A Portable Radioactivity Detection System for Outdoor Measurement of Concentration of Radioactive Caesium in a Mushroom Bed Log at a Low-level Contaminated Environment

Abstract

Log cultivation of shiitake mushrooms has been declining in Fukushima Prefecture and its surrounding areas due to the Fukushima Dai-ichi Nuclear Power Plant accident. The Forestry Agency has set a maximum concentration limit for radioactive caesium of 50 Bq/kg for bed logs to cultivate safe shiitake mushrooms (<100 Bq/kg). The development of a portable radioactivity detection system that can be operated outdoors is necessary to detect safe bed logs at cultivation locations that are potentially contaminated. In this study, we developed a low-cost portable radioactivity detection system without radiation shielding material. The safe bed logs were selected using a screening test with the portable radioactivity detection system even at a for low-levels of contamination (~0.1 µSv/h).