Air concentration estimation of radionuclides discharged from Fukushima Daiichi Nuclear Power Station using NaI(Tl) detector pulse height distribution measured in Ibaraki Prefecture

Air concentrations of ¹³³Xe, ¹³¹I, ¹³²I, ¹³³I, ¹³²Te, ¹³⁴Cs, ¹³⁶Cs, and ¹³⁷Cs in the early stage of the Fukushima Daiichi Nuclear Power Station (FNPS1) accident were estimated for six locations in Ibaraki Prefecture from pulse height distributions measured with NaI(Tl) scintillation detectors continuously operated as a part of monitoring station systems. Air concentration of ¹³³Xe in Ibaraki was estimated for the first time, which showed the maximum value of 150 kBq m^?3 in the plume arrived at the southern part of Ibaraki around noon of 15 March 2011. The plume was found to consist mainly of noble gases without other nuclides at significant level and to correspond to the hydrogen explosion at Unit 3. Spatiotemporal distributions of ¹³¹I and other nuclides were discussed for the plumes detected during the periods of 15–16 and 20–21 March. Variations in radionuclide composition among the plumes and within each plume were also discussed.     

福岛核事故期间山西地区辐射环境应急监测

日本福岛核电站受地震影响发生事故后,中国辐射防护研究院随即启动了应急监测,监测内容包括γ辐射剂量率,以及气溶胶、空气碘、沉降灰、降水、地表水、生物和土壤等环境介质的放射性水平.监测结果表明:γ辐射剂量率没有发生明显变化;气溶胶、空气碘、沉降灰、降水、地表水和生物样品中均测出了131 I ,部分样品中测出了137 Cs和134 Cs ;土壤样品中131 I 低于探测限.     

One-year time variations of anthropogenic radionuclides in aerosols in Tokyo after the Fukushima Dai-ichi Nuclear Power Plant reactor failures

We report on the results of monitoring of environmental radiation for one year (13 March 2011 to 12 March 2012), including air dose rates and the concentrations of radionuclides in aerosols in Tokyo, after the reactor failures at the Fukushima Dai-ichi Nuclear Power Plant. The air dose rates began to increase at 4:00–5:00 JST on 15 March 2011, and the maximum rate was observed at 10:00–11:00 JST. Two peaks were observed before 23 March 2011, and then the air dose rates decreased until March 2012. The time variations of concentrations of radionuclides in aerosols showed tendencies similar to those of air dose rates. Short-lived radionuclides (⁹⁹Mo (^99mTc), ^129mTe (¹²⁹Te), ^131mTe, ¹³²Te (¹³²I), ¹³³I and ¹³⁶Cs) were under the detection limit during April 2011. Iodine-131 was detected until early June 2011, and long-lived radionuclides (¹³⁴Cs and ¹³⁷Cs) were detected intermittently for one year. Based on our results, gamma doses and committed effective doses resulting from inhalation were estimated.     

Source term estimation of atmospheric release due to the Fukushima Dai-ichi Nuclear Power Plant accident by atmospheric and oceanic dispersion simulations

The source term of the atmospheric release of ¹³¹I and ¹³⁷Cs due to the Fukushima Dai-ichi Nuclear Power Plant accident estimated by previous studies was validated and refined by coupling atmospheric and oceanic dispersion simulations with observed ¹³⁴Cs in seawater collected from the Pacific Ocean. By assuming the same release rate for ¹³⁴Cs and ¹³⁷Cs, the sea surface concentration of ¹³⁴Cs was calculated using the previously estimated source term and was compared with measurement data. The release rate of ¹³⁷Cs was refined to reduce underestimation of measurements, which resulted in a larger value than that previously estimated. In addition, the release rate of ¹³¹I was refined to follow the radioactivity ratio of ¹³⁷Cs. As a result, the total amounts of ¹³¹I and ¹³⁷Cs discharged into the atmosphere from 5 JST on March 12 to 0 JST on March 20 were estimated to be approximately 2.0 × 10¹⁷ and 1.3 × 10¹⁶ Bq, respectively.     

福岛核事故期间西藏地区辐射环境应急监测

福岛核事故发生后,西藏辐射环境监督站在拉萨立即展开辐射应急.通过对γ辐射剂量率,以及气溶胶中137 Cs 、134 Cs 和131 I 活度浓度的监测分析,结果表明,福岛核事故未对西藏地区的辐射环境产生明显影响.     

