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Ochi K, Funaki H, Yoshimura K, Iimoto T, Matsuda N, Sanada Y. Validation study of ambient dose equivalent conversion coefficients for radiocaesium distributed in the ground: lessons from the Fukushima Daiichi Nuclear Power Station accident. Radiat Environ Biophys 2022; 61:147-159. [PMID: 35201424 DOI: 10.1007/s00411-022-00969-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Accepted: 11/20/2021] [Indexed: 06/14/2023]
Abstract
Ambient dose equivalent conversion coefficients (ADCRCs) for converting a radiocaesium inventory to ambient dose equivalent rates (air dose rates) depend on the vertical distribution of radiocaesium in soil. To access the validity of ADCRCs, the air dose rate at 1 m above ground and the vertical distribution of radiocaesium in the soil around the Fukushima Daiichi Nuclear Power Station (FDNPS) present between 2011 and 2019 were measured in the current study. ADCRCs were calculated using air dose rates and three different parameters representing the vertical distribution of radiocaesium in soil: (1) relaxation mass depth (β), (2) effective relaxation mass depth (βeff) and (3) relaxation mass depth recommended by the International Commission on Radiation Units and Measurements before the FDNPS accident (βICRU). When ADCRCs based on β and βeff were compared to those based on β and βICRU, a positive correlation was found. To confirm the applicability of the ADCRCs based on the three types of β values, radiocaesium inventories were estimated using the air dose rates and ADCRCs, and the obtained results were compared to the radiocaesium inventory calculated using soil sample measurements. Good agreement was observed between the radiocaesium inventories estimated using the ADCRCs based on β and βeff and measured by investigating soil samples. By contrast, the radiocaesium inventory estimated using the ADCRCs based on βICRU was overestimated compared with that measured by investigating soil samples. These findings support the applicability of ADCRCs based on β and βeff in the Fukushima region. Furthermore, the βICRU result suggests that differences in soil characteristics between Japan and other countries should be considered for evaluating ADCRCs.
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Affiliation(s)
- Kotaro Ochi
- Fukushima Environmental Monitoring Division, Collaborative Laboratories for Advanced Decommissioning Science, Japan Atomic Energy Agency, 45-169 Sukakeba, Kaihama-aza, Haramachi, Minamisoma, Fukushima, 975-0036, Japan.
- Department of Environment Systems, Graduate School of Frontier Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8654, Japan.
| | - Hironori Funaki
- Fukushima Environmental Monitoring Division, Collaborative Laboratories for Advanced Decommissioning Science, Japan Atomic Energy Agency, 45-169 Sukakeba, Kaihama-aza, Haramachi, Minamisoma, Fukushima, 975-0036, Japan
| | - Kazuya Yoshimura
- Fukushima Environmental Monitoring Division, Collaborative Laboratories for Advanced Decommissioning Science, Japan Atomic Energy Agency, 45-169 Sukakeba, Kaihama-aza, Haramachi, Minamisoma, Fukushima, 975-0036, Japan
| | - Takeshi Iimoto
- Department of Environment Systems, Graduate School of Frontier Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8654, Japan
| | - Norihiro Matsuda
- Nuclear and LWR Engineering Division, Nuclear Science and Engineering Center, Japan Atomic Energy Agency, 2-4 Shirakata, Tokai-mura, Naka-gun, Ibaraki, 319-1195, Japan
| | - Yukihisa Sanada
- Fukushima Environmental Monitoring Division, Collaborative Laboratories for Advanced Decommissioning Science, Japan Atomic Energy Agency, 45-169 Sukakeba, Kaihama-aza, Haramachi, Minamisoma, Fukushima, 975-0036, Japan
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2
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Stöhlker U, Bleher M, Mlinarzik R, Harms W, Luff R, Feuerstein C, Prommer B. Spectro-dosemeter-based gamma dose rate network in Germany. Appl Radiat Isot 2022; 182:110077. [PMID: 35121275 DOI: 10.1016/j.apradiso.2021.110077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Revised: 11/07/2021] [Accepted: 12/19/2021] [Indexed: 11/26/2022]
Abstract
As a consequence of the Chernobyl accident in 1986 the Integrated Measurement and Information System (IMIS) was established (Weiss and Leeb, 1993) which includes on-line monitoring networks for the surveillance of radioactivity in Germany. Today, the German Federal Office for Radiation Protection (BfS) operates a gamma dose rate network with 1800 ambient dose equivalent rate H*(10) (ADER) stations almost equally distributed over the German territory. The ADER network integrates Geiger-Müller (GM) based detectors which, if low and high dose rate tubes are combined, are known to have excellent long-term stability and an extended dose rate range from environmental background level (20 nSv/h) up to several Sv/h. However, one main drawback is the lack of information about nuclides contributing to the observed dose rate. Therefore BfS has started to integrate LaBr3-based spectrometric detector systems (so-called spectro-dosemeters) in the existing ADER network. In this paper detector design, quality assurance and quality control (QA/QC) procedures are described as well as efforts required to characterize and operate monitoring networks based on spectrometric detectors.
