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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

Sensitivity of radioactive nuclide leaching rate under the sub-surface disposal

Tsuji, Tomoyuki; Nakamura, Yasuo; Nakatani, Takayoshi

JAEA-Technology 2015-014, 34 Pages, 2015/06

[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.] In order to dispose of radioactive wastes for sub-surface disposal, JAEA has studied the safety assessment for likely scenario and less-likely scenario. Radioactive nuclide leaching rate under the sub-surface disposal is important parameter in the safety assessment because radioactive nuclides in activated metal wastes are released with its corrosion. In this report, sensitivity of radioactive nuclide leaching rate is studied for the safety assessment. As the result, it is confirmed that Cl-36 which is dominant for the safety assessment in groundwater scenario is sensitive to radioactive nuclide leaching rate, but Nb-94 which is dominant in tunnel excavation scenario is not sensitive to radioactive nuclide leaching rate but to distribution coefficients in engineered barrier.

JAEA Reports

Environmental impact of nitrate nitrogen in sub-surface disposal system on surface water and sensitivity analysis of distribution coefficient of nitrate ion and porosity of waste layer on the environmental safety assessments

Nakamura, Yasuo; Nakatani, Takayoshi

JAEA-Technology 2014-048, 18 Pages, 2015/03

JAEA-Technology-2014-048.pdf:7.75MB

Sodium nitrate is included bituminized waste generating from the reprocessing plant of spent fuel which is disposed of in sub-surface disposal facility. Because the sodium nitrate is soluble material in surface water, it is a concern impact on surface water. Such as non-radioactive materials are not strictly regulated by "the Law for the Regulations of Nuclear Source Material, Nuclear Fuel Material and Reactors", but should be considered by related laws and regulations according to former basic policy. Because it is regulated as nitrate nitrogen by "The Basic Environment Law", the valuation of the environmental impact on general sub-surface disposal system was carried out. As the results, the concentration of nitrate nitrogen in river water whose annual quantity of water is rather than 110 $^{5}$ m $^{3}$ /y is below the regulated value at the small scale surface waters as evaluation point.

JAEA Reports

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

Sakatani, Keiichi; Nakamura, Yasuo; Tsuji, Tomoyuki; Nakatani, Takayoshi

JAEA-Data/Code 2014-020, 38 Pages, 2014/11

JAEA-Data-Code-2014-020.pdf:30.04MB

The safety assessment for sub-surface disposal of radioactive wastes should ensure that calculated dose will be lower than the dose assigned to the scenario in question over the whole evaluation period of hundreds of thousands years. We have developed several assessment tools for the safe disposal of radioactive wastes on the GoldSim platform, and calculated doses since JFY 2008. These assessment tools have been improved reflecting the last view of assessment. In addition, we have developed an assessment tool for the gas migration scenario. This report describes concept of assessment model and structure of tool for the gas migration scenario.

JAEA Reports

Study on measurement of spatial dose rates from simulated products made from recycled metal below clearance levels arising from dismantling of nuclear facilities (Contract research)

Okamoto, Akiko; Kitami, Yasuo*; Ando, Yoshiaki*; Nakamura, Hisashi; Saito, Kimiaki; Nakashima, Mikio

JAERI-Tech 2002-051, 40 Pages, 2002/06

JAERI-Tech-2002-051.pdf:3.63MB

In order to contribute to safety assessment of recycling products made from dismantling metal wastes, metal ingots containing $^{60}$ Co were produced and spatial dose rates from the ingots were evaluated by gamma-ray measurement and calculation. Stripping operations were made using detector response functions calculated by Monte Carlo program to derive spatial dose rates from measured gamma-ray spectra. In the computer simulation, Monte Carlo and point kernel calculation codes were used. Agreement between measured and calculated values was satisfactory in spite of an extremely low concentration of $^{60}$ Co in the ingots and a complicated geometric condition between detector and samples.