Radiocaesium accumulation capacity of epiphytic lichens and adjacent barks collected at the perimeter boundary site of the Fukushima Dai-ichi Nuclear Power Station

We investigated the radiocaesium content of nine epiphytic foliose lichens species and the adjacent barks of Zelkova serrata (Ulmaceae, "Japanese elm") and Cerasus sp. (Rosaceae, "Cherry tree") at the boundary of the Fukushima Dai-ichi Nuclear Power Station six years after the accident in 2011. Caesium-137 activities per unit area (the 137Cs-inventory) were determined to compare radiocaesium retentions of lichens (65 specimens) and barks (44 specimens) under the same growth conditions. The 137Cs-inventory of lichens collected from Zelkova serrata and Cerasus sp. were respectively 7.9- and 3.8-times greater than the adjacent barks. Furthermore, we examined the radiocaesium distribution within these samples using autoradiography and on the surfaces with an electron probe micro analyzer (EPMA). Autoradiographic results showed strong local spotting and heterogeneous distributions of radioactivity in both the lichen and bark samples, although the intensities were lower in the barks. The electron microscopy analysis demonstrated that particulates with similar sizes and compositions were distributed on the surfaces of the samples. We therefore concluded that the lichens and barks could capture fine particles, including radiocaesium particles. In addition, radioactivity was distributed more towards the inwards of the lichen samples than the peripheries. This suggests that lichen can retain 137Cs that is chemically immobilised in particulates intracellularly, unlike bark.

Radiocesium concentrations in mushrooms collected in Kawauchi Village five to eight years after the Fukushima Daiichi Nuclear Power Plant accident

Following the Fukushima Daiichi Nuclear Power Plant accident in March 2011, radionuclides such as iodine-131, cesium-134 and cesium-137 were released into environment. In this study, we collected wild mushrooms from the Kawauchi Village of Fukushima Prefecture, located less than 30 km southwest of the Fukushima nuclear power plant, to evaluate their radiocesium (134Cs+137Cs) concentrations and the risk of internal radiation exposure in local residents. 342 mushroom samples were collected from 2016 to 2019. All samples were analysed for radiocesium content by a high-purity germanium detector. Among 342 mushroom samples, 260 mushroom samples (76%) were detected the radiocesium exceeding the regulatory limit of radiocesium (100 Bq/kg for general foods in Japan). The median of committed effective dose from ingestion of wild mushrooms was in the range of 0.015-0.053 mSv in 2016, 0.0025-0.0087 mSv in 2017, 0.029-0.110 mSv in 2018 and 0.011-0.036 mSv in 2019 based on the assumption that Japanese citizens consumed wild mushrooms for 1 year. Thus, our study showed that although radiocesium is still detected in mushrooms collected in Kawauchi village even after 5 to 9 years later, the committed effective dose due to consuming mushrooms was lower than 1 mSv per year. Long-term comprehensive follow-up should monitor radiocesium concentrations in wild mushrooms to support the recovery of the community after the nuclear disaster.

Remediation of 137Cs-contaminated concrete rubble by supercritical CO2 extraction

The removal of cesium contamination is a critical issue for the recycling of concrete rubble in most decommissioning operations. The high solvent strength and diffusivity of supercritical CO₂ make it an attractive choice as vector for extractant system in this context. Experimental extraction runs have been carried out in a radioactive environment on rubble contaminated with ¹³⁷Cs. The best extraction system was found to be CalixOctyl (25,27-Bis(1-octyloxy)calix[4]arene-crown-6, 1,3-alternate) with pentadecafluorooctanoic acid as a modifier. The effects of various operating parameters were investigated, namely the coarseness of rubble, the temperature of supercritical CO₂, the residual water and initial cesium concentrations, and the amounts of extractant and modifier used. The yields from direct extraction were low (<30%), because of the virtually irreversible sorption of Cs in concrete. The best extraction yield of ∼55% was achieved by leaching concrete rubble with nitric acid prior to supercritical CO₂ extraction.

Sodium-copper hexacyanoferrate-functionalized magnetic nanoclusters for the highly efficient magnetic removal of radioactive caesium from seawater

Sodium-copper hexacyanoferrate (NaCuHCF)-functionalized magnetic nanoadsorbents were fabricated for the highly efficient magnetic removal of radioactive caesium from seawater. The magnetic nanoclusters (MNCs), composed of many individual Fe₃O₄ nanoparticles, were covalently coated with polyethyleneimine (PEI) to functionalize the MNC surfaces with NaCuHCF. After simple immobilization of Cu and Na ferrocyanide on the NC surface, the resulting NaCuHCF-functionalized MNCs showed good magnetic properties and a significant adsorption capacity for Cs⁺ with a high content of NaCuHCF (36.04%). The adsorption kinetics and isotherms were well fit to a pseudo-second-order model and Langmuir isotherm, respectively. The sorption of 97.35% Cs by the NaCuHCF-PEI-MNCs completed in less than 5 min, and the maximum adsorption capacity of the adsorbent was 166.67 mg/g. The NaCuHCF-PEI-MNCs selectively adsorbed Cs even in the presence of various competing ions, such as Na, K, Mg, and Ca, and the Cs removal mechanism was revealed as ion exchange between Cs in solution and Na in the NaCuHCF-PEI-MNCs. In radioactive tests, our adsorbent displayed excellent removal performance in real seawater with a high removal efficiency exceeding 99.73%, a decontamination factor exceeding 372, and a high stability in water over a wide pH range from 4 to 10 with negligible leaching of Fe.

