<Superscript>137</Superscript>Cs content and vertical migration in littoral soil of two lakes in Bryansk Oblast

The dynamics and present state of the radioactive contamination with ¹³⁷Cs of littoral soil of Lake Kozhanovskoe and Lake Svyatoe on the Besed’ River are presented. The parameters of the vertical migration of ¹³⁷Cs in soil-the rate of directional transfer with soil moisture, the diffusion coefficient, and the average velocity of vertical migration-are estimated by comparing the experimental and model distributions of ¹³⁷Cs content over soil depth. It is shown that at the present time the two 5-cm layer of soil can contain 20–90% ¹³⁷Cs depending on the type of soil and landscape. The average values of the diffusion coefficient, the rate of directional transfer, and the vertical migration velocity for 12-, 13-, and 20-year periods after the Chernobyl accident are 0.1–2.8 cm²/yr, 0.1–0.3 cm/yr, and 0.1–0.8 cm/yr, respectively. __________ Translated from Atomnaya énergiya, Vol. 102, No. 5, pp. 306–311, May, 2007.     

Migration of 137Cs Adsorbed on Fine Soil Particles through Soil Layer

The experiments on the migration of ¹³⁷Cs adsorbed on fine soil particles in unsaturated sandy soil layers were carried out. The soil layer reduced the concentration of ¹³⁷Cs in the effluent, but did not retard its migration. The concentration of ¹³⁷Cs remained in the soil layer increased in proportion to the amount of ¹³⁷Cs introduced.

By the measurement of size distribution of fine soil particles, it was revealed that the concentration of ¹³⁷Cs in the effluent decreased exponentially with the length of layer in the case of monodispersed fine soil particles.

From these results, the first-order irreversible reaction formula was obtained in order to formulate the reaction of ¹³⁷Cs adsorbed on fine soil particles with soil layer. A good agreement was obtained between the predicted result by polydispersed irreversible model and experimental one.     

Evaluation of Migration of Cesium-137 Adsorbed on Fine Soil Particles through Natural Aerated Soil Layer

In order to evaluate migration of ¹³⁷Cs adsorbed on fine soil particles in natural aerated soil layers, filtration constants of fine soil particles between soil and pore water were determined by the inverse analysis of the results of a large scale indoor migration test (STEM) using the soil layer samples collected from the natural aerated soil layers of Tokai and Rokkasho-mura without any disturbance. The amounts of ¹³,Cs which migrated through the soil layer samples with the movement of fine soil particles were also determined by the inverse analysis. The filtration constant for a loamy soil layer was larger than that for a sandy soil layer and the dependence of the filtration constant on mean diameter was the same as that obtained in small scale column experiments. On the other hand, the amount of ¹³⁷Cs which migrated through the soil layer sample with the movement of fine soil particles was 0.15~6.5% of introduced ¹³⁷Cs and dependent on size distribution and solidification degree of the soil layer sample. Therefore, it seems that the amount of ¹³⁷Cs which migrates to a long distance with the movement of fine soil particles is small in the case of a fine and solidified soil layer. A trial evaluation of the migration of ¹³⁷Cs adsorbed on fine soil particles using the result of the analysis showed that the concentration decreasing effect of Rokkasho's soil layer including the loamy soil layer was larger than that of Tokai's sandy soil layer.     

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.     

Migration of Radionuclides (60Co, 85Sr and 137Cs) in Alkaline Solution (pH 12) through Sandy Soil Layer

Column experiments have been carried out on the migration of ⁶⁰Co, ⁸⁵Sr and ¹³⁷Cs in an alkaline solution (pH 12) through a sandy soil layer. Radionuclide--concentration distributions in both an effluent and a sandy soil layer were measured after pouring 200ml of aqueous solution containing the radionuclides on the layer, followed by eluting with 3,800 ml of distilled water.

Strontium-85 and ¹³⁷Cs gave a similar distribution pattern in the soil layer, while ⁶⁰Co migrated deeper into the layer. The migration velocity followed the order; ⁶⁰Co>⁸⁵Sr≧¹³⁷Ca. The order was different from that obtained with the radionuclides existed in a neutral solution. This suggested that the migration behavior of the radionuclides is significantly affected by the pH of the solution in which the radionuclides exist.

The sandy soil layer used here is considered as a linear system for the migration of in the solution of pH 12.     

