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JAEA Reports

Requirements and issues for commentary against facility design on trench disposal of radioactive wastes generated from research, industrial and medical

Ogawa, Rina; Amazawa, Hiroya; Nakata, Hisakazu; Sugaya, Toshikatsu; Sakai, Akihiro

JAEA-Review 2023-011, 116 Pages, 2023/08


Japan Atomic Energy Agency (JAEA) is the implementing agency for the disposal business of radioactive waste generated from research, industrial and medical facilities (Institutional radioactive waste). In 2010, JAEA implemented a conceptual design of the disposal facility that conformed to the laws and regulations at the time. However, since 2013, the laws and regulations for nuclear facilities including the Category-2 Waste Disposal were amended. Since then, design of various nuclear facilities including disposal facilities has been reviewed. Therefore, JAEA decided to do additional studies toward the basic design for the disposal facility. When JAEA gets a license of the disposal business of Institutional radioactive waste, it is necessary to show that the disposal facility complies with the rule of design for disposal facility under the law. Therefore, JAEA is examining technical studies of the disposal facility to conform to the new standard. In this report, we organized the requirements of the rule for design of trench disposal facility and extracted the issues to design the disposal facility that conform to the requirements.

JAEA Reports

Evaluation of flow rate of groundwater into and out of concrete vault disposal facility according to geological environment and deterioration of the facility

Ogawa, Rina; Totsuka, Masayoshi*; Sakai, Akihiro

JAEA-Technology 2023-012, 57 Pages, 2023/07


Concrete vault disposal facility is assumed to be installed below the groundwater table because it is necessary to install them on the ground that has enough bearing capacity. Therefore, the flow rates of groundwater into and out of concrete vault were evaluated by taking into account the permeability coefficients of the geological environment surrounding the facility and of the engineered structure of the facility. Groundwater flow analysis was performed by using the groundwater flow analysis code MIG2DF based on finite element method. In the evaluation of considering the geological environment, since the flow rate of groundwater into and out of the bottom of concrete vault was larger than the flow rates into and out of other sides of the vault in previous technical studies, the evaluation of the flow rate was performed by varying the permeability coefficient of the bedrock adjacent to the bottom of concrete vault. In addition, the other evaluation of the flow rate was conducted assuming the deterioration of concrete vault and of bentonite-mixed soil. As a result, it was found that the permeability coefficient of bedrock adjacent to concrete vault greatly contributed to flow rates of groundwater into and out of concrete vault. In addition, as the permeability coefficient of the bentonite-mixed soil increased due to chemical deterioration, the flow rate of leachate into the surrounding cover soil increased. From the above results, it was found that these permeability coefficients were important influencing factors in the engineering design and safety evaluation of concrete vault disposal facilities.

JAEA Reports

Skyshine dose evaluation of trench disposal facilities for waste generated from research, industrial and medical facilities

Nakamura, Mizuki; Izumo, Sari; Ogawa, Rina; Nakata, Hisakazu; Amazawa, Hiroya; Sakai, Akihiro

JAEA-Technology 2022-025, 73 Pages, 2022/12


Japan Atomic Energy Agency (JAEA) has been establishing as the implementing body of the near surface disposal of low-level radioactive waste (LLW) generated from research facilities and other facilities in order to actualize the near surface disposal. It is necessary to evaluate the effective doses by direct and skyshine $$gamma$$-rays from disposal facilities and reduce the doses below the target dose (50$$mu$$ Sv/y) at the site boundary for the safety assessment during operation. It was shown at the results of conceptual design that the distance from the trench disposal facilities to site boundary needed to be kept more than 120m in order to satisfy the target dose. However, the design of trench disposal facilities was changed because of increasing amount of waste subject to the trench disposal. Therefore, the dose by skyshine $$gamma$$-rays from trench disposal facilities was recalculated by use of two-dimensional discrete ordinates Sn code DOT 3.5. As a result, it was evaluated that the dose by skyshine $$gamma$$-rays from each trench facility at the site boundary whose distance was 120m from a trench facility was lower than 50$$mu$$ Sv/y, respectively, and the dose added up the doses from trench facilities was also lower than 50$$mu$$ Sv/y. In addition, it was suggested to reduce the target skyshine dose by thickening the covered soil on the top layer.

JAEA Reports

Design study on cover soil in the trench disposal facility for very low-level radioactive waste generated from research facilities and other facilities

Ogawa, Rina; Nakata, Hisakazu; Sugaya, Toshikatsu; Sakai, Akihiro

JAEA-Technology 2022-010, 54 Pages, 2022/07


Japan Atomic Energy Agency has considered trench disposal as one of the disposal methods for radioactive wastes generated from research facilities and other facilities. The trench disposal facility is regulated by "Act on the Regulation of Nuclear Source Material, Nuclear Fuel Material and Reactors". In particular, the design of the trench facility is regulated by a rule under the law. When the rule was amended in 2019, the design of the trench disposal facility required equipment to reduce ingress of rain water and groundwater. In the report, studies on the design of a trench disposal facility to adapt to the amended rule were performed. The trench disposal facility has considered being established in a place lower than groundwater level. Therefore, it was decided to study covering soil at the upper part of the trench facility, because the ingress water in the facility is mainly derived from rain water. In this study, it was decided to evaluate the design of covering soil of the radioactive waste categorized into chemically stable materials. Therefore, as the examination method, a parameter study on varying the permeability coefficient and thickness of the layers composing cover soil. In the parameter study, the velocity of the water infiltrating into the trench facility was evaluated. Based on the results, more efficient design of the layers composing the covering soil was considered. The result showed that the impermeable efficiency of the covering soil was different depending on the thickness and the permeability conductivity of each layer. As a result, it was possible to understand the impermeable performance of covering soil by the permeability coefficient and thickness of each layer. We will plan to decide the specification of the cover soil while examination of future tasks and cost in the basic design.

