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Takai, Shizuka; Kimura, Hideo*; Uchikoshi, Emiko*; Munakata, Masahiro; Takeda, Seiji
JAEA-Data/Code 2020-007, 174 Pages, 2020/09
JAEA-Data-Code-2020-007.pdf:4.23MB
The MIG2DF computer code is a computer program that simulates groundwater flow and radionuclide transport in porous media for the safety assessment of radioactive waste disposal. The original version of MIG2DF was released in 1992. The original code employs a two-dimensional (vertical or horizontal cross-section, or an axisymmetric configuration) finite-element method to approximate the governing equations for density-dependent saturated-unsaturated groundwater flow and radionuclide transport. Meanwhile, for geological disposal of radioactive wastes, landscape evolution such as uplift and erosion needs to be assessed as a long-term geological and climate events, considering site conditions. In coastal areas, the impact to groundwater flow by change of salinity distribution to sea level change also needs to be considered. To deal with these events in the assessment, we have revised the original version of MIG2DF and developed the external program which enables MIG2DF to consider unsteady landscape evolution. In these developments, this report describes an upgrade of MIG2DF (Version 2) and presents the configuration, equations, methods, and verification. This reports also give the explanation external programs of MIG2DF: PASS-TRAC (the particle tracking code), PASS-PRE (the code for dataset preparation), and PASS-POST (the post-processing visualization system).
Kimura, Hideo; Takita, Hayato
JAEA-Technology 2020-002, 50 Pages, 2020/05
JAEA-Technology-2020-002.pdf:5.03MB
Japan Atomic Energy Agency is strongly promoting business process re-engineering (BPR) of the entire organization in order to achieve more efficient, centralized and IT-style work. As part of this BPR, we have been studying the introduction of robotic process automation (RPA), which has been making remarkable progress in recent years, in order to further streamline and improve efficiency mainly for administrative work. In order to implement an appropriate RPA, the characteristics of each RPA software were clarified by investigating the functions of major RPA software and developing sample robots. Furthermore, we categorized various tasks that are expected to utilize RPA software and examined the application of RPA software to each business pattern.
Takai, Shizuka; Shimada, Asako; Sawaguchi, Takuma; Takeda, Seiji; Kimura, Hideo
Radiation Protection Dosimetry, 188(1), p.1 - 7, 2020/01
Times Cited Count：0 Percentile：0.01(Environmental Sciences)After the Fukushima Nuclear Power Plant accident, most of radiocesium-contaminated soil generated from decontamination activities outside Fukushima prefecture has been stored at decontamination sites such as schools, parks and residential lands (storage at sites) according to the Decontamination Guidelines. However, additional exposure due to the present storage has not been evaluated. Moreover, entering storage sites, which is not restricted for storage at sites, was not considered in safety assessment conducted in the guidelines. To continue the storage and confirm the effectiveness, understanding of present possible exposures is important. In this study, we evaluated exposure doses for residents and users of storage sites based on the present situation. As a result, annual doses due to residence were 10
to 10
mSv y
and doses due to annual entries were of the order of 10 mSv y. Hence, we confirmed that the exposure due to present storage outside Fukushima is significantly less than 1 mSv y.
Kimura, Hideo; Hikasa, Naoki*; Kugenuma, Yuji*; Doi, Toshiharu*; Kikuchi, Yoshitaka*
JAEA-Technology 2019-004, 25 Pages, 2019/05
JAEA-Technology-2019-004.pdf:3.02MB
JAEA has developed the "Financial and contract information system" for effective and efficient accomplishment of the mission-critical tasks. Because the development of the next system was necessary with the end in the support time limit of the current system, we carried out the development of the next system in 2018. While the addition of the electronic approval function or the adoption of the latest package software largely performed a functional enhancement until now by applying distributed systems construction technique based on the separation procurement that we devised progressively, in development, we extremely realized procurement with the low cost.
