Comparison of stable cesium and radiocesium on dietary intakes by japanese subjects using 18 food categories

Dietary intakes of radiocesium and non-radioactive cesium in Japanese were estimated using a market basket study and found to be 61 mBq and 9.1 ng per person per day, respectively. Food categories having higher Cs contents (per g-fresh) were found to be as follows: mushrooms 35.9 ng; nuts and seeds 33.6 ng; meats 26.8 ng; fishes and shellfishes 21.6 ng; potatoes 19.2 ng; seaweeds 10.2 ng; and milk and milk products 7.19 ng. For¹³⁷Cs, higher contents (per kg-fresh) were as follows: mushrooms 1.7 Bq; nuts and seeds 0.23 Bq; fishes and shellfishes 0.16 Bq; meats 0.13 Bq; potatoes 0.11 Bq; seaweeds 0.092 Bq; and milk and milk products 0.089 Bq. Distributions of stable cesium in the 18 food categories were similar to those of radiocesium.     

Estimation of dietary iodine and bromine intakes of Ukrainians

Total diet samples for Ukrainians and Japanese were collected by duplicate portion studies in relation to the Chernobyl accident. Stable iodine and bromine in the diet samples were determined by using ICP-MS after chemical separation. Daily intakes of iodine for Ukrainians and Japanese were found to be 110±104 and 1770±1610 μg per person per day, respectively. Daily intakes of Br were as follows: Ukrainians 3.47±2.12 mg; Japanese 11.4±2.4 mg. Daily iodine intake in Ukrainians was lower than the recommended dietary allowance (150 μg) and showed the relationship of high prevalence of goiter in this area.     

A simple preparation of calibration curve standards of134Cs and137Cs by serial dilution of a standard reference material

Two sets of calibration standards for¹³⁴Cs and¹³⁷Cs were prepared by small serial dilution of a natural matrix standard reference material, IAEA-154 whey powder. The first set was intended to screen imported milk powders which were suspected to be contaminated with¹³⁴Cs and¹³⁷Cs. Therefore the concentration range of the calibration standards were about 40–400 Bq/kg. The precision of the preparation of the standard with about 7 Bq/kg of¹³⁴Cs and 39 Bq/kg of¹³⁷Cs at measurement time was 7.4% and 3.2%, respectively. The preparation of a similar standard by spiking the matrix with radioisotope solutions resulted in a poorer precision, about double that of the former technique. The other set of calibration standards was prepared to measure the environmental levels of¹³⁷Cs in commercial Venezuelan milk powders. Their concentration ranged from 3–10 Bq/kg of¹³⁷Cs. The accuracy of these calibration curves was checked by using IAEA-152 and A-14 milk powders. Their measured values were in good agreement with their certified values. Finally, it is shown that these preparation techniques by serial dilution of a standard reference material were simple, rapid, precise, accurate and cost-effective.This work was partly funded by a research contract PC-075 from the Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICIT).     

Radiocesium concentration in milk after the Chernobyl accident in Japan

Radiocesium concentrations in cow's milk from two producing districts in Japan were measured monthly for three years following the Chernobyl accident. The Chernobyl contribution in¹³⁷Cs concentration was evaluated from the¹³⁴Cs concentration and the¹³⁷Cs/¹³⁴Cs ratio. The highest¹³⁷Cs concentration of 0.6 Bq l^–1 was observed in May 1986 and the Chernobyl contribution has decreased during three years to levels corresponding to the contribution from past nuclear weapons fallout. Annual values of child internal dose through milk consumption were estimated at 0.6, 0.3 and 0.1 Sv for the first, the second and the third year following the accident, respectively.     

Concentration of <Superscript>137</Superscript>Cs in seawater surrounding East Malaysia

Studies of ¹³⁷Cs distribution in East Malaysia were carried out as part of a marine coastal environment project. The results of measurements will serve as baseline data and background reference level for Malaysia coastline. Twenty-one locations were identified along the coastline of East Malaysia, and from each location water samples were collected at the surface of the seawater. Ten near-shore locations were also selected and seawater was collected at three different depths. Large volumes of seawater were collected and the co-precipitation technique was employed to concentrate cesium. A known amount of ¹³⁴Cs tracer was added as yield determinant, followed by addition of copper(II) nitrate salt and a solution of potassium hexacyanoferrate(II) trihydrate, to precipitate the total cesium. The precipitate slurry was oven dried at 60 °C for 1–2 days, finely ground and counted using gamma-ray spectrometry. The activity of ¹³⁷Cs was determined by measuring the peak area under the photopeak of the gamma-spectrum at 661 keV, which is equivalent to gamma-intensity corrected for detection efficiency, percentage of gamma-ray abundance of the radionuclide and recovery of ¹³⁴Cs tracer. There were no significant differences of ¹³⁷Cs activities both in surface and bottom water samples at 95% confidence level. The activity of ¹³⁷Cs (for all samples) was found to be in the range of 1.47 to 3.36 Bq/m³ and 1.69 to 3.32 Bq/m³ for Sabah and Sarawak, respectively.     

