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To assess public exposure to radon, thoron, and their progeny, measurements were conducted in 50 dwellings within the bauxite-rich area of Fongo-Tongo in western Cameroon. Passive integrating radon-thoron discriminative detectors (specifically RADUET) were employed for radon and thoron measurements. Additionally, concentrations of short-lived radon and thoron progeny were estimated using Direct Radon Progeny Sensors (DRPSs) and Direct Thoron Progeny Sensors (DTPSs) based on LR-115 detectors. The findings revealed indoor radon concentrations ranging from 31 to 123 Bq m -3 with a geometric mean (GM) of 62 Bq m -3 , and indoor thoron concentrations ranging from 36 to 688 Bq m -3 with a GM of 242 Bq m -3 . The Equilibrium Equivalent Radon Concentration (EERC) ranged from 3 to 86 Bq m -3 with a GM of 25 Bq m -3 , while the Equilibrium Equivalent Thoron Concentration (EETC) ranged from 1.2 to 12.5 Bq m -3 with a GM of 7.6 Bq m -3 . Notably, all dwellings recorded radon concentrations below 100 Bq m -3 . Arithmetic means of radon and thoron equilibrium factors were calculated as 0.47 and 0.04, respectively. To assess annual effective doses from radon and thoron inhalation, equilibrium factors were used along with direct measurements of EERC and EETC. The differences observed in annual effective doses were 4.5% for radon and 42.5% for thoron. Furthermore, the contribution of thoron and its decay products to the annual effective dose from radon, thoron, and their progeny ranged from 12 to 94%, with an average contribution of 58%. Thus, this study found that the effective dose due to thoron inhalation in the study area exceeded that due to radon inhalation. It is concluded that, when evaluating radiation doses and health risks, it is crucial to consider both thoron and its progeny alongside radon and its progeny. This underscores the importance of considering direct measurements for accurately estimating radiation doses., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

In this study, the activity concentrations of radon (222Rn), thoron (220Rn) and thoron progeny were measured simultaneously in Djeno (Pointe-Noire, Republic of Congo) using RADUET detectors to evaluate the air quality and the radiological risks due to the inhalation of these radionuclides. Activity concentrations of radon progeny were calculated from those of radon. Indoor radon, thoron and progenies followed a lognormal distribution ranging between 20 and 40, 6 and 62, 8 and 17.6 and 0.4 and 19.6 Bq m-3 for radon, thoron, radon progeny and thoron progeny, respectively. Mean values for radon were lower than the worldwide values estimated by the United Nation Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), which are 40 Bq m-3 (arithmetic mean) and 45 Bq m-3 (geometric mean). Radon concentrations in the dwellings under study were below the World Health Organization and the International Commission on Radiological Protection recommended reference levels, which are, respectively, 100 and 300 Bq m-3. The mean concentration of thoron was twice the world average value of 10 Bq m-3 estimated by UNSCEAR. Thoron progeny mean concentration was sharply greater than the typical value (0.3 Bq m-3) for indoor atmosphere provided by UNSCEAR. Annual effective dose ranges were 0.40-0.87 mSv (arithmetic mean, 0.57 ± 0.11 mSv) for radon and 0.10-4.14 mSv (arithmetic mean, 0.55 ± 0.77 mSv) for thoron. The mean value for radon was lower than the value (1.15 mSv) estimated by UNSCEAR, while the mean value for thoron was five times higher than the UNSCEAR value (0.10 mSv). The study showed that the use of the typical equilibrium factor value given by UNSCEAR to compute effective dose led to an error above 80%. Finally, the results of this study showed that the excess relative risk of radon-induced cancer was low, below 2% for the population under 55 y. The results presented in the present study prove that the population of Djeno is exposed to a relatively low potential risk of radon- and thoron-induced cancer., (© The Author(s) 2024. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

This article discusses tritium concentrations in monthly precipitation in part of the Difficult-to-Return Zone in Namie Town during 2012-2021. The tritium concentrations, which were measured with a low background liquid scintillation counter after carrying out an enrichment procedure, fluctuated seasonally from 0.10 ± 0.02 to 0.85 ± 0.02 Bq L -1 . This range of concentrations is concluded to not be unusual based on comparisons with the concentrations at other sites and estimates of the past range of the concentrations. Moreover, no significant variations in observed tritium concentrations were observed due to decommissioning work at the Fukushima Dai-ichi Nuclear Power Plant. These results contribute to understanding the background level of tritium concentration in precipitation before the oceanic discharge of treated water from the Fukushima plant. In addition, this article evaluates the amount of tritium supplied to the ocean by terrestrial rainwater pouring into the Pacific Ocean via Ukedo River, which flows through Namie Town; this information will contribute to the discussion on the impact of the oceanic discharge of treated water., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