Sugiyama, Daisuke*; Kimura, Hideo; Tachikawa, Hirokazu*; Iimoto, Takeshi*; Kawata, Yosuke*; Ogino, Haruyuki*; Okoshi, Minoru*
Journal of Radiological Protection, 38(1), p.456 - 462, 2018/03
Times Cited Count：0 Percentile：0.01(Environmental Sciences)Experience after the accident at the Fukushima Daiichi Nuclear Power Station has shown that there is a need to establish radiation protection criteria for radioactive waste management consistent with the criteria adopted for the remediation of existing exposure situations. A stepwise approach to setting such criteria is proposed. Initially, a reference level for annual effective dose from waste management activities in the range 1-10 mSv should be set, with the reference level being less than the reference level for ambient dose. Subsequently, the reference level for annual effective dose from waste management activities should be reduced in one or more steps to achieve a final target value of 1 mSv. The dose criteria at each stage should be determined with relevant stakeholder involvement. Illustrative case studies show how this stepwise approach might be applied in practice.
Hemmi, Ko; Yamaguchi, Tetsuji; Takeda, Seiji; Kimura, Hideo
Genshiryoku Bakkuendo Kenkyu (CD-ROM), 24(1), p.3 - 14, 2017/06
Conditions of contaminated sources and ranges of forest decontamination that significantly reduce the air dose rate in residential areas were investigated by means of a sensitivity analysis related to the decontamination of the forest contaminated by radiocesium deriving from the accident at Fukushima Daiichi Nuclear Power Station. The contaminated sources including 
Cs and 
Cs were assumed to be a layer of sedimented organic matter (the A
layer) and surface soils (the A
layer). The air dose rates were calculated using the three-dimensional Monte Carlo transport code MCNP. A slope number of the forest, angles, state of contaminant distribution, radiocesium content in the forest soils, decontamination ranges, distance from the forest boundary to an evaluation point, and height at the evaluation point were adopted as the parameters. The decontamination of a litter (A) layer within the distance of 20 m from the forest boundary was revealed to be effective in reducing the air dose rate when the source distribution was homogeneous. The air dose rates were significantly reduced by the decontamination of the A layer within a distance of 40 m from the forest boundary on condition that the radiocesium content of the A layer was larger than that of the A layer and the source distribution was non-homogeneous, such as the forest areas beyond 20 m from the forest boundary, which were more heavily contaminated than those within 20 m.
Sawaguchi, Takuma; Takeda, Seiji; Kimura, Hideo; Tanaka, Tadao
Hoken Butsuri, 50(1), p.36 - 49, 2015/03
It is desirable that the disaster wastes contaminated by radioactive cesium after the severe accident at the Fukushima Nuclear Plant are reused as much as possible in order to minimize the quantity to be disposed of. Ministry of the Environment showed the policy that the wastes containing cesium of higher concentration than the clearance level (100 Bq/kg) were reusable as materials of construction such as subbase course materials of pavements under controlled condition with measures to lower exposure doses. In this study, in order to provide technical information for making a guideline on the use of contaminated concrete materials recycled from disaster wastes as pavement, doses for workers and the public were estimated, and the reusable concentration of radioactive cesium in the wastes was evaluated. It was shown that the external exposure of the public (children) residing near the completed pavement gave the minimum radiocesium concentration in order to comply with the dose criteria. The recycled concrete materials whose average concentration of cesium lower than 2,700 Bq/kg can be used as the subbase course materials of pavements.
Takai, Shizuka; Seki, Masaya; Kimura, Hideo; Takeda, Seiji
Hoken Butsuri, 50(1), p.50 - 66, 2015/03
Wood (thinned wood from forest etc.) and wooden wastes (demolished wood etc.) potentially contaminated by radioactive cesium released by Fukushima Daiichi Nuclear Power Plant have been used for various purposes as wooden chips. However, there has been no dose estimation for use of such contaminated wood so far. Up to now, use of wood has been conducted according to a standard value of 100 Bq/kg for radioactive cesium based on clearance level of concrete and metal generated at nuclear power plant. The purpose of this study is to evaluate the safety of present use of wood by dose estimation for reuse of contaminated wooden chips, which are reused for main five use purposes (particle board, paper, compost, biomass power fuel, mulching). We also calculated activity concentrations of radioactive cesium in wooden chips corresponding to standard dose for safety reuse of radioactive wastes and regarded the minimum calculated activity concentration as a standard value of activity concentration for each reuse purposes. From the result, the minimum standard value of activity concentration of radioactive cesium in wooden chips for all reuse purposes is estimated to be 120 Bq/kg for reuse of wooden chips for particle board. Since this standard value is more than 100 Bq/kg, the safety of present use of wood is confirmed.
