Dose estimation in recycling of removed soil as seaside protection forest (Contract research)

Sawaguchi, Takuma; Takai, Shizuka; Takeda, Seiji

JAEA-Research 2020-005, 47 Pages, 2020/06

JAEA-Research-2020-005.pdf:5.09MB

After the Fukushima Daiichi Nuclear Power Station accident, large quantities of radiocesium-contaminated soil were generated from decontamination activities in the Fukushima prefecture. The removed soil has been stored in the prefecture until its final disposal. To complete the final disposal outside Fukushima prefecture, reducing the disposal volume through recycling can prove effective. The Ministry of the Environment, Japan (MOE) has presented a policy to recycle low-radioactive removed soil as recycled materials under the management of public authority. The recycling is limited to civil engineering structures in public projects. In this study, to contribute to guideline development for removed soil recycling by MOE, dose estimation in recycling of removed soil as embankment materials of seaside protection forest was conducted. First, additional doses to workers and the public in construction and service scenarios were evaluated. From the result, the radioactive cesium concentration level of recycled materials, where all additional doses meet the radiation criterion of 1 mSv/y, was derived to be 5,000 Bq/kg. Then, construction conditions were reviewed to reduce additional doses to the public in a service scenario. With the derived radioactivity level of 5,000 Bq/kg, the covered soil thickness of 39 cm or more limited the doses to less than 10 Sv/y. Finally, additional doses in a disaster scenario were evaluated. The doses were confirmed to be below 1 mSv/y when the removed soil of 5,000 Bq/kg was used.

Challenges for enhancing Fukushima environment resilience, 6; The Use of the reclaimed materials derived from the removed soil on the basis of the security

Okada, Takashi; Takeda, Seiji; Nakata, Hisakazu

Nihon Genshiryoku Gakkai-Shi ATOMO, 59(10), p.603 - 607, 2017/10

Because the reclaimed material is used, quantity of disposal of the removal soil can decrease. It is a strategic key to utilize the reclaimed material. As for this report, it is explained to about the fundamentals of the safe use of the reclaimed materials derived from the removed soil.

Challenges for enhancing Fukushima environmental resilience, 4; Development of physical and heat treatment methods on aiming at decontamination, volume reduction and reuse of contaminated soil

Yaita, Tsuyoshi; Honda, Mitsunori; Shimoyama, Iwao; Ito, Kenichi*; Mampuku, Yuzo*; Tsuji, Takuya; Matsumura, Daiju

Nihon Genshiryoku Gakkai-Shi ATOMO, 59(8), p.483 - 487, 2017/08

no abstracts in English

Volume reduction of cesium contaminated soil by high gradient magnetic separation using superconducting magnet

Nishijima, Shigehiro*; Yukumatsu, Kazuki*; Horie, Hiroki*; Nomura, Naoki*; Akiyama, Yoko*; Mishima, Fumihito*; Sekiyama, Tomio; Mitsui, Seiichiro; Kato, Mitsugu

no journal, , 

The amount of Cs contaminated soil originating from decontamination work after the accident of Fukushima Dai-ichi Nuclear Power Plant is estimated as large as 20 million m in maximum, and its volume reduction is required to optimize final disposal of the contaminated soil outside Fukushima pref. We have proposed a new method to reduce the volume of the contaminated soil by the combination of wet classification and high gradient magnetic separation (HGMS). In this study, we have been investigating selective separation of paramagnetic 2:1 type clay minerals and mica, which strongly absorb and fix Cs ions, by superconducting magnetic separation on silt/clay suspension as a volume reduction technique. We conducted magnetic separation experiments of contaminated soil in Fukushima utilizing a superconducting magnet based on results of particle trajectory simulation for various particle size.

Approach of radiation protection on recycling materials contaminated by radionuclides

Miwa, Kazuji; Iimoto, Takeshi*

no journal, , 

ICRP Publ.103 shows that reference levels are used for radiation protection of public exposure in existing exposure situation. However, there is no specific description about actual operation of reference levels. There is a possibility that a more rational radiation protection concept can be applied depending on the scale of environmental pollution in the existing exposure situation. This study proposes variation of radiation protection concept for public exposure assuming reusing radiation contaminated material which is in existing exposure situation.