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Shimada, Taro; Miwa, Kazuji; Takeda, Seiji
Nihon Genshiryoku Gakkai-Shi ATOMO
, 61(7), p.531 - 534, 2019/07
Rubbles less than 5 
Sv/h of surface dose rate, which are stored outdoor in the Fukushima Daiichi NPS (1F) site, will be recycled and applied in a restricted reuse only within 1F site in the future. However, there is no precedent for establishing the reference values such as dose and/or concentration for reuse or recycling under the existing exposure situation. In this study, we suggested a concept for establishing the reference radioactive concentration of recycling material for the restricted use in the 1F site. In addition, based on the concept, we calculated the reference radiocesium concentrations of the recycling material used for paved roads and the bases of concrete building.
Shimada, Taro; Miwa, Kazuji; Takeda, Seiji
Progress in Nuclear Science and Technology (Internet), 6, p.203 - 207, 2019/01
Rubbles less than 5 Sv/h of surface dose rate, which are stored outdoor in the Fukushima Daiichi NPS (1F) site, will be recycled and applied in a restricted reuse only within 1F site in the future. In this study, we suggested a concept for establishing the reference radioactive concentration of recycling material for the restricted use in the 1F site. Reference radiocesium concentration is calculated so that increased dose rate by restricted reuse does not exceed 1 Sv/h which is the minimum value of dose rate map in the 1F entire site. In order to justify the restricted reuse under the reference concentration calculated, additional occupational dose, dose rate at the site boundary and groundwater concentration at the outlet to the ocean are evaluated and confirmed that the values are below 2 mSv/y, 1 mSv/y and 1 Bq/cm
of 
Cs and 
Cs, respectively. And then calculated the reference radiocesium concentrations of the recycling material used for paved roads and the bases of concrete building.
Shimada, Asako; Ozawa, Mayumi; Yabuki, Koshi*; Kimiyama, Kazuhiro; Sato, Kenji; Kameo, Yutaka
Journal of Chromatography A, 1371, p.163 - 167, 2014/12
Times Cited Count：14 Percentile：48.55(Biochemical Research Methods)Sugita, Yutaka; Fujita, Tomoo; Tanai, Kenji; Hasegawa, Hiroshi; Furuichi, Mitsuaki*; Okutsu, Kazuo*; Miura, K.*
JNC TN8400 99-039, 58 Pages, 1999/11
Regarding disposal techniques of high-level radioactive waste (HLW), the HLW is vitrified and then stored for cooling for a period of 30 to 50 years. After cooling, the HLW is isolated in the deep underground. The concept of geological disposal is based on the requirement to enclose the HLW in the deep underground for the long-term durability of the human's environmental safety. Backfilling of a repository is a unique activity on the geological disposal. If underground tunnels excavated to construct the repository are left, they may have significant influences on the barrier performance of an entire repository, such as: the mechanical stability of a tunnel may be damaged by rock stresses and a tunnel may provide a fast pathway for ground water flow. Therefore, the underground facilities are expected to be backfilled with a backfilling material after emplacement of the HLW and a buffer material. The material for the backfilling of the underground facilities is backfilling material. In this report, bentonite-aggregate mixture is considered, as one of the candidate materials for the backfilling material. Aggregate imitates the muck that is generated during construction phase of the underground facilities. The combination of backfilling, plugging and grouting is considered in some underground situations. Plug is composed of concrete material or clay-based one. Grouting material is concrete material or clay-based one, too. In this report, the concept of the backfilling, mechanical and hydrological characteristics of the bentonite-aggregate mixture, the function, work methods and a schedule of the backfilling materials, plugging and grouting are considered, and items of quality control for the bentonite-aggregate mixture, concrete material and grouting are listed.
Aoki, Kenji*; Hibiya, Keisuke*; Shiogama, Yukihiro*; Toida, Masaru*; Fukazawa, E.*; Taira, K.*; *
PNC TJ1100 95-001, 66 Pages, 1995/03
None
; *;
JAERI-M 82-068, 16 Pages, 1982/07
no abstracts in English
; *
JAERI-M 8005, 50 Pages, 1979/01
no abstracts in English
;
Atsuryoku Gijutsu, 14(4), p.169 - 176, 1976/04
no abstracts in English
;
Atsuryoku Gijutsu, 14(3), p.127 - 134, 1976/03
no abstracts in English
Shimada, Taro; Takai, Shizuka; Takeda, Seiji
no journal, ,
In order to recycle contaminated debris of which concentration is relatively lower in Fukushima Daiichi Nuclear Power Station, it is necessary to confirm that the mean radioactive concentration is lower than a reference value with consideration of the distribution by measurement and evaluation. We studied a method combining radiation measurement and inverse analysis to obtain the distribution of radioactivity concentration of recycled material. Plastic scintillation fiber will be applied to radiation measurement to obtain dose rates outside the container containing recycled material at many measurement points. As a result of application of 7 inverse analysis methods to typical two types of distribution, GVSPM and ML-EL methods can evaluate true values in the trials.
