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Some areas around the world have anomalies with high natural radiation that may affect public health due to chronic-low-dose radiation exposure. In the paper, we summarized several studies that find Mamuju, Indonesia, a unique high natural radiation area. The majority of the relevant papers are about monitoring, main sources, and influential factors for the enhancement of radon and dose assessments. Under these circumstances, the Mamuju region is regarded as a promising area for conducting epidemiological studies, and it will provide a unique opportunity for improving and expanding low-dose-rate data on human health effects.

The radioactivity of cesium in the water and sediments of two major rivers was measured along with airborne radioactivity in Namie Town, after the recent partial lift on the evacuation order in 2017. The observed concentrations were up to 384 ± 11 mBq/L for 137Cs in unfiltered water and 1.28 ± 0.09 mBq m−3 for 137Cs in air, while the sediment had a maximum of 44,900 ± 23 Bq kg−1 for 137Cs. The potential yearly committed effective dose was estimated based on the data.

Most radiation protection items made from modern lead contain 210Pb. This study estimated the impact on eye lens of radiation derived from the 210Pb in three types of radiation protection glasses. The counts from the glasses were measured using a Geiger–Müeller survey meter. The net count rate was 92 ± 1 cpm at a distance of 0.5 cm for one type of glasses. Additionally, we conducted a qualitative γ-ray spectrum analysis using a high-purity germanium semiconductor detector. The absorbed dose in the eye lens was related to 210Pb and its daughter radionuclide, 210Bi; this dose was calculated by applying dose conversion coefficients provided by the International Commission on Radiological Protection. The absorbed dose rate in eye lens was conservatively calculated to be on the order of 10 nGy/h for the type of glasses containing the most 210Pb. The dose from β-rays accounted for >99%. In addition, we investigated the dose-reduction effect using a thin acrylic plate. The count rate approximately decreased to background level by inserting a plate with a thickness of 1 mm. We conclude that the impact of 210Pb contained in radiation protection glasses is negligibly small, particularly considering the usefulness of the significant external exposure reduction.

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 m3) 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.

In this study, to get a better understanding in characterizing groundwater and ensure its effective management, the radon concentrations in water samples were measured through Ryukyu limestone in southern Okinawa Island, Japan. Water samples were collected from a limestone cave (Gyokusendo cave, dropping water) and two springs (Ukinju and Komesu, spring water), and the radon concentrations were measured by liquid scintillation counters. The radon concentrations in the samples from the Gyokusendo cave, and Ukinju and Komesu springs were 10 &plusmn, 1.3 Bq L&minus, 1, 3.2 &plusmn, 1.0 Bq L&minus, 1, and 3.1 &plusmn, 1.1 Bq L&minus, 1, respectively. The radon concentrations showed a gradually increasing trend from summer to autumn and decreased during winter. The variation of radon concentrations in the dripping water sample from the Gyokusendo cave showed a lagged response to precipitation changes by approximately 2&ndash, 3 months. The estimated radon concentrations in the dripping water sample were calculated with the measured radon concentrations from the dripping water obtained during the study period. Based on our results, groundwater in the Gyokusendo cave system was estimated to percolate through the Ryukyu limestone in 7&ndash, 10 days, and the residence time of groundwater in the soil above Gyokusendo cave was estimated to be approximately 50&ndash, 80 days. This work makes a valuable contribution to the understanding of groundwater processes in limestone aquifers, which is essential for ensuring groundwater sustainability.

Mamuju is a region of Indonesia with relatively high exposure to natural radiation. Since 2012, Mamuju has been a uranium and thorium exploration area. Several mapping studies of the region have been carried out to depict NORM (naturally occurring radioactive material) areas and areas with uranium anomalies. This paper is the first study to use radioactivity measurements of laterite and volcanic rocks to determine the characteristics of radionuclides and other mineral measurements, which are essential for categorising Mamuju rocks and exploring the region as a potential mining area. The radioactivity of the samples was measured using a high-purity germanium (HPGe) detector. Furthermore, we used X-ray fluorescence (XRF) to determine the rock mineral composition. Mamuju is anomalous due to its high content of 238U and 232Th concentrations of 539&ndash, 128,699 Bq&middot, kg&minus, 1 (average: 22,882 Bq&middot, 1) and 471&ndash, 288,639 Bq&middot, 1 (average: 33,549 Bq&middot, 1), respectively. The major elements are dominant, including Fe2O3, SiO2, Al2O3, and Na2O, with several other major elements such as MnO, TiO2, and CaO.