Radioactivity of plutonium isotopes, <Superscript>137</Superscript>Cs and their ratio in sediment,seawater and biota from the east coast of Peninsular Malaysia

This study with sampling expeditions of marine sediment, seawater and biota were performed at 30 stations within Malaysian Exclusive Economic Zone (EEZ). A total of >400 samples were collected to determine the activity concentration of anthropogenic radionuclides (^239+240Pu, ¹³⁷Cs) and their activity ratio (^239+240Pu/¹³⁷Cs) in sediments, seawater and biota. The purpose of this study was to determine the concentration levels for these radionuclides and to evaluate any occurrence of radioactive contamination. Sediment cores were obtained using multicorer device, while water samples via co-precipitation techniques and biota was purchased from local fishermen. The activity concentrations of ^239+240Pu in sediment, seawater and biota were ranged 0.21–0.45 Bq/kg dry wt., 2.33–7.95 mBq/m³ and <0.008 Bq/kg fresh wt., respectively. Meanwhile, the values of ¹³⁷Cs were ranged <1.00–2.71 Bq/kg dry wt. in sediment, 3.40–5.89 Bq/m³ in seawater and <0.05–0.41 Bq/kg fresh wt. in biota, respectively. Activity ratios of ^239+240Pu to ¹³⁷Cs obtained seem to confirm that these artificial radioactivities were mainly due to global nuclear fallout.     

Development of a method for nuclide leaching from glass fiber in HEPA filter

For the disposal of the high efficiency particulate air (HEPA) glass filter to environment, the glass fiber should be leached to lower its radioactive concentration. To derive the optimum method for removal of Co and Cs from HEPA glass fiber, four methods were applied in this study. Results of electrochemical leaching of glass fiber by 4.0 M HNO₃–0.1 M Ce(IV) solution showed that the removal efficiency of ¹³⁴Cs, ¹³⁷Cs, and ⁶⁰Cs from glass fiber after 5 h was 96.4, 93.6, and 93.8%, respectively. Results by 5 wt% NaOH solution showed that the removal efficiency of ¹³⁴Cs, ¹³⁷Cs, and ⁶⁰Cs after 30 h was 81.7, 82.1, and 10.0%, respectively. Results by repeat 2.0 M HNO₃ solution showed that the removal efficiencies of ¹³⁴Cs, ¹³⁷Cs, and ⁶⁰Cs after 2 h of three repetitions were 96.2, 99.4, and 99.1%, respectively. Finally, results by repeat 4.0 M HNO₃ solution showed that the removal efficiencies of ¹³⁴Cs, ¹³⁷Cs, and ⁶⁰Cs after 4 h of three repetitions were 100, 99.9, and 99.9%, respectively, and their radioactivities were below 0.1 Bq/g. Therefore, the chemical leaching method by 4.0 M HNO₃ solution was considered as an optimum one for removal of cesium and cobalt from HEPA glass fiber for self disposal. Also the removal efficiencies of ⁶⁰Co, ¹³⁴Cs, and ¹³⁷Cs from the waste-solution after its precipitation-filtration treatment for reuse of 4.0 M HNO₃ waste-solution were 88.0, 95.0, and 99.8%.     

Determination of137Cs and134Cs in air samples collected near Belgrade /Yugoslavia/ following the Chernobyl accident

This paper presents the results of measurements of¹³⁷Cs and¹³⁴Cs content in air sampled during May 1986. Maximum concentrations:¹³⁷Cs 2.94±0.01 Bq m^–3 and¹³⁴Cs 1.38±0.01 Bq m^–3 were registered on May 3. Several other long lived radionuclides having -energies in the region 33 keV to 1365 keV were registered in the same samples two years later. The results of measurements of the total -activity in air for the same period are also presented.     

90Sr and137Cs in fallout from Chernobyl in the Bucharest-Măgurele area during 1986–1987

This work shows the variation of⁹⁰Sr and¹³⁷Cs in atmospheric fallout in the Bucharest-Mgurele area during 1986–1987. The amount of⁹⁰Sr in the fallout was estimated to be about 900 Bq.m^–2 in 1986 and about 9.2 Bq.m^–2 in 1987. The amount of¹³⁷Cs was estimated to be 13300 and 615 Bq.m^–2 in 1986 and 1987, respectively.     