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Affiliation(s)
- Ulrich Stöhlker
- German Federal Office for Radiation Protection (BfS), Willy-Brandt-Str. 5, 38226, Salzgitter, Germany
| | - Martin Bleher
- German Federal Office for Radiation Protection (BfS), Willy-Brandt-Str. 5, 38226, Salzgitter, Germany
| | - Robert Mlinarzik
- German Federal Office for Radiation Protection (BfS), Willy-Brandt-Str. 5, 38226, Salzgitter, Germany
| | - Walter Harms
- German Federal Office for Radiation Protection (BfS), Willy-Brandt-Str. 5, 38226, Salzgitter, Germany
| | - Roger Luff
- German Federal Office for Radiation Protection (BfS), Willy-Brandt-Str. 5, 38226, Salzgitter, Germany
| | - Claus Feuerstein
- German Federal Office for Radiation Protection (BfS), Willy-Brandt-Str. 5, 38226, Salzgitter, Germany.
| | - Bernhard Prommer
- German Federal Office for Radiation Protection (BfS), Willy-Brandt-Str. 5, 38226, Salzgitter, Germany
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Malins A, Imamura N, Niizato T, Takahashi J, Kim M, Sakuma K, Shinomiya Y, Miura S, Machida M. Calculations for ambient dose equivalent rates in nine forests in eastern Japan from 134Cs and 137Cs radioactivity measurements. J Environ Radioact 2021; 226:106456. [PMID: 33217723 DOI: 10.1016/j.jenvrad.2020.106456] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 10/29/2020] [Accepted: 11/04/2020] [Indexed: 06/11/2023]
Abstract
Understanding the relationship between the distribution of radioactive 134Cs and 137Cs in forests and ambient dose equivalent rates (H˙∗(10)) in the air is important for researching forests in eastern Japan affected by the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. This study used a large number of measurements from forest samples, including 134Cs and 137Cs radioactivity concentrations, densities and moisture contents, to perform Monte Carlo radiation transport simulations for H˙∗(10) between 2011 and 2017. Calculated H˙∗(10) at 0.1 and 1 m above the ground had mean residual errors of 19% and 16%, respectively, from measurements taken with handheld NaI(Tl) scintillator survey meters. Setting aside the contributions from natural background radiation, 134Cs and 137Cs in the organic layer and the top 5 cm of forest soil generally made the largest contributions to calculated H˙∗(10). The contributions from 134Cs and 137Cs in the forest canopy were calculated to be largest in the first two years following the accident. Uncertainties were evaluated in the simulation results due to the measurement uncertainties in the model inputs by assuming Gaussian measurement errors. The mean uncertainty (relative standard deviation) of the simulated H˙∗(10) at 1 m height was 11%. The main contributors to the total uncertainty in the simulation results were the accuracies to which the 134Cs and 137Cs radioactivities of the organic layer and top 5 cm of soil, and the vertical distribution of 134Cs and 137Cs within the 5 cm soil layers, were known. Radioactive cesium located in the top 5 cm of soil was the main contributor to H˙∗(10) at 1 m by 2016 or 2017 in the calculation results for all sites. Studies on the 137Cs distribution within forest soil will therefore help explain radiation levels henceforth in forests affected by the FDNPP accident. The merits of this study are that it modelled multiple forests for a long time period, with the important model inputs being informed by field measurements, and it quantified how the measurement uncertainties in these inputs affected the calculation results.
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Affiliation(s)
- Alex Malins
- Japan Atomic Energy Agency, Center for Computational Science and e-Systems, 178-4-4 Wakashiba, Kashiwa, Chiba, 277-0871, Japan.