Non-Exchangeable Organically Bound Tritium (Nx-OBT) in a biological reference material: NIST 1575a Pine Needles was determined by radiometry and noble gas mass spectrometry. Nx-OBT concentration ranged from 1.08 to 1.45 Bq L−1-combustion water (CW) (n = 4) with mean value (± S.D.) of 1.25 ± 0.15 Bq L−1-CW in radiometry and ranged from 1.12 to 1.35 Bq L−1-CW (n = 3) with mean value of 1.22 ± 0.25 Bq L−1-CW in mass spectrometry. For the Pine Needles reference material, there is no proposed value about Nx-OBT, but our results showed a good agreement with the data determined by different methods. Thus, it is useful material for the quality control of Nx-OBT measurements.

The caesium retention characteristics of a potassium-nickel hexacyanoferrate resin in a polyacrylnitrile (KNiFC–PAN) matrix were tested in fresh water over the range of 2.5–400 mL min−1. The experimental setup used 2 mL resin and 4-L aliquots of freshwater samples. The results showed nearly 100% retention at speeds below 10 mL min−1, above 80% up to 100 mL min−1, and approached 50% at 400 mL min−1. Using 100 mL min−1 flow rate and KNiFC–PAN resin in a well-type HPGe detector, the minimum detectable concentration was reduced to 3 mBq kg−1 for 4-L aliquots of water samples from the previous 15 mBq kg−1 achieved by Powdex ion-exchange resin and a planar type HPGe detector.

A car-borne survey was carried out in Douala, the largest city in Cameroon to make a detailed distribution map of the absorbed dose rate in the city, to locate the high natural radiation areas useful later to carry out indoor radon, thoron, and thoron progeny measurements. Gamma-ray dose rates were measured using 3-in × 3-in NaI(Tl) detector. Activity concentrations of238U,232Th and40K in soil from Douala city were determined by two methods: the first, usingin situgamma spectrometry and the second, at the laboratory using a NaI(Tl) detector. A heterogeneous distribution of absorbed dose rates in air was observed on the dose rate distribution map, and varies from 29 to 86 nGy h−1with an average of 50 nGy h−1, lower than the world average value of 59 nGy h−1. The activity concentrations with NaI(Tl) detector varied from 18 to 47 Bq kg−1for238U, 21 to 54 Bq kg−1for232Th, and 10 to 410 Bq kg−1for40K with averages of 29, 38, and 202 Bq kg−1respectively, forin situmeasurements. They vary between 29–98 Bq kg−1for238U, 29–92 Bq kg−1for232Th, and 40 to 79 Bq kg−1for40K, with averages of 60, 57, and 56 Bq kg−1respectively for soil samples collected at Douala III subdivision. The highest value of the annual effective dose forin situmeasurements by car was observed at Ndogbong and was found to be 0.7 mSv y−1, higher than the world average value of 0.5 mSv y−1.

In the present study, a continuous radioactive aerosol measurement system (CRAMS) was developed for measurements of radioactive plume (e.g. 131I, 134Cs and 137Cs) under the emergency situation, and measurements of radon/thoron progeny under the existing situation. As a result, it is suggested that the CRAMS could follow the variation of radon concentration, and the detection limit of the CRAMS under ambient dose equivalent rate of 20µSvh-1, where the temporary evacuation is required within one week in the Japanese regulation, was evaluated to be 129Bqm-3 in the manner of ISO11929.

Most studies of the properties of airborne radionuclides emitted from the Fukushima Daiichi Nuclear Power Plant have focused on the relatively early stages of the accident, and little is known about the characteristics of radiocesium in the long-term. In this study, we analyzed activity size distributions of airborne radiocesium collected over 5 months in Tsukuba, Japan. Radiocesium in the accumulation mode size range (0.1-2 μm in aerodynamic diameter) was overwhelming in the early aerosol samples and decreased with time, while that associated with coarse aerosols remained airborne. We examined the radiocesium adsorbed onto airborne soil particles, and found that the size dependence of 137Cs surface density adsorbed on soil particles was weak. That is, radiocesium was distributed homogeneously throughout the aerodynamic diameter range of 2.1-11 μm. This characteristic may be related to the reported structure of radiocesium-bearing soil particles collected from the ground, which consisted of an aggregate of specific clay minerals and other non-cesium adsorbing particles. The resuspension factors for the first two aerosol samples collected during late April and May 2011 were close to those in European cities in the months following the Chernobyl accident, despite different soil and weather conditions.

