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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.
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 
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.
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.
Nakata, Hisakazu; Hayashi, Hirokazu; Amazawa, Hiroya; Sakai, Akihiro
no journal, ,
no abstracts in English
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.