| | - Naohiro Imamura
- Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan
| | - Tadafumi Niizato
- Japan Atomic Energy Agency, Collaborative Laboratories for Advanced Decommissioning Science (CLADS) Environmental Research Group, 10-2 Fukasaku, Miharu-machi, Tamura-gun, Fukushima, 963-7700, Japan
| | - Junko Takahashi
- Center for Research in Isotopes and Environmental Dynamic, University of Tsukuba, Tennodai 1-1-1, Tsukuba-shi, Ibaraki, 305-8572, Japan
| | - Minsik Kim
- Japan Atomic Energy Agency, Center for Computational Science and e-Systems, 178-4-4 Wakashiba, Kashiwa, Chiba, 277-0871, Japan
| | - Kazuyuki Sakuma
- Japan Atomic Energy Agency, Collaborative Laboratories for Advanced Decommissioning Science (CLADS) Environmental Research Group, 10-2 Fukasaku, Miharu-machi, Tamura-gun, Fukushima, 963-7700, Japan
| | - Yoshiki Shinomiya
- Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan
| | - Satoru Miura
- Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki, 305-8687, Japan
| | - Masahiko Machida
- Japan Atomic Energy Agency, Center for Computational Science and e-Systems, 178-4-4 Wakashiba, Kashiwa, Chiba, 277-0871, Japan
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Encabo RR, Cruz PTF, Bonga AC, Dela Sada CL, Omandam VJ, Olivares JU, Iwaoka K, Feliciano CP. Measurement of ambient gamma dose rate in Metro Manila, Philippines, using a portable NaI(TI) scintillation survey meter. Environ Monit Assess 2020; 192:400. [PMID: 32468213 DOI: 10.1007/s10661-020-08361-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Accepted: 05/13/2020] [Indexed: 06/11/2023]
Abstract
Radiological data such as ambient dose equivalent rate obtained from radiation monitoring in Metro Manila are useful for the detection of any anomalous increase of radiation dose rate levels due to nuclear or radiological emergencies. In this study, ambient dose equivalent rates were measured in different locations in Metro Manila using a portable NaI(Tl) scintillation survey meter to determine the background radiation levels within the capital. Ambient dose equivalent rates measured range from 32.7 ± 2.2 to 59.3 ± 8.7 nanosieverts per hour (nSv/h) with computed mean and median values of 41.7 and 39.6 nSv/h, respectively. These values were lower than the Philippines' average dose rate which is 52 nanograys per hour (nGy/h). No significant trend was also observed in the monthly variation of ambient dose equivalent rate for most locations, with the dose rates being relatively consistent throughout a year. No significant trend was further observed in the monthly variation of ambient dose equivalent rate for the whole Metro Manila. Data obtained in this study were used to develop a dose rate distribution map of Metro Manila which could be used as a baseline reference of emergency responders for environmental radioactivity monitoring during nuclear or radiological emergencies that may affect Metro Manila.
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Affiliation(s)
- Rosario R Encabo
- Health Physics Research Section, Atomic Research Division, Department of Science and Technology (DOST-PNRI), Philippine Nuclear Research Institute, Commonwealth Avenue, 1101 Diliman, Quezon City, Philippines.
| | - Paolo Tristan F Cruz
- Health Physics Research Section, Atomic Research Division, Department of Science and Technology (DOST-PNRI), Philippine Nuclear Research Institute, Commonwealth Avenue, 1101 Diliman, Quezon City, Philippines
| | - Antonio C Bonga
- Health Physics Research Section, Atomic Research Division, Department of Science and Technology (DOST-PNRI), Philippine Nuclear Research Institute, Commonwealth Avenue, 1101 Diliman, Quezon City, Philippines
| | - Christian L Dela Sada
- Health Physics Research Section, Atomic Research Division, Department of Science and Technology (DOST-PNRI), Philippine Nuclear Research Institute, Commonwealth Avenue, 1101 Diliman, Quezon City, Philippines
| | - Vanessa J Omandam
- Health Physics Research Section, Atomic Research Division, Department of Science and Technology (DOST-PNRI), Philippine Nuclear Research Institute, Commonwealth Avenue, 1101 Diliman, Quezon City, Philippines
| | - Juanario U Olivares
- Health Physics Research Section, Atomic Research Division, Department of Science and Technology (DOST-PNRI), Philippine Nuclear Research Institute, Commonwealth Avenue, 1101 Diliman, Quezon City, Philippines
| | - Kazuki Iwaoka
- National Institutes for Quantum and Radiological Sciences and Technology, 4-9-1 Anagawa, Inage, Chiba, 263-8555, Japan
| | - Chitho P Feliciano
- Health Physics Research Section, Atomic Research Division, Department of Science and Technology (DOST-PNRI), Philippine Nuclear Research Institute, Commonwealth Avenue, 1101 Diliman, Quezon City, Philippines
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Andoh M, Mikami S, Tsuda S, Yoshida T, Matsuda N, Saito K. Decreasing trend of ambient dose equivalent rates over a wide area in eastern Japan until 2016 evaluated by car-borne surveys using KURAMA systems. J Environ Radioact 2019; 210:105813. [PMID: 30348530 DOI: 10.1016/j.jenvrad.2018.09.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Revised: 05/29/2018] [Accepted: 07/11/2018] [Indexed: 06/08/2023]