Cesium-induced inhibition of bacterial growth of Pseudomonas aeruginosa PAO1 and their possible potential applications for bioremediation of wastewater

Radioactive isotopes and fission products have attracted considerable attention because of their long lasting serious damage to the health of humans and other organisms. This study examined the toxicity and accumulation behavior of cesium towards P. aeruginosa PAO1 and its capacity to remove cesium from waste water. Interestingly, the programmed bacterial growth inhibition occurred according to the cesium environment. The influence of cesium was analyzed using several optical methods for quantitative evaluation. Cesium plays vital role in the growth of microorganisms and functions as an anti-microbial agent. The toxicity of Cs to P. aeruginosa PAO1 increases as the concentration of cesium is increased in concentration-dependent manner. P. aeruginosa PAO1 shows excellent Cs removal efficiency of 76.1% from the contaminated water. The toxicity of cesium on the cell wall and in the cytoplasm were studied by transmission electron microscopy and electron dispersive X-ray analysis. Finally, the removal of cesium from wastewater using P. aeruginosa PAO1 as a potential biosorbent and the blocking of competitive interactions of other monovalent cation, such as potassium, were assessed. Overall, P. aeruginosa PAO1 can be used as a high efficient biomaterial in the field of radioactive waste disposal and management.

No effect of digestate amendment on Cs-137 and Sr-90 translocation in lysimeter experiments

The soil-plant transfer of Cs-137 and Sr-90 in different crops was determined with respect to the present-day amendment practice of using digestate from biogas fermenters. The studies were performed using large lysimeters filled with undisturbed luvisol monoliths. In contrast to the conservative tracer, Br^-, neither of the studied radionuclides showed a significant vertical translocation nor effect of the applied digestate amendment compared to a non-amended control was found. Furthermore, no significant plant uptake was measured for both nuclides in wheat or oat as indicated by the low transfer factors between soil-shoot for Cs-137 (TF 0.001-0.010) and for Sr-90 (0.10-0.51). The transfer into nutritionally relevant plant parts was even lower with transfer factors for soil-grain for Cs-137 (TF 0.000-0.001) and for Sr-90 (0.01-0.06). Hence, the amendment with biogas digestate is unfortunately not an option to further reduce plant uptake of these radionuclides in agricultural crops, but it does not increase plant uptake either.

Cadmium and other elements in tissues from four ungulate species from the Mackenzie Mountain region of the Northwest Territories, Canada

Tissue samples from four ungulate species from the south Mackenzie Mountain region of the Northwest Territories (NT), Canada, were analysed for stable and radioactive elements and (15)N and (13)C stable isotopes. Elevated Cd concentrations in moose (Alces americanus) kidney have been observed in the region and are a health care concern for consumers of traditional foods. This study examined the factors associated with, and potential renal effects from, the accumulation of cadmium, and interactions with other elements in four sympatric ungulate species. Mean renal Cd concentration was highest in moose (48.3mg/kg ww), followed by mountain caribou (Rangifer tarandus caribou) (13.9mg/kg ww) and mountain goat (Oreamnos americanus) (5.78mg/kg ww). No local sources of Cd were evident and the elevated levels in moose are considered to be natural in origin. Conversely, total Hg concentration was significantly higher in mountain caribou kidney (0.21mg/kg ww) than in moose (0.011mg/kg ww). (134)Cs (t½=2.1 y) in mountain goat and Dall's sheep (Ovis dalli) muscle is evidence of deposition from the Fukushima reactor accident in 2011. (137)Cs (t½=30.2 y) in all four ungulates is primarily a remnant of the nuclear weapons tests of the 1960s. The levels of both nuclides are low and the risk to the animals and people consuming them is negligible. Stable isotope δ(15)N and δ(13)C signatures in muscle showed a separation between the mountain caribou, with a lichen-dominated diet, and moose, which browse shrubs and forbs. Isotope signatures for mountain goat and Dall's sheep showed generalist feeding patterns. Differences in elemental and radionuclide levels between species were attributed to relative levels of metal accumulation in the different food items in the diets of the respective species. Kidneys from each species showed minor histological changes in the proximal tubule and glomerulus, although glomerular changes were rare and all changes were rare in mountain goat kidney. Kidney function was not expected to be affected in any species. Provisional Monthly Intake recommendations from the WHO indicate that Cd in moose organs will continue to be a public health care concern. However, traditional foods continue to be an important nutritional component of northern diets, particularly in consideration of the shift towards store-bought food.

Effect of Remediation Parameters on in-Air Ambient Dose Equivalent Rates When Remediating Open Sites with Radiocesium-contaminated Soil

Calculations are reported for ambient dose equivalent rates [H˙*(10)] at 1 m height above the ground surface before and after remediating radiocesium-contaminated soil at wide and open sites. The results establish how the change in H˙*(10) upon remediation depends on the initial depth distribution of radiocesium within the ground, on the size of the remediated area, and on the mass per unit area of remediated soil. The remediation strategies considered were topsoil removal (with and without recovering with a clean soil layer), interchanging a topsoil layer with a subsoil layer, and in situ mixing of the topsoil. The results show the ratio of the radiocesium components of H˙*(10) post-remediation relative to their initial values (residual dose factors). It is possible to use the residual dose factors to gauge absolute changes in H˙*(10) upon remediation. The dependency of the residual dose factors on the number of years elapsed after fallout deposition is analyzed when remediation parameters remain fixed and radiocesium undergoes typical downward migration within the soil column.

Effectiveness of Protective Activities for Rehabilitation of the Forage Lands in Russia and Belarus Contaminated as a Result of the Chernobyl Accident

Regularities of changes in the content of (137)Cs in green fodder during the remote period after the CNPP accident depending on application of agro-technical and agrochemical activities are analyzed. It is revealed that the use of mineral fertilizers reduces receipt of (137)Cs from the soil to forage and further to a food chain. It is also established that agrochemical activities are more effective than agro-technical ones.