In-situ measurements by gamma-ray spectrometry using a NaI(Tl) scintillation spectrometer are performed to discriminate primordial and artificial radionuclides contributing to ambient gamma dose rates in the living environment to quantify prolonged influence of nuclear accidents. However, low energy resolution of the spectrometer causes poor discrimination in the measurements at high-dose-rate points, which leads to overestimation of ambient gamma dose rate from the primordial radionuclides. The present study clarified that photon fluxes originating from 40K and 214Bi were affected by the presence of 134Cs, whereas those from 208Tl were independent of it. In addition, the absorbed dose rates in air were strongly correlated with the 208Tl photon fluxes. These findings indicate that 208Tl photon fluxes can be used to evaluate absorbed dose rates in air from the primordial radionuclides. When estimated from the 208Tl photon fluxes only, the absorbed dose rates in air in Namie Town and Okuma Town, locations affected by the Fukushima Dai-ichi Nuclear Power Plant accident, were 19-71 and 20-47 nGy h-1, respectively., (© The Author(s) 2023. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Results of the preliminary measurements of indoor radon, thoron and progeny concentrations showed very high values of thoron concentrations in the eastern coastal region of Odisha, India. Therefore, measurements of thoron and its progeny concentrations were extended to a larger number of houses in this area for the assessment of the radiation dose received by the public. The measured values of thoron concentrations were used for the calculation of annual effective doses. The estimated values of the annual effective dose due to thoron exposure were observed in the range of 0.2-14.7 mSv. The estimated radiation doses responsible for thoron exposure were observed considerably high in the region. The results obtained are compared with those obtained in other studies performed so far in the study area and a review of different studies involving different measurement techniques is presented in the paper. The results of this study support the preliminary studies showing high values of thoron levels in the study area., (© The Author(s) 2023. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Portable-type electrostatic-collection radon monitors (RAD7) are often used for in-situ measurements of radon in water. In this study, we evaluated the calibration factors and their uncertainties for two RAD7 monitors based on comparative measurements with the liquid scintillation counting method. In the first experiment, we found that both RAD7 monitors had relatively large uncertainties due to leakage of radon gas that bubbled from the gaps between the lids of the desiccant container and the glass vial. Therefore, for the second experiment, these gaps were closed as much as possible using parafilm and clay, respectively. As a result, the relative uncertainties for both RAD7 monitors were significantly decreased. Furthermore, we collected spring water samples to confirm the reliability of radon concentrations. After closing the leakage point, the uncertainty of radon concentrations in spring water we measured using the typical protocol of the RAD7 were significantly lower, which improves the measurement., (© The Author(s) 2023. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Site-specific Dose Conversion Factors (DCFs) for radon progeny were estimated based on the aerosol measurement results in an outdoor environment and a tourist cave. The Activity Median Diameter (AMD) and unattached fraction were measured and used to calculate the effective dose per unit intake of radon progeny. The AMDs in the outdoor environment was in the range of 0.24-0.71 μm with the unattached fraction of 0.17. In the tourist cave, two peaks were found in the aerosol size distribution at nucleation and accumulation modes and the unattached fraction was measured to be 0.69 with a range of 0.36-0.85. The DCFs at the outdoor environment did not differ from those from the publication of the International Commission on Radiological Protection; however, the DCF in the tourist cave was significantly higher due to the discrepancy in the unattached fraction and the aerosol size distribution. It was found that these two factors would significantly affect the DCF so that we should be aware of it., (© The Author(s) 2023. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

The radon-prone area of the Adamawa region in Cameroon is characterized by high natural radiation background resulting from the high concentrations of radium-226, thorium-232, and indoor radon. To produce a radon-risk map, radon measurements in soil were carried out in the city of Ngaoundere. The radon activity concentration in soil gas ranged from 256 to 166 kBq m -3 with a mean of 80 kBq m -3 and a standard deviation of 38 kBq m -3 . The area is mostly classified as high risk (80%) according to the Swedish classification, and 20% as medium risk. A low-risk area was not observed. Granite-like geology sites were characterized by higher radon concentration. A ratio of about 295:1 was obtained for soil radon gas to indoor radon concentrations, with a positive correlation (R = 0.40), and a transfer factor of 3 per mil. These results demonstrate that in situ measurements of radon concentration in soil can provide accurate information on the level of indoor radon concentrations. Geostatistical and deterministic interpolation techniques have been used to obtain a radon map by comparing the suitability of ordinary kriging and inverse-distance-weighted (IDW) interpolation methods. It turned out that there is not much difference in the prediction errors of the two techniques (Root Mean Square Error = 34.4 for ordinary kriging and 34.3 for IDW). It is concluded that both methods give acceptable results. In situ measurements and geostatistical analysis allow assessment of expected indoor radon exposure in a given area at reduced costs and time required. However, for the investigated area, more research is needed to produce reliable radon-risk maps., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

To formulate necessary protective measures after a large-scale nuclear accident, it is crucial to understand the levels of radiation to which persons living in radionuclide-contaminated areas are exposed. Individual monitoring using personal dosemeters (PDs) plays a role in this, although PDs were not originally intended to be used by members of the public. The present study investigated PD responses in areas highly affected by the Fukushima Daiichi nuclear accident, as well as the dependence of those measurements on body size. Three types of commercially available electronic PDs, including D-shuttle, which has often been used in Fukushima, were placed on the front surfaces of three age-specific anthropometric phantoms imitating a 5-y-old, a 10-y-old and an adult male, and these phantoms were then exposed to radiation in an open field in the affected area. In the case of D-shuttle, the ratios of PD readings to the ambient dose rate for the 5-y-old phantom and the adult male phantom were 0.79 and 0.72, respectively. The ratios were somewhat higher for the other PDs; any PDs showed higher readings than the effective doses estimated by simulations based on the assumed ground deposition of 134Cs and/or 137Cs over the affected areas., (© The Author(s) 2023. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

With a history of more than 200 years of tin mining, Bangka Island has brought along a byproduct of heavy minerals containing radionuclide elements. There are some concerns about this byproduct material contributing to natural radiation in the environment. In this study, a car-borne survey was conducted to accurately assess natural background radiation in Bangka Island. Indoor and outdoor ambient dose rates in 146 houses were also measured to assess the radiation dose from external exposure received by the public. Soil samples were collected and measured using a gamma spectroscopy system to evaluate the contributions of specific radionuclides to external terrestrial exposure. From 3790 measurement points during the car-borne survey, the highest ambient dose equivalent rate was 596 nSv h -1 measured in Muntok area, with a mean value of 101 nSv h -1 and a median value of 95 nSv h -1 . The ambient dose equivalent rate distribution map showed a relatively higher value in the northern coastal area of the island, where the Pemali tin deposit is located. The annual effective dose received from external radiation in the 146 houses in Bangka Island ranged from 0.44 to 1.30 mSv year -1 , with a median value of 0.66 mSv year -1 . The soil contained a relatively high amount of thorium ( 232 Th), which contributed 69% to external radiation exposure in Bangka Island., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

A pilot study was carried out to measure indoor radon concentrations in a uranium mining area of northern Kazakhstan. A total of 80 places at kindergartens, elementary schools, and dwellings were selected in Aqsu village and Astana city as the uranium mining area and background area for comparison, respectively. In Astana and Aqsu, the 3-month radon concentrations from late summer to autumn in 2022 were measured using the RADUET passive radon detectors. Radon concentrations ranged from 4 to >2000 Bq m -3 (mean ± standard deviation: 290 ± 173 Bq m -3 ) throughout the study areas. The concentrations were higher in Aqsu, and 70% of the dwellings there exceeded 300 Bq m -3 , whereas only 5% of them exceeded 300 Bq m -3 in Astana. Accordingly, the new dose conversion factor for radon recommended by International Commission on Radiological Protection Publication 137 was applied to calculate the annual effective dose. The annual effective dose from the inhalation of radon was estimated to be 3.6 ± 4.6 mSv y -1 for Astana and 23.7 ± 15.6 mSv y -1 , for Aqsu, which are both higher than the world average value of 2.5 mSv y -1 ., (© 2023 Society for Radiological Protection. Published on behalf of SRP by IOP Publishing Limited. All rights reserved.)