Abstract
As part of the investigation of the distribution of ambient dose equivalent rates around the Fukushima Dai-ichi Nuclear Power Plant (FDNPP), car-borne surveys using Kyoto University RAdiation MApping (KURAMA) systems have been conducted over a wide area in eastern Japan since 2011. The enormous volume of measurement data collected until 2016, including those until 2012 which were reported in the previous paper, was analyzed, and dependencies of the decreasing trend of the dose rates in regions within 80 km of the FDNPP on land-use categories, evacuation order areas and magnitude of the dose rates were examined. The air dose rates within 80 km of the FDNPP tended to decrease considerably with respect to the physical decay of radiocaesium. The decrease of the dose rate in the "forest" was slower than its decrease in other regions, while that in "urban area" was the fastest. The decrease in the air dose rate from 2011 was the fastest outside the evacuation order area until 2015, and it was the slowest in the "difficult-to-return zone". However, the decreasing trend starting from 2013 showed that the decrease in the "zone in preparation for the lifting of the evacuation order" and in the "residence restriction area" was the fastest. It was found that the air dose rates decreased depending on the magnitude of the dose rates and elapsed time from the FDNPP accident, i.e. the decrease in air dose rates in areas with relatively low dose ranges (such as 0.2-0.5 μSv/h) was the largest during a period relatively early after the accident, and the decreasing rate in the dose rate ranges of 1.9-3.8 and 3.8-9.5 μSv/h were the fastest after 2013. The averaged ratios were analyzed to obtain the ecological half-lives of the fast and slow decay components, and those in whole area within 80 km of FDNPP were estimated to be 0.44 ± 0.05 y and 6.7 ± 1 y, respectively. The ecological half-lives with respect to the land use categories, evacuation order areas and magnitude of the dose rates were also evaluated. The decrease in the dose rates obtained by the car-borne survey was larger than that obtained on flat ground with few disturbances using the NaI(Tl) survey meter during approximately 1.5 y after the FDNPP accident. Thereafter, the difference of decreasing tendencies in the air dose rates between both the measurements was negligibly small, with the ratio of dose rates by the car-borne survey to those by the fixed-point measurement of 0.72-0.77.
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Affiliation(s)
- Masaki Andoh
- Japan Atomic Energy Agency, 11601-13 Nishi-jusanbugyo, Hitachinaka-city, Ibaraki 319-1206, Japan.
| | - Satoshi Mikami
- Japan Atomic Energy Agency, 11601-13 Nishi-jusanbugyo, Hitachinaka-city, Ibaraki 319-1206, Japan
| | - Shuichi Tsuda
- Japan Atomic Energy Agency, 11601-13 Nishi-jusanbugyo, Hitachinaka-city, Ibaraki 319-1206, Japan
| | - Tadayoshi Yoshida
- Japan Atomic Energy Agency, 11601-13 Nishi-jusanbugyo, Hitachinaka-city, Ibaraki 319-1206, Japan
| | - Norihiro Matsuda
- Japan Atomic Energy Agency, 11601-13 Nishi-jusanbugyo, Hitachinaka-city, Ibaraki 319-1206, Japan
| | - Kimiaki Saito
- Japan Atomic Energy Agency, 11601-13 Nishi-jusanbugyo, Hitachinaka-city, Ibaraki 319-1206, Japan
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Andoh M, Yamamoto H, Kanno T, Saito K. Measurement of ambient dose equivalent rates by walk survey around Fukushima Dai-ichi Nuclear Power Plant using KURAMA-II until 2016. J Environ Radioact 2019; 210:105812. [PMID: 30424885 DOI: 10.1016/j.jenvrad.2018.09.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Revised: 04/13/2018] [Accepted: 04/28/2018] [Indexed: 06/09/2023]
Abstract
Ambient dose equivalent rates in various environments related to human lives were measured by walk surveys using the KURAMA-II systems from 2013 to 2016 within an 80-km radius of the Fukushima Dai-ichi Nuclear Power Plant. The dose rate of the locations where the walk survey was performed decreased to about 38% of its initial value in the 42 months from June 2013 to the December 2016, which was beyond that attributable to the physical decay of radiocaesium. The ecological half-life of the slow decreasing component was evaluated to be 4.1 ± 0.2 y. The air dose rates decreased depending on the level of the evacuation areas, and the decrease in the dose rates was slightly larger in populated areas where humans are active. The dose rates as measured by walk surveys exhibited a good correlation with those by car-borne surveys, suggesting that car-borne survey data are reflecting the air dose rates in living environments surrounding roads. The comparison of walk survey data with car-borne survey data indicated that the air dose rate varies largely even within a 100 m square area, and the variation is enhanced by human activities. The dose rates measured by the walk surveys were estimated to be medial of those along roads and those of undisturbed flat ground, and they were found to be decreasing quickly compared with the air dose rate from the flat ground fixed-point measurements.