Solvent-free synthesis and application of nano-Fe/Ca/CaO/[PO4] composite for dual separation and immobilization of stable and radioactive cesium in contaminated soils

This study assessed the synthesis and application of nano-Fe/Ca/CaO-based composite material for use as a separation and immobilizing treatment of dry soil contaminated by stable ((133)Cs) and radioactive cesium species ((134)Cs and (137)Cs). After grinding with nano-Fe/CaO, nano-Fe/Ca/CaO, and nano-Fe/Ca/CaO/[PO4], approximately 31, 25, and 22 wt% of magnetic fraction soil was separated. Their resultant (133)Cs immobilization values were about 78, 81, and 100%, respectively. When real radioactive cesium contaminated soil obtained from Fukushima was treated with nano-Fe/Ca/CaO/[PO4], approximately 27.3 wt% of magnetic and 72.75% of non-magnetic soil fractions were separated. The highest amount of entrapped (134)Cs and (137)Cs was found in the lowest weight of the magnetically separated soil fraction (i.e., 80% in 27.3% of treated soil). Results show that (134)Cs and (137)Cs either in the magnetic or non-magnetic soil fractions was 100% immobilized. The morphology and mineral phases of the nano-Fe/Ca/CaO/[PO4] treated soil were characterized using SEM-EDS, EPMA, and XRD analysis. The EPMA and XRD patterns indicate that the main fraction of enclosed/bound materials on treated soil included Ca/PO4 associated crystalline complexes. These results suggest that simple grinding treatment with nano-Fe/Ca/CaO/[PO4] under dry conditions might be an extremely efficient separation and immobilization method for radioactive cesium contaminated soil.

[Dynamics of Radioecological State of the Fresh-Water Ecosystems Affected by a Long-Term Impact from Nuclear Power Plant in the Frontiers of the Zone under Observation]

The results of radioecological studies of six small rivers situated in the surveillance zone of the Beloyarskaya NPP (BNPP) and around the cooling pond of the power plant are presented. 21 radionuclides and the total α- and β-activity were studied in the main components of the aquatic ecosystems. It is shown that after the 1st and 2nd BN PP blocks decommissioning the content of 60Co and 137Cs in the Beloyarskoye storage pond water, sediments, fish fauna and macrophytes dropped tens and hundreds of times. The fundamental importance of this fact is that in a large range of time the aquatic ecosystem mechanism of self-purification from radionuclides is working due to radioactive substances decay as well as redistribution of radionuclides from water to other components, primarily to the sediments. Of 6 small rivers the maximum levels of radioactive substances is found in the river Olkhovka, which for several years has been subjected to the low-level radioactive water discharges from Beloyarskaya NPP. The radionuclide content in the main components of the aquatic ecosystems of the other five rivers studied after BNPP 47-year operation period corresponds to the regional background.

Copper Ferrocyanide-Functionalized Magnetic Nanoparticles for the Selective Removal of Radioactive Cesium

Copper ferrocyanide-functionalized magnetite nanoparticles (Cu-FC-MNPs) were successfully synthesized by immobilizing copper and ferrocyanide on the surfaces of [1-(2 amino-ethyl)-3-aminopropyl] trimethoxysilane-modified magnetite nanoparticles. Radioactive cesium (Cs) adsorption tests were conducted to investigate the effectiveness of the Cu-FC-MNPS toward the removal of radioactive Cs. The Cu-FC-MNPs showed excellent separation properties using an external magnet in an aqueous solution.

Decontamination of radiological agents from drinking water infrastructure: a literature review and summary

This report summarizes the current state of knowledge on the persistence of radiological agents on drinking water infrastructure (such as pipes) along with information on decontamination should persistence occur. Decontamination options for drinking water infrastructure have been explored for some important radiological agents (cesium, strontium and cobalt), but important data gaps remain. Although some targeted experiments have been published on cesium, strontium and cobalt persistence on drinking water infrastructure, most of the data comes from nuclear clean-up sites. Furthermore, the studies focused on drinking water systems use non-radioactive surrogates. Non-radioactive cobalt was shown to be persistent on iron due to oxidation with free chlorine in drinking water and precipitation on the iron surface. Decontamination with acidification was an effective removal method. Strontium persistence on iron was transient in tap water, but adherence to cement-mortar has been demonstrated and should be further explored. Cesium persistence on iron water infrastructure was observed when flow was stagnant, but not with water flow present. Future research suggestions focus on expanding the available cesium, strontium and cobalt persistence data to other common infrastructure materials, specifically cement-mortar. Further exploration chelating agents and low pH treatment is recommended for future decontamination studies.

The effect of environmental remediation on the cesium-137 levels in white-tailed deer

Due to activities involving nuclear energy research during the latter half of the 1900 s, environmental contamination in the form of elevated cesium-137 levels was observed within the Brookhaven National Laboratory, a US Department of Energy facility. Between the years 2000 and 2005, the laboratory carried out a major soil cleanup effort to remove cesium-137 from contaminated sites. In this study, we examine the effectiveness of the cleanup effort by comparing the levels of cesium-137 in the meat of white-tailed deer found within and around the laboratory. Results suggest that the cleanup was effective, with mean concentration of cesium-137 in the meat from within the laboratory decreasing from 2.04 Bq/g prior to 1.22 Bq/g after cleanup. At the current level, the consumption of deer would not pose any human health hazard. Nevertheless, statistically higher levels of cesium-137 were detected in the deer within the laboratory as opposed to levels found in deer 1 mi beyond the laboratory site.