Retrospective Determination of the Internal Irradiation Dose Due to 131I to the Thyroid Gland According to the 137Cs Local Fallout Density

A method is proposed for performing retrospective determination of the internal irradiation dose to the thyroid gland in man as a result of ¹³¹I uptake with fresh cow milk according to the total local ¹³⁷Cs fallout density resulting from nuclear explosions. It is shown that during local fallout the ratio of the numbers of ¹³¹I and ¹³⁷Cs atoms on particle surfaces is about 0.46 and is independent of the fissioning material (²³⁹Pu or ²³⁸U) used in the nuclear charge. This makes it possible to determine the fallout density of ¹³¹I on soil from the local component of the total ¹³⁷Cs fallout density. The information about the total ¹³⁷Cs fallout density on soil is used to calculate the effect of the irradiation dose of ¹³¹I to the thyroid gland in children and adults who lived in the populated points in Altai krai during the nuclear tests conducted in the Semipalatinsk test area. The estimates agree satisfactorily with those obtained by a different method.     

Analysis of cesium isotope compositions in environmental samples by thermal ionization mass spectrometry-3

Cesium was recovered from soil samples obtained in Fukushima prefecture. Isotopic analysis of Cs was performed by γ-spectrometry to determine the activity ratio of ¹³⁴Cs/¹³⁷Cs and thermal ionization mass spectrometry was used to determine the isotopic ratios of ¹³³Cs/¹³⁷Cs and ¹³⁵Cs/¹³⁷Cs. The analytical results showed that both the activity ratio of ¹³⁴Cs/¹³⁷Cs and the isotopic ratio of ¹³⁵Cs/¹³⁷Cs were within the expected values for the Fukushima Daiichi Nuclear Power Plant estimated using the ORIGEN-II code, suggesting that most of the radioactive Cs in the soil sample originated from the Fukushima Daiichi Nuclear Power Plant. The concentration of ¹³⁷Cs and the contribution of radioactive Cs from global fallout were correlated to the distance from the Fukushima Daiichi Nuclear Power Plant, while the contribution of radioactive Cs from each reactor did not show any similar distance dependence.     

Estimation of release rate of iodine-131 and cesium-137 from the Fukushima Daiichi nuclear power plant

The atmospheric release rates of I-131 and Cs-137 from the Fukushima Daiichi nuclear power plant in March 2011 were estimated by comparing environmental monitoring data of air concentration and deposition rate on a regional scale with calculated values from an atmospheric dispersion model. Although the release rates were not estimated for all days after 11 March, because of lack of monitoring data, temporal changes in the release rates were reasonably estimated with estimated uncertainties in a factor of 3.3 and 2.9 for I-131 and Cs-137, respectively. A large release was estimated from the night of 14 March to at least the afternoon of 15 March, with maximum values of 7.2 × 10¹⁵ Bq h^?1 for I-131 and 1.5 × 10¹⁴ Bq h^?1 for Cs-137. The release rates during other periods were estimated at one- to two-orders of magnitude smaller than the largest release rate on 15 March. Uncertainty in the estimated release rate for 15 and 20 March was larger than for other periods. The significant release during 14 and 15 March and the trend of the release rate by the end of March were consistent with previous reports. This agreement, despite using different datasets, shows robustness of the temporal changes estimated in the studies.     

137Cs vertical migration and contamination density in the soil of southern transbaikal

The mechanism of vertical migration of radionuclides along the soil profile is studied. For large averaging, the process can be described by the sum of the rates of effective diffusion and vertical advection of a radionuclide. The results of theoretical calculations of the¹³⁷Cs concentration profiles in light and heavy soils for actually observed atmospheric fallout in 1954–1999 are compared with the experimental profiles in mountain frozen-taiga and mountain frozen-forest tundra soils of southern Transbaikal. The rate of vertical migration is estimated and the reasons for the high¹³⁷Cs contamination density of soil in this region are discussed. 4 figures, 27 references. Scientific and Industrial Association “Taifun.” GP “Sosnovgeolservis.” Translated from Atomnaya énergiya, Vol. 88, No. 3, pp. 207–213, March, 2000.     

Seven-year temporal variation of Caesium-137 discharge inventory from the port of Fukushima Daiichi Nuclear Power Plant: continuous monthly estimation of Caesium-137 discharge in the period from April 2011 to June 2018

ABSTRACT

After direct discharges of highly contaminated water of the Fukushima Daiichi Nuclear Power Plant (1 F) from April to May 2011, Kanda suggested that relatively small amounts of run-off of radionuclides from the 1 F port into the Fukushima coastal region subsequently continued by his estimation method. However, the estimation period was limited to up to September 2012. Therefore, this paper estimatesthe discharge inventory up to June 2018. In the missing period, the Japanese government and Tokyo Electric Power Company Holdings have continued efforts to stop the discharge, and consequently, the radionuclide concentration in seawater inside the 1 F port has gradually diminished. We show the monthly discharge inventory of ¹³⁷Cs up to June 2018 by two methods, i.e., Kanda method partially improved by the authors and a more sophisticated method using Voronoi tessellation reflecting the increase in the number of monitoring points inside the 1 F port. The results show that the former always yields overestimated results compared with the latter, but the ratio of the former to the latter is less than one order of magnitude. Using these results, we evaluate the impact of the discharge inventory from the 1 F port into the coastal area and radiation dose upon fish ingestion.     