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Affiliation(s)
- Masaki Andoh
- Japan Atomic Energy Agency, 11601-13 Nishi-jusanbugyo, Hitachinaka-city, Ibaraki 319-1206, Japan.
| | - Hideaki Yamamoto
- Japan Atomic Energy Agency, 11601-13 Nishi-jusanbugyo, Hitachinaka-city, Ibaraki 319-1206, Japan
| | - Takashi Kanno
- Japan Atomic Energy Agency, 11601-13 Nishi-jusanbugyo, Hitachinaka-city, Ibaraki 319-1206, Japan
| | - Kimiaki Saito
- Japan Atomic Energy Agency, 11601-13 Nishi-jusanbugyo, Hitachinaka-city, Ibaraki 319-1206, Japan
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Kim M, Malins A, Yoshimura K, Sakuma K, Kurikami H, Kitamura A, Machida M, Hasegawa Y, Yanagi H. Simulation study of the effects of buildings, trees and paved surfaces on ambient dose equivalent rates outdoors at three suburban sites near Fukushima Dai-ichi. J Environ Radioact 2019; 210:105803. [PMID: 30236974 DOI: 10.1016/j.jenvrad.2018.09.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Revised: 08/10/2018] [Accepted: 09/02/2018] [Indexed: 06/08/2023]
Abstract
The influence of buildings, trees and paved surfaces on outdoor ambient dose equivalent rates (H˙∗(10)) in suburban areas near to the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) was investigated with Monte Carlo simulations. Simulation models of three un-decontaminated sites in Okuma and Tomioka were created with representations of individual buildings, trees and roads created using geographic information system (GIS) data. The 134Cs and 137Cs radioactivity distribution within each model was set using in-situ gamma spectroscopy measurements from December 2014 and literature values for the relative radioactive cesium concentration on paved surfaces, unpaved land, building outer surfaces, forest litter and soil layers, and different tree compartments. Reasonable correlation was obtained between the simulations and measurements for H˙∗(10) across the sites taken in January 2015. The effect of buildings and trees on H˙∗(10) was investigated by performing simulations removing these objects, and their associated 134Cs and 137Cs inventory, from the models. H˙∗(10) were on average 5.0% higher in the simulations without buildings and trees, even though the total 134Cs and 137Cs inventory within each model was slightly lower. The simulations without buildings and trees were then modified to include 134Cs and 137Cs in the ground beneath locations where buildings exist in reality, and the inventory of paved surfaces modelled as if they had high retention of 134Cs and 137Cs fallout like soil areas. H˙∗(10) increased more markedly in these cases than when considering the shielding effect of buildings and trees alone. These results help clarify the magnitude of the effect of buildings, trees and paved surfaces on H˙∗(10) at the un-decontaminated sites within Fukushima Prefecture.
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Affiliation(s)
- Minsik Kim
- Japan Atomic Energy Agency, Center for Computational Science and e-Systems, 178-4-4 Wakashiba, Kashiwa, Chiba 277-0871, Japan.
| | - Alex Malins
- Japan Atomic Energy Agency, Center for Computational Science and e-Systems, 178-4-4 Wakashiba, Kashiwa, Chiba 277-0871, Japan
| | - Kazuya Yoshimura
- Japan Atomic Energy Agency, Fukushima Environmental Safety Center, 45-169 Sukakeba, Kaibana, Haramachi-ku, Minamisoma City, Fukushima 975-0036, Japan
| | - Kazuyuki Sakuma
- Japan Atomic Energy Agency, Fukushima Environmental Safety Center, 45-169 Sukakeba, Kaibana, Haramachi-ku, Minamisoma City, Fukushima 975-0036, Japan; Japan Atomic Energy Agency, Fukushima Environmental Safety Center, 10-2 Fukasaku, Miharu-machi, Tamura-gun, Fukushima, 963-7700, Japan
| | - Hiroshi Kurikami
- Japan Atomic Energy Agency, Center for Computational Science and e-Systems, 178-4-4 Wakashiba, Kashiwa, Chiba 277-0871, Japan; Japan Atomic Energy Agency, Fukushima Environmental Safety Center, 10-2 Fukasaku, Miharu-machi, Tamura-gun, Fukushima, 963-7700, Japan