[Radiological control of silvicultural production in Perm Krai]

Results of the studies carried out in 2009-2012 on the 137Cs content in edible fungi, berries and fruits of wild-growing bushes and the low shrubs growing in forest ecosystems of a number of regions of the Perm Krai are presented. It is shown that the activity of radio caesium in the studied samples does not exceed the maximal allowed levels approved in the Russian Federation.

[Spatial variability of quasidiffusion coefficients for 137Cs in grey forest soils in the distant zone of contamination from the Chernobyl NPP]

The calculated values of quasidiffusion coefficients for 137Cs for the 15-year period after the Chernobyl fallout in the top mineral thickness of grey forest soils of the Tula region vary within 0.18-0.35 cm2/year, accruing among biogeocenoses: pine forest < oak forest < birch forest < pasture. Correlations are revealed and the equations of linear regression for quasidiffusion coefficients for 137Cs depending on soil properties are constructed. Estimates of the periods of effective residence half-time of 137Cs in grey forest soils are made: for a layer of 0-5 cm - 11-14 years 0-15 cm - 22-25 years, 0-30 cm - 27-28 years. The periods necessary for the decrease in the contents of 137Cs in a 0-5 cm layer of soils to the level of 37 kBq/m2 are considered, taking into account a spatial variation of fallout and heterogeneity of quasidiffusion. Forecasts of the vertical migration of 137Cs on the basis of the diffusive model with spatially distributed soil parameters are submitted.

Preferential removal and immobilization of stable and radioactive cesium in contaminated fly ash with nanometallic Ca/CaO methanol suspension

In this work, the capability of nanometallic Ca/CaO methanol suspension in removing and/or immobilizing stable ((133)Cs) and radioactive cesium species ((134)Cs and (137)Cs) in contaminated fly ash was investigated. After a first methanol and second water washing yielded only 45% of (133)Cs removal. While, after a first methanol washing, the second solvent with nanometallic Ca/CaO methanol suspension yielded simultaneous enhanced removal and immobilization about 99% of (133)Cs. SEM-EDS analysis revealed that the mass percent of detectable (133)Cs on the fly ash surface recorded a 100% decrease. When real radioactive cesium contaminated fly ash (containing an initial 14,040Bqkg(-1)(134)Cs and (137)Cs cumulated concentration) obtained from burning wastes from Fukushima were reduced to 3583Bqkg(-1) after treatment with nanometallic Ca/CaO methanol suspension. Elution test conducted on the treated fly ash gave 100BqL(-1) total (134)Cs and (137)Cs concentrations in eluted solution. Furthermore, both ash content and eluted solution concentrations of (134)Cs and (137)Cs were much lower than the Japanese Ministry of the Environment regulatory limit of 8000Bqkg(-1) and 150BqL(-1) respectively. The results of this study suggest that the nanometallic Ca/CaO methanol suspension is a highly potential amendment for the remediation of radioactive cesium-contaminated fly ash.

Removal efficiency of radioactive cesium and iodine ions by a flow-type apparatus designed for electrochemically reduced water production

The Fukushima Daiichi Nuclear Power Plant accident on March 11, 2011 attracted people’s attention, with anxiety over possible radiation hazards. Immediate and long-term concerns are around protection from external and internal exposure by the liberated radionuclides. In particular, residents living in the affected regions are most concerned about ingesting contaminated foodstuffs, including drinking water. Efficient removal of radionuclides from rainwater and drinking water has been reported using several pot-type filtration devices. A currently used flow-type test apparatus is expected to simultaneously provide radionuclide elimination prior to ingestion and protection from internal exposure by accidental ingestion of radionuclides through the use of a micro-carbon carboxymethyl cartridge unit and an electrochemically reduced water production unit, respectively. However, the removability of radionuclides from contaminated tap water has not been tested to date. Thus, the current research was undertaken to assess the capability of the apparatus to remove radionuclides from artificially contaminated tap water. The results presented here demonstrate that the apparatus can reduce radioactivity levels to below the detection limit in applied tap water containing either 300 Bq/kg of ¹³⁷Cs or 150 Bq/kg of ¹²⁵I. The apparatus had a removal efficiency of over 90% for all concentration ranges of radio–cesium and –iodine tested. The results showing efficient radionuclide removability, together with previous studies on molecular hydrogen and platinum nanoparticles as reactive oxygen species scavengers, strongly suggest that the test apparatus has the potential to offer maximum safety against radionuclide-contaminated foodstuffs, including drinking water.

[The assessment of the content of 137Cs of the global and Chernobyl origin in forest soils and some types of edible fungi]

The article analyzes the density of pollution of the soil by radioisotopes of caesium and the content of 137Cs in fruit bodies of some species of forest mushrooms on the "long" trail of radioactive fallout in the Republic of Belarus in 1994 and 2012. On the basis of the calculated density of pollution of the soil with 134Cs in 1986 the contribution to the total density of pollution with 137Cs of the global radioactive fallout and emissions owing to the accident at the Chernobyl nuclear power plant was defined for the studied territory. It was established that at the density of pollution of the soil by 137Cs of 12-19 kBq/m2 in 1986 about 35% of pollution was caused by the global radioactive fallout. In 1994 and 2012, a specific activity and transfer factor of 137Cs were analyzed for fruit bodies of some species of forest mushrooms. The transfer factors of 137Cs for fruit bodies of Boletus edulis are at level of 10 x 10(-3) m2/kg, Leccinum scabrum and Leccinum aurantiacum - (15-20) x 10(-3) m2/kg, Xerocomus badius--(60-80) x 10(-3) m2/kg.