At present, much emphasis is placed on the health risks associated with radioactivity present in the environment, especially since the accident at the Fukushima Daiichi Nuclear Power Plant. In this study, a walking survey was conducted in Hirosaki City using a NaI(Tl) scintillation spectrometer to estimate and map the distribution of the ambient dose equivalent rate to monitor the radiological safety of the general public in Hirosaki City, where many nuclear facilities are located nearby. The average (±standard deviation) ambient dose equivalent rate was 0.056 ± 0.020 µSv h -1 . By comparison with the measurement data, it was found that the values of 85% of the data obtained using the walking survey technique deviated within ±20% relative to those obtained by spot measurements. Furthermore, the distribution of dose rates obtained in the nighttime survey was not significantly different from those obtained in the daytime.

Researchers have used various methods to obtain the exhalation rates of radon and thoron from soil and building materials. One of the typical methods for radon exhalation rate is the circulation method using an accumulation container, an external or internal sampling pump and a continuous radon monitor. However, it is necessary to consider sampling flow rate if this method is applied to exhalation rate measurement for thoron due to its short half-life. Based on a calibration experiment, the measured thoron concentrations obtained by an electrostatic collection type radon and thoron monitor (RAD7) were found to be influenced strongly by the sampling flow rate. It was also found that the thoron exhalation rate from a soil sample depended on the pressure difference which was proportional to the increasing sampling flow rate. The thoron exhalation rate measured at the generally used sampling flow rate of the internal sampling pump of the RAD7 was overestimated compared with the value at 0 L min-1., (© The Author(s) 2022. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

To understand the behavior of atmospheric 129I that originated from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, activity concentrations of 129I in samples of atmospheric particulate matter (PM), comprising coarse (>1.1 μm) and fine (<1.1 μm) fractions (separated using a single stage impactor), were measured on a nearly monthly basis from October 2012 to October 2014 at a site in an area evacuated after the FDNPP accident. Total atmospheric 129I activity concentrations in PM at the site ranged between 0.15 and 2.17 nBq m-3. Specific activity concentration of 129I in total atmospheric PM ranged between 40.8 and 336 mBq kg-1, with a mean and standard deviation of 142 and 77.6 mBq kg-1, respectively. The specific activity in PM tended to be higher than not only the background values reported from soil collected before the FDNPP accident but also than those reported from the contaminated soil after the accident (range: 1.6-57 mBq kg-1; mean and standard deviation: 10.6 and 12.3 mBq kg-1, respectively). Total 129I/127I atomic ratios in PM ranged from 2.0 × 10-8 to 59.8 × 10-8, with a mean and standard deviation of 15.0 × 10-8 and 14.4 × 10-8, respectively. These ratios were generally lower than those of the contaminated soil collected after the FDNPP accident (range: 4.9 × 10-8-443 × 10-8; mean and standard deviation: 74.2 × 10-8 and 85.4 × 10-8, respectively). The 129I concentration and 129I/127I atomic ratio in atmospheric PM showed different characteristics from that of contaminated soils, suggesting that the presence of other atmospheric PMs plays a more important role as the host for 129I., (© The Author(s) 2022. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

A passive integrating discriminative radon-thoron monitor (Raduet) and a radon-thoron progeny monitor with a solid-state nuclear tracking detector were used for estimating indoor radon, thoron and their progeny concentrations in residential areas around the old mines of southern Thailand. Exposure to high background radiation levels from natural 238U and 232Th in the tin mine areas or active fault areas may increase the risk of lung cancer in the respiratory system when considering the health effects of the surrounding inhabitants. In this study, radon thoron and their progeny concentrations from inhalation in the study site have been assessed in dose at volunteer houses to confirm radiation effects. The annual effective doses due to inhalation of radon-thoron, radon progeny and thoron progeny using the ICRP latest dose conversion factors were estimated to be 3.0-4.6, 2.5-3.7 and 0.4-1.0 mSv, respectively, and as 5.9-9.0 mSv in total., (© The Author(s) 2022. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Radiation exposure due to radon contributes most of the ionizing radiation exposure to people among natural radiation sources. This research measured the 222 Rn, 220 Rn by the RADUET and their progeny concentrations by the improved deposition based 222 Rn and 220 Rn progeny monitor, and the contribution of outdoor PM 2.5 concentrations to indoors by a modified steady-state mass balance model in Beijing, Changchun, China and Aomori, Japan. Based on these results, we preliminarily explored the relevance between the city level outdoor PM 2.5 exposure and indoor 222 Rn, 220 Rn inhalation exposure in these three metropolises with different air quality levels. The average equilibrium equivalent radon concentration (EERC) and equilibirum equivalent thoron concentration (EETC) indoor were 17.2 and 1.1 Bq m -3 in Beijing, 19.4 and 1.3 Bq m -3 in Changchun, and 10.8 and 0.9 Bq m -3 in Aomori, respectively. The indoor EERC and EETC in Beijing showed 1.4 and 2.2 times as high as that measured in 2006. The indoor radiation dose due to inhalation presented in a descending order as Changchun, Beijing and Aomori, which were in accordance with their outdoor 222 Rn concentrations. The indoor radiation doses due to 220 Rn contributed 30% of the total dose in the three cities, indicating that 220 Rn cannot be neglected when evaluating indoor radiation dose. It should be noted that, the indoor PM 2.5 concentrations of outdoor origin presented strong correlation (r = 0.772) with indoor EETC and moderate correlation (r = 0.663) with indoor EERC, indicating that the PM 2.5 of outdoor origin can break the concentration balance of the indoor PM 2.5 , then affect the indoor 222 Rn and 220 Rn behaviors, and further affect the inhalation exposure of radon., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

222 Rn and 226 Ra concentrations of less than a few to several thousands of Bq L - 1 have been observed in several underground bodies of water around the world. Although regulations for these concentrations in water have been implemented internationally, there are currently no regulations in place in Japan. However, concentrations that exceed these internationally recognized regulatory values have also been observed in Japan. In this study, concentrations in spring water in the northern part of Japan were measured and the effective dose from intake of the water was evaluated. 222 Rn concentrations were measured using a liquid scintillation counter, and 226 Ra concentrations were measured using a high purity germanium detector after chemical preparation. The measured 222 Rn concentrations (=12.7 ± 6.1 Bq L -1 ) and 226 Ra concentrations (<0.019-0.022 Bq L -1 ) did not exceed the reference values set by international and European/American organizations. A conservative estimate of the annual effective ingestion dose of 8 μSv for 222 Rn and 226 Ra obtained in this study is much smaller than the estimated overall annual effective dose of 2.2 mSv from natural radiation to the Japanese population. However, this dosage accounts for 8% of the WHO individual dosing criteria of 0.1 mSv/year for drinking water.