| | - Akihiro Kitamura
- Japan Atomic Energy Agency, Center for Computational Science and e-Systems, 178-4-4 Wakashiba, Kashiwa, Chiba 277-0871, Japan; Japan Atomic Energy Agency, Fukushima Environmental Safety Center, 10-2 Fukasaku, Miharu-machi, Tamura-gun, Fukushima, 963-7700, Japan
| | - Masahiko Machida
- Japan Atomic Energy Agency, Center for Computational Science and e-Systems, 178-4-4 Wakashiba, Kashiwa, Chiba 277-0871, Japan
| | - Yukihiro Hasegawa
- Research Organization for Information Science and Technology, 2-4 Shirakata, Tokai-mura, Ibaraki-ken, 319-1106, Japan
| | - Hideaki Yanagi
- Research Organization for Information Science and Technology, 2-4 Shirakata, Tokai-mura, Ibaraki-ken, 319-1106, Japan
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Andoh M, Mikami S, Tsuda S, Yoshida T, Matsuda N, Saito K. Decreasing trend of ambient dose equivalent rates over a wide area in eastern Japan until 2016 evaluated by car-borne surveys using KURAMA systems. J Environ Radioact 2018; 192:385-398. [PMID: 30048901 DOI: 10.1016/j.jenvrad.2018.07.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Revised: 05/29/2018] [Accepted: 07/11/2018] [Indexed: 06/08/2023]
Abstract
As part of the investigation of the distribution of ambient dose equivalent rates around the Fukushima Dai-ichi Nuclear Power Plant (FDNPP), car-borne surveys using Kyoto University RAdiation MApping (KURAMA) systems have been conducted over a wide area in eastern Japan since 2011. The enormous volume of measurement data collected until 2016, including those until 2012 which were reported in the previous paper, was analyzed, and dependencies of the decreasing trend of the dose rates in regions within 80 km of the FDNPP on land-use categories, evacuation order areas and magnitude of the dose rates were examined. The air dose rates within 80 km of the FDNPP tended to decrease considerably with respect to the physical decay of radiocaesium. The decrease of the dose rate in the "forest" was slower than its decrease in other regions, while that in "urban area" was the fastest. The decrease in the air dose rate from 2011 was the fastest outside the evacuation order area until 2015, and it was the slowest in the "difficult-to-return zone". However, the decreasing trend starting from 2013 showed that the decrease in the "zone in preparation for the lifting of the evacuation order" and in the "residence restriction area" was the fastest. It was found that the air dose rates decreased depending on the magnitude of the dose rates and elapsed time from the FDNPP accident, i.e. the decrease in air dose rates in areas with relatively low dose ranges (such as 0.2-0.5 μSv/h) was the largest during a period relatively early after the accident, and the decreasing rate in the dose rate ranges of 1.9-3.8 and 3.8-9.5 μSv/h were the fastest after 2013. The averaged ratios were analyzed to obtain the ecological half-lives of the fast and slow decay components, and those in whole area within 80 km of FDNPP were estimated to be 0.44 ± 0.05 y and 6.7 ± 1 y, respectively. The ecological half-lives with respect to the land use categories, evacuation order areas and magnitude of the dose rates were also evaluated. The decrease in the dose rates obtained by the car-borne survey was larger than that obtained on flat ground with few disturbances using the NaI(Tl) survey meter during approximately 1.5 y after the FDNPP accident. Thereafter, the difference of decreasing tendencies in the air dose rates between both the measurements was negligibly small, with the ratio of dose rates by the car-borne survey to those by the fixed-point measurement of 0.72-0.77.
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Affiliation(s)
- Masaki Andoh
- Japan Atomic Energy Agency, 11601-13 Nishi-jusanbugyo, Hitachinaka-city, Ibaraki 319-1206, Japan.