[Distribution of 137Cs, 90Sr and their chemical analogues in the components of an above-ground part of a pine in a quasi-equilibrium condition]

The additional study of the distribution of radioactive isotopes of caesium and strontium and their chemical analogues in the above-ground components of pine in the remote from the accident period was carried out. The results of the research confirmed the existence of analogy in the distribution of these elements on the components of this type of wood vegetation in the quasi-equilibrium (relatively radionuclides) condition. Also shown is the selective possibility of using the data on the ash content of the components of forest stands of pine and oak as an information analogue.

[Man-made radionuclides and their accumulation by plants of different taxonomic groups from the soils of the eastern ural radioactive trace]

Investigations of the spatial and vertical distribution of 90Sr, 137Cs and 239, 240Pu in the soils of the Eastern Ural Radioactive Trace (EURT) and accumulation of these radionuclides by plants were carried out in 2003-2011. Investigations showed that the spatial distribution of the radionuclides with increasing distances from the epicenter of the accident is satisfactorily approximated by the exponential function. During the post-accidental period the essential amount of radionuclides is located in the 15-20 cm root layer of the soil. Uptake by plants of 90Sr is determined, first of all, by the level of the soil contamination. For 137Cs, reliable differences in its accumulation ability between representatives of the higher plants and lower ones are remained in the whole gradient of contamination.

Evaluation of vegetables in Tsukuba for contamination with radioactive materials from the accident at Fukushima Daiichi nuclear power plant

A large amount of radioactive material was released into the atmosphere after the accident of the Fukushima Daiichi Nuclear Power Plant following the Tohoku earthquake on 11 March 2011, and traces of these materials were detected in Tsukuba. Because radioactive materials can adhere to vegetables, the authors made a qualitative evaluation of vegetables in Tsukuba, estimated internal exposure dose based on quantitative measurement results, and investigated several decontamination methods. Qualitative analysis of vegetable contamination was done by autoradiography. Quantitative analysis was done using a high-purity germanium detector. To assess decontamination, two methods were tested: one with running water and the other with boiling water. In addition, boiled soup stock was measured. In the qualitative evaluation by autoradiography, radioactive materials were not uniformly distributed but adhered to vegetables in clumps and hot spots. In the quantitative evaluation to measure contamination of outer and inner leaves of sanchu lettuce, it was observed that the concentration of I was 8,031.35 ± 764.79 Bq kg in the outer leaves and 115.28 ± 20.63 Bq kg in the inner leaves. In addition, the concentration of Cs was 1,371.93 ± 366.45 Bq kg in the outer leaves and 9.68 ± 15.03 Bq kg in the inner leaves. This suggests that one can greatly reduce internal exposure dose by removing the outer leaves if one has to eat vegetables just after a nuclear accident. In the decontamination assessment, a decontamination efficiency of up to 70% was achieved by boiling vegetables for 20 min.

[Prognosis of dynamics and risk of exceeding permissible levels of 137Cs and 90Sr contents in fish in the Kiev Reservoir at the late phase of the Chernobyl accident]

On the basis of the radionuclide specific activity measurements made on 832 samples of fish in 2009-2011 and taking into account literature data, the parameters of the stochastic model have been derived to describe the 137Cs and 90Sr contents in typical commercial fish species in the Kiev Reservoir at the late phase of the Chernobyl accident, including: statistical variability, seasonal changes and monotonous long-term trends. At any fixed moment of the year the standard deviations of logarithms of the 137Cs and 90Sr specific activities in carnivorous and benthophage fish species do not reliably differ, making up at average 0.4. The maximum vari- ation of the 137Cs specific activity (a four-fold decrease from April to November) was observed in pike. The obtained values of the ecological half-life periods for 137Cs and 90Sr (1.3-14 years) in fish of the Kiev reservoir in 2002-2012 were significantly lower than both the radioactive decay periods and the estimates of the IAEA Chernobyl Forum. Based on the obtained model parameters, the dynamics of the 137Cs and 90Sr specific ac- tivities in main commercial fish of the Kiev reservoir has been described and the risk of exceeding the permis- sible levels of these radionuclides in fish at the late phase of the Chernobyl accident has been estimated. Now the risk of catching fish with the specific activities of 137Cs and 90Sr above the permissible levels (150 Bq/kg and 35 Bq/kg, respectively) does not exceed 10% (except perch in the spring spawning period that is banned for fishing in Ukraine). Corresponding risks for roach, white bream and rudd are less than 0.1%.

Decontamination of outdoor school swimming pools in Fukushima after the nuclear accident in March 2011

Because of radioactive fallout resulting from the Fukushima Daiichi Nuclear Power Plant (NPP) accident, water discharge from many outdoor swimming pools in Fukushima was suspended out of concern that radiocesium in the pool water would flow into farmlands. The Japan Atomic Energy Agency has reviewed the existing flocculation method for decontaminating pool water and established a practical decontamination method by demonstrating the process at eight pools in Fukushima. In this method, zeolite powder and a flocculant are used for capturing radiocesium present in pool water. The supernatant is discharged if the radiocesium concentration is less than the targeted level. The radioactive residue is collected and stored in a temporary storage space. Radioactivity concentration in water is measured with a NaI(Tl) or Ge detector installed near the pool. The demonstration results showed that the pool water in which the radiocesium concentration was more than a few hundred Bq L was readily purified by the method, and the radiocesium concentration was reduced to less than 100 Bq L. The ambient dose rates around the temporary storage space were slightly elevated; however, the total increase was up to 30% of the background dose rates when the residue was shielded with sandbags.