JAEA Reports

Preliminary evaluation of environmental uranium concentration originated from trench disposal facilities

Ogawa, Rina; Abe, Daichi*; Sugaya, Toshikatsu; Sakuma, Kota; Saito, Tatsuo; Sakai, Akihiro

JAEA-Technology 2022-008, 46 Pages, 2022/05


Japan Atomic Energy Agency (JAEA) has planned to dispose of the Uranium-bearing waste, whose radioactivity concentration is low, in trench disposal facility. In Japan, uranium is a material to impact on human health, therefore Environmental quality standards for water pollution for uranium has been established, and the standard value is 0.002mg/L. Safety of trench disposal facilities will be assessed that radionuclides contained in the radioactive waste are transferred to the biosphere by seepage water and groundwater. Therefore, JAEA considers that not only dose evaluation but also environmental pollution evaluation is needed as a safety assessment. In this report, we examined whether the concentration of uranium leaching from the trench facility in the aquifer can meet the Environmental quality standards. In addition, parameter study under various conditions of disposal facility were done. Based on the results, conditions and issues of future basic design of trench disposal facility were discussed. The uranium concentration in the aquifer was calculated by the one-dimensional dose evaluation code "GSA-GCL2" for the disposal of LLW. As the result, the uranium concentration in the aquifer significantly changed depending on the conditions of design of disposal facility and so on. However, if the shape and arrangement of the trench facility to groundwater flow direction, the distribution coefficient of uranium of the waste layer, the specification of the impermeable layer and their combination are appropriately designed we consider that the uranium concentration of aquifer can made to adapt the environmental quality standard.

Journal Articles

Thermally altered subsurface material of asteroid (162173) Ryugu

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Takagi, Yasuhiko*; Nakamura, Tomoki*; Hiroi, Takahiro*; Matsuoka, Moe*; et al.

Nature Astronomy (Internet), 5(3), p.246 - 250, 2021/03

 Times Cited Count:30 Percentile:96.39(Astronomy & Astrophysics)

Here we report observations of Ryugu's subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. However, the strength and shape of the OH feature still suggests that the subsurface material experienced heating above 300 $$^{circ}$$C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 $$^{circ}$$C at the estimated excavation depth of 1 m, even if the semimajor axis is reduced to 0.344 au. This supports the hypothesis that primary thermal alteration occurred due to radiogenic and/or impact heating on Ryugu's parent body.

Journal Articles

Root-endophytic Chaetomium cupreum chemically enhances aluminium tolerance in $$Miscanthus sinensis$$ via increasing the aluminium detoxicants, chlorogenic acid and oosporein

Haruma, Toshikatsu*; Yamaji, Keiko*; Ogawa, Kazuyoshi*; Masuya, Hayato*; Sekine, Yurina; Kozai, Naofumi

PLOS ONE (Internet), 14(2), p.e0212644_1 - e0212644_16, 2019/02

 Times Cited Count:21 Percentile:80.74(Multidisciplinary Sciences)

Miscanthus sinensis Andersson is a pioneer plant species that grows naturally at mining sites. $$Miscanthus sinensis$$ can detoxify aluminium (Al) by producing phytosiderophores. Root-endophytic Chaetomium cupreum, which produces microbial siderophores, enhances Al tolerance in M. sinensis. We identified the siderophore produced by C. cupreum as oosporein. It was revealed that oosporein could detoxify Al. Inoculation test of C. cupreum onto M. sinensis in acidic mine soil showed that C. cupreum promoted seedling growth, and enhanced Al tolerance.

Journal Articles

Highly polarized electrons from GaAs-GaAsP and InGaAs-AlGaAs strained-layer superlattice photocathodes

Nishitani, Tomohiro; Nakanishi, Tsutomu*; Yamamoto, Masahiro*; Okumi, Shoji*; Furuta, Fumio*; Miyamoto, Masaharu*; Kuwahara, Makoto*; Yamamoto, Naoto*; Naniwa, Kenichi*; Watanabe, Osamu*; et al.

Journal of Applied Physics, 97(9), p.094907_1 - 094907_6, 2005/05

 Times Cited Count:64 Percentile:87.5(Physics, Applied)

no abstracts in English

Journal Articles

Nonlinear absorption of high power free-electron-laser-generated microwaves at electron cyclotron resonance heating frequencies in the MTX tokamak

S.L.Allen*; M.D.Brown*; J.A.Byers*; T.A.Casper*; B.I.Cohen*; R.H.Cohen*; M.E.Fenstermacher*; J.H.Foote*; E.B.Hooper*; C.J.Lasnier*; et al.

Physical Review Letters, 72(9), p.1348 - 1351, 1994/02

 Times Cited Count:17 Percentile:72.48(Physics, Multidisciplinary)

no abstracts in English

Oral presentation

Evaluation of the amount of infiltration and leachate from concrete-pit facilities for radioactive waste generated from research, industrial and medical use

Ogawa, Rina; Totsuka, Masayoshi*; Nakata, Hisakazu; Sakai, Akihiro

no journal, , 

no abstracts in English

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