Although the epidemiological studies provide evidence for an increased risk of lung cancer risk associated with residential radon, an issue of radon-thoron discrimination remains to be solved. In this study, an updated evaluation of lung cancer risk among the residents in Gansu, China was performed where one of the major epidemiological studies on indoor radon demonstrated an increased risk of lung cancer. We analyzed data from a hospital-based case-control study that included 30 lung cancer cases and 39 controls with special attention to internal exposure assessment based on the discriminative measurement technique of radon isotopes. Results from the analyses showed non-significant increased lung cancer risks; odds ratios ( OR s) adjusted for age, smoking, and total income were 0.35 (95% CI : 0.07-1.74) and 0.27 (95% CI : 0.04-1.74) for groups living in residences with indoor radon concentrations of 50-100 Bq m -3 and over 100 Bq m -3 , respectively, compared with those with < 50 Bq m -3 indoor radon concentrations. Although the small sample size hampers the usefulness of present analyses, our study suggests that reevaluation of lung cancer risk associated with residential radon in the epidemiological studies will be required on the basis of precise exposure assessment., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Kudo, Yoshinaga, Li, Lei, Zhang, Sun, Koriyama, Akiba and Tokonami.)

222Rn and 220Rn surface exhalation rates from earthen building materials used in high background radiation areas of Homa and Ruri, Kenya have been measured using an accumulation chamber coupled with RAD7 detector. Activity concentrations of 226Ra and 232Th in the building materials were determined by γ-ray spectroscopy. In Homa the average 222Rn surface exhalation was 1 ± 0.1 mBqm-2 s-1, while that of 220Rn was 18 ± 2 Bqm-2 s-1; in Ruri 222Rn was 0.9 ± 0.1 mBqm-2 s-1 and 220Rn was 25 ± 3 Bqm-2 s-1. 222Rn was 26 times lower than world average and 220Rn was higher by a factor of 21. Average 232Th in Ruri was 1094 ± 55 Bq/kg, three times that in Homa; 226Ra was 129 ± 10 and 111 ± 6 Bq/kg in Homa and Ruri, respectively. There was a strong correlation between exhalation rate of 222Rn and concentration of 226Ra, as well as between 232Th and 220Rn. Thus, 220Rn was the major contributor to the inhaled dose in earthen dwellings of the two regions., (© The Author(s) 2021. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

In this study, a portable cascade impactor was developed to more efficiently determine the activity size distribution of attached radon and thoron progeny in a natural environment. The developed impactor consisted of four stages with a backup filter stage for collection of the aerosol samples. The aerosol cut points were set for 10, 2.5, 1, and 0.5 μm at a sampling rate of 4 L min -1 . Five CR-39 chips were used as alpha detectors for each stage. To separate the alpha particles emitted from radon and thoron progeny, the CR-39 detectors were covered with aluminium-vaporized Mylar films. The thickness of each film was adjusted to allow alpha particles emitted from radon and thoron progeny to reach the surface of the CR-39 detectors. The particle cut-off characteristics of each stage were determined by mono-dispersive aerosols with particle sizes ranging from 0.1 to 1.23 μm from the collection efficiency curve. The test results showed that the respective cut-off size of stages 3 and 4 were close to the designed cut-points. Validation of the technique by comparison with two commercial devices confirmed that the developed technique could provide the necessary information to estimate the activity size distribution of attached radon and thoron progeny for dose assessment, especially, in a field survey where direct electric power is not available., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Emergency medical responders (EMRs) who treat victims during a radiation emergency are at risk of radiation exposure. In this study, the exposure dose to EMRs treating hypothetically contaminated patients was estimated using a Monte Carlo simulation, and the findings may be useful for educating EMRs and reducing their anxiety. The Monte Carlo simulation estimated radiation doses for adult computational phantoms based on radioactive contamination conditions and radiation dosages from previous studies. At contamination conditions below the typical upper limit of general Geiger-Müller survey meters, the radiation doses to EMRs were estimated to be less than 1 μSv per hour. In cases with greater contamination due to mishandling of an intense radioactive source (hundreds of GBq), the radiation doses to EMRs could reach approximately 100 mSv per hour. These results imply that a radiological accident with a highly radioactive source could expose EMR to significant radiation that exceeds their dose limit. Thus, authorities and other parties should ensure that EMRs receive appropriate education and training regarding measures that can be taken to protect themselves from the possibility of excessive radiation exposure. The results of this study may provide EMRs with information to take appropriate protective measures, although it is also important that they not hesitate to perform lifesaving measures because of concerns regarding radiation.

A long-term measurement technique of radon exhalation rate was previously developed using a passive type radon and thoron discriminative monitor and a ventilated type accumulation chamber. In the present study, this technique was applied to evaluate the thoron exhalation rate as well, and long-term measurements of radon and thoron exhalation rates were conducted for four years in Gifu Prefecture. The ventilated type accumulation chamber (0.8 × 0.8 × 1.0 m 3 ) with an open bottom was embedded 15 cm into the ground. The vertical distributions of radon and thoron activity concentrations from the ground were obtained using passive type radon-thoron discriminative monitors (RADUETs). The RADUETs were placed at 1, 3, 10, 30, and 80 cm above the ground inside the accumulation chamber. The measurements were conducted from autumn 2014 to autumn 2018. These long-term results were found to be in good agreement with the values obtained by another methodology. The radon exhalation rates from the ground showed a clearly seasonal variation. Similar to findings of previous studies, radon exhalation rates from summer to autumn were relatively higher than those from winter to spring. In contrast, thoron exhalation rates were not found to show seasonal variation.

