A low-cost and high-performance gamma-ray spectrometer has been successfully constructed by using 3″φ × 3″ NaI(Tl) scintillation probes, standard lead bricks and others for the measurement of radioactive-cesium concentration of various surrounding materials. A faced double detector system with signal mixing has been employed for the improvement of total-absorption detection efficiency for radioactive-cesium. Uniquely-shaped containers covering the double detectors have been made of acrylic pipes and plates. The total-absorption detection efficiency for radioactive-cesium in the homemade container was experimentally determined by using a standard voluminous source made of soil in Fukushima. The detection efficiency determined from the experiments almost agreed results from Monte Carlo calculations with the PHITS code. It was confirmed from radioactivecesium measurement on fly ash that the subtraction of energy spectral data of background radiations was useful for low-level radioactive-cesium measurement.

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  Passive diffusion sampling has been widely used to monitor organic and inorganic pollutants in the environment. We herein developed a new and simple passive diffusion sampling method to monitor ¹⁴C in the indoor working environment of radioisotope facilities. The badge-type Shikata sampler is an open-end type with no diffusion cap that fits a collection filter with a diameter of 25 mm. This sampler could efficiently collect indoor ¹⁴C with good reliability and a collection efficiency that was 10-fold higher than that of the conventional active pumped method. The Shikata sampler is small, simple, and easy to handle. It may be subsidiary used to monitor indoor ¹⁴C concentrations in radioisotope working rooms, in which radioactivity must be measured once a month as recommended by the Industrial Safety and Health Law.

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  Radioactive cesium (Cs) is extracted effectively from various polluted samples such as soil, silt, and burned ash by washing with a detergent solution comprised of KCl, MgCl₂, and hydroxyethyl cellulose in a 5% H₂SO₄ aqueous solution. Repeatedly washing extracts more than 65% of the radioactive Cs.

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