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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

JAEA-Review-2023-011.pdf:2.6MB

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 radioactivity concentration corresponding to dose criterion for near surface disposal of radioactive waste generated from research, medical, and industrial facilities, Volume 2

Sakuma, Kota; Abe, Daichi*; Okada, Shota; Sugaya, Toshikatsu; Nakata, Hisakazu; Sakai, Akihiro

JAEA-Technology 2022-013, 200 Pages, 2022/08

JAEA-Technology-2022-013.pdf:8.41MB

Japan Atomic Energy Agency has aims to carry out near surface disposal of low-level radioactive waste generated from research, medical, and industrial facilities. Therefore, Radioactivity Concentration Corresponding to Dose Criterion for near surface disposal for nuclides in the waste were calculated for the purpose of discussion for radioactivity limits between trench and concrete vault disposal, and key nuclides related to them. This report uses the results of sensitivity analysis and evaluation of the amount of leachate from the disposal facility for concrete vault disposal, and incorporates a new assessment pathway and exposure form that widely assume the conditions of the disposal facility. This trial calculation was carried out and compared with the trial calculation in the previous report, "Evaluation of Radioactivity Concentration Corresponding to Dose Criterion for Near Surface Disposal of Radioactive Waste Generated from Research, Medical, and Industrial Facilities, Volume 1". The results of Radioactivity Concentration Corresponding to Dose Criterion calculated in this report will be used as reference values when selecting key nuclides and for classification into concrete vault disposal when the location has not been decided. After deciding the location of the site, it is necessary to evaluate the dose based on the location conditions.

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

JAEA-Technology-2022-010.pdf:11.07MB

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

JAEA-Technology-2022-008.pdf:3.09MB

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.

JAEA Reports

Basic policy for rational measures of radioactive waste processing and disposal; Results of studies for acceleration of waste processing

Nakagawa, Akinori; Oyokawa, Atsushi; Murakami, Masashi; Yoshida, Yukihiko; Sasaki, Toshiki; Okada, Shota; Nakata, Hisakazu; Sugaya, Toshikatsu; Sakai, Akihiro; Sakamoto, Yoshiaki

JAEA-Technology 2021-006, 186 Pages, 2021/06

JAEA-Technology-2021-006.pdf:54.45MB

Radioactive wastes generated from R&D activities have been stored in Japan Atomic Energy Agency. In order to reduce the risk of taking long time to process legacy wastes, countermeasures for acceleration of waste processing and disposal were studied. Work analysis of waste processing showed bottleneck processes, such as evaluation of radioactivity concentration, segregation of hazardous and combustibles materials. Concerning evaluation of radioactivity concentration, a radiological characterization method using a scaling factor and a nondestructive gamma-ray measurement should be developed. The number of radionuclides that are to be selected for the safety assessment of the trench type disposal facility can decrease using artificial barriers. Hazardous materials, will be identified using records and nondestructive inspection. The waste identified as hazardous will be unpacked and segregated. Preliminary calculations of waste acceptance criteria of hazardous material concentrations were conducted based on environmental standards in groundwater. The total volume of the combustibles will be evaluated using nondestructive inspection. The waste that does not comply with the waste acceptance criteria should be mixed with low combustible material waste such as dismantling concrete waste in order to satisfy the waste acceptance criteria on a disposal facility average. It was estimated that segregation throughput of compressed waste should be increased about 5 times more than conventional method by applying the countermeasures. Further study and technology development will be conducted to realize the plan.

JAEA Reports

Evaluation of radioactivity concentration corresponding to dose criterion for near surface disposal of radioactive waste generated from research, medical, and industrial facilities, Volume 1

Sugaya, Toshikatsu; Abe, Daichi*; Okada, Shota; Nakata, Hisakazu; Sakai, Akihiro

JAEA-Technology 2021-004, 79 Pages, 2021/05

JAEA-Technology-2021-004.pdf:2.86MB
JAEA-Technology-2021-004(errata).pdf:0.38MB

JAEA has aims to carry out near surface disposal of low-level radioactive waste generated from research, medical, and industrial facilities. Therefore, radioactivity concentration corresponding to dose criteria of near surface disposal for 220 nuclides in the waste were calculated for the purpose of discussion for radioactivity limits between trench and concrete vault disposal, and key nuclides related to them. We calculated the radioactivity concentrations with consideration of not only the exposure pathways used at calculation of the radioactivity concentration limits of waste packages for near surface disposal by Nuclear Safety Commission but also ones used at the concentration limits for intermediate depth disposal. We also assumed the capacities of the disposal facilities as 44,000 m$$^{3}$$ for pit disposal and 150,000 m$$^{3}$$ for trench disposal. The radioactivity concentrations calculated in this report is used as the reference values because the disposal site has not been decided yet. Addition to this, the radioactivity concentrations will be revised according to circumstances of development of disposal facilities and so on. In the future, we will decide the radioactivity and radioactive concentration of a waste package described in the license application documents based on the dose assessment taken into consideration the disposal site conditions.