Accumulation of137Cs by mushrooms from Rogozno area of Poland over the period 1984–1988

The concentration of naturally occurring⁴⁰K and¹³⁷Cs from fallout were determined in various mushrooms as well as in a few samples of forest soil from the same region over the period of 1984–1988. The¹³⁷Cs content in mushrooms before the reactor accident at Chernobyl was generally below 500 Bq kg⁻¹ dry matter, except Paxillus involutus /2700 Bq kg⁻¹/. A remarkable increase of the¹³⁷Cs activity /up to ten times/ was observed in 1986. For almost all examined species this activity remained basically at the same level for the next two years. No correlation between⁴⁰K and¹³⁷Cs in mushrooms has been found.     

Geographical and vertical distribution of radiocesium levels in coniferous forest soils in Izmir

Preliminary picture of ¹³⁷Cs radioactivity levels in forested areas in and around Izmir is illustrated. Both activity concentrations and activity depositions of ¹³⁷Cs in soil samples were determined. Their values varied from 8.29±0.27 to 445±3.16 Bq.kg⁻¹ (d.w.) and 0.63±0.01 to 11.6±0.08 kBq.m^–2 (d.w.), respectively. It was found that while activity deposition of ¹³⁷Cs is normally distributed, activity concentration of ¹³⁷Cs is log-normally distributed in forest soils and the activity deposition is less variable than the activity concentration. Cesium-137 activities in soils increase with increasing elevation, annual average rainfall and soil organic matter.     

The study on radioactive contamination in foodstuffs imported from Japan after the Fukushima accident

During the Fukushima nuclear accident, a large number of radionuclides were released, causing direct radioactive contamination to the environment and the ecosystem, and eventually indirect contamination to the foodstuffs. The Radiation Monitoring Group, Office of Atoms for Peace (OAP) in cooperation with the Food and Drug Administration (FDA), has been monitoring the foodstuffs imported from Japan, especially the Fukushima and nearby areas. This monitoring program covered the potentially contaminated foodstuffs. The measurements were mainly conducted using Gamma spectroscopy systems in order to analyze the radioactive concentration of ¹³¹I, ¹³⁴Cs, and ¹³⁷Cs fission products. From 442 samples collected between after the nuclear accident to the end of September 2012, 28 of contaminated food products of fission isotopes have been found with the contamination ranges of 0.63–15.25 Bq/kg fresh, 1.45–44.70 Bq/kg fresh, and 0.45–51.10 Bq/kg fresh) for ¹³¹I, ¹³⁴Cs, and ¹³⁷Cs, respectively. However, the contamination levels are still well under the Thailand standard of food contaminated with radionuclide and the relevant international standards. Finally, the research also investigated the relationship between the times the samples were collected and the contamination levels.     

Proficiency test exercise on the determination of natural levels of radionuclides in mushroom reference material

The results from a proficiency test exercise for the determination of natural levels of radionuclides in mushroom reference material carried out by laboratories in six different countries are discussed. These laboratories submitted data on seven radionuclides, namely ¹³⁴Cs, ¹³⁷Cs, ⁴⁰K, ⁹⁰Sr, ²⁴¹Am, ²²⁶Ra, and ²¹⁰Po. However, only the data received for three of these radionuclides could be statistically evaluated to obtain consensus mean values and confidence intervals (at a significance level of 0.05). The contents of ¹³⁴Cs, ¹³⁷Cs and ⁴⁰K were quantified as 4.4, 2,899 and 1,136 Bq/kg, respectively.     

Transfer of 137Cs and stable Cs in soil-grass-milk pathway in Aomori, Japan

The soil-to-grass transfer factors and grass-to-milk transfer coefficients were determined for ¹³⁷Cs and stable Cs in soil, grass and milk samples collected in Aomori Prefecture, Japan. The concentrations of ¹³⁷Cs in the soil and grass samples collected from 25 sampling sites were 13±12 Bq.kg^-1 and 2.0±2.1 Bq.kg^-1 dry wt., respectively. The geometric mean of soil-to-grass transfer factor of ¹³⁷Cs was 0.13 and its 95% confidence interval was 0.017-0.98. The transfer factor of ¹³⁷Cs was higher than that of stable Cs, and they had a positive correlation. The concentration of K in the soil affected both transfer factors. The concentration of ¹³⁷Cs in milk samples collected from 16 sites was 76±43 mBq.kg^-1 fresh wt. and had a good correlation with that of stable Cs. The geometric mean of grass-to-milk transfer coefficient of ¹³⁷Cs was 0.0027, assuming that a cow's total daily intake was 20 kg of dry grass. The transfer coefficient of ¹³⁷Cs was positively correlated with that of stable Cs.     