Ten years have elapsed since the accident at the Fukushima Daiichi Nuclear Power Plant in 2011, and the relative contribution of natural radiation is increasing in Fukushima Prefecture due to the reduced dose of artificial radiation. In order to accurately determine the effective dose of exposure to artificial radiation, it is necessary to evaluate the effective dose of natural as well as artificial components. In this study, we measured the gamma-ray pulse-height distribution over the accessible area of Namie Town, Fukushima Prefecture, and evaluated the annual effective dose of external exposure by distinguishing between natural and artificial radionuclides. The estimated median (range) of absorbed dose rates in air from artificial radionuclides as of 1 April 2020, is 133 (67-511) nGy h -1 in the evacuation order cancellation zone, and 1306 (892-2081) nGy h -1 in the difficult-to-return zone. The median annual effective doses of external exposures from natural and artificial radionuclides were found to be 0.19 and 0.40 mSv in the evacuation order cancellation zone, and 0.25 and 3.9 mSv in the difficult-to-return zone. The latest annual effective dose of external exposure discriminated into natural and artificial radionuclides is expected to be utilized for radiation risk communication.

The world community has long used natural hot springs for tourist and medicinal purposes. In Indonesia, the province of West Java, which is naturally surrounded by volcanoes, is the main destination for hot spring tourism. This paper is the first report on radon measurements in tourism natural hot spring water in Indonesia as part of radiation protection for public health. The purpose of this paper is to study the contribution of radon doses from natural hot spring water and thereby facilitate radiation protection for public health. A total of 18 water samples were measured with an electrostatic collection type radon monitor (RAD7, Durridge Co., USA). The concentration of radon in natural hot spring water samples in the West Java region, Indonesia ranges from 0.26 to 31 Bq L -1 . An estimate of the annual effective dose in the natural hot spring water area ranges from 0.51 to 0.71 mSv with a mean of 0.60 mSv for workers. Meanwhile, the annual effective dose for the public ranges from 0.10 to 0.14 mSv with an average of 0.12 mSv. This value is within the range of the average committed effective dose from inhalation and terrestrial radiation for the general public, 1.7 mSv annually.

The biological effects of low dose-rate radiation exposures on humans remains unknown. In fact, the Japanese nation still struggles with this issue after the Fukushima Dai-ichi Nuclear Power Plant accident. Recently, we have found a unique area in Indonesia where naturally high radiation levels are present, resulting in chronic low dose-rate radiation exposures. We aimed to estimate the comprehensive dose due to internal and external exposures at the particularly high natural radiation area, and to discuss the enhancement mechanism of radon. A car-borne survey was conducted to estimate the external doses from terrestrial radiation. Indoor radon measurements were made in 47 dwellings over three to five months, covering the two typical seasons, to estimate the internal doses. Atmospheric radon gases were simultaneously collected at several heights to evaluate the vertical distribution. The absorbed dose rates in air in the study area vary widely between 50 nGy h -1 and 1109 nGy h -1 . Indoor radon concentrations ranged from 124 Bq m -3 to 1015 Bq m -3 . That is, the indoor radon concentrations measured exceed the reference levels of 100 Bq m -3 recommended by the World Health Organization. Furthermore, the outdoor radon concentrations measured were comparable to the high indoor radon concentrations. The annual effective dose due to external and internal exposures in the study area was estimated to be 27 mSv using the median values. It was found that many residents are receiving radiation exposure from natural radionuclides over the dose limit for occupational exposure to radiation workers. This enhanced outdoor radon concentration might be as a result of the stable atmospheric conditions generated at an exceptionally low altitude. Our findings suggest that this area provides a unique opportunity to conduct an epidemiological study related to health effects due to chronic low dose-rate radiation exposure., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The present paper outlines characteristics of thoron and its progeny in the indoor environment. Since the half-life of thoron ( 220 Rn) is very short (55.6 s), its behavior is quite different from the isotope radon ( 222 Rn, half-life 3.8 days) in the environment. Analyses of radon and lung cancer risk have revealed a clearly positive relationship in epidemiological studies among miners and residents. However, there is no epidemiological evidence for thoron exposure causing lung cancer risk. In contrast to this, a dosimetric approach has been approved in the International Commission on Radiological Protection (ICRP) Publication 137, from which new dose conversion factors for radon and thoron progenies can be obtained. They are given as 16.8 and 107 nSv (Bq m -3 h) -1 , respectively. It implies that even a small quantity of thoron progeny will induce higher radiation exposure compared to radon. Thus, an interest in thoron exposure is increasing among the relevant scientific communities. As measurement technologies for thoron and its progeny have been developed, they are now readily available. This paper reviews measurement technologies, activity levels, dosimetry and resulting doses. Although thoron has been underestimated in the past, recent findings have revealed that reassessment of risks due to radon exposure may need to take the presence of thoron and its progeny into account.

An improved passive CR-39-based direct 222 Rn/ 220 Rn progeny detector with 3 detection channels was designed and tested in this study to measure and calculate equilibrium equivalent concentration (EEC) of both 222 Rn and 220 Rn without the equilibrium factor. A theoretical model was established to calculate the EEC with optimization. Subsequently, an exposure experiment was carried out to test the performance of this detector, and we compared the chamber experiment and the theoretical model by estimating and measuring various parameters. The deposition flux of progeny derived from the prediction agreed well with the value measured in the exposure chamber. The energy-weighted net track density (NTD) measured by this detector is much more reliable to reflect the linear relation between NTD and time-integrated EEC. Since the detector is sensitive to the exposure environmental condition, it is recommended to apply the detector to measure the EEC after its calibration in a typical indoor environment.