JAEA Reports

Study on the evaluation method to determine the radioactivity concentration in radioactive waste generated from the dismantling of research reactors

Murakami, Masashi; Hoshino, Yuzuru; Nakatani, Takayoshi; Sugaya, Toshikatsu; Fukumura, Nobuo*; Sanda, Toshio*; Sakai, Akihiro

JAEA-Technology 2019-003, 50 Pages, 2019/06

JAEA-Technology-2019-003.pdf:4.42MB

Toward the establishment of a common approach to determine the radioactivity concentrations in dismantling wastes arising from research reactors, radionuclide concentrations in the reactor structure materials of aluminum, carbon steel, shield concrete, and graphite of TRIGA Mark II reactor at Rikkyo University, Japan, were evaluated with both radiochemical analysis and theoretical calculation. The measured nuclides by the radiochemical analysis were $$^{3}$$H, $$^{60}$$Co, and $$^{63}$$Ni in aluminum, $$^{3}$$H, $$^{60}$$Co, $$^{63}$$Ni, and $$^{152}$$Eu in carbon steel, $$^{3}$$H, $$^{60}$$Co, and $$^{152}$$Eu in shield concrete, and $$^{3}$$H, $$^{14}$$C, $$^{60}$$Co, $$^{63}$$Ni, and $$^{152}$$Eu in graphite. Neutron-flux distributions and neutron-induced activities were computed with DORT and ORIGEN-ARP codes, respectively. Using the results of material composition analysis, radioactivity concentrations were conservatively predicted with good accuracy except for graphite material.

JAEA Reports

Corrosion test of Fugen pressure tube (Zr-2.5wt%Nb alloy) under the sub-surface disposal environment, 2; Examination of long-term corrosion rate by 5 years keeping sample

Sugaya, Toshikatsu; Nakatani, Takayoshi; Sakai, Akihiro

JAEA-Technology 2017-032, 21 Pages, 2018/01

[The article has been found to have a problem about reliability of the corrosion data acquisition, and thus it is unavailable to download the full text in accordance with authors' intentions to retract the report.] For the purpose of the setting of the rate of nuclide elution necessary to safety assessment, we planned the gas-accumulating type corrosion test on Zr-2.5wt%Nb alloy in order to obtain long-term corrosion rate under low temperature, low oxygen and alkaline conditions assuming the disposal environment. A corrosion rate over a testing period of 5 years is acquired with the aim to grasp a long-term corrosion rate behavior in this report. This corrosion rate is compared with the same data that was previously acquired over a testing period of 2 years. As a result, it is confirmed that an evaluation method that is proportional to the minus cubic root of corrosion time squared can be applicable to the corrosion rate behavior acquired this time over a testing period of 5 years, which is the same result in evaluating the corrosion rate behavior acquired over a testing period of 2 years.

JAEA Reports

Technological study about a disposal measures of low-level radioactive waste including uranium and long-half-life radionuclides

Sugaya, Toshikatsu; Nakatani, Takayoshi; Sasaki, Toshihisa*; Nakamura, Yasuo*; Sakai, Akihiro; Sakamoto, Yoshiaki

JAEA-Technology 2016-036, 126 Pages, 2017/02

JAEA-Technology-2016-036.pdf:7.28MB

At the Radioactive Waste Management and Disposal Project Department Sector of Decommissioning and Radioactive Waste Management, we performed the technological study about the disposal measures of the low-level radioactive waste targeted for uranium-bearing waste and intermediate depth disposal-based waste occurring from the process of the nuclear fuel cycle.

JAEA Reports

Calculation of the dose equivalent rate based on the unit concentration of contaminated soil in a flexible container

Sugaya, Toshikatsu; Abe, Daichi; Takebe, Shinichi; Nakatani, Takayoshi; Sakai, Akihiro

JAEA-Technology 2016-018, 20 Pages, 2016/09

JAEA-Technology-2016-018.pdf:2.41MB

Decontamination to the pollution which occurred with an accident of a nuclear power plant with Tohoku-district Pacific offing earthquake has been performed. The contaminated soil which occurred in decontamination stores it in the flexible container back, and is the kept situation. To presume concentration of radioactivity of contents from the dose of the flexible container, the 1cm dose equivalent rate per the unit concentration of radioactivity was calculated with QAD-CGGP2R.

