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In recent years, a growing number of geothermal power plants has been operating in the world as one of the energy generating industries. In the Philippine, although there are relatively many geothermal power plants compared with other countries, radiological information in these plants is scarce. In this study, measurements of activity concentration of scale and soil and ambient dose equivalent rate in a geothermal power plant in the Philippines were performed. The ambient equivalent dose rates in all work sites ranged from 0.038 to 0.051 μSv h−1, which were less than average value of those in the Philippines. The activity concentrations of the 238U series, 232Th series and 40K in the samples were lower than the relevant values (10 Bq g−1 for 40K and 1 Bq g−1 for all other radionuclides of natural origin) in the IAEA Safety Standards.

Uranium, thorium and rare earth elements (REEs) in soil samples contaminated by Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident was determined using inductively coupled plasma-mass spectrometry (ICP-MS). This information provides knowledge about concentration levels of REEs in soil samples as a background data after FDNPP accident. Chondrite-normalised REEs pattern does not show enrichment in concentrations of REEs, which could be related to FDNPP accident. The high concentration of these elements at few sampling points may be due to soil formation process from granitic rocks.

The latest car-borne survey was carried out by Hirosaki University in order to grasp the local distribution of the absorbed dose rate in air after the evacuation order was lifted on Namie Town in 2017. The car-borne survey of absorbed dose rate in air was carried out on most of the roads which were accessible by car in Namie Town using a 3-in × 3-in NaI(Tl) scintillation spectrometer. The range of the absorbed dose rate in air was calculated to be 0.041–11 μGy h−1. The distribution maps of the absorbed dose rate in air were drawn based on the data obtained during the surveys in 2011, 2015 and 2017. The comparison of these absorbed dose rates in air suggests that the elevated absorbed dose rate in air in Namie Town caused by the FDNPP accident may be decreasing faster than natural decline which includes weathering effect and physical decay due to the artificial decontamination.

The Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident has caused significant radionuclide contamination. Pu isotopes at the level of GBq were released from the damaged reactors to terrestrial and marine ecosystems. In this work, 35 samples were collected at different locations of Fukushima. Samples consisted of three types, soil, forest litter and alluvial dust (road dust, sludges from drainage systems and below gutter pipe outflows). The obtained activity ratios of 238Pu/(239+240)Pu ranged from 0.030 to 1.86. 14 of our samples contained trace amounts of Pu originating from the damaged reactors (2SM verification). Our study identified a few previously unknown “hot spots” of 238Pu/(239+240)Pu activity ratio localized in an area between 15 and 30 km in the northwest direction from the FDNPP. Additionally, results obtained in this study combined with previously published data allowed us to prepare a map of spatial distribution of the Pu isotope fingerprints (238Pu/(239+240)Pu) in Fukushima Prefecture.

In order to evaluate internal exposure to radon and thoron, concentrations for radon, thoron, and thoron progeny were measured for 259 dwellings located in high background radiation areas (HBRAs, outdoor external dose: 3–5 mGy y−1) and low background radiation areas (control areas, outdoor external dose: 1 mGy y−1) in Karunagappally Taluk, Kerala, India. The measurements were conducted using passive-type radon-thoron detectors and thoron progeny detectors over two six-month measurement periods from June 2010 to June 2011. The results showed no major differences in radon and thoron progeny concentrations between the HBRAs and the control areas. The geometric mean of the annual effective dose due to radon and thoron was calculated as 0.10 and 0.44 mSv, respectively. The doses were small, but not negligible compared with the external dose in the two areas.

Radon concentrations are measured using a PICO-RAD activated charcoal collector, which is usually fitted with a conventional liquid scintillation counter (LSC) and its dedicated software. In this study, PICO-RAD collectors were exposed to a known radon concentration in a chamber at the National Institute of Radiological Science (NIRS), and evaluated by the LSC (without the dedicated software) using an integral counting method. In addition, a conversion equation was determined between counting rate and radon concentration. We showed that radon concentration could be measured by the PICO-RAD collector using a conventional and simplified LSC instrument. It is required that the minimum detectable Rn concentration should be kept at 10% of the recommended reference level. Simplified LSC produced an approximately six-fold higher background level than its conventional counterpart, however it exhibited a minimum detectable radon concentration as low as 30 Bq m−3.

A comprehensive study was carried out to determine the radioactivity concentration of soil samples from different sites of a high background radiation area in the eastern coast of India, Odisha state. The dose rate measured in situ varied from 0.25 to 1.2 mSv h-1. The gamma spectrometry measurements indicated Th series elements as the main contributors to the enhanced level of radiation and allowed the authors to find the mean level of the activity concentration (+SD) for 226Ra, 228Th and 40K as 130+97, 1110+890 and 360+140 Bq kg21, respectively. Human exposure from radionuclides occurring outdoor was estimated based on the effective dose rate, which ranged from 0.14+0.02 to 2.15+0.26 mSv and was higher than the UNSCEAR annual worldwide average value 0.07 mSv. Additionally, X-ray fluorescence analysis provided information about the content of major elements in samples and indicated the significant amount of Ti (7.4+4.9 %) in soils.

