reported.
Ito, Masanori; Funasaka, Hideyuki; Namekawa, Takashi
Proceedings of European Nuclear Conference 2007 (ENC 2007) (CD-ROM), 7 Pages, 2007/09
The FaCT project in Japan is implemented purposing to decide the adoption of innovative technologies by 2010 and to judge the prospect of the applicability of innovative technologies to the commercialized fast reactor cycle system by 2015. Innovative technologies to be developed are identified as six development issues for advanced aqueous reprocessing system and six ones for simplified pelletizing method fuel fabrication system. As for reprocessing technology, uranium crystallization and extraction chromatography are important. Wide range of development work from chemical fundamental study to engineering-scale equipment operation are planned and practiced. As for fuel fabrication, conversion and granulation are important to get the source MOX powder with good flowability. Development of modular equipments with grater remote maintenance performance and repairing system in a hot cell is essential to put the low decontaminated TRU fuel fabrication into practical use.
Funasaka, Hideyuki; Ito, Masanori
Proceedings of International Conference on Advanced Nuclear Fuel Cycles and Systems (Global 2007) (CD-ROM), p.259 - 267, 2007/09
FaCT Project taking over from Feasibility Study on Commercialized FR cycle system (FS) has been launched in 2006 by Japanese joint team with the participation of all parties concerned in Japan. Combination system of (the sodium-cooled reactor,) the advanced aqueous reprocessing system and the simplified pelletizing fuel fabrication (MOX fuel) is evaluated as the most promising fuel cycle system concept so that it has potential conformity to the design requirements, as well as a high level of technical feasibility as the final report of Phase II in FS. Current status and R&D prospects for this combination system of the advanced aqueous reprocessing system and the simplified pelletizing fuel fabrication (MOX fuel) system until around 2015 have been studied.
Washiya, Tadahiro; Komaki, Jun; Funasaka, Hideyuki
Proceedings of International Conference on Advanced Nuclear Fuel Cycles and Systems (Global 2007) (CD-ROM), p.1467 - 1473, 2007/09
Japan Atomic Energy Agency (JAEA) has been developing the new aqueous reprocessing system named "NEXT" (New Extraction system for TRU recovery), which provides many advantages as waste volume reduction, cost savings by advanced components and simplification of process operation. Advanced head-end systems in the "NEXT" process consist of fuel disassembly system, fuel shearing system and continuous dissolver system. We developed reliable fuel disassembly system with innovative procedure, and short-length shearing system and continuous dissolver system can be provided highly concentrated dissolution to adapt to the uranium crystallization process. We have carried out experimental studies, and fabrication of engineering-scale test devices to confirm the systems performance. In this paper, research and development of advanced head-end systems are described.
Funasaka, Hideyuki; Koma, Yoshikazu; Sato, Koji; Nakajima, Yasuo; Shiotani, Hiroki; Kato, Atsushi; Higuchi, Tatsuya; Namba, Takashi
Proceedings of International Waste Management Symposium 2006 (WM '06) (CD-ROM), 13 Pages, 2006/02
Feasibility Study on commercialized FR cycle systems has been carried out by a Japanese joint team with the participation of all parties concerned in Japan since 1999. The result of the PhaseII (JFY 2001-2005) will work out until March 2006, and then the prospective of the promising concepts and the key issues for the commercialization will be summarized. In this paper, the candidate reprocessing systems studied in the Phase II are reviewed from the view point of compatibility with the reduction of environmental burden.
Namba, Takashi; Funasaka, Hideyuki; Nagaoki, Yoshihiro; Sagayama, Yutaka
Proceedings of International Conference ATALANTE 2004 Advances for Future Nuclear Fuel Cycles (CD-ROM), 0 Pages, 2004/00
Experimental Study on Temperature Fluctuation Phenomena at T-pipe Junction(6)
Nakajima, Yasuo; Funasaka, Hideyuki; ; Nagaoki, Yoshihiro
Proceedings of 11th International Conference on Nuclear Engineering (ICONE-11) (CD-ROM), 0 Pages, 2003/00
; Nomura, Shigeo; Ojima, Hisao; Funasaka, Hideyuki
Proceedings of International Conference on Advanced Nuclear Energy and Fuel Cycle Systems (GLOBAL 2003) (CD-ROM), p.1290 - 1298, 2003/00
None
Nomura, Shigeo; Ojima, Hisao; Funasaka, Hideyuki
Proceedings of International Conference on Advanced Nuclear Energy and Fuel Cycle Systems (GLOBAL 2003) (CD-ROM), 1290 Pages, 2003/00
Three candidate systems of spent fuel reprocessing integrated with fuel fabrication process,i.e.advanced aqueous,oxide electrowinning and metal electrorefining are studied as the Feasibility Study(FS)Phase-2 for advanced fast reactor fuel cycle.
Funasaka, Hideyuki; ;
JNC TN1200 2001-002, 209 Pages, 2001/01
JNC-TN1200-2001-002.pdf:7.84MB
no abstracts in English
; ; ; Myochin, Munetaka; ; Funasaka, Hideyuki
Saikuru Kiko Giho, (6), p.108 - 110, 2000/06
None
Oda, Yoshihiro; Funasaka, Hideyuki; Wang, X.*; Obara, Kenji*; Wada, Hitoshi*
JNC TY8400 2000-002, 47 Pages, 2000/03
JNC-TY8400-2000-002.pdf:2.53MB
no abstracts in English
