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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

Waste acceptance criteria for waste packages destined for near surface disposal containing radioactive waste from research, industrial and medical facilities; Study on a method that fills voidage in waste package with sandy soil

Nakata, Hisakazu; Hayashi, Hirokazu; Amazawa, Hiroya; Sakai, Akihiro

JAEA-Technology 2017-031, 41 Pages, 2018/01

JAEA-Technology-2017-031.pdf:5.27MB

JAEA plans to install disposal facilities for radioactive waste arising from research institutes. It must meet the technical standards specified in the relevant rule. One technical standard is that the disposal facilities shall be performance so as not to be left with the voids after the backfilling with soil. Additionally, the rule also requires this radioactive waste be enclosed in a container in which no harmful voids remain. In order to contribute to the development of a method that adapts the disposal facilities to these technical standards, JAEA adopts a waste conditioning artifice that aims for reducing a quantity of voidage in each waste container by a vibration filling method using sandy soil, providing with average void ratios inside the disposal facilities being adequately controlled. In this reports, filling property tests are conducted in the light of filling sand characteristics, types of metal waste and vibration conditions.

JAEA Reports

Method and result for calculation of radioactivity concentration of radionuclide corresponding to dose criterion for near surface disposal of radioactive waste generated from research, medical, and industrial facilities

Okada, Shota; Kurosawa, Ryohei; Sakai, Akihiro; Nakata, Hisakazu; Amazawa, Hiroya

JAEA-Technology 2015-016, 44 Pages, 2015/07

JAEA-Technology-2015-016.pdf:5.8MB

In this report, we calculated radioactivity concentration of radionuclides potentially contained in low level radioactive waste (LLW) generated from research, medical, and industrial facilities corresponding to dose criterion (10 $$mu$$Sv/y) for near surface disposal. 220 kinds of nuclides whose half-life are more than 30 days were selected. Radioactivity concentrations corresponding to dose criterion of 40 nuclides among 220 ones were calculated by using the representative model because the concentrations of 40 nuclides had not been calculated yet. Skyshine dose from each of 19 nuclides, whose radioactivity concentration were invalid values that are larger than the specific radioactivity of nuclides, during operation of disposal facility was calculated. These radioactivity concentrations can be used as criteria of categorization of LLW between trench type and concrete vault type disposal and of preliminary selection of important nuclides of these disposals in the generic conditions.

Oral presentation

Plan and technical development status of disposal of low-level radioactive waste generated from research facilities

Sakai, Akihiro

no journal, , 

Plan of disposal of LLW generated from research facilities and recent topics of technical development of the disposal are explained. At first, regarding the radioactivity evaluation of waste, a study about the reduction of the number of important nuclides by the method that enhances the safety functions of the trench disposal facility is introduced. The installation of impermeable layers and sorption layers in order to reduce the leaching of nuclides and the installation of a cover structure with resistance to human intrusion into the waste layer are examined as the safety functions. Then, regarding the design and operation of trench disposal facilities, a measure that increase the slope angle of the cover soil beforehand is explained in order to prevent the cover soil from settlement caused by voids in the waste containers at the trench disposal facility. We will continue to study the specific design of trench disposal facilities to realize the measures to these issues.

Oral presentation

Present status of LLW disposal project by JAEA

Sakai, Akihiro

no journal, , 

no abstracts in English

Oral presentation

Study of radionuclide migration model for concrete-pit and trench disposal

Sakai, Akihiro

no journal, , 

no abstracts in English

Oral presentation

Oral presentation

Study of determination methods to classify the disposal category of radioactive waste generated from research, medical, and industrial facilities

Izumo, Sari; Sugaya, Toshikatsu; Nakata, Hisakazu; Sakai, Akihiro

no journal, , 

no abstracts in English

Oral presentation

Design study for impermeable function of trench disposal facility for very low level waste generated from research, industrial and medical facilities

Sakai, Akihiro; Nakata, Hisakazu; Amazawa, Hiroya; Kurosawa, Ryohei*; Sato, Makoto*; Kitamura, Yoichi*

no journal, , 

We consider that very low level waste slightly including chemical toxicity material among radioactive waste generated from research, industrial and medical facilities is disposed of in trench disposal facility which is equipped with impermeable layers. We studied the impermeable system which has high performance to prevent the radioactive material from leaching out of waste layer taking into account the combination of geomembrane liners and low permeable materials.

Oral presentation

Disposal project of LLW generated in research, medical and industrial facilities; Investigation of method filling voids in waste for trench disposal

Nakata, Hisakazu; Izumo, Sari; Amazawa, Hiroya; Sakai, Akihiro

no journal, , 

JAEA is working toward the establishment of disposal facilities for waste from research facilities in Japan, in accordance with the Law and the government's basic policy (2008). For burial disposal, it is necessary to make burial waste that meet the acceptance criteria for safety. This report presents the results of tests conducted to confirm the method meeting the waste acceptance criteria for voids as for trench disposal.

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