The vertical distribution of radio-caesium (137Cs and 134Cs) in undisturbed soil profiles of grassland and forest soils, derived from the Fukushima-Daiichi Nuclear Power Plant (FDNPP) accident that occurred on 11 March 2011, was studied. Surface soil and depth profile soil samples were collected from six locations within the 20 km zone of FDNPP, during November 2012 and June 2013. The activity ratio for 137Cs and 134Cs was found to be almost constant about 1 within the soil profiles as well as in the surface soil, indicative of FDNPP accident origin. From soil depth profile distribution of Cs activity, it is observed that Cs is strongly bound to soil materials, which slows Cs migration. N90% of the activity was found to be retainedwithin the upper 5 cm layer. Retardation of Cs movement has been quantified by measuring sorption of Cs in soil in terms of distribution coefficient (Kd) using the laboratory batch method. Faster migration has been observed in case of forest land soil compared to grassland soil. The empirical migration velocity of Cs radio isotope was estimated from the depth profile Cs concentration and found to vary from 1.1 to 1.7 and 0.85 to 3.5 cm y−1 in grassland and forest soil, respectively. The residential half life for Cs isotopes was found to be 1.03–7.75 y and 1.18–4.67 y for grassland and forest land respectively using a compartmental model. In addition to the empirical analysis of the profiles, analytical models were fitted to the data which may help elucidate the physical nature of the transport of trace elements.

General survey for the environmental radon and thoron has been performed in Minamidaitojima, Okinawa prefecture, southwestern part of Japan. In situ measurements of the radon and thoron exhalation rates were conducted at a total of 7 points using an accumulation technique with a ZnS(Ag) scintillation detector. The medians of radon and thoron exhalation rates were estimated to be 31 mBq m-2 s-1 and 3,970 mBq m-2 s-1, respectively. The atmospheric radon concentrations were measured at 2 points with an ionization chamber, and the maximum concentration was estimated to be 94 Bq m-3. For the surface soil samples collected at the measurement points of the exhalation rates, arithmetic means for 238U and 232Th series concentration were estimated to be approximately 145 Bq kg-1 dry and 101 Bq kg-1 dry, respectively. These results indicated that the environmental radon and thoron levels in Minamidaito-jima are fairly higher than those of the average of Japan. And it is strongly suggested that the exhalation rates and the concentrations are enhanced mainly due to the surface soil with the relatively high radioactivity.

A method based on liquid scintillation counting system has been developed for the measurement of 90Sr in Fukushima soil samples due to contamination of 134Cs and 137Cs. Three soil samples were collected within 30 km radius from the Fukushima Daiichi Nuclear Power Plant (FDNPP). Activity concentration of 134Cs and 137Cs were measured using a gamma spectroscopy system with high-purity germanium detector. 90Sr contamination is little elevated but comparable with the background contamin- ation level that originated from atmospheric nuclear weapon tests, whereas radiocesium contamination has increased significant- ly. Activity concentration of 90Sr in the soil samples varied in the range of 10.4+0.6–22.0+1.2 Bq kg21. Activity concentrations of 134Cs and 137Cs in the soil samples were in the range of 28.2+0.2–56.3+0.2 kBq kg21 and 35.2+0.1– 70.2+0.2 kBq kg21, respectively (reference date for decay correction is 1 December 2011).

The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident has resulted in the deposition of radioactive contamination of soils mainly by 134Cs and 137Cs. The contaminated areas are of a great concern since external radiation may lead to significant long-term doses to humans and animals. External dose rate above ground will decrease with physical decay of the radionuclides and as they migrate deeper into the soil with time. In the present study, depth profiles of Cs radioisotopes have been studied at dif- ferent times over a period of 1 y. Radiocaesium inventories for 134Cs and 137Cs down to a depth of 10 cm at the four measurement times varied from 2.09 to 4.14 MBq m22 with coefficient of variation (CV): 27.4 %, n 5 4 and from 2.13 to 4.23 MBq m22 with CV: 27.3 %, n 5 4, respectively. The activity ratio for 134Cs/137Cs decreased from 0.62 to 0.46 during 1 y of measurement i.e. July 2012 to June 2013. However, the ratio with decay correction (15 March 2011) was found to be constant ∼1, indicating con- tamination from FDNPP origin. In order to understand the radiocaesium distribution in soil profile, physico-chemical character- isation of soil has been carried out.

The present study focuses on internal exposure caused by the inhalation of radon and thoron progenies because the internal exposures have not yet been clarified. For their dose assessment, radon, thoron and thoron progeny concentrations were measured by passive monitors over a long period (for 6 months). Consequently, radon, thoron and equilibrium equivalent thoron concen- trations were given as 124 + 78, 1247 + 1189 and 7.8 + 9.1 Bq m23, respectively. Annual effective doses are estimated to be 3.1 + 2.0 mSv for radon and 2.2 + 2.5 mSv for thoron. Total dose are estimated to be 5.3 + 3.5 mSv a21. The present study has revealed that the radon dose was comparable with the thoron dose, and the total dose was ∼2 times higher than the worldwide average.