| | - Satoshi Mikami
- Japan Atomic Energy Agency, 11601-13 Nishi-jusanbugyo, Hitachinaka-city, Ibaraki 319-1206, Japan
| | - Shuichi Tsuda
- Japan Atomic Energy Agency, 11601-13 Nishi-jusanbugyo, Hitachinaka-city, Ibaraki 319-1206, Japan
| | - Tadayoshi Yoshida
- Japan Atomic Energy Agency, 11601-13 Nishi-jusanbugyo, Hitachinaka-city, Ibaraki 319-1206, Japan
| | - Norihiro Matsuda
- Japan Atomic Energy Agency, 11601-13 Nishi-jusanbugyo, Hitachinaka-city, Ibaraki 319-1206, Japan
| | - Kimiaki Saito
- Japan Atomic Energy Agency, 11601-13 Nishi-jusanbugyo, Hitachinaka-city, Ibaraki 319-1206, Japan
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Andoh M, Yamamoto H, Kanno T, Saito K. Measurement of ambient dose equivalent rates by walk survey around Fukushima Dai-ichi Nuclear Power Plant using KURAMA-II until 2016. J Environ Radioact 2018; 190-191:111-121. [PMID: 29778897 DOI: 10.1016/j.jenvrad.2018.04.025] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Revised: 04/13/2018] [Accepted: 04/28/2018] [Indexed: 06/08/2023]
Abstract
Ambient dose equivalent rates in various environments related to human lives were measured by walk surveys using the KURAMA-II systems from 2013 to 2016 within an 80-km radius of the Fukushima Dai-ichi Nuclear Power Plant. The dose rate of the locations where the walk survey was performed decreased to about 38% of its initial value in the 42 months from June 2013 to the December 2016, which was beyond that attributable to the physical decay of radiocaesium. The ecological half-life of the slow decreasing component was evaluated to be 4.1 ± 0.2 y. The air dose rates decreased depending on the level of the evacuation areas, and the decrease in the dose rates was slightly larger in populated areas where humans are active. The dose rates as measured by walk surveys exhibited a good correlation with those by car-borne surveys, suggesting that car-borne survey data are reflecting the air dose rates in living environments surrounding roads. The comparison of walk survey data with car-borne survey data indicated that the air dose rate varies largely even within a 100 m square area, and the variation is enhanced by human activities. The dose rates measured by the walk surveys were estimated to be medial of those along roads and those of undisturbed flat ground, and they were found to be decreasing quickly compared with the air dose rate from the flat ground fixed-point measurements.
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Affiliation(s)
- Masaki Andoh
- Japan Atomic Energy Agency, 11601-13 Nishi-jusanbugyo, Hitachinaka-city, Ibaraki 319-1206, Japan.
| | - Hideaki Yamamoto
- Japan Atomic Energy Agency, 11601-13 Nishi-jusanbugyo, Hitachinaka-city, Ibaraki 319-1206, Japan
| | - Takashi Kanno
- Japan Atomic Energy Agency, 11601-13 Nishi-jusanbugyo, Hitachinaka-city, Ibaraki 319-1206, Japan
| | - Kimiaki Saito
- Japan Atomic Energy Agency, 11601-13 Nishi-jusanbugyo, Hitachinaka-city, Ibaraki 319-1206, Japan
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10
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Bossew P, Cinelli G, Hernández-Ceballos M, Cernohlawek N, Gruber V, Dehandschutter B, Menneson F, Bleher M, Stöhlker U, Hellmann I, Weiler F, Tollefsen T, Tognoli PV, de Cort M. Estimating the terrestrial gamma dose rate by decomposition of the ambient dose equivalent rate. J Environ Radioact 2017; 166:296-308. [PMID: 26926960 DOI: 10.1016/j.jenvrad.2016.02.013] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Revised: 02/11/2016] [Accepted: 02/13/2016] [Indexed: 06/05/2023]
Abstract
An extensive network of dose rate monitoring stations continuously measures ambient dose rate across Europe, as part of the EURDEP system. Its purpose is early warning in radiological emergencies and documenting its temporal and spatial evolution. In normal conditions, when there is no contribution to the dose rate signal coming from fresh anthropogenic contamination, the data represent the radiation "background", i.e. the combined natural radiation and existing anthropogenic contamination (by global and Chernobyl fallout). These data are being stored, but have so far not been evaluated in depth, or used for any purpose. In the framework of the EU project 'European Atlas of Natural Radiation' the idea has emerged to exploit these data for generating a map of natural terrestrial gamma radiation. This component contributes to the total radiation exposure and knowing its geographical distribution can help establishing local 'radiation budgets'. A further use could be found in terrestrial dose rate as a proxy of the geogenic radon potential, as both quantities are related by partly the same source, namely uranium content of the ground. In this paper, we describe in detail the composition of the ambient dose equivalent rate as measured by the EURDEP monitors with respect to its physical nature and to its sources in the environment. We propose and compare methods to recover the terrestrial component from the gross signal. This requires detailed knowledge of detector response. We consider the probes used in the Austrian, Belgian and German dose rate networks, which are the respective national networks supplying data to EURDEP. It will be shown that although considerable progress has been made in understanding the dose rate signals, there is still space for improvement in terms of modelling and model parameters. An indispensable condition for success of the endeavour to establish a Europe-wide map of terrestrial dose rate background is progress in harmonising the European dose rate monitoring network.
