We have developed a simple method for the long-term monitoring of the seasonal variation of the radiocaesium radioactivity in trees using commercially available integrating dosimeters. Experiments and Monte Carlo simulations were performed to assess whether the proposed dosimeter-based method could measure the seasonal variation. From the experimental results, the performance variation among individual dosimeters was found to be 1.6%, which is sufficiently small compared with the expected seasonal variation. Moreover, the simulation results indicated that the measured value of the dosimeter increased owing to the photons passing through a stem, and a correction factor was necessary to compensate the influence of photon absorption and scattering in stem. We suggested that the simple and easy dosimeter-based method could be useful to measure the seasonal variations of radioactivity in trees.
The level of natural radioactivity has been evaluated for soil samples collected from the uranium and thorium bearing region of Lolodorf in the southwestern Cameroon. Specific activities of 226Ra, 232Th and 40K in these soil samples were determined using γ-ray spectrometry with sodium iodide (NaI(Tl)) detector. The specific activities for the whole study areas where consist of five inhabited localities were compared with the world average and permissible recommended limits. Specific activities of 226Ra, 232Th and 40K ranged from 5–120, 2–170 and 50–253 Bq kg−1, with average values of 22±2, 37±6 and 98±7 Bq kg−1, respectively. The average values of absorbed dose rate in air (Da), external effective dose (Eext), radium equivalent activity (Raeq), external hazard index (Hext) and representative level index (Iγ) were 36.7±5.0 nGy h−1, 0.29±0.04 mSv y−1, 83±14 Bq kg−1, 0.22±0.03 and 0.58±0.10 respectively, which, were lower than their recommended values. Although this study shows that radioactivity level is normal in the study areas, except some areas where the uranium and potassium anomalies had been found by previous investigations, the possibility of developing cancer cases among individuals must not be neglected. The soil from the sampling areas in this study can be used safely as building materials apart from some points within Ngombas and Kribi.
We have developed a personal radiation dosimeter “D-shuttle” in order to measure radiation dose in daily life after the accident of the Fukushima Dai-ichi Nuclear Power Plant. This dosimeter is small, lightweight, and can be used for more than one year without battery exchange. Furthermore, the user can check the total radiation dose and one day dose using a display module. In this article, we discuss history of the development, its specifications, and applications to real time monitoring.
D-Shuttle is a compact, light, long-battery-life, cumulative electronic personal dosimeter co-developed by Chiyoda Technol Corporation and National Institute of Advanced Industrial Science and Technology. D-shuttle was developed after Fukushima Dai-ichi Nuclear Power Plant Accident, and supplied to public from March, 2013. Because of the separation of dosimeter part and the display part, we successfully developed a dosimeter which can continuously operate for more than 1 year and record hourly dose data. The calibration of a detector is performed when the dosimeter is sent to the manufacturer for battery exchange, thus, the general public can easily perform dosimetry and reduce their dose. This review paper shows general characteristics of this new dosimeter and introduces application examples performed around Fukushima area. Finally it shows future directions such as environmental measurements and the use in nuclear medicine facilities.