The International Commission on Radiological Protection (ICRP) recently recommended a new dose conversion factor for radon based on the latest epidemiological studies and dosimetric model. It is important to evaluate an inhalation dose from radon and its progeny. In the present study, a passive radon personal monitor was designed using a small container for storing contact lenses and its performance was evaluated. The conversion factor for radon ( 222 Rn), the effect of thoron ( 220 Rn) concentration and the air exchange rate were evaluated using the calibration chamber at Hirosaki University. The minimum and maximum detectable radon concentrations were calculated. The conversion factor was evaluated as 2.0 ± 0.3 tracks cm -2 per kBq h m -3 ; statistical analyses of results showed no significant effect from thoron concentration. The minimum and maximum detectable radon concentrations were 92 Bq m -3 and 231 kBq m -3 for a measurement period of three months, respectively. The air exchange rate was estimated to be 0.26 ± 0.16 h -1 , whose effect on the measured time-integrated radon concentration was small. These results indicate that the monitor could be used as a wearable monitor for radon measurements, especially in places where radon concentrations may be relatively high, such as mines and caves.

Activity concentrations of 234 U, 235 U, 238 U, 226 Ra, 228 Ra, 222 Rn, 210 Po, 210 Pb, 40 K, 3 H, 14 C, 134 Cs and 137 Cs were determined in 20 different Japanese bottled drinking water commercially available in Japan. The origins of the mineral water samples were geographically distributed across different regions of Japan. Activity concentrations above detection limits were measured for the radionuclides 234 U, 235 U, 238 U, 226 Ra, 228 Ra and 210 Po. An average total annual effective dose due to ingestion was estimated for adults, based on the average annual volume of bottled water consumed in Japan in 2019, reported to be 31.7 L/y per capita. The estimated dose was found to be below the recommended World Health Organisation (WHO) guidance level of 0.1 mSv/y for drinking water quality. The most significant contributor to the estimated dose was 228 Ra.

Natural background gamma radiation was measured along the main roads in the eastern, western and southern regions of Thailand using a car-borne survey system with a 3-in × 3-in NaI (Tl) scintillation spectrometer. The system was able to quickly survey a large area and obtain outdoor absorbed dose rate in air from a gamma ray pulse height distribution. A total of 19 219 data of the outdoor absorbed dose rate in air were collected. The average outdoor absorbed dose rate in air in the eastern, western and southern regions were found to be 8-127, 16-119 and 16-141 nGy h -1 , respectively. The highest outdoor absorbed dose rate in air was detected in the southern region of Thailand. The corresponding average outdoor annual effective dose to the public ranged from 11.7 to 80.8 μSv., (© The Author(s) 2019. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Radon ( 222 Rn) and thoron ( 220 Rn), sources of natural background radiation, have been the subjects of long-standing studies, including research into radon and thoron as major causes of lung cancer at domestic and international levels. In this regard, radon and thoron measurement studies have been widely conducted all over the world. Generally, the techniques used relate to passive nuclear track detectors. Some surveys have shown that passive monitors for radon are sensitive to thoron, and hence some measured results have probably overestimated radon concentrations. This study investigated radon and thoron measurements in domestic and international surveys using the passive radon-thoron discriminative monitor, commercially named RADUET. This paper attempts to provide an understanding of discriminative measurements of radon isotopes and to present an evidence-based roadmap.

Air exchange through a porous medium depends partly on a pressure gradient induced in it, i.e., air-flow conditions of the outer air. Consequently, response of diffusion-type detectors to radon and thoron may vary with air-flow conditions surrounding the detectors. This effect may be significant for thoron measurement because thoron has a shorter half-life than radon. The present study examined response of diffusion-type detectors (RADUETs and one AlphaGUARD) to thoron with respect to wind speed using a thoron calibration chamber. Response of RADUETs to thoron increased with wind speed. Response of the AlphaGUARD increased with wind speed, but it became constant at a high wind speed. Different response trends to thoron between the RADUETs and the AlphaGUARD could be qualitatively explained by flow states induced by the pressure gradient in the filter or the sponge of these detectors. For RADUETs, laminar (Darcy) flow was induced in the sponge in the examined wind speed range, which meant that thoron entry into the detector increased with wind speed. For the AlphaGUARD, laminar flow was induced in the filter in the low wind speed range, whereas flow was changed to turbulent (non-Darcy) flow at a high wind speed for which thoron entry into the detector did not depend on wind speed.

Radon (Rn), thoron (Tn), and thoron progeny (TnP) were measured in seven inhabited areas of the uranium and thorium bearing region of Lolodorf, located in southwestern Cameroon. Then the equilibrium factor (F Tn ) between thoron and its progeny was determined in order to show the importance of direct progeny measurements for correct estimation of effective dose due to radon, thoron and their progenies. A total of 220 RADUET detectors were used to measure indoor radon and thoron and 130 TnP monitors for thoron progeny indoors. The arithmetic and geometric mean concentrations of Rn, Tn, and TnP were 103 and 89 Bq m -3 , 173, and 118 Bq m -3 , 10.7, and 7.4 Bq m -3 , respectively. Total effective dose determined from radon, thoron, and their progenies was estimated at 4.2 ± 0.5 mSv y -1 . Thoron equilibrium factor varied according to seasons, the type of dwelling, building materials and localities. Thoron (Tn and TnP) contribution to effective dose ranged between 3 and 80% with the average value of 53%. Total effective dose estimated from the world average equilibrium factor of 0.02 given by UNSCEAR was 2.7 ± 0.2 mSv y -1 . The effective dose due to thoron varied greatly according to the different values taken by F Tn and was different from that determined directly using TnP concentrations. Thus, effective dose due to thoron determined from the equilibrium factor is unreliable. Therefore, the risk of public exposure due to thoron (Tn and TnP) may therefore be higher than that of radon (Rn and RnP) in many parts of the world if F Tn is no longer used in estimating total effective dose. This is not in contradiction with the UNSCEAR conclusions. It is therefore important to directly measure the radon and thoron progeny for a correct estimate of effective dose., (Copyright © 2020 Bineng, Saïdou, Tokonami, Hosoda, Tchuente Siaka, Issa, Suzuki, Kudo and Bouba.)