Takai, Shizuka; Takeda, Seiji; Kimura, Hideo
JAEA-Research 2014-028, 13 Pages, 2015/02
JAEA-Research-2014-028.pdf:1.92MB
A large amount of waste contaminated by radioactive cesium released by Fukushima Daiichi Nuclear Power Plant has been recycled as much as possible in order to reduce the quantity to be disposed of and to use resources effectively. At present, a standard concentration of radioactive cesium for recycled products from disaster waste is defined as 100 Bq/kg. In order to understand the actual situation of radioactivity concentration of recycled products, Ministry of the Environment conducted a survey on recycled products. The survey found that several recycled products had relatively high radioactive cesium concentration. In this study, we specified exposure pathways to calculate doses for using the recycled products detected high cesium concentration in the survey. We calculate the doses based on the survey of concentration of the recycled products and compare them with a dose criterion of 10
Sv/y for the use of recycled products. It was shown that the calculated doses were less than 10Sv/y for all recycled products but one sample of recycled asphalt with 26Sv/y. However, 26Sv/y is within the range of trivial dose indicated in ICRP Pub.104 and safety for reuse of the recycled asphalt is ensured.
Takeda, Seiji; Sawaguchi, Takuma; Kimura, Hideo
Materials Research Society Symposium Proceedings, Vol.1665, p.103 - 109, 2014/09
Some kinds of material in the environment due to the accident at the Fukushima Nuclear Plant have been contaminated by radioactive cesium, which are represented by dehydrated sludge, surface soil, disaster wastes generated by the 2011 off the Pacific coast of Tohoku Earthquake and so on. Treatment (transportation, temporary storage or incineration) and disposal of the contaminated materials should be carried out while ensuring the safety of radiation for the workers and the public. In this study, in order to provide the technical information for making the guideline, the dose estimate for scenarios on the treatment and disposal is conducted, based on the method used for driving the clearance levels in Japan. Minimum activity concentration in contaminated material is calculated from the dose results, corresponding to the effective dose criterions indicated by the Nuclear Safety Commission of Japan (June 3, 2011). From the calculation result, it is suggested that it is necessary to forbid reusing the disposal site as construction, resident and agriculture in which the calculated doses for the public are higher than those in the other exposure pathways. Minimum activity concentration of radioactive cesium is derived to be 8.9 Bq/g for exposure pathway in landfill work under the condition of limited reuse of the site. In the case of the activity concentration below 8.9 Bq/g, the calculated dose of the resident due to direct and sky-shine radiation from the temporary storage place is less than 1 mSv/y, irrespective of the distance from the storage place.
Takeda, Seiji; Kimura, Hideo
Progress in Nuclear Science and Technology (Internet), 4, p.68 - 71, 2014/04
The rice straw contaminated by radioactive cesium was distributed to the market to feed beef cattle after the severe accident of Fukushima Nuclear Plant. It is necessary to decide the suitable method of interim storage and the guidelines of radiation control for the worker engaged for transportation and storage of contaminated straw and for the resident living near the storage place. In order to provide with their technical information, dose analyses for the scenarios on transportation and interim storage of the straw were conducted. The results of transportation scenario suggest that the worker needs the measures to decrease the dose for the dominant external exposure pathway in radioactive cesium concentration of 700,000 Bq/kg. The calculated results for interim storage scenario indicate the relation between the radioactive cesium concentration in the rice straws and the distance to suppress the dose for the resident within effective dose criterion of 1 mSv/y.
Tokunaga, Tomonori*; Watanabe, Hideo*; Yoshida, Naoaki*; Nagasaka, Takuya*; Kasada, Ryuta*; Lee, Y.-J.*; Kimura, Akihiko*; Tokitani, Masayuki*; Mitsuhara, Masatoshi*; Hinoki, Tatsuya*; et al.
