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 H, Co, and Ni in aluminum, H, Co, Ni, and Eu in carbon steel, H, Co, and Eu in shield concrete, and H, C, Co, Ni, and 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.

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.

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.

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.

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: 10Sv/y, Less-likely Scenarios: 300Sv/y).

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).