Indoor radon (Rn), thoron (Tn) and thoron progeny (TnP) were simultaneously measured in the gold mining areas of Betare-Oya using RADUET detectors and TnP monitors. Rn and Tn concentrations range between 88-282 and 4-383 Bq m-3, respectively, with the arithmetic means of 133 ± 39 and 93 ± 76 Bq m-3. The 76% of houses for Rn and 25% for Tn exceed the WHO reference level of 100 Bq m-3 and 3% of the houses exceed the ICRP threshold of 300 Bq m-3. The equilibrium equivalent thoron concentration ranges between 1 and 19 Bq m-3 with a mean value of 6 ± 4 Bq m-3. The thoron equilibrium factor ranges between 0.01 and 0.55 with arithmetic mean of 0.11, higher than the world average value of 0.02 given by UNSCEAR. The total inhalation dose due to Rn, Tn and their progeny ranges between 1.8 and 6.2 mSv y-1 with the arithmetic mean of 3.8 ± 1.1 mSv y-1., (© The Author(s) 2019. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Comparison is an important role in the quality control and quality assurance for any measuring system. Due to the future legal regulations regarding radon levels in the air, maintaining the system quality and harmonization of results as well as validation of radon and thoron measuring systems is important. The aim of this work is to validate the degrees of equivalence and measurement precisions of the existing five radon and four thoron measuring systems located in four Asian countries (China, India, Japan and Thailand) through comparison experiment. In this project, comparison experiment was performed in order to derive the ratio between assigned value obtained from one transfer measurement device for radon and one transfer measurement device for thoron belongs to National Institutes for Quantum and Radiological Science and Technology and participants' value from their measuring instrument. As a result, the ratio value associated with measurement uncertainty was derived for each activity concentration. Finally, measurement bias and degrees of equivalence between the assigned values and values of measurement quantity from participants' measuring instruments were statistically analysed and presented.

Urine, hair and nail samples were collected from a population of both sex aged from 40 to 87 years in Niška Banja (227 km south of Belgrade, Serbia) with a high level of natural radioactivity (HLNRA). To assess and monitor the public exposure, urine samples for each subject (24 h period) were collected and concentration of uranium (U) was analysed using alpha-particle spectrometry. Human hair and nails considered as bio-indicators of the public exposure to radionuclides over a long period of months or even years and concentration of U was determined using inductively coupled plasma-mass spectrometry. The mean concentrations of U in urine, hair and nail were 123 ng/L, 17 ng/g and 8 ng/g, respectively. There was a large variation and may be due to geological origin., (© The Author(s) 2019. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Namie Town in Fukushima Prefecture, the majority of which was an evacuation area as a result of the effects of the Fukushima Daiichi Nuclear Power Plant accident, carried out a 'temporal stay' in September 2016 so that residents could check their houses. Therefore, in cooperation with the town authorities, the authors distributed personal dosemeters and behaviour record forms to record the personal dose equivalent rate and investigate the relationship between residents' external radiation dose and their behaviour. When the personal dose equivalent rate was calculated from the measured personal dose equivalent per hour, the median was 0.12 μSv h-1, the maximum value and the minimum value were 0.58 and 0.06 μSv h-1, respectively. Meanwhile, since personal fluctuations were observed in personal dose equivalent, grasping the relationship between residents' behaviour and exposed dose can be applied to risk communication., (© The Author(s) 2019. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Monitoring of radioactive materials has been reported in rivers and soil in Fukushima post the Fukushima Daiichi Nuclear Power Plant accident in March 2011. However, there are few reports on the influence of this event on bacteria in forest soils and rivers. Therefore, through amplicon sequencing of 16S rDNA we compared the bacterial flora in river sediment soils from Fukushima prefecture and from an area not exposed to radioactive contamination, Aomori prefecture. The bacterial composition in the Aomori prefecture soil and Fukushima soil were found to be very similar at the phylum level. However, Fukushima soil had significantly fewer Bacteroidetes than the Aomori soil (p = 0.014), while the content of Firmicutes and Latescibacteria (WS3) was significantly higher (p = 0.001, 0.013 respectively). However, no increase in the content of radioactive-resistant bacteria was observed. In future studies, it is necessary to standardise the conditions for soil collection to assess its content of radioactive substances., (© The Author(s) 2019. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

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 Author(s) 2019. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Soil samples from the surface to a 5 cm depth were collected at a residential house in Koriyama City, Fukushima Prefecture using a scraper plate every three months from March 2014 to September 2014 to evaluate the vertical distribution profiles and inventories of 134Cs and 137Cs in soil. The vertical distribution profiles of radiocesium (134Cs and 137Cs) in soil showed that greater than 86% of the total radiocesium was absorbed in the upper 2 cm 3 years after the accident. Radiocesium in the surface layer seems to move to the lower layer over time. The migration of radiocesium in surface layer might be influenced by the ground surface runoff by rainfall. Radiocesium inventories in June increased significantly over the short period between March and June. In contrast, the radiocesium inventories in September did not increase significantly compared to the values in June. Radiocesium resuspension and deposition caused by decontamination work and meteorological events might be one possible reason for the increased radiocesium inventories observed in June., (© The Author(s) 2019. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

The World Health Organisation (WHO) recommends that the concentration of radon in water should be no more than 100 kBq m-3 (100 BqL-1) and the Codex Alimentarius Commission states that the limit of quantification (LOQ) of a method should be no more than one-fifth of this value. In this study, a degassing method with an RAD7 device was used to measure radon concentrations in water, compared to a liquid scintillation counter (LSC) method used as the reference, to investigate whether the numerical value of the LOQ of this method was more than 1/5 (20 kBq m-3) of 100 kBq m-3. The degassing method with leak prevention was shown to reach a target value of 20 kBq m-3 or less under a relative humidity of 6% or lower in the chamber of the RAD7 device. Accordingly, the RAD7 degassing method with leak prevention can be used to accurately measure radon concentrations in water within the guidance level set out by the WHO., (© The Author(s) 2019. Published by Oxford University Press.)

