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.     

Fukushima-derived radionuclides in ground-level air of Central Europe: a comparison with simulated forward and backward trajectories

Results of forward and backward modeling of air mass transport from Fukushima Daiichi nuclear power plant to Slovakia were compared with aerosol radioactivity measurements. Several radionuclide maxima (¹³¹I, ¹³⁴Cs and ¹³⁷Cs) were observed in the Bratislava ground-level air in March–April 2011. The ¹³¹I/¹³⁷Cs activity ratio records showed the presence of two different fresh air masses in the Bratislava air, supported by simulations of forward and backward trajectories between Fukushima and Bratislava.     

Radionuclides from Fukushima accident in Thessaloniki, Greece (40°N) and Milano, Italy (45°)

¹³¹I, ¹³⁷Cs and ¹³⁴Cs were observed in environmental samples in Milano (40°N), Italy and Thessaloniki (45°N), Greece, soon after the nuclear accident in Fukushima, Japan. The radionuclide concentrations were determined and studied as a function of time. In Thessaloniki the ¹³¹I in air was observed for the first time on March 24, 2011. In Milano, the first evidence of Fukushima fallout has been confirmed with ¹³¹I and ¹³⁷Cs measured in wet precipitation collected 2 days later. The maximum ¹³¹I activity concentration in air of 467 ± 25 μBq m^?3, observed in Milano on April 3–4, 2011, was almost similar to the highest value of 497 ± 53 μBq m^?3 observed in Thessaloniki. The ¹³⁴Cs/¹³⁷Cs activity ratio values in air were around 1 in both regions. Soil, grass and milk samples were contaminated with ¹³¹I and ¹³⁷Cs at a low level. Finally, a dose assessment for these two areas showed clearly that the detected activities in all environmental samples were far below levels of concern.     

Distribution of 131I, 134Cs, 137Cs and 239,240Pu concentrations in Korean rainwater after the Fukushima nuclear power plant accident

Radionuclides such as ¹³¹I, ¹³⁴Cs, ¹³⁷Cs, and ^239,240Pu in Korean rainwater have been analyzed by Korea Research Institute of Standards and Science (KRISS) since the Fukushima nuclear power plant accident in March 2011 to investigate the activity level, distribution pattern, and temporal variation and to assess the radiation dose the public is exposed to. The concentration of ¹³¹I in the Korean rainwater samples varied between 0.033 (minimum detectable activity; MDA) and 1.30 Bq kg^?1 and the concentrations tended to decrease exponentially with time. The concentrations of ¹³⁴Cs and ¹³⁷Cs in rainwater ranged from 0.01 to 334 ± 74 and 0.29 ± 0.01 to 276 ± 1 mBq kg^?1, respectively. The mean activity ratio of ¹³⁷Cs/¹³⁴Cs in the rainwater samples collected from April 18 to May 12 was estimated to be 0.44 ± 0.21, and this value is lower than that (ca. 1) observed in Fukushima, Japan, when there was an escape from the nuclear reactors. When an attempt was made to analyze Pu isotopes in rainwater samples, no Pu isotopes were detected above the MDA in any of the rainwater samples. Although the locations investigated were different from Asia to Europe, the concentrations of ¹³¹I, ¹³⁴Cs and ¹³⁷Cs in the rainwater are comparable, which suggests a global contamination of ¹³¹I, ¹³⁴Cs, and ¹³⁷Cs occurred because of the Fukushima nuclear power plant accident.     

Determination of potassium traces in foodstuffs by natural <Superscript>40</Superscript>K radiation

Summary After the Chernobyl accident in April 1986, Mexico imported from one European country a shipment of 28,000 tons of milk powder contaminated with the fission product ¹³⁷Cs. Since then, the local authorities of Public Health have established as a compulsory condition to obtain through gamma-spectroscopy a certificate of no radioactive contamination either to imported or exported foodstuffs. But at the same time, the absence of long-lived, gamma-emitters fission products is certified, it is also possible to find the concentration of the important trace element K in foodstuffs, by the peak of 1461 keV from ⁴⁰K, invariably present in the gamma-spectra. Taking advantage of the fact that it does not require any previous manipulation of the sample, this paper describes the general procedure in milk powder or any other foodstuff.     