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Affiliation(s)
- P Bossew
- German Federal Office for Radiation Protection (BfS), Berlin, Munich, Freiburg, Germany
| | - G Cinelli
- European Commission, DG Joint Research Centre (JRC), Institute for Transuranium Elements, Ispra, Italy
| | - M Hernández-Ceballos
- European Commission, DG Joint Research Centre (JRC), Institute for Transuranium Elements, Ispra, Italy
| | - N Cernohlawek
- Austrian Federal Ministry of Agriculture, Forestry, Environment and Water Management, Vienna, Austria
| | - V Gruber
- Austrian Agency for Health and Food Safety (AGES), Vienna and Linz, Austria
| | - B Dehandschutter
- Belgian Federal Agency for Nuclear Control (FANC), Brussels, Belgium
| | - F Menneson
- Belgian Federal Agency for Nuclear Control (FANC), Brussels, Belgium
| | - M Bleher
- German Federal Office for Radiation Protection (BfS), Berlin, Munich, Freiburg, Germany
| | - U Stöhlker
- German Federal Office for Radiation Protection (BfS), Berlin, Munich, Freiburg, Germany
| | - I Hellmann
- German Federal Office for Radiation Protection (BfS), Berlin, Munich, Freiburg, Germany
| | - F Weiler
- German Federal Office for Radiation Protection (BfS), Berlin, Munich, Freiburg, Germany
| | - T Tollefsen
- European Commission, DG Joint Research Centre (JRC), Institute for Transuranium Elements, Ispra, Italy
| | - P V Tognoli
- European Commission, DG Joint Research Centre (JRC), Institute for Transuranium Elements, Ispra, Italy
| | - M de Cort
- European Commission, DG Joint Research Centre (JRC), Institute for Transuranium Elements, Ispra, Italy
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11
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Stojanovska Z, Boev B, Zunic ZS, Ivanova K, Ristova M, Tsenova M, Ajka S, Janevik E, Taleski V, Bossew P. Variation of indoor radon concentration and ambient dose equivalent rate in different outdoor and indoor environments. Radiat Environ Biophys 2016; 55:171-183. [PMID: 26943159 DOI: 10.1007/s00411-016-0640-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Accepted: 02/20/2016] [Indexed: 06/05/2023]
Abstract
Subject of this study is an investigation of the variations of indoor radon concentration and ambient dose equivalent rate in outdoor and indoor environments of 40 dwellings, 31 elementary schools and five kindergartens. The buildings are located in three municipalities of two, geologically different, areas of the Republic of Macedonia. Indoor radon concentrations were measured by nuclear track detectors, deployed in the most occupied room of the building, between June 2013 and May 2014. During the deploying campaign, indoor and outdoor ambient dose equivalent rates were measured simultaneously at the same location. It appeared that the measured values varied from 22 to 990 Bq/m(3) for indoor radon concentrations, from 50 to 195 nSv/h for outdoor ambient dose equivalent rates, and from 38 to 184 nSv/h for indoor ambient dose equivalent rates. The geometric mean value of indoor to outdoor ambient dose equivalent rates was found to be 0.88, i.e. the outdoor ambient dose equivalent rates were on average higher than the indoor ambient dose equivalent rates. All measured can reasonably well be described by log-normal distributions. A detailed statistical analysis of factors which influence the measured quantities is reported.
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Affiliation(s)
- Zdenka Stojanovska
- Faculty of Medical Sciences, Goce Delcev University, Krste Misirkov No.10-A, P. O. 201, 2000, Stip, Republic of Macedonia.
| | - Blazo Boev
- Faculty of Natural and Technical Sciences, Goce Delcev University, Krste Misirkov No.10-A, P. O. 201, 2000, Stip, Republic of Macedonia
| | - Zora S Zunic
- Institute of Nuclear Sciences "Vinča", University of Belgrade, P. O. Box 522, Belgrade, 11000, Serbia
| | - Kremena Ivanova
- National Center of Radiobiology and Radiation Protection, 3 Sv. Georgi Sofiyski st., 1606, Sofia, Bulgaria
| | - Mimoza Ristova
- Faculty of Natural Sciences and Mathematic, Institute of Physics, University in Ss. Cyril and Methodius, Arhimedova 3, 1000, Skopje, Republic of Macedonia
| | - Martina Tsenova
- National Center of Radiobiology and Radiation Protection, 3 Sv. Georgi Sofiyski st., 1606, Sofia, Bulgaria
| | - Sorsa Ajka
- Croatian Geological Survey, Sachsova 2, P. O. Box 268, Zagreb, Croatia
| | - Emilija Janevik
- Faculty of Medical Sciences, Goce Delcev University, Krste Misirkov No.10-A, P. O. 201, 2000, Stip, Republic of Macedonia
| | - Vaso Taleski
- Faculty of Medical Sciences, Goce Delcev University, Krste Misirkov No.10-A, P. O. 201, 2000, Stip, Republic of Macedonia
| | - Peter Bossew
- German Federal Office for Radiation Protection, div. SW 1.1, 120-130 Köpenicker Allee, 10318, Berlin, Germany
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