Influence of the migration of137Cs on its vertical profile in the soil of terrain subjected to accumulative denudation

An analysis was made of the vertical distribution profile of¹³⁷Cs in azonal terrain of small river valleys and gorges with a predominance of accumulative denudation processes in the redistribution of the soil mass (the valley of the River Lokna, the Plava area of the Tula region). The established correlation between the inventory of¹³⁷Cs and its depth penetration into the soil confirms the proposition that the former is incremented by soil particles containing absorbed¹³⁷Cs being washed in. A negative correlation was revealed between the exposure dose rates and the inventory of¹³⁷Cs. Global Climate and Ecology Institute. Translated from Atomnaya énergiya, Vol. 86, No. 2, pp. 134–139, February, 1999.     

Migration Behavior of Radionuclides (60Co, 85Sr and 137Cs) in Aerated Sandy Soil Layer

Differences of the migration behavior and desorption process for radionuclides (⁶⁰Co, ⁸⁵Sr and ¹³⁷Cs) in aerated sandy soil layer were studied by sprinkle of distilled water into the contaminated soil with above nuclides in column. Influence of difference desorption process on radionuclide migration was examined by changing the volume of distilled water sprinkled like rain on the contaminated soil.

Quantity of sprinkled water affected the concentration distribution of each radionuclide in soil layer. Each nuclide migrated deeper in the layer according to the increase of water amount, and especially, migration behavior of ⁸⁵Sr was remarkably influenced by water amount. It is observed that as to ⁸⁵Sr maximum contamination part in soil layer moved to deeper layer with increase of water amount, and that, as to ⁶⁰Co and ¹³⁷Cs, it moved almost never. On the other hand, activity concentration of ⁶⁰Co or ¹³⁷Cs in effluent was rather high (10^?6 μCi/ml) compared with that of ⁸⁵Sr, which could not be detected therein.     

Distribution of the 134Cs/137Cs ratio around the Fukushima Daiichi nuclear power plant using an unmanned helicopter radiation monitoring system

Large amounts of radioactive substances were released into the environment by the Fukushima Daiichi nuclear power plant (FDNPP) accident. Several research institutes have mapped the distribution of nuclides with long half-lives, such as ¹³⁴Cs and ¹³⁷Cs. Although the ratio of ¹³⁴Cs and ¹³⁷Cs has been believed to be equal without depending on the location of the contaminated area, several researchers report that it is different depending on places quite a little. We measured the energy spectrum of gamma rays in high resolution within an approximately 3-km radius of the FDNPP by using an unmanned helicopter equipped with a LaBr₃(Ce) scintillation detector. Then, we analyzed the ¹³⁴Cs/¹³⁷Cs ratio in the area from these measured data in detail. The results show that the ¹³⁴Cs/¹³⁷Cs ratio is different between the plume trace extending north and the other plume traces. We have obtained valuable data for identification of which radioactive substances were released by individual reactor units.     

Effects of Neutron-Irradiation on Tensile Properties of 3.5%Ni Steel

In an aerated soil layer under natural condition, water that infiltrates into it flows discontinuously because of repeated cycles of rainfall and drying. Therefore, column tests, in which 2,000 mi of deionized water was fed into sandy soil layer dried for 3~90 days after it is contaminated by ⁶⁰Co, ⁸⁵Sr and ¹³⁷Cs aqueous solution, were carried out to examine influence of the drying period on migration behavior of those nuclides.

All the radionuclides showed both a steeply decreasing part corresponding to their cationic form and a gradually decreasing part corresponding to their particulate form in the concentration distribution curve along the soil column depth. In the vicinity of the top surface of soil layer, no influence of drying on ⁶⁰Co and ¹³⁷Cs concentrations was observed, but ^S5Sr moved a little into a deeper part from the top surface with longer drying period. Such moving tendency of ^8ESr was found to be connected with the Ca²⁺ concentration in the interstitial water. In the deeper soil layer, no influence of drying on ⁸⁵Sr concentration was observed, but the ⁶⁰Co and ¹³⁷Cs concentrations were increased with the drying period. This is considered to be caused from that each product of the movable ⁶⁰Co(OH)₂ and the ¹³¹Cs adsorbed on the fine particle increased with the rise of pH and the fine particle concentration, respectively, during the drying period. Thus, this study has suggested possible causes affecting on the radionuclide migration under discontinuous flow condition.     

Transformation of the forms of90Sr and137Cs in soil and bottom deposits

A method is proposed for estimating the distribution factors of¹³⁷Cs and⁹⁰Sr in soil and deposits. The method is based on predicting the forms in which these radionuclides occur and estimating the exchange distribution factor. It is shown that fixation of the radionuclides is a reversible process. A model is proposed for the transformation of the chemical forms of¹³⁷Cs and⁹⁰Sr. including leaching from fuel particles, fixation, and remobilization. It is shown that a first-order kinetic model satisfactorily describes the transformation of the forms of⁹⁰Sr as well as¹³⁷Cs for time periods of about one month. For longer periods of time, a diffusion fixation model is best for¹³⁷Cs. Recommendations are made for the key parameters for various types of soils. 1 figure, 2 tables, 11 references. Scientific and Industrial Association “Taifun.” Translated from Atomnaya énergiya, Vol. 88, No. 1, pp. 55–60, January, 2000.     