Radiation conditions in the Moscow Region in the period 1957–2005

Information about the radiation conditions in the Moscow region in 1957–2005 is presented. It is shown that the total activity of the β-emitting radionuclides, ⁹⁰Sr and ¹³⁷Cs, in atmospheric air, fallout, and food products changes. These data are used to estimate the total individual irradiation dose to the public, which does not exceed 0.2 mSv/yr. This is much less than the dose limit (1 mSv/yr) established in NRB-99. It is concluded that the radiation conditions in the Moscow region are satisfactory in the period studied. __________ Translated from Atomnaya énergiya, Vol. 100, No. 3, pp. 225–231, March, 2006.     

Atmospheric radionuclides from Fukushima Dai-ichi nuclear accident detected in Lanzhou,China

After the Fukushima Dai-ichi nuclear power plant accident on March 11,2011,the radioactivity released from the accident was transported around the globe by atmospheric processes.The radioactivity monitoring program on atmospheric particulate in Lanzhou,China was activated by GSCDC to detect the input radionuclides through atmospheric transport.Several artificial radionuclides were detected and measured in aerosol samples from March 26 to May 2,2011.The peaked activity concentrations(in m Bq/m3)were:1.194(131I),0.231(137Cs),0.173(134Cs)and 0.008(136Cs),detected on April 6,2011.The average activity ratio of131I/137Cs and134Cs/137Cs in air were 13.5 and 0.78.The significant increase of137Cs activity concentration,one order of magnitude higher than pre-Fukushima accident levels,in ground level aerosol was observed in 2013,as its resuspension from soil.The back-trajectory analysis simulated by NOAA-ARL HYSPLIT shows a direct transfer of the air masses released from Fukushima to Lanzhou across the Pacific Ocean,North America and Europe at the height close to 9000 m AGL.The value of effective dose for inhalation is close to one millionth of the annual limit for the general public.     

基于三角圆筒铅屏蔽NaI探测器的放射源定位研究

随着放射源和放射装置的广泛应用,放射源事故的发生概率不断增大。因此,一旦发现放射源丢失,如何尽快将其定位并安全找回尤为重要。本文设计了一种三角圆筒铅屏蔽的NaI探测器,用于放射源的定位探测。实验研究了测量时间、铅屏蔽厚度、源与探测器间距、伽马射线能量等因素对放射源定位的影响。结果表明:对于137 Cs源,在空气吸收剂量率≥0.028μGy/h处,定位平均角度偏差≤1.24°;对于60 Co源,在空气吸收剂量率0.4μGy/h处,测量的平均角度偏差为1.16°;对于距离约1.5 m的9.25×105 Bq 137 Cs源,定位偏差约为0.097m。     

Radiological monitoring results of the ambient environment around Qinshan Nuclear Power Plant

1 Introduction Qinshan Nuclear Power Plant (QNPP), a300 MW pressurized-water reactor, was built in 1983,and put into operation in December 1991. In order toestimate the impact QNPP exerted on the ambient en-vironment and the radiation dose the public received,the lab monitoring system and instantaneous landgamma radiation dose-rate monitoring system wereestablished in 1985, and worked from 1988. This pa-per provides the part results of the lab monitoring sys-tem.2 Monitoring pr…     

Dynamics of <Superscript>137</Superscript>Cs bottom contamination of the Tsimlyanskoe reservoir

Analysis of data obtained in 1990 and 2000 on the ¹³⁷Cs contamination of the bottom of the Tsimlyanskoe reservoir near the dam has revealed the salient variations of this contamination. The global fallout enters the water in the section near the dam from side tributaries and as a result of erosion from the closest water catchment areas. The fallout due to the accident at the Chernobyl nuclear power plant is added primarily with the solid runoff from the more highly contaminated catchment basins of the Don River. It is shown that shore abrasion, flows, and removal of sediment through the water outflow area influence the distribution of the ¹³⁷Cs content over the zones and the characteristics of the variation of this distribution in time. __________ Translated from Atomnaya énergiya, Vol. 103, No. 4, pp. 260–263, October, 2007.     