Chernobyl radioactivity on the Black Sea coast of Turkey

After the Chernobyl reactor accident, Eastern Black Sea coast was one of the heavily contaminated regions of Turkey. Clouds loaded with radioactive isotopes arrived the region on May 1986 and emptied their contents with the heavy rains that are frequently seen in the region. In order to asses the current level of contamination, several different samples, moss, lichen, litter, surface soil and soil cores were collected on August 1994. Samples were brought to the laboratory and their moisture, pH and organic matter contents were determined. Gamma-ray spectra of the samples were collected with a HpGe detector. ¹³⁷Cs was the major isotope observed. Activity of most litter samples were below 1000 Bq/kg, while most of the moss samples had activities below 5000 Bq/kg, there were a few with higher ¹³⁷Cs activities. Surface soil samples generally had activities less than 2000 Bq/kg and depth profiles of cesium activities in the soil cores showed regional variations.     

The ambient gamma dose-rate and the inventory of fission products estimations with the soil samples collected at Canadian embassy in Tokyo during Fukushima nuclear accident

In this study, soil samples were collected at Canadian embassy in Tokyo (about 300 km from Fukushima) on 23 March and 23 May of 2011 for purposes of estimating concentrations of radionuclides in fallout, the total fallout inventory, the depth distribution of radionuclide of interest and the elevated ambient gamma dose-rate at this limited location. Some fission products and actinides were analyzed using gamma-ray spectrometry, alpha spectrometry and liquid scintillation counting. The elevated activity concentration levels of ¹³¹I, ¹³²I, ¹³⁴Cs, ¹³⁷Cs, ¹³⁶Cs, ¹³²Te, ¹²⁹mTe, ¹²⁹Te, ¹⁴⁰Ba and ¹⁴⁰La were measured by the gamma-ray spectrometer in the first sample collected on 23 March. Two months after the accident, the ¹³⁴Cs and ¹³⁷Cs became only detectable nuclides. A mass relaxation depth of 3.0 g/cm² was determined by the activities on the depth distribution of ¹³⁷Cs in a soil core. The total fallout inventory was thus calculated as 225 kBq/m² on March sampling date and 25 kBq/m² on May sampling date. The ambient gamma dose-rates in the sampling area estimated by the fallout fission products inventory and ¹³⁷Cs depth distribution ranged from 184 to 38 nGy/h. There was no detectable americium or plutonium in the soil samples by alpha spectrometry. Although ⁹⁰Sr or ⁸⁹Sr were detected supposedly as a result of this accident, it was less than the detection limit, which was about 0.4 Bq/kg in the soil samples.     

Dietary intakes of radioactive cesium for Ukrainians

Daily intakes of ¹³⁴Cs and ¹³⁷Cs in Ukrainians were estimated in relation to the health effects on habitants after the Chernobyl accident. Two hundred and sixty-eight diet samples were collected from 25 oblasts (regions) using a duplicate portion method. For Ukrainians, the range and median daily intakes of ¹³⁷Cs were 0.53–571 and 8.8 Bq per person, respectively. Intakes of ¹³⁴Cs were also detected in highly ¹³⁷Cs contaminated areas. Daily intakes of ¹³⁴Cs were in the range of not detected to 3.6 Bq per person. Using the highest radiocesium intakes, annual effective doses for ¹³⁴Cs and ¹³⁷Cs were estimated to be 2.5·10⁻² and 2.7 mSv, respectively.     

Radiation measurements and radioecological aspects of fallout from the Fukushima nuclear accident

Fallout from the Fukushima Nuclear Accident has been monitored for about 1 month in Thessaloniki, Northern Greece. Three different radionuclides, one short-lived, one relatively long-lived and one long-lived fission product were identified in air, precipitation, soil, grass and milk samples. The ¹³¹I, ¹³⁷Cs and ¹³⁴Cs activity concentrations in air reached 497, 145 and 126 μBq m⁻³, respectively on 4 April, 2011. The external exposure dose rate to humans of the order of 14.4 pSv per day due to ¹³⁷Cs deposited on the ground was very small compared to the normal background level. The accumulated dose equivalent to the adult thyroid from inhaled ¹³¹I varied from 0.4 to 3.5 nSv per day was insignificant and there was not any problem for the Greek population and no preventive measures were needed to be provided against the nuclear accident according to the Greek Atomic Energy Commission, the official agent of the Greek Government. Some special radioecological aspects in the air-grass-cow-milk-man pathway for ¹³¹I were particularly studied.     