Pu isotopes and137Cs in the surrounding areas of the former Soviet Union's Semipalatinsk nuclear test site

Field missions were sent to Semipalatinsk City and several settlements near the former Semipalatinsk nuclear test site to investigate the current radioactive contamination levels of the land coming from long-lived radionuclides. The soil was sampled at about 20 sites, including some settlements such as Mostik, Dolon and Chagan, forest and pasture areas, along the roads from Semipalatinsk City to Kurchatov City and to Korosteli settlement in the direction of the Altai District. The radioactivities of¹³⁷Cs,²³⁸Pu and^239,240Pu as well as²⁴⁰Pu/²³⁹Pu atomic ratios in the soil were determined by non-destructive γ-ray spectrometry and radiochemical separation followed by α-ray spectrometry and/or ICP-MS, respectively. The results showed a distinction of¹³⁷Cs and^239,240Pu inventories in soil depending on the site where we visited. While the overall¹³⁷Cs levels were as same as or slightly lower than the domestic global fallout level (3·10³–7·10³ Bq/m²),^239,240Pu levels at some sites were several to a few ten times higher than the domestic level (40–120 Bq/m²). The atomic ratios of²⁴⁰Pu/²³⁹Pu in the soil were in the range of 0.024–0.125, which were significantly lower than the value of 0.18 commonly accepted for global fallout Pu.     

Low level detection of <Superscript>135</Superscript>Cs and <Superscript>137</Superscript>Cs in environmental samples by ICP-MS

The measurement of fission product cesium isotopes ¹³⁵Cs and ¹³⁷Cs at low femtogram (fg) 10⁻¹⁵ levels in ground water by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) is reported. To eliminate the natural barium isobaric interference on the cesium isotopes, in-line chromatographic separation of the cesium from barium was performed followed by high sensitivity ICP-MS analysis. A high efficiency desolvating nebulizer system was employed to maximize ICP-MS sensitivity ~10 cps/fg. The three sigma detection limit for ¹³⁵Cs was 2 fg/mL (0.1 μBq/mL) and for ¹³⁷Cs 0.9 fg/mL (0.0027 Bq/mL) measured from the standard with analysis time of less than 30 min/sample. Cesium detection and 135/137 isotope ratio measurement at very low femtogram levels using this method in a spiked ground water matrix is also demonstrated.     

Measurement of fallout with rain in Hiroshima and several sites in Japan from the Fukushima reactor accident

Fallout with rain from the Fukushima reactor accident was monitored for about two months in Higashi-Hiroshima City, Hiroshima, Japan, from March 20 to May 23, 2011. Gamma-ray (γ-ray) spectra measured using a low background HPGe spectrometer showed clear evidence of fission products—¹³¹I, ¹³⁷Cs, and ¹³⁴Cs. The ¹³¹I was observed on March 27 and April 8, while ¹³⁷Cs and ¹³⁴Cs were observed on March 27, April 18, and April 22. The ¹³¹I, ¹³⁷Cs, and ¹³⁴Cs activity concentrations in rainwater collected in Hiroshima reached 0.44 ± 0.09 on April 8, 0.17 ± 0.01 on April 18, and 0.15 ± 0.01 Bq/L on April 18, 2011, respectively. These activity levels were compared with global results collected from the Northern Hemisphere. Several samples of rainwater that were collected in Chiba (Kashiwa) on March 21, April 11, and May 12; Tokyo (Nerima) on March 21 and April 11; Osaka (Hirano) on April 8; Nara (Kitakatsuragi) on April 9; and Fukushima (Fukushima) on April 19, were also measured by our spectrometer and compared. Among these samples of rainwater collected at different locations in Japan, the one collected at Kashiwa City, Chiba Prefecture, on March 21 showed the highest activity concentrations of 6072 ± 1,   632 ± 4,   766 ± 3,   637 ± 1,   97.6 ± 0.8, and 752 ± 2 Bq/L for ¹³¹I,   ¹³²I,   ¹³²Te,   ¹³⁴Cs,   ¹³⁶Cs, and ¹³⁷Cs, respectively. The health risks due to these high activity levels were considered in terms of several regulations. The ratio of the activites for the isotopes ¹³¹I to ¹³⁷Cs and ¹³⁴Cs to ¹³⁷Cs were compared with the other measurements and discussed.     

