We updated our imaging system, namely real-time radioisotope imaging system (RRIS) to observe 32 P movement in large plants using a large size scintillator. In the previous version of RRIS, the view was limited by the size of a CsI (Tl) scintillator deposited on a fiber optic plate (FOS). However, owing to the high price and difficulty in handling of FOS, the view area was limited to 100×200 mm. In this study, we evaluated 5 large and low-cost plastic scintillators and showed that plastic scintillators can be used in RRIS for the quantitative analysis of 32 P. We also evaluated the resolution of the imaging system with plastic scintillator.

The objects of this study are only radioactive consumer products added NORM (NRCP). In Japanese current markets, many NRCP are sold claiming some effects like hormesis. The existence of NRCP in the living environments here may raise the radiation exposure dose of the user. The activity concentrations in many kinds of NRCP have been determined by gamma-ray spectrometry and the radiation exposure doses from NRCP were calculated in the case of normal use and misuse. The results show that there are some inhalation risks in the cases of NRCP misuse. Furthermore, many kinds of NRCP and ores were analysed by prompt gamma-ray activation analysis method and the results show the added radioactive materials in NRCP are monazite. The three principles of the radioprotection should be applied for users of NRCP. The Japanese NORM guideline of 2009 mentions requirements for optimisation (ALARA) and dose criteria, without justification. Justification is most important for an effective use of radioactive ores that are added in NRCP.

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