[Forecasting model of transfer of 137Cs to the plants]

The forecasting model of the concentration ratio (CR) of 137Cs in the plants taking into consideration organic carbon, pH, mobile and total content of potassium in soil has been developed on the basis of the radioecological investigations in the valleys of the Resseta and Vytebet rivers. The type of functional dependence of CR from soil characteristics can be used for an estimation of the content of radionuclides in various species and productive parts of plants.

Removal of radioactive Cs from gravel conglomerate using water containing air bubbles

Remediation of sites contaminated with radioactive material such as Cs is important because of the risk posed to human health. Here, we report the effectiveness of water containing air bubbles with a diameter around 100 nm (nanobubbled water, NB water) for the removal of radioactive Cs. Laboratory experiments confirmed that NB water is more effective than purified water and as effective as water with neutral detergent in the removal of Cs-137 from gravel. Moreover, NB water retains its effectiveness even after storage for 7 d. Finally, NB water produced onsite from tap water was found to be effective for removal of radioactive Cs from gravel conglomerate in Fukushima, Japan.

[The forecasting of vertical distribution of 37Cs and 90Sr in the forest soils of the Republic of Belarus]

The study analyzes the distribution of 137Cs and 90Sr in the vertical profile of soil of forest biogeocenoses with different modes of moisture and species composition of woody vegetation on the "long" trail of radioactive fallout in the Republic of Belarus. The parameters of radionuclide migration are calculated for the two component quasi-diffusion equation, also based on this equation, pollution of root zone soil layers is predicted, as well as semi-refined periods and the contribution of migration in this process are defined. The intensity of radionuclide migration in the vertical profile of forest soils is found to increase with the change of the soil moisture regime from automorphic to hydromorphic.

Decontamination efficiencies of pot-type water purifiers for ¹³¹I, ¹³⁴Cs and ¹³⁷Cs in rainwater contaminated during Fukushima Daiichi nuclear disaster

Rainwater was contaminated by a large release of radionuclides into the environment during the Fukushima Daiichi nuclear disaster. It became a matter of concern for Japan when several water purification plants detected ¹³¹I contamination in the drinking water. In the present study, the decontamination efficiency of two easily obtainable commercial water purifiers were examined for rainwater contaminated with ¹³¹I, ¹³⁴Cs and ¹³⁷Cs. The water purifiers removed 94.2–97.8% of the ¹³¹I and 84.2–91.5% of the ¹³⁴Cs and ¹³⁷Cs after one filtration. Seven filtrations removed 98.2–99.6% of the ¹³¹I and over 98.0% of the ¹³⁴Cs and ¹³⁷Cs. From a practical perspective, over the fourth filtrations were not needed because of no significant improvements after the third filtration.

Relevance of Radiocaesium Interception Potential (RIP) on a worldwide scale to assess soil vulnerability to 137Cs contamination

The extent of radiocaesium retention in soil is important to quantify the risk of further foodchain contamination. The Radiocaesium Interception Potential (RIP -Cremers et al., 1988, Nature 335, 247-249) is an intrinsic soil parameter which can be used to categorize soils or minerals in terms of their capacity to selectively adsorb radiocaesium. In this study, we measured RIP for a large soil collection (88 soil samples) representative of major FAO soil reference groups on a worldwide scale and tested the possibility to predict the RIP on the basis of other easily accessible or measurable soil data. We also compared RIP values with those obtained from separate chemical extraction experiments. The range of measured RIP values (1.8-13300 mmol kg(-1)) was shown to include nearly all possible cases of agricultural soil contamination. Only Podzols, Andosols and Ferralsols were clearly characterized by a very low RIP (<2000 mmol kg(-1)). On a worldwide scale, RIP was in fact slightly related to soil reference type or other simple major physicochemical parameters such as clay percentage or organic matter. Conversely our results indicated a link between the RIP and radiocaesium extractability across very different soils. We showed that, with the proposed scale of RIP values, a simple acid extraction method can provide an operational result highly predictive of potential RIP despite very contrasting soil properties. The RIP could be estimated from the empirical equation: RIP = (-31.701 ∗ log(AER) + 58.886)(2) where AER is the fraction of acid-extractable radiocaesium.

Colloid stable sorbents for cesium removal: preparation and application of latex particles functionalized with transition metals ferrocyanides

In this paper we suggest a principally new approach to preparation of colloid stable selective sorbents for cesium uptake using immobilization of transition metals (cobalt, nickel, and copper) ferrocyanides in nanosized carboxylic latex emulsions. The effects of ferrocyanide composition, pH, and media salinity on the sorption properties of the colloid stable sorbents toward cesium ions were studied in solutions containing up to 200 g/L of sodium nitrate or potassium chloride. The sorption capacities of the colloid sorbents based on mixed potassium/transition metals ferrocyanides were in the range 1.3-1.5 mol Cs/mol ferrocyanide with the highest value found for the copper ferrocyanide. It was shown that the obtained colloid-stable sorbents were capable to penetrate through bulk materials without filtration that made them applicable for decontamination of solids, e.g. soils, zeolites, spent ion-exchange resins contaminated with cesium radionuclides. After decontamination of liquid or solid radioactive wastes the colloid-stable sorbents can be easily separated from solutions by precipitation with cationic flocculants providing localization of radionuclides in a small volume of the precipitates formed.