Miwa, Kazuji; Shimada, Taro; Takai, Shizuka; Nabekura, Nobuhide; Takeda, Seiji
no journal, ,
A part of the debris with relatively lower radioactive concentrations, which have been stored in the site of Fukushima Daiichi Nuclear Power Station (1F), have been planned to be recycled for restricted purpose in the 1F site. In this study, we evaluated reference values of upper radiocesium concentrations which are practicable to recycle materials for some applications such as road. Radiation doses for all workers in the 1F site are controlled. There is no previous reference values estimated for restricted recycling under the condition of controlled radiation doses for workers in the 1F site. Therefore, we evaluated the reference values not to exceed the additional air radiation dose as 1Sv/h with recycling the debris, which is the estimated minimum dose rate in the 1F site regarded as background. As a result, the highest value of radiocesium concentration of recycling materials was evaluated to be 100,000 Bq/kg in the case of use as the sub-base in the concrete paving road.
Shimada, Taro; Miwa, Kazuji; Takeda, Seiji
no journal, ,
Rubbles less than 5Sv/h of surface dose rate, which are stored in the Fukushima Daiichi NPS (1F) site, will be recycled and applied in a restricted use only within 1F site in the future. In this study, we suggested a concept for establishing the reference radioactive concentration of recycling material for the restricted use in the 1F site, and then calculated the reference radiocesium concentrations of the recycling material used for paved roads and the bases of concrete building. In order to prevent the working time from being decreased, it is necessary for the restricted use to suppress the additional dose to a level of value. Therefore, focusing on the current background air dose rate in the 1F site, we suggested the required condition that air dose rate increased by use of contaminated recycling material instead of non-contaminated did not exceed the variation range of the background dose rate. In addition, to validate the restricted use under the reference concentration, following three items should be confirmed; (1) additional dose for worker using the recycling material does not exceed 2mSv/y, 10% of worker dose limit; (2) the impact to air dose rate evaluated at the 1F site boundary does not exceed the 1mSv/y including direct and skyshine radiations from wastes stored in the site; (3) the impact of migrated radionuclides into groundwater does not exceed the operational target value. The reference radiocesium concentrations for recycling aggregate taken from contaminated concrete rubbles were evaluated for paved road and bases of concrete building.
Miwa, Kazuji; Shimada, Taro; Takeda, Seiji
no journal, ,
In this study, in order to validate the restricted use of recycling material at the reference radiocesium concentration (determined in series report (1)), we evaluated worker annual doses, air dose rate at the site boundary and impact of migrated radiocesium into groundwater. Firstly, we evaluated the additional annual dose for workers, on the assumption that typical workers coming in contact with the source after construction (Road: 1.3 mSv/y, Building: 1.3 mSv/y). Secondly, we evaluated the air dose rates by distance from road and building including recycling material, and investigated the distance for not exceeding 1mSv/y (including additional dose rate by recycling and background dose rate of 0.6 mSv/y) at the site boundary (Road: 25 m, Building: 1 m). Thirdly, we evaluated the Cs and Sr migration in groundwater, and investigated the distance required for satisfying the operation target value (Cs-134: 1 Bq/L, Cs-137: 1 Bq/L, Sr-90: 5 Bq/L) at the boundary (coastal line) (Road: 10 m, Building: 10 m).
Shimada, Taro; Namekawa, Masakazu*; Takai, Shizuka; Takeda, Seiji
no journal, ,
It is necessary to confirm the radioactive concentration of recycling contaminated rubbles which is less than the reference concentration for restricted use in the site of Fukushima Daiichi NPS. In order to develop measurement and evaluation methods in the combination of plastic scintillation fiber and inverse analysis for confirmation survey in the 1F site, we studied the measurement methods and geometrical system. We carried out the radiation measurement for simulated recycling rubbles using sealed radiation sources and analyzed gamma radiation fluxes on the PSF. The measurement result was almost agreed with the analytic result by means of correction of position resolution and detecting efficiency for the 
-ray energy of the PSF. It suggested that it was possible to estimate the radioactive concentration of recycling rubbles.
Shimada, Taro; Miwa, Kazuji; Takeda, Seiji
no journal, ,
Rubbles less than 5 Sv/h of surface dose rate, which are stored outdoor in the Fukushima Daiichi NPS (1F) site, will be recycled and applied in a restricted reuse only within 1F site in the future. However, there is no precedent for establishing the reference values such as dose and/or concentration for reuse or recycling under the existing exposure situation. In this study, we suggested a concept for establishing the reference radioactive concentration of recycling material for the restricted use in the 1F site. In addition, based on the concept, we calculated the reference radiocesium concentrations of the recycling material used for paved roads and the bases of concrete building.