Atmospheric 85Kr and 133Xe activity concentrations at locations across Japan following the Fukushima Dai-ichi Nuclear Power Plant accident

Atmospheric ⁸⁵Kr and ¹³³Xe activity concentrations were determined from weekly air samples collected at Sapporo, Akita and Chiba, Japan, throughout 2011. The results demonstrated that the Fukushima Dai-ichi Nuclear Power Plant accident in early March 2011 resulted in high ¹³³Xe activity concentrations as well as elevated levels of ⁸⁵Kr activity; there was a striking increase in the concentrations of both isotopes over the week running from 14 to 22 March as the radioactive plume released from the plant was captured. At Chiba, following the accident, the ⁸⁵Kr activity concentration increased from 1.38 to 17.7 Bq/m³, while the ¹³³Xe levels increased from below the minimum detectable concentration (MDC ≤ 1.9 × 10^?3 Bq/m³) to 1.3 × 10³ Bq/m³. Conversely, at Sapporo and Akita, high ⁸⁵Kr activity concentrations were not observed, due to differences in air transportation mechanisms based on wind directions. Duplicate samples were collected at Chiba to allow the simultaneous analyses of ⁸⁵Kr and ¹³³Xe at the Japan Chemical Analysis Center and the Bundesamt für Strahlenschutz in Germany and the results were in good agreement. The external effective radiation doses resulting from ⁸⁵Kr and ¹³³Xe releases following the accident were estimated to be approximately 7.0 × 10^?3 and 1.3 μSv, respectively, based on the activity concentrations of these nuclides from March to June in 2011 at Chiba.     

Emission of Radionuclides from the Destroyed Unit of the Chernobyl Nuclear Power Plant

Investigations of radionuclide emission resulting from the Chernobyl accident are briefly reviewed. Three ways to estimate emission are examined: direct investigations of radionuclides emitted from the destroyed unit; study of the quantity and composition of radionuclides emitted on the territory after the active stage of the accident was over; study of the quantity and composition of radionuclides remaining in the No. 4 unit. All three methods suffer from serious difficulties which are examined in the paper. New data are presented. These data concern estimates of the emission of fuel particles, ¹³⁷Cs, and ¹³¹I. 6 tables, 17 references.     

Metadata on the radioactive contamination of environmental objects on the territories of Russia and the USSR

A unique data archive, accumulated at the Taifun Scientific and Industrial Association in 1954–2005, on the radioactive contamination of the environment on the territory of the USSR and Russia is presented. The archive contains data on the yearly total β activity of atmospheric fallout on the underlying surface, the total volume β activity in the atmosphere at the ground, the results of measurements of the ⁹⁰Sr and ¹³⁷Cs content in samples combined over one month or quarter, atmospheric aerosols and fallout on individual points, the volume activity of tritium and ⁹⁰Sr in water, rivers, lakes and seas, and the radionuclide contamination density of the territories of populated points as a result of the Chernobyl accident. __________ Translated from Atomnaya énergiya, Vol. 101, No. 2, pp. 149–152, August, 2006.     

Application of Fibrous Carbon Ferrocyanide Sorbents for Removing Cesium and Cobalt from Large Volumes of Sea Water

The results of comparative tests of the FN sorbent based on iron diferrocyanide with a matrix base form of fibrous carbon with known commercial and laboratory analogs are presented. The possibility of using this sorbent for selective removal of ¹³⁷Cs and ⁶⁰Co for large volumes of sea water and producing fast methods of analysis is examined. Information is presented on the content of technogenic radionuclides in sea water in regions of disposal of radioactive wastes in the Sea of Japan and in the region of the accident on a nuclear powered submarine. It is shown that the disposal of radioactive wastes in the Sea of Japan did not change the background radioecological conditions. The radioactivity of sea water at the epicenter of the accident in Bukhta Chazhma is a consequence of the accident and is due to ⁶⁰Co; the presence of ¹³⁷Cs and ⁹⁰Sr is due to global fallout. The concentration of technogenic radionucldes in water and hydrobionts does not exceed admissable norms. Consumption of up to 100 kg/yr of marine products does not increase dose loads above the limit of the yearly individual lifetime risk established for the public and corresponds to a low radiation danger.     

基于三晶体耦合γ射线方向探测器的放射源定位

为了快速定位并寻回丢失的放射源,设计了一种由NaI、CsI、锗酸铋(Bi4Ge3O12,BGO)三种晶体与铅耦合组成的γ射线方向探测器,并采用基于蒙特卡罗方法的通用软件包MCNP(Monte Carlo N Particle Transport Code)研究了铅晶比例、射线能量、剂量率等因素对探测器角度分辨率的影响。结果表明,对于137Cs源,在空气吸收剂量率≥0.331μGy·h~(-1)处,定位角度偏差≤0.99°;对于60Co源,在空气吸收剂量率0.586μGy·h~(-1)处,测量的平均角度偏差为0.46°;对于水平距离7 m、高度4 m的3.7×107Bq 137Cs源,相对定位偏差约为5%。