Selective separation of radio-cesium from acidic solutions using supported liquid membrane containing chlorinated cobalt dicarbollide (CCD) in phenyltrifluoromethyl sulphone (PTMS)

A supported liquid membrane method was developed using chlorinated cobalt dicarbollide (CCD) in phenyltrifluoromethyl sulphone (PTMS) as the carrier, impregnated in PTFE flat sheet membranes for the selective separation of Cs(I) from nitric acid feed solution. Solvent extraction studies were carried out for optimizing the feed as well as strip conditions. >95% Facilitated transport of Cs(I) was observed in about 3h when 1M HNO(3) and 8M HNO(3) were used as the feed and strip solutions, respectively while 0.025M CCD in PTMS was used as the carrier extractant. Selectivity studies, carried out using a mixture of radiotracers viz. (51)Cr, (59)Fe, (99)Mo, (99m)Tc, (106)Ru, (137)Cs, (152)Eu and (241)Am, indicated selective transport of Cs(I) with DF values >100. Though reproducibility of the transport data was excellent when carried out in two successive transport experiments with freshly loaded carrier solvent, the stability of the membrane was poor which restricts its long term use.

Selectivity of 90Sr urine bioassay technique over 241Am, 238/239PU, 210PO, 137CS and 60CO

The selectivity of a rapid (90)Sr bioassay technique over (241)Am, (238/239)Pu, (210)Po, (137)Cs and (60)Co has been investigated. Similar to (90)Sr, these radionuclides are likely to be used in radiological dispersive devices. The purpose of this study was to demonstrate the degree to which the (90)Sr bioassay technique is free from interference by these radionuclides if present in a urine matrix. The interfering radionuclides were removed (from (90)Sr) by their retention on an anion exchange column. While, recovery of the target radionuclide ((90)Sr) was found to be >or= 90 %, contributions from (241)Am, (242)Pu and (208)Po were found to be <or= 3 % indicating minimal interference from these radionuclides. The breakthrough for (60)Co, however, was found to be <or=19 % indicating that it will have some interference contribution to the (90)Sr measurement if present in the urine sample. As (137)Cs was not retained at all by the anion exchange column, the method as such was not selective over (137)Cs. However, a slight modification of the method through the ammonium molybdophosphate treatment quantitatively removed Cs from the urine sample, thereby; making it selective for (90)Sr despite any (137)Cs that is present.

Sorption of 137Cs, 133Ba and 154Eu by synthesized sodium aluminosilicate (Na-AS)

Sodium aluminosilicate has been synthesized by solution route for use as a sorbent for various radionuclides. It was characterized by XRD, zeta potential, BET surface area, FTIR spectroscopy and site density measurement. Sorption studies of (137)Cs, (133)Ba and (154)Eu on synthesized sodium aluminosilicate have been carried out at varying pH (3-10). Sorption of all the metal ions was found to increase with pH of suspension with the saturation value increasing with the oxidation state of metal ion. Effect of Aldrich humic acid (2mg/l) on sorption was also investigated. In case of (137)Cs, the sorption was not affected by the presence of humic acid, while in case of (133)Ba and (154)Eu, sorption was enhanced at lower pH and decreased at higher pH in presence of HA. A series of experiments were carried out for (154)Eu sorption on sodium aluminosilicate at various conditions. Sorption of europium was analyzed by different sorption isotherms, viz., Freundlich and D-R isotherm. Thermodynamic data reveal sorption phenomena as endothermic and spontaneous. Studies were further extended to find out effect of diverse ions (Ca(2+) and CO(3)(2-)) on sorption of europium.

134Cs uptake by four plant species and Cs-K relations in the soil-plant system as affected by Ca(OH)2 application to an acid soil

Three rates of Ca(OH)(2) were applied to an acid soil and the (134)Cs uptake by radish, cucumber, soybean and sunflower plants was studied. The (134)Cs concentration in all plant species was reduced from 1.6-fold in the sunflower seeds to 6-fold in the soybean vegetative parts at the higher Ca(OH)(2) rate. Potassium (K) concentration in plants was also reduced, but less effectively. The significantly decreased (134)Cs-K soil to plant distribution factors (D.F.) clearly suggest a stronger effect of soil liming on (134)Cs than on K plant uptake. This observation was discussed in terms of ionic interactions in the soil matrix and within the plants. The results also indicated that the increased Ca(2+) concentration in the exchange phase and in the soil solution along with the improved root activity, due to the soil liming, enhanced the immobilization of (134)Cs in the soil matrix and consequently lowered the (134)Cs availability for plant uptake.

Recovery and purification of 4.66 TBq(126Ci) of 137Cs from a 20-year-old spent sealed source

An attempt to recover and purify 4.66 TBq(126Ci) of (137)Cs as solution from a 20-year-old doubly encapsulated sealed source containing (137)CsCl was made successfully. The primary capsule was first cut open to retrieve the secondary capsule. The top end of the secondary SS capsule was then cut to render it as an open cylinder and the (137)CsCl pellet inside was dissolved in small aliquots of water. Each aliquot of the (137)CsCl solution was dispensed into glass vials, sealed, assayed and stored. Barium formed during the radioactive decay of (137)Cs was removed by carbonate precipitation. Chloride was removed by heating with HNO(3) and evaporation. About 91.8% of the total activity could be recovered and used subsequently for making brachytherapy sources.

Selectivity of cesium from fission radionuclides using resorcinol-formaldehyde and zirconyl-molybdopyrophosphate as ion-exchangers

Two ion-exchangers, the first is organic in nature and the other is inorganic named as resorcinol-formaldehyde (R-F) and zirconyl-molybdopyrophosphate (ZMPP) were synthesized and applied to decontaminate some fission radionuclides from radioactive waste streams. The distribution coefficients of the studied radionuclides for the two ion-exchanges at varying pH conditions are evaluated and the data showed that the selectivity sequence of resorcinol-formaldehyde for the studied cations is Cs(+)>Co(2+)>Eu(3+)>Zn(2+) which is the same sequence of zirconyl-molybdopyrophosphate while as the X-ray diffraction characterization showed that resorcinol-formaldehyde resin is an amorphous material but zirconyl-molybdopyrophosphate is a semicrystalline one and both of resorcinol-formaldehyde and zirconyl-molybdopyrophosphate are considered as promising materials specially for the decontamination of cesium from radioactive waste solutions.