Migration Behavior of Radionuclides (60Co, 85Sr and 137Cs) in Aquifer

The migration behavior of radionuclides (⁶⁰Co, ⁸⁵Sr and ¹³⁷Cs) in aquifer has been studied under a steady flow of water by using aquifer model apparatus.

In the portion of high concentration (≧ 10^?3 μCi/g), water flow has slight influence on migration of these radionuclides. On the other hand, in the portion of low concentration (10^?4 μCi/g), ⁶⁰Co and ¹³⁷Cs are particularly influenced by the flow, but the migration of ⁸⁵Sr is relatively small. Such phenomena support that the migration of ⁸⁵Sr is subject to the ion exchange reaction, and the migration of ⁶⁰Co and ¹³⁷Cs may be due to both ion exchange reaction and particulate moving mechanism.

The concentration distribution observed is compared with that of the calculation by predicting equation based on ion exchange reaction. In the distribution of high concentration portion, the observed on each radionuclide is almost same as to the calculated, but in the distribution of low concentration portion, both observed on ⁶⁰Co and ¹³⁷Cs are very different from the calculated. Since migration behavior of ⁶⁰Co and ¹³⁷Cs cannot be described by predicting equation only based on ion exchange reaction, it is, therefore, necessary to predict those migration by the equation consisting of ion exchange reaction and particulate moving mechanism.     

90Sr and137Cs exchange distribution coefficient in soil-water systems

Two methods are proposed for estimating the exchange distribution coefficient of¹³⁷Cs and⁹⁰Sr in natural soil-water systems: effective selectivity and selective sorption of¹³⁷Cs. Principles for classifying soils and deposits as a function of the effective selectivity coefficient are proposed. Using the first method, the⁹⁰Sr distribution coefficient can be estimated if the sorption properties of the medium are known to within 50%; for¹³⁷Cs. the distribution coefficient can be estimated only in order of magnitude. The uncertainty in the prediction of the¹³⁷Cs distribution can be decreased by determining the characteristics of the selective sorption of¹³⁷Cs: the capacity of selective sorption centers and/or the radiocesium interception potential. 3 tables, 8 references. Scientific and Industrial Association Taifun. Translated from Atomnaya énergiya, Vol. 88, No. 2, pp. 152–158, February, 2000.     

Three Year Experimental Study of Leaching Phenomena from Low Level Radioactive Cement-Based Waste Forms

Abstract

This study was carried out in order to demonstrate the safety of homogeneous cementbased waste forms (hereinafter called cement forms) for BWR's low level radioactive wastes as engineered barriers. Eighteen full scale simulated cement forms were manufactured with the addition of ¹³⁷Cs, ⁶⁶Co and ⁹⁰Sr.

Leaching tests on these forms were carried out for approximately three years. In order to study the relationship of leachability to environments at disposal sites, this Three Year Leaching Test was conducted for three kinds of environmental conditions, sea water, land water and soil. After the tests, all of these forms were cut to measure the distribution of the radionuclide's density within them. In case of the soil tests, the distribution of radionuclide in the soil was also measured.

The radionuclide leachability results reveal that ⁶⁰Co was almost completely retained in the cement forms and that ¹³⁷Cs leached from cement forms was mostly adsorbed by the soil. On the other hand, ⁹⁰Sr was not trapped in the forms and leaked through the soil around them in retard. This study also showed that simulated cement forms buried in the soil were more physically and chemically stable, and had longer term stable radionuclide containment capability than those which were submerged in sea or land water.     

Elemental Composition and Radioactivity of Certain Sedimentary Rocks, Soils, and Plants in Uzbekistan

Instrument neutron-activation, x-ray fluorescence, atomic-absorption analysis, and spectrometry are used to determine the elemental composition and radioactivity of more than 700 samples of sedimentary rocks, soil, and plants in Uzbekistan. The fluctuations and average content of the elements in the types of samples investigated and the concentration and character of the vertical migration of technogenic ¹³⁷Cs and cosmogenic ⁷Bi in soil from various sites are determined.     