Local distribution of radioactivity in tree leaves contaminated by fallout of the radionuclides emitted from the Fukushima Daiichi Nuclear Power Plant

We analyzed fresh and dead leaves collected in forests in Fukushima after the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, using autoradiography. Both fresh and dead leaves of Cryptomeria japonica were contaminated by radionuclides (¹³⁴Cs and ¹³⁷Cs). Contamination of the fresh leaves was possibly attributed to interception of radionuclides by tree canopies, whereas the dead leaves indicated the direct deposition of radionuclides by fallout and/or washout of radionuclides intercepted by tree canopies. Translocation of radiocesium from a contaminated branch to new leaves growing after the FDNPP accident was not clearly observed, although transfer of radiocesium from leaf parts to male flowers occurred. Fallen leaves of Quercus serrata, which started growing after the FDNPP accident, did not show radioactivity, indicating that significant amounts of translocation from other parts to new leaves did not occur. Fallen leaves of Q. serrata collected from a litter showed hot spots originating from direct fallout. Needles of Pinus densiflora were also contaminated by fallout. Leaching with pure water removed soluble fractions of radiocesium and hot particles from the surface of the contaminated leaves, but significant amounts of radioactivity remained. This means that foliar absorption occurred in both fresh and dead leaves. Further leaching experiments using surfactant and acetone could not remove the remaining radiocesium from the leaves. The leaching experiments indicate that radiocesium in the contaminated leaves is strongly fixed in leaf tissues and is not readily released unless leaf tissues are decomposed.     

Semi-quantitative analysis of leaf surface contamination by radioactivity from the Fukushima Daiichi nuclear power plant accident using HPGe and imaging plate

After the nuclear power plant accident at Fukushima Daiichi on 11 March 2011, green-leaves from trees, dead-leaves and grass on ground were collected from March to June 2011 in Japan. Radioactive concentrations were measured by a high purity germanium detector. Five radionuclides including ^129mTe, ¹³²Te, ¹³¹I, ¹³⁴Cs and ¹³⁷Cs were detected. The fission product concentration of the dead-leaves was higher than those of the green-leaves in many cases. The highest concentration observed was found on the dead-leaves collected at Iwaki, 60 km far from Fukushima Daiichi. A total activity of 2,000 Bq g^?1 was measured for all 5 radionuclides. Clear images of radioactivity of the highly contaminated leaves were obtained with an imaging plate (IP) after <24 h exposure time without using a shielded box. The photostimulated luminescence values (PSL) of leaves arranged on half size of IP were roughly in proportion to their activities except for the low activity samples. Semi-quantitative analysis was possible by using PSL values with a large region of interest of half size of IP, because the radioactivity released in the case of the nuclear power plant accident was uniform in the early days.     

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).     

Combination of atomic lines and molecular bands for uranium optical isotopic analysis in laser induced plasma spectrometry

Radionuclide concentrations in wharf roaches inhabiting coastal areas of Honshu, Japan, were investigated in October 2011 and June 2012. Relative high concentrations of ^110mAg (2.1–127 Bq kg-wet^?1), ¹³⁴Cs (2.6–61 Bq kg-wet^?1), and ¹³⁷Cs (3.5–92 Bq kg-wet^?1) were detected in specimens from the eastern Honshu areas. Significantly lower ¹³⁷Cs concentrations (0.7–1.6 Bq kg-wet^?1) were detected in specimens from western and northern Honshu. The decay-corrected ¹³⁷Cs concentration was significantly inversely correlated with the distance from the Fukushima Dai-ichi Nuclear Power Plant. Thus, wharf roach may serve as a good bioindicator for monitoring radioactive contamination of its habitats.     

Comparison of radioactive and stable cesium uptake in aquatic macrophytes affected by the Fukushima Dai-ichi Nuclear Power Plant accident

Concentrations of ^134+137Cs and ¹³³Cs in aquatic macrophytes, water, and sediment were measured in samples collected from Fukushima Prefecture, Japan. The concentrations of ¹³⁷Cs in submerged and floating-leaved plants were higher than the values for emergent plants according to their main Cs uptake mode. The geometric mean water-to-plant concentration ratio for ¹³⁷Cs and ¹³³Cs was comparable observed in submerged and floating-leaved plants, while the geometric mean sediment-to-plant concentration ratio for ¹³⁷Cs in emergent plants was higher than that of ¹³³Cs, which suggest that the mobility of Fukushima accident-derived ¹³⁷Cs is not in steady state 4–5 years after the accident.