JAEA Reports

Development of the assessment tools for land use scenarios concerning sub-surface disposal

Sakatani, Keiichi; Sugaya, Toshikatsu; Nakatani, Takayoshi; Funabashi, Hideyuki

JAEA-Data/Code 2014-008, 53 Pages, 2014/06

JAEA-Data-Code-2014-008.pdf:39.9MB

The safety assessment of the sub-surface disposal system should ensure that calculated dose will be lower than the dose assigned to the scenario in question during the period from now to future. In order to realize the safety disposal, we have developed several assessment tools on the GoldSim platform and calculated doses since 2008, and these assessment tools have been improved reflecting the last view of assessment. This report describes idea of assessment models and structure of assessment tools for land use scenarios.

JAEA Reports

Development of the assessment tool for groundwater scenario concerning sub-surface disposal

Sakatani, Keiichi; Sugaya, Toshikatsu; Nakatani, Takayoshi; Funabashi, Hideyuki

JAEA-Data/Code 2013-015, 63 Pages, 2013/11

JAEA-Data-Code-2013-015.pdf:8.75MB

The safety assessment of the sub-surface disposal system should ensure that calculated dose will be lower than the dose assigned to the scenario in question during the period from now to future. In order to realize the safety disposal, we have developed several assessment tools on the GoldSim platform and calculated doses since 2008, and these assessment tools have been improved reflecting the last view of assessment. This report describes safety functions of the disposal system, idea of nuclide migration, formulas for nuclides migration, formulas of exposure dose and structure of assessment tool for groundwater scenario.

JAEA Reports

Study of parameters for safety assessment of sub-surface disposal; Tunnel-excavating speed and thickness of additional soil in residential land development by filling

Ishitoya, Kimihide; Sugaya, Toshikatsu; Funabashi, Hideyuki

JAEA-Research 2011-046, 32 Pages, 2012/02

JAEA-Research-2011-046.pdf:3.52MB

Nuclear Safety Commission of Japan (NSC) issued "Policy of the Safety Assessment of Sub-surface Disposal after the Period for Active Control" (April 1, 2010). Then, we investigated the parameters for dose assessment in tunnel excavation scenario and large-scale land use scenario which were described in the "Policy of the Safety Assessment", in order to perform the assessment based on actual conditions. To be concrete, we investigated the tunnel excavating speeds in Japan for the former scenario, and investigated technical standards of the filling for the latter scenario. We studied the realistic parameters for the dose assessment with the results of those investigations.

JAEA Reports

Study of "Inadvertent Human Intrusion or Rare Natural Event Scenarios" for sub-surface disposal of radioactive waste

Nakatani, Takayoshi; Ishitoya, Kimihide; Funabashi, Hideyuki; Sugaya, Toshikatsu; Sone, Tomoyuki; Shimada, Hidemitsu*; Nakai, Kunihiro*

JAEA-Research 2009-064, 104 Pages, 2010/03

JAEA-Research-2009-064.pdf:14.45MB

The purpose of this study was to assess exposure dose of "Inadvertent Human Intrusion or Rare Natural Event Scenarios" on sub-surface disposal. It was one of "Classification of three types scenarios" in "Basic Policy for Safety Regulation Concerning Land Disposal of Low-Level Radioactive Waste (Interim Report)" formulated by the Nuclear Safety Commission of Japan. Selection of the assessed scenarios, development of the assessment tool and preliminary exposure dose assessment were conducted. Exposure dose of "Well water drinking scenario" was the highest in the assessed scenarios. This scenario assumed that the groundwater in Excavation Disturbed Zone (EDZ) was directly used as drinking water without any dilution. Although this was very conservative condition and the result exceeded 10 mSv/y, it was under the upper limit of standard dose value (10$$sim$$100 mSv/y) in the Interim Report for "Inadvertent Human Intrusion or Rare Natural Event Scenarios".