Radiometric Method for Measuring 137Cs Activity in Bottom Deposits Using a Submersible Water Detector

Field radiometry has been developing intensively in the last few years. Field radiometers make it possible to perform efficient examination of the surface soil on radionuclide-contaminated territories. In this paper it is suggested that this class of devices be expanded to study radionuclide contamination of bottom deposits of rivers and reservoirs. The possibility of using a radiometer with a submersible water detector for determining ¹³⁷Cs store in bottom deposits is examined. A method for determining the ¹³⁷Cs contamination density, using three energy regions of the instrumental spectrum of the submersible detector, is described in detail. The radiometer and possibilities of using it are briefly described for measurement of the ¹³⁷Cs distribution profile in the bottom deposits of the Iput' River. This instrument also gives more representative sampling of bottom deposits.     

~(60)Co.~(85)Sr和~(137)Cs在黄土包气带中迁移的模拟实验

从野外试验场用专门研制的原状土柱采样装置采得未扰动土柱 ,以60 Co、85Sr和 13 7Cs三种核素为示踪剂 ,在人工喷淋条件下研究核素在土柱中的迁移行为。采用直接测量和解体测量两种方法测定了核素在土柱中的垂向浓度分布。实验结果表明 ,在日均喷淋强度为 7.96 mm/d的喷淋条件下 ,近一年时间内 85Sr浓度峰在实验土柱中的下移距离 ,按直接测量和解体测量分别约为 6 .0和 8.0 cm;60 Co和 13 7Cs浓度峰基本仍在原位。此结果与野外现场核素迁移示踪试验结果基本一致     

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.     

Stepped decontamination of <Superscript>137</Superscript>Cs-contaminated sandy soil

The possibilities of reagent-based processing of sandy soil contaminated with ¹³⁷Cs are examined. To attain a high decontamination factor, the process is conducted in several steps. First, water-gravity separation is used to separate finely dispersed matter (first step). The main goal of the next (second) reagent-based processing step is to destroy the strongly bound fragments and hydroxide films with which a part of the finely dispersed fraction is bound. At the next step, part of the ¹³⁷Cs is extracted into the reagent solution from the purely sandy fraction; repeated water-gravity separation (third step) makes it possible to completely separate the finely dispersed substance. The subsequent steps of reagent-based processing give ¹³⁷Cs concentration in the sandy fraction of the initial soils that meets the sanitary norms.     

Development of regional downscaling capability in STEAMER ocean prediction system based on multi-nested ROMS model

Oceanic regional downscaling capability was implemented into Short-Term Emergency Assessment system of Marine Environmental Radioactivity (STEAMER) developed by Japan Atomic Energy Agency to enable us to predict more realistically the oceanic dispersion of radionuclides at higher spatiotemporal resolutions for broader applications. The system consisted of a double-nested oceanic downscaling circulation model with tidal forcing and an oceanic radionuclide dispersion model. This system was used to comparatively examine downscaling and tidal effects on the dispersion of radionuclides hypothetically released from the Fukushima Daiichi Nuclear Power Plant in the colder season. The simulated dissolved ¹³⁷Cs distribution was different from that obtained using coarser-resolution models because downscaling enhanced both horizontal and vertical mixing. The suppression of horizontal mixing and the promotion of vertical mixing by tidal forcing synergistically reduced offshore ¹³⁷Cs transport. In addition, the submesoscale effects strengthened the three-dimensional ¹³⁷Cs fluctuations by <10 times, while the tidal effects promoted slightly increased the intensity of three-dimensional ¹³⁷Cs fluctuations by approximately 3%. This indicated that the submesoscale effects substantially surpassed tidal forcing in oceanic mixing in the coastal margin off Fukushima in the colder season.     

Analysis of cesium isotope compositions in environmental samples by thermal ionization mass spectrometry – 1. A preliminary study for source analysis of radioactive contamination in Fukushima prefecture

Cesium was recovered from plant samples obtained from Fukushima prefecture. The isotopic ratios of ¹³⁴Cs/¹³⁷Cs and ¹³⁵Cs/¹³⁷Cs were analyzed by thermal ionization mass spectrometry with a single filament method using a TaO activator. Samples containing 5 Bq of ¹³⁷Cs were analyzed with typical analytical errors of approximately 0.5% for ¹³⁴Cs/¹³⁷Cs and approximately 0.1% for ¹³⁵Cs/¹³⁷Cs. Measurements of both ratios showed profiles that were characteristic of the measurements of among other environmental samples reported in the literature. The results showed the isotopic ratios of ¹³⁴Cs/¹³⁷Cs and ¹³⁵Cs/¹³⁷Cs were applicable for the source analysis of radioactive Cs in Fukushima prefecture.