Within the framework of a joint research project on natural radiation exposure and its health effects in Cameroon from 2014 to 2017, the Institute of Geological and Mining Research and the Hirosaki University worked together to carry out natural radiation survey in mining and ore bearing regions of Cameroon. Air kerma rates were measured using car-borne survey method. In-situ gamma spectrometry was used to determine activity concentrations of 238U, 232Th and 40K in soil. A total of 450 RADUET detectors and 350 thoron progeny monitors were deployed in dwellings of the study areas for 2–3 months, collected and analysed. Although natural radioactivity level seems to be normal in most of the surveyed areas, there are many points where activity concentrations of natural radionuclides are largely above the world average values. Indoor radon, thoron and thoron progeny results show the importance to put in place the national radon plan in Cameroon. It was also pointed out that thoron cannot be neglected when assessing inhalation dose.

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.

Concentrations of iodine-129 (129I) and atomic ratios of 129I/127I in livestock (grass and milk), agricultural (cabbage, Japanese radish, and rice), and fishery (flatfish and brown alga) products collected from locations around the first Japanese commercial spent nuclear fuel reprocessing plant in Rokkasho were measured from 2006 to 2016. The actual spent nuclear fuel rods were cut and processed to test the functioning of the plant that discharged controlled amounts of 129I to the atmosphere and coastal seawater during the period from 2006 to 2008 (the “cutting period”). Statistically significant increases in 129I concentration and 129I/127I ratio were observed during the cutting period in livestock products and flatfish. On the other hand, these parameters were statistically comparable during and after the cutting period in the other products. The radiation dose through the ingestion of the maximum 129I concentrations, measured in the different products, was estimated to be in the nanoSievert per year level. This value is much smaller than 1 mSv yr—1, which is the permissible authentic radiation dose for the general public. The 129I levels in the samples, especially in milk and flatfish, are discussed in context of the 129I discharge history from the plant.

Experimental and analytical studies on hydrogen-tritium isotope separation by a dual temperature dual pressure catalytic exchange (DTDP-CE) with liquid phase chemical exchange columns were carried out in order to apply it to a part of the water detritiation system for DEMO fuel cycle. A prototype DTDP-CE apparatus was successfully operated and it was confirmed that tritium was separated by the apparatus as significantly distinguishable. A calculation code was developed based on the channeling stage model. The values of separation factors and the effects of some operating parameters were well predicted by the separative analyses with the code.

A pilot study to measure ambient gamma dose rate and radon and thoron progeny concentrations was made for eight dwellings selected in Yangjiang, China. Indoor and outdoor ambient gamma dose rates were 110–370 and 100–220 nGy h−1, respectively. Doses received from indoor terrestrial radiation were estimated to be 0.6–1.8 mSv year−1. Radon, thoron and thoron progeny concentrations were 19–98, 18–1120 and 0.4–10.3 Bq m−3, respectively. This pilot study showed that the position of passive-type monitors to be placed and the deployment period should be carefully determined for estimating reliable annual average concentrations.

The spent nuclear fuel reprocessing plant in Rokkasho, Japan, has been undergoing final testing since March 2006. The concentrations of 129I in environmental water samples collected around the reprocessing plant were measured from 2005 to 2012. The 129I concentrations in water samples of the brackish lake adjacent to a plant from 2006 to 2008 which the spent fuel rods were cut and chemically processed, was higher than the background level. The major source of 129I in the lake was dominated by the direct deposition of 129I from the atmosphere than that from the ocean.

大気エアロゾルの供給源を明らかにする手法の一つとして，大陸起源エアロゾルの指標として利用されてきた大気中210Pb濃度と非海塩性硫酸イオンの硫黄同位体比(nssδ34S)を組み合わせて利用することを試みた。その結果，両者には正の相関が認められ，両者を組み合わせた方が，より大陸起源エアロゾルの指標として有効であった。

東アジア地域において，産出・使用されている石炭の硫黄同位体比分析を行った。その結果，黄土高原グループの硫黄同位体比は＋4.7～＋7.1‰(平均値：＋5.7‰)，雲南省グループは－20.0～＋9.9‰(平均値：－4.1‰)，トルファングループは＋8.6‰と＋1.9‰，プリモルスキーは＋6.1‰，モンゴル中央部グループは－2.5～＋5.0‰(平均値：＋1.1‰)，モンゴル東部グループは＋6.1～＋8.7‰(平均値：＋6.9‰)，韓国炭は－9.7‰であった。一方，インドネシア炭の硫黄同位体比は＋3.2～＋9.8‰(平均値：＋6.5‰)，オーストラリア炭は＋4.3‰と＋9.3‰であった。