Short-term measurements were made in four different types of Chinese cave dwellings, 'ground', 'open-cut', 'aboveground' and 'underground', located in Gansu Province, China, in order to evaluate the diurnal and seasonal variations in indoor radon (222Rn) and thoron (220Rn) concentrations. As a result, in most of the 'ground' and 'open-cut' cave dwellings in summer, the indoor 222Rn concentrations during the nighttime were higher than those during the daytime. In the winter, such fluctuation was not observed. The daily indoor 222Rn concentrations in summer were higher than those in winter, excluding the 'aboveground' cave dwelling, and these concentrations depended on dwelling type, exhalation from the building materials and ventilation. In contrast with 222Rn, there seemed to be only very slight clear variations in 220Rn., (© The Author(s) 2019. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Human beings are continuously exposed to ionising radiation originating from natural or artificial sources. Uranium-238 and Thorium-232 found in building materials are important sources of radon and thoron in the indoor environment. The concentration levels of radon, thoron and thoron progeny were measured in mud-walled, metallic or iron sheet-walled and stone-walled modern houses in Kilimambogo region, Kenya for 3 months. Radon and thoron concentration levels were measured using passive radon-thoron discriminative monitors (RADUET), while thoron progeny concentrations as the equilibrium equivalent thoron concentration (EETC) were measured using thoron progeny monitors. The mean radon concentration levels in mud, metallic and stone-walled dwellings were 67 ± 11, 60 ± 10 and 75 ± 10 Bq m-3, respectively. The mean thoron concentration levels in the corresponding dwellings were 195 ± 36, 71 ± 24 and 161 ± 31 Bq m-3, respectively, while EETCs were 12 ± 2, 3 ± 1 and 7 ± 1 Bq m-3, respectively. The annual effective doses for radon were 1.3 ± 0.2, 1.1 ± 0.1 and 1.4 ± 0.2 mSv y-1 in mud, metallic and stone-walled houses while those from thoron estimated from EETC were 2.4 ± 0.4, 0.5 ± 0.1 and 1.5 ± 0.2 mSv y-1 in the corresponding houses, respectively., (© The Author(s) 2019. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

After the Fukushima Daiichi Nuclear Power Plant accident, the radiation dose for first responders was not evaluated accurately due to lack of the monitoring data. It has been important to evaluate a radiation dose for workers in emergency response at a nuclear accident. In this study, a new device which can evaluate both of external and internal exposure doses was developed and the performance of various environmental radiation monitors including commercially available monitors were tested and compared from the viewpoint of an environmental monitoring at emergency situation. Background counts of the monitors and the ambient dose equivalent rate were measured in Fukushima Prefecture. The detection limit for beta particles was evaluated by the method of ISO11929. The sensitivity for gamma-rays of the dust monitor using a ZnS(Ag) and a plastic scintillator was high, but that of the external exposure monitor using a silicon photodiode with CsI(Tl) crystal was relatively low. The detection limit ranged 190-280 Bq m-3 at 100 μSv h-1, exceeding the detection limit of 100 Bq m-3 in the minimum requirement by the National Regulation Authority in Japan. Use of the shielding with lead is necessary to achieve the minimum requirement. These results indicate that the dust monitor using a ZnS(Ag) scintillator and a plastic scintillator is suitable for the external exposure monitor and the developed internal exposure monitor is for the internal exposure monitor at emergency situation among the evaluated monitors. In the future study, the counting efficiency, the relative uncertainty and the performance of the detection for alpha particles will be evaluated, and it will be considered which type of a monitor is suitable after taking the portability into account., (© The Author(s) 2019. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

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 Author(s) 2019. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

A performance test was carried out using five different gamma-ray spectrometers applicable to thyroid monitoring. The energy resolution and efficiency for 7.6-cm × 7.6-cm NaI(Tl), 5.1-cm × 5.1-cm CeBr3, 3.8-cm × 3.8-cm SrI2(Eu), and 2.5-cm × 2.5-cm SrI2(Eu) gamma-ray scintillation spectrometers and a CdTe gamma-ray semiconductor spectrometer were evaluated using the Oak Ridge Institute for Nuclear Studies thyroid-neck phantom with a mock I source for prompt thyroid monitoring after a nuclear emergency. The respective energy resolutions of the full-energy peak for ~0.360 MeV of 3.8-cm × 3.8-cm SrI2(Eu) and 2.5-cm × 2.5-cm SrI2(Eu) scintillation spectrometers were 4.2% and 4.3%, and these values were very close to the value obtained by the CdTe semiconductor spectrometer. The efficiencies of four of the gamma-ray spectrometers were compared based on the efficiency of the 7.6-cm × 7.6-cm NaI(Tl) scintillation spectrometer at 0 cm from the phantom surface, and these values were ~70% for 5.1-cm × 5.1-cm CeBr3, ~30% for 3.8-cm × 3.8-cm SrI2(Eu), 10% for 2.5-cm × 2.5-cm SrI2(Eu) and 2% for 1-cm × 0.1-cm CdTe. Furthermore, the detection limits at various dose rates for the four gamma-ray scintillation spectrometers were evaluated using the method based on International Organization for Standardization publication ISO 11929:2010.

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 238 Pu/ (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 238 Pu/ (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 ( 238 Pu/ (239+240) Pu) in Fukushima Prefecture., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

222 Rn, 220 Rn and their short-lived progenies are well known radioactive indoor pollutants, identified as the leading environmental cause of lung cancer next to smoking. Apart from the conventional measurement methods, numerical modeling methods are developed to simulate their physical and decay processes in 222 Rn and 220 Rn's life cycle, estimate their levels, concentration distributions, as well as effects of control strategies in the indoor environment. In this article, we summarized the numerical models used to illustrate the physical processes of each source of 222 Rn and 220 Rn entry into the indoor environment, and the application of Jacobi room models and CFD (Computational Fluid Dynamic) models used to present the behaviors of indoor 222 Rn, 220 Rn and their progenies. Furthermore, we consider that the development of numerical modeling of 222 Rn and 220 Rn would have a bright prospect in the directions of stochastic methods based on a steady-state model, the fine simulation of the time-dependent model as well as the multi-dimension model., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Monazite is a naturally occurring radioactive material that is processed for use in a variety of domestic applications. At present, there is little information available on potential radiation doses experienced by people working with monazite. The ambient dose rate and activity concentration of natural radionuclides in raw materials, products, and dust in work sites as well as the Rn and Rn concentrations in work sites were measured in a monazite processing plant in Japan. Dose estimations for plant workers were also conducted. The activity concentration of the U series in raw materials and products for the monazite processing plant was found to be higher than the relevant values described in the International Atomic Energy Agency Safety Standards. The ambient dose rates in the raw material yard were higher than those in other work sites. Moreover, the activity concentrations of dust in the milling site were higher than those in other work sites. The Rn concentrations in all work sites were almost the same as those in regular indoor environments in Japan. The Rn concentrations in all work sites were much higher than those in regular indoor environments in Japan. The maximum value of the effective dose for workers was 0.62 mSv y, which is lower than the reference level range (1-20 mSv y) for abnormally high levels of natural background radiation published in the International Commission of Radiological Protection Publication 103.