Radiological status of Rongelap Island in 1999

A radiological survey and whole body counting of ¹³⁷Cs were carried out in Rongelap Island (main island) of Rongelap Atoll in July 1999. The maximum values of ¹³⁷Cs contamination and of g-ray dose rate were 39 kBq/m² and 0.033 mSv/h, respectively. The maximum a and b gross counting rates on the surface of ground were 1 cpm and 182 cpm in active area of 72 cm², respectively. Activity of ^239,240Pu for soil was 80 Bq/kg in the top 5 cm and aerial deposition was 3.4 kBq/m² in Rongelap Island in 1999. The body burden of ¹³⁷Cs was observed to be 27±11 Bq/kg for 6 workers. Assessment of external and internal annual doses (0.1 and 0.07 mSv/y) indicates that as of 1999 there is no large risk to the inhabitants of Rongelap Island from a radiological point of view. The radiological status of Rongelap Island, which was severely contaminated by the radiological fallouts of nuclear testings carried out in 1954, has improved year by year as shown by the decrease of ¹³⁷Cs. The effective halftime of ¹³⁷Cs, which is estimated to be 6.6 y is much shorter than the physical half-life of ¹³⁷Cs. Radioactive contamination in Kaballe Island, (a part of the northern islands used for farming) which is located 25 km northeast of Rongelap Island, was still high in 1999. One site nearby a beach was highly contaminated with ¹³⁷Cs, where the maximum activity of ¹³⁷Cs was 3.4 MBq/m², a-ray of 2 cpm, b-ray of 1205 cpm and g-ray of 0.73 mSv/h. Activity of ^239,240Pu in soil (n = 1) was 294 Bq/kg (top 5 cm) and 16 kBq/m².     

Application of reference materials in the accurate calibration of the detection efficiency of a low-level gamma-ray spectrometry assembly for environmental samples

A new assembly dedicated for the low-level ψ-ray spectrometric measurements of environmental samples have been installed recently at the International Atomic Energy Agency's Laboratories, Seibersdorf. Calibration of the detection efficiency was performed by a set of 14 IAEA Certified Reference Materials, a standardized solution of¹³⁴Cs, solutions of 2 pure potassium salts, and 2 mixed radionuclide gamma reference standard solutions. These materials, in 1.3 liter Marinelli beakers, were measured by a large HPGe detector. The high precision and accuracy of the calibration procedure is shown by the high significance achieved in the linear fits of the efficiency results, which are traceable to certified and standard reference materials. Small biases between some calibrands were detected. A new corrected result is the 1.37±0.05 Bq/kg activity concentration of¹³⁷Cs in IAEA-A-14 Milk Powder.     

Current levels and distribution of 137Cs and Pu isotopes in soil on the Kazakhstan territory of the Kazakhstan-Chinese border: Semipalatinsk and Lob Nor nuclear test sites detonation

More than 100 soil samples were collected from 46 sites along roads and some settlements connecting Alma-Ata to Semipalatinsk City of the Kazakhstan-Chinese border and analyzed for ¹³⁷Cs and Pu isotopes (²³⁸Pu, ²³⁹Pu and ²⁴⁰Pu). The mean ¹³⁷Cs inventory at each site was within the range of 1,000-3,000 Bq/m² for most of the sites. The ^239,240Pu concentration and its inventories were observed in the wide range of 0.18-2.6 Bq/kg and 28-677 Bq/m², respectively. At the most northern sites in the areas studied, higher^239,240Pu inventories were found corresponding to the increase of ^239,240Pu fraction which was not leached by hot digestion with conc. HNO₃+H₂O₂. The ^239,240Pu/¹³⁷Cs activity ratios for the soil samples from the southern areas lie in the narrow range of 0.016–0.039 (most of data being 0.02–0.03), probably indicative of global fallout origin. On the other hand, a little or several higher ratios (0.05 to 0.22) were found for soil samples from the northern areas. These higher ratios demonstrate strongly that there was additional Pu input of local fallout due to the atomic explosions. From ²⁴⁰Pu/²³⁹Pu atomic ratios measured, contribution of local fallout ^239,240Pu, probably from the SNTS, was found to be higher (60–86%) in the sites around the northern areas than the southern ones. The present data might serve not only as a current baseline information on distribution and contamination levels of the long-lived fallout radionuclides in the Kazakhstan areas of the Kazakhstan-Chinese border, but also as a aid of selection of control area for epidemiological projects.