     

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.     

Determination of Cs and Cs in environmental samples: A review

Radionuclides of caesium are environmentally important since they are formed as significant high yield fission products (¹³⁵Cs and ¹³⁷Cs) and activation products (¹³⁴Cs and ¹³⁶Cs) during nuclear fission. They originate from a range of nuclear activities such as weapons testing, nuclear reprocessing and nuclear fuel cycle discharges and nuclear accidents. Whilst ¹³⁷Cs, ¹³⁴Cs and ¹³⁶Cs are routinely measurable at high sensitivity by gamma spectrometry, routine detection of long-lived ¹³⁵Cs by radiometric methods is challenging. This measurement is, however, important given its significance in long-term nuclear waste storage and disposal. Furthermore, the ¹³⁵Cs/¹³⁷Cs ratio varies with reactor, weapon and fuel type, and accurate measurement of this ratio can therefore be used as a forensic tool in identifying the source(s) of nuclear contamination. The shorter-lived activation products ¹³⁴Cs and ¹³⁶Cs have a limited application but provide useful early information on fuel irradiation history and have importance in health physics.     

Airborne gamma-ray emitters from Fukushima detected in New York State

An air-sampling network that operates continuously as part of New York State’s environmental surveillance program collected radionuclides emitted as a result of the Fukushima nuclear accident. Samples were collected, typically for 7 days each, by drawing ~600 m³ of air through a particulate-collecting filter followed in series by a canister containing activated charcoal. Additional air sampling was implemented at ~3-day intervals at two locations. Gamma-ray spectroscopy was used to confirm the detection of ¹³¹I, ¹³⁷Cs, ¹³⁴Cs, and ⁷Be in the particulate phase at all sites, with maximum concentrations near 1,260, 160, 160, and 5,200 μBq/m³, respectively. Gas-phase ¹³¹I, collected on activated charcoal, exhibited a maximum concentration of 3,400 μBq/m³ at the sites. Assessment of radionuclide levels in the air samples suggests that there were minimal health impacts from the airborne radionuclides as the activities contributed an insignificant amount to the annual human dose.     

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.     

Environmental radioactivity measurements in north–western Greece following the Fukushima nuclear accident

The impact of the Fukushima nuclear accident in north–western Greece was assessed through an environmental monitoring programme activated by the Nuclear Physics Laboratory of the University of Ioannina. Measurements of ¹³¹I were carried out in atmospheric particulate, ovine milk and grass samples. In daily aerosol samplings, radioiodine was first detected on March 25–26, 2011 and reached maximum levels, up to 294 μBq m^?3, between April 2 and April 4, 2011. In ovine milk samples, ¹³¹I concentrations ranged from 2.0 to 2.7 Bq L^?1 between April 2 and April 6, 2011, while an average activity of 2.7 Bq kg^?1 was measured in grass samples on April 4, 2011. The ^134,137Cs isotopes were below detection limits in all samples and could only be determined in the air, by analysis of multiple daily filters. A maximum average activity concentration of ¹³⁷Cs amounting to 24 μBq m^?3 was measured during the period from April 5 to April 9, 2011, with the ¹³⁴Cs/¹³⁷Cs activity ratio being close to unity. Activity concentrations were consistent with measurements conducted in other parts of the country and were well below those reported in May 1986 after the Chernobyl accident. The committed effective dose to the whole body and to the thyroid gland from inhalation of ¹³¹I was estimated for the adult and infant population and was found to be of no concern for the public health.     

A simple correction method for isobaric interferences induced by lead during uranium isotope analysis using secondary ion mass spectrometry

The present study is to determine the activity concentration of radioactive nuclide in plant fertilizers used in agriculture in Iraqi Kurdistan region using high- purity germanium detector (HPGe) gamma spectrometer. The results showed that the range of activity concentrations for ²²⁶Ra, ²³²Th, ⁴⁰K and ¹³⁷Cs in chemicals and organic fertilizers are (0.1–134), (0.1–74), (1–12,000) and (0–1) Bq/kg respectively, based on the measured activities that were used to assess the radiological hazards. Radium equivalent activity in some samples exceeds the value (370 Bq/kg) which recommended by the OECD.