JAEA Reports

Study of "Likely Scenarios" and "Less-likely Scenarios" for sub-surface disposal of radioactive waste

Sugaya, Toshikatsu; Sone, Tomoyuki; Nakatani, Takayoshi; Ishitoya, Kimihide; Funabashi, Hideyuki; Sasaki, Ryoichi*; Shimoda, Satoko*; Kurosawa, Mitsuru*

JAEA-Research 2009-063, 80 Pages, 2010/03

JAEA-Research-2009-063.pdf:8.35MB

The purpose of this study was to assess exposure dose of "Likely Scenarios" and "Less-likely Scenarios" on sub-surface disposal. They were two of "Classification of three types scenarios" in "Basic Policy for Safety Regulation Concerning Land Disposal of Low-Level Radioactive Waste (Interim Report)" formulated by the Nuclear Safety Commission of Japan. Selection of the assessed scenarios, development of the assessment tool and preliminary exposure dose assessment were conducted. Maximum exposure doses for "Likely Scenarios" and "Less-likely Scenarios" were less than each standard dose value in the Interim Report (Likely Scenarios: 10$$mu$$Sv/y, Less-likely Scenarios: 300$$mu$$Sv/y).

Oral presentation

Dose assessment for sub-surface disposal of radioactive waste, 1; Study of "Likely Scenarios" and "Less-likely Scenarios"

Nakatani, Takayoshi; Sugaya, Toshikatsu; Sone, Tomoyuki; Ishitoya, Kimihide; Funabashi, Hideyuki; Sasaki, Ryoichi*; Shimoda, Satoko*; Kurosawa, Mitsuru*

no journal, , 

The propose of study was safety assessment of "Likely scenarios" and "Less-likely scenarios" on sub-surface disposal. They were two of "Classification of three types scenarios" in "Basic Policy for Safety Regulation Concerning Land Disposal of Low-Level Radioactive Waste (Interim Report)" formulated by the NSC. Selection of the assessed scenarios, development of the assessment tool and preliminary exposure dose assessment were conducted according to the standard of the AESJ. As the results, Maximum exposure doses for "Likely Scenarios" and "Less-Likely Scenarios" were less than each standard dose value in the Interim Report (Likely Scenarios: 10$$mu$$Sv/y, Less-Likely Scenarios: 300$$mu$$Sv/y).

Oral presentation

Dose assessment for sub-surface disposal of radioactive waste, 2; Study on "Inadvertent Human Intrusion or Rare Natural Event Scenarios"

Sugaya, Toshikatsu; Nakatani, Takayoshi; Sone, Tomoyuki; Ishitoya, Kimihide; Funabashi, Hideyuki; Nakai, Kunihiro*; Shimada, Hidemitsu*

no journal, , 

The purpose of this study was safety assessment of "Inadvertent Human Intrusion or Rare Natural Event Scenarios" on sub-surface disposal. It was one of "Classification of three types scenarios" in "Basic Policy for Safety Regulation Concerning Land Disposal of Low-Level Radioactive Waste (Interim Report)" formulated by the NSC. Considering of assessed scenario, selection of the assessed scenarios, development of the assessment tool and preliminary exposure dose assessment were conducted according to the standard of the AESJ. As the results, exposure dose of "Well water drinking scenario" was the highest in the assessment scenarios. This scenario assumed that the groundwater in Excavation Disturbed Zone (EDZ) was directly used as drinking water without any dilution. Although, this was very conservative condition and the result exceeded 10 mSv/y, it stayed under the upper limit of standard dose value for "Inadvertent Human Intrusion or Rare Natural Event Scenarios" (10-100 mSv/y).

Oral presentation

Trial calculation of radioactivity concentration corresponding to dose criterion for concrete vault disposal of radioactive waste generated from research, medical, and industrial facilities

Sakuma, Kota; Sugaya, Toshikatsu; Abe, Daichi*; Sakai, Akihiro

no journal, , 

Japan Atomic Energy Agency has aims to carry out Concrete Vault Disposal of low-level radioactive waste generated from research facilities and other facilities. Therefore, Radioactivity Concentration Corresponding to Dose Criterion for 220 nuclides in the waste were calculated for the purpose of discussion for Acceptance Standards for Radioactivity Concentration.

Oral presentation

Disposal project of LLW generated in research, medical and industrial facilities; Evaluation of radioactivity concentration corresponding to dose criterion

Saito, Tatsuo; Sugaya, Toshikatsu; Sakai, Akihiro; Kamei, Gento

no journal, , 

In Japan, low-level radioactive wastes generated from research institutes, universities and medical institutions are continuously stored without being buried. Therefore, the Japan Atomic Energy Agency (JAEA) has been an implementation body of the burial project of the radioactive wastes from research facilities. In this report, the characteristics of the wastes and the conceptional design of the JAEA burial facilities are introduced, and the current status of the study on the radioactivity concentrations corresponding to dose criterion for trench disposal and pit disposal is also presented.

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