Journal of Nuclear Materials, 442(1-3), p.S287 - S291, 2013/11
Times Cited Count：11 Percentile：64.2(Materials Science, Multidisciplinary)
Mo manufacturing process, 1; Reusability evaluation of Mo absorbent (Joint research)Kimura, Akihiro; Niizeki, Tomotake*; Kakei, Sadanori*; Chakrova, Y.*; Nishikata, Kaori; Hasegawa, Yoshio*; Yoshinaga, Hideo*; Chakrov, P.*; Tsuchiya, Kunihiko
JAEA-Technology 2013-025, 40 Pages, 2013/10
JAEA-Technology-2013-025.pdf:2.62MB
Neutron Irradiation and Testing Reactor Center has developed the production of a medical isotope of Mo, the parent nuclide of 
Tc by the (n,
) method using JMTR. The (n,) method has an advantage of easy manufacturing process and low radioactive wastes generation. However, the low radioactivity concentration of Tc is remaining as an issue. Therefore, PZC and PTC have been developed as adsorbent of molybdenum. Meanwhile, it is necessary to recycle the absorbent and Mo for the reduction of the radioactive waste of used-adsorbent and the effective use of limited resources, respectively. This report summarizes results of the synthesis of Mo adsorbents such as PZC and PTC, and the performance tests.
Takeda, Seiji; Inoue, Yoshihisa; Kimura, Hideo
Materials Research Society Symposium Proceedings, Vol.1518, p.237 - 242, 2013/10
The sensitive analysis of radionuclide migration for the scenarios on deterioration or loss of safety functions expected in HLW disposal system due to the human error (initial defective scenarios) is performed in this study. Release rates for Cs-135 and Se-79 are estimated from Monte Carlo-based analysis. Maximum release rates of radionuclides for initial defective scenarios, buffer (colloidal transport case) and sealing plugs (pathway of short-circuit), are about one or two order magnitude higher than that normal scenario. From a viewpoint of future safety review, these results especially indicate the need to understand the feasibility on two types of initial defective scenario for the buffer and sealing plugs, leading to the loss of restraint of colloidal migration in the buffer and the loss of restraint with the plugs from migration through dominant pathway in tunnels and their vicinity.
Kakei, Sadanori*; Kimura, Akihiro; Niizeki, Tomotake*; Ishida, Takuya; Nishikata, Kaori; Kurosawa, Makoto; Yoshinaga, Hideo*; Hasegawa, Yoshio*; Tsuchiya, Kunihiko
Proceedings of 6th International Symposium on Material Testing Reactors (ISMTR-6) (Internet), 7 Pages, 2013/10
The Japan Materials Testing Reactor (JMTR) is expected to contribute to the expansion of industrial utilization, such as the domestic production of Mo for the medical diagnosis medicine 
Tc. Production by the (n, ) method is proposed as domestic Mo production in JMTR because of the low amount of radioactive wastes and the easy Mo/Tc production process. Molybdenum oxide (MoO
) pellets, poly zirconium compounds (PZC) and poly titanium compounds (PTC) are used as the irradiation target and generator for the production of Mo/Tc by the (n, ) method. However, it is necessary to use the enriched 
MoO, which is very expensive, to increase the specific activity of Mo. Additionally, a large amount of used PZC and PTC is generated after the decay of Mo. Therefore, this recycling technology of used PZC/PTC has been developed to recover molybdenum (Mo) as an effective use of resources and a reduction of radioactive wastes. The total Mo recovery rate of this process was 95.8%. From the results of the hot experiments, we could demonstrate that the recovery of MoO and the recycling of PZC are possible. In the future, the equipment of recovering Mo will be installed in JMTR-Hot Cell, and this recycling process will be able to contribute to the reduction of production costs of Tc and the reduction of radioactive wastes.
Sakai, Ryutaro; Takeda, Seiji; Munakata, Masahiro; Kimura, Hideo
JAEA-Research 2013-006, 18 Pages, 2013/07
JAEA-Research-2013-006.pdf:2.77MB
In the safety assessment for a geological disposal of radioactive waste, it is important to establish validation methods for deep groundwater flow to estimate radionuclide migration to human environment through groundwater flow. Costal sedimentary rocks in our country provide dominant fossil water formed during sub-seabed sedimentation and chemical compositions of the water mixed with meteoric water and fossil water depend on the initial fossil water composition and groundwater flow conditions. Analytical study on the effects of groundwater flow on the mixed water quality as a indicator of its Cl/
O ratios was carried out in case of Horonobe district, where geochemical data is now being stored.
