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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.
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.
Cs discharge characteristics from a forested catchment of the Ohta RiverSakuma, Kazuyuki; Yoshimura, Kazuya; Nakanishi, Takahiro; Funaki, Hironori; Tsuruta, Tadahiko; Ochi, Kotaro; Hayashi, Seiji*; Tsuji, Hideki*; Ozaki, Hirokazu*
no journal, ,
Cesium-137 leaching from decomposing forest litter is thought to be one pathway by which dissolved Cs enters rivers from forests. To clarify whether this process contributes or not, we studied the correlation between humin-like matter from microorganism-induced plants decomposition and dissolved Cs concentrations. River water samples were collected approximately once a month from April 2017 to August 2019 at 10 locations (7 locations from April 2019) from the upstream of the Ohta River in the Namie and Minamisoma districts. These samples were filtered through 0.45-
m-pore size membrane filters. The dissolved Cs concentrations and fluorescence intensities of humin-like matter were measured. A positive correlation was found between the fluorescence intensities of humin-like matter and normalized dissolved Cs concentration (R
= 0.17, p 
0.001). The results indicate that Cs leaching from forest litter because of litter decomposition can contribute to increasing the dissolved Cs concentration in river water in forested catchments.
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.