Development of a non-destructive specific activity inspection system for mushroom logs

Sodai Takyu, Keizo Ishii, Tetsuo Matsuyama, Toshiro Yamaguchi, Mitsuyoshi Sato, Tohru Ohnuma

Research output: Contribution to journalArticlepeer-review


Following the Fukushima Daiichi nuclear disaster, a specific activity inspection system is required to ensure that raw wood used for cultivating shiitake (Lentinus edodes) is safe. Although most radioactive materials adhere to tree bark, as of 2016, the current inspection method measures the specific activity of the whole log. To resolve issues with the current inspection method and contribute to the reconstruction of agriculture and forestry in the disaster area, we developed an inspection system to measure the specific activity of the bark without cutting the tree in the forest. The gamma-ray detector used in this system consisted of four radiation detection modules that could enclose the tree. The external surfaces of the four detectors were covered with lead to block background radiation from the environment. Log samples were analyzed by this system and by an HP-Ge semiconductor detector, and the results were compared. A quantification factor was determined to convert the counts measured by this system into the specific activity of the bark. The field test was conducted in the northern parts of Miyagi and Fukushima prefectures. The results confirmed that the system had reasonable measurement accuracy and could determine the direction from which radiocesium had been transported.

Original languageEnglish
Pages (from-to)1024-1033
Number of pages10
Journaljournal of nuclear science and technology
Issue number9
Publication statusPublished - 2018 Sep 2


  • Fukushima Daiichi nuclear disaster
  • Gamma ray detector
  • Specific activity inspection
  • decontamination

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Nuclear Energy and Engineering


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