Takeda, Seiji; Nishimura, Yuki; Munakata, Masahiro; Sawaguchi, Takuma; Kimura, Hideo
Genshiryoku Bakkuendo Kenkyu (CD-ROM), 19(2), p.23 - 38, 2012/12
In safety assessments of the geological disposal of TRU waste, it is important to understand the possibility and extents of influence of hyperalkaline groundwater derived from the degradation of cementitious materials that are used as forms for the containment of waste and as constructional materials in the disposal facilities of TRU waste. In this research, reactive transport analyses of hyperalkaline plume induced by cementitious materials were performed to clarify the extent of the hyperalkaline groundwater spreading and the type of alterations occurring with or without considering the precipitation of zeolite. The effect of the groundwater velocities on the spread of hyperalkaline groundwater was also examined. The analysis results indicate that whether zeolites precipitate or not significantly affect extent of hyperalkaline groundwater and the amount of precipitation of secondary minerals. In the case that groundwater velocity was 10 times higher, hyperalkaline groundwater spread broader than the original groundwater velocity case. It might be due to our kinetic dissolution model of host rock minerals, which limits chemical reactions neutralizing hyperalkaline groundwater.
Takeda, Seiji; Kimura, Hideo
Hoken Butsuri, 47(4), p.247 - 259, 2012/12
The dose estimate for scenarios on the incineration and disposal is conducted to provide the technical information for making the guideline on the incineration and disposal of dehydrated sludge contaminated by radioactive cesium. From the result of dose calculation, it is suggested that it is necessary to forbid reusing the disposal site as construction, resident and agriculture in which the calculated effective doses for the public are higher than those in the other exposure pathways. Minimum activity concentration of radioactive cesium in dehydrated sludge and incineration ashes, corresponding to the effective dose criterion indicated by Nuclear Safety Commission of Japan, is estimated to be 8.9 Bq/g under the condition of limited reuse of the site. In the case of the activity concentration below 8.9 Bq/g, the calculated dose of the resident due to direct and skyshine radiation from the temporary storage place is less than 1 mSv/y, irrespective of the distance from the storage place.
Sakai, Ryutaro; Munakata, Masahiro; Kimura, Hideo
JAEA-Research 2011-054, 19 Pages, 2012/03
JAEA-Research-2011-054.pdf:2.07MB
In the safety assessment for a geological disposal of radioactive waste, it is important to establish validation methods for deep groundwater flow system to estimate radionuclide migration to human environment through groundwater flow. This study discussed the method which estimates groundwater mixing condition and groundwater flow process using principal component analysis (PCA) to groundwater chemistry and isotopic compositions, together with data of groundwater age and trace element in case of Horonobe area. The results show that hydrochemical system can be divided into two systems: (1) three deep groundwater mixing system at depths greater than 200 to 400 m, (2) mixing area of deep groundwater and surface water at depths less than 200 to 400 m. Groundwater in the deep aquifer is suggested to be discharged at surface through Omagari Fault.
Saito, Hironori*; Takeda, Seiji; Kimura, Hideo
JAEA-Research 2011-032, 92 Pages, 2011/11
JAEA-Research-2011-032.pdf:2.11MB
The objective of this study is to estimate the parameter uncertainty of soil-to-plant transfer factor used in the safety assessment. The database on the soil-to-plant factors was improved to clarify the factors associated with the uncertainty of soil-to-plant transfer factor. The factors were specified based on investigating the relation between published data of soil-to-plant transfer factor and some kinds of experimental conditions. Under the assumption of stylization by both general habits of ingestion of farm products and soil conditions in Japan, we proposed the procedure to estimate the parameter uncertainty of soil-to-plant transfer factor according to the investigation results of the factors. Based on the procedure, the variation of soil-to-plant transfer factors for main radionuclides of high level radioactive waste and TRU waste were estimated in this report.