Atmospheric aerosol samples were collected from 1993 to 2003 at Tsuruoka, Japan, a coastal area on the Sea of Japan. Concentration of water-soluble chemical components and sulfur isotopic ratios of sulfate in aerosol samples were measured to evaluate the temporal variation and identify the source. The samSO4 2‐ and nssSO4 2‐ concentrations range from 7.6 to 354.4 and 3.7 to 335.6 neq m ‐3 , respectively, and there was no clear seasonal variation. Sulfur isotope ratios of total sulfate (samδ 34 S) and non-sea salt sulfate (nssδ 34 S) in aerosols are +1.0 to +15.1 with a mean value of +5.7‰ and ‐4.4 to +14.5 with a mean value of +4.1‰, respectively. The values of samδ 34 S and nssδ 34 S are relatively low in summer and high in the other three seasons. The nssδ 34 S values of aerosols in fall to spring agree with the average sulfur isotope ratios of coal used in northern China, considering the isotope fractionation. These results indicate the possibility of long-range transport of sulfate from the Asian continent to Japan. The variations of atmospheric samSO4 2‐ and nssSO4 2‐ concentrations decreased gradually and reach a minimum in 1999. The decline of SO2 emission in China due to reduction in industrial coal use, a slowdown of the Chinese economy, and the closure of small and inefficient plants would be among the causes of this decreasing observed trend. On the other hands, the variation ranges of samδ 34 S and nssδ 34 S values abruptly changed after 2000. The introduction of fuel-gas desulfurization technologies to industrial plants of coke production and thermal power stations would be one of the most important causes of this change.

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 concentrations were given as 124 ± 78, 1247 ± 1189 and 7.8 ± 9.1 Bq m(-3), 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 a(-1). 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.

冬季に,日本海側を中心に湿性降下物中に含まれる非海塩性硫酸イオン濃度が増加する現象が見られ,その原因として中国から冬季北西季節風によって硫黄化合物が輸送されてきていると言われている.その現象を明らかにするために,日本各地の湿性降下物に含まれる非海塩性硫酸イオンの硫黄同位体比を測定した.その結果,硫黄同位体比は各地とも夏に低く,冬に高いという季節変化を示した.しかし,冬季の高い硫黄同位体比に違いが見られた.そこで高層天気図を用いた流跡線解析と東アジア地域で産出・使用されている化石燃料の硫黄同位体比から硫黄同位体比の違いを検討した.中国では北部ほど高い同位体比を持った石炭が燃料として使用されていることから,冬季北日本には中国北部からロシア極東地域で排出された高い同位体比の石炭燃焼起源硫黄酸化物が輸送され,また西南日本には朝鮮半島付近から中国中部及び南部で排出されたものが混合して,同位体比が平均化されて輸送されてくることが推定できた.

大気降下物の起源を明らかにするため,東アジア地域の石炭に含まれる硫黄の同位体比を測定し,山形県酒田市で採取した湿性降下物に含まれる非海塩性硫酸イオンの硫黄同位体比と比較検討した.また,日本に到達する空気塊の経路を知るために,酒田市を出発点とした流跡線解析を行い,以下のことが明らかになった.(1) 東アジア地域の石炭に含まれる硫黄の同位体比は-27.3～＋28.9‰の範囲に分布し,平均値は+4.2±9.6‰であった.(2) 北緯30度以南のものは－15～0‰と負の値を取る試料が多く,平均値は＋3.8±6.3‰であった.一方,北緯30度以北の試料は0～＋15‰の範囲に分布する試料が多く,平均値は＋7.4±8.8‰であった.また,北緯39度～42度の大同や北京付近の試料は＋15～＋30‰と特に高い値を示すものもあり,平均値は＋9.6±10.8‰であった.(3) 冬季に酒田市に到達する空気塊は極東ロシア,中国東北部,渤海周辺域,北京周辺域を経由したものである.(4) 酒田市の冬季降水には極東ロシア,中国東北部,渤海周辺域,北京周辺域を通過した際に取り込んだ化石燃料起源の硫黄酸化物が含まれていると推定される.

For a better understanding of the soil-to-plant transfer of radionuclides, their behavior in the soil solution should be elucidated, especially at the interface between plant roots and soil particles, where conditions differ greatly from the bulk soil because of plant activity. This study determined the concentration of stable Cs and Sr, and U in the soil solution, under plant growing conditions. The leafy vegetable komatsuna (Brassica rapa L.) was cultivated for 26 days in pots, where the rhizosphere soil was separated from the non-rhizosphere soil by a nylon net screen. The concentrations of Cs and Sr in the rhizosphere soil solution decreased with time, and were controlled by K+NH(4)(+) and Ca, respectively. On the other hand, the concentration of U in the rhizosphere soil solution increased with time, and was related to the changes of DOC; however, this relationship was different between the rhizosphere and non-rhizosphere soil.