Soil and waste generated by decontamination have been sealed in containers such as large weatherproof sandbags and flexible container bags (Fig. 1) according to guidelines 1) made by the Japanese government and tentatively stored at temporary storage sites. These containers are temporary materials, and it was initially assumed that the use period would be around 3 years. But in fact, at many temporary storage sites, they had been used for 3 years or longer, which raised concern over their durability. Therefore, the tensile test was conducted (Fig. 2) with storage containers that had been actually used at temporary storage sites to assess the strength variation for a long term.

As a result of the test, it was found that as long as the containers were in the environment shielded with water-impermeable sheets or the like to block sunlight, even if the containers had been used for 7.3 years at the maximum, the strength exceeded the standard strength of new containers (Fig. 3). Additionally, based on aging deterioration of tensile strength, it was estimated that they would withstand storage for around 10 years.

Fig.1　Storage containers (left: large weatherproof sandbags, right: flexible container bags)

Fig.2　Tensile test

Fig.3　Tensile strength of flexible container bags (light-shielded storage)

More（Japanese only）

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Reference

1. 原子力規制委員会, “放射線量等分布マップの作成等に関する報告書（第1編）”.
2. 原子放射線の影響に関する国連科学委員会, 電離放射線の線源、影響およびリスク; UNSCEAR 2013年報告書, 第Ⅰ巻 国連総会報告書 科学的附属書A: 2011年東日本大震災後の原子力事故による放射線被ばくのレベルと影響, United Nation, 2015, 306p.ed Nation, 2015, 306p.
3. 文部科学省，“放射線量等分布マップ拡大サイト”.