Removal of radioactive caesium from low level radioactive waste (LLW) streams using cobalt ferrocyanide impregnated organic anion exchanger

The volumes of low level waste (LLW) generated during the operation of nuclear reactor are very high and require a concentration step before suitable matrix fixation. The volume reduction (concentration) is achieved either by co-precipitating technique or by the use of highly selective sorbents and ion exchange materials. The present study details the preparation of cobalt ferrocyanide impregnated into anion exchange resin and its evaluation with respect to removal of Cs in LLW streams both in column mode and batch mode operations. The Kd values of the prepared exchanger materials were found to be very good in actual reactor LLW solutions also. It was observed that the exchanger performed very well in the pH range of 3-9. A batch size of 6 g l(-1) of the exchanger was enough to give satisfactory decontamination for Cs in actual reactor LLW streams. The lab scale and pilot plant scale performance of the exchanger material in both batch mode and column mode operations was very good.

Simulation study on the use of strippable coatings for radiocesium decontamination of concrete

The contamination and decontamination of concrete by a soluble contaminant (radiocesium) was modeled using the finite element method. The decontamination process relied on the application of a hyper-accumulating strippable polymer (HASP™) [corrected] to sequester contaminant that was transported to the concrete surface. The model accounted for the transport of cesium by diffusion, capillary pressure-driven convection, and equilibrium adsorption of cesium within the concrete substrate and HASP™ [corrected] coating. The influence of HASP™ [corrected] properties (porosity, thickness, and cesium distribution coefficient), and a wide range of operation variables (HASP™ [corrected] contact time, delay time until HASP™ [corrected] decontamination begins, influence of evaporative boundary conditions) on final decontamination efficacy were explored. Transient saturation (moisture content) and cesium concentration profiles were used to understand key factors in the decontamination process, and water wicking experiments were performed to validate the capillary convection model. The results showed that prompt HASP™ [corrected] application after the initial contamination event is critical for high decontamination efficacies. A 30-day HASP™ [corrected] treatment removed about 90% of the contaminant when HASP™ [corrected] was applied within 30min of the initial contamination event, whereas the decontamination process removed less than half as much cesium if months were allowed to elapse months prior to decontamination. Multiple applications of fresh HASP™ [corrected] were also shown to improve decontamination performance under certain circumstances.

Determination of low (137)Cs concentration in seawater using ammonium 12-molybdophosphate adsorption and chemical separation method

A new method has been developed for analyzing (137)Cs in a small volume of seawater. Ammonium 12-molybdophosphate (AMP) was used two times during pretreatment procedure. The first step was to adsorb (137)Cs in seawater samples into AMP in order to reduce sample volume, and the second was to remove (87)Rb, interference nuclide for beta counting. The AMP adsorbing (137)Cs was dissolved by sodium hydroxide solution, and then (137)Cs was finally formed to be cesium chloroplatinate precipitate by adding 10% hexachloroplatinic acid. The beta rays emitted from (137)Cs were measured with a low background gas-proportional alpha/beta counter. This method was applied to several seawater samples taken in the East Sea of Korea. Compared to the routinely used gamma-spectrometry method, this new AMP method was reliable and suitable for analyzing (137)Cs in deep seawater.

Use of illite clay for in situ remediation of 137Cs-contaminated water bodies: field demonstration of reduced biological uptake

We hypothesized that adding micaceous minerals to 137Cs-contaminated aquatic systems would serve as an effective in situ remediation technique by sequestering the contaminant and reducing its bioavailability. Results from several laboratory studies are presented from which an effective amendment material was chosen for a replicated field study. The field study was conducted over a 2-year period and incorporated 16 3.3-m diameter column-plots (limnocorrals) that were randomly placed in a 137Cs-contaminated pond. The limnocorrals received three rates of amendment treatments to their water surfaces. The amendment material was a commercially available mineral with high sorption (Kd > 9000 L kg(-1)) and low desorption (<20%) characteristics for cesium, even in the presence of high concentrations of the competing cation, NH4+. In the treated limnocorrals, 137Cs concentrations were reduced some 25-30-fold in the water, 4-5-fold in aquatic plants, and 2-3-fold in fish. The addition of the amendment did not adversely affect water chemistry, although increased turbidity and subsequent siltation did alter the aquatic macroinvertebrate insect community. This in situ technology provides a valuable, less-environmentally intrusive alternative to costly ex situ technologies that require the contaminated sediment to be excavated prior to treatment, or excavated and disposed of elsewhere.

Removal of 137Cs in Japanese catfish during preparation for consumption

Japanese catfish contaminated by (137)Cs have been used to investigate how dressing and cooking methods affect the removal of radioactivity from the fish. During the dressing, 6.0% of the initial (137)Cs activity in live fish was removed by washing them, and a further 30.3% of this activity relative to the washed fish was removed by discarding the nonedible body parts (such as the skeleton, fins, visceral mass, liver, and kidney) and by washing the chopped edible remains. Fish curry was cooked with various spices, vegetable oil, and greens and other vegetables following a method commonly used in Southeast Asian and East Asian countries. The cooking process removed a further 61.6% of the (137)Cs activity relative to the activity in dressed fish. Taken together, this normal domestic fish dressing and culinary process removed 74.7% of the initial (137)Cs activity that had been present in the live fish. During the cooking, the radioactivity removed from the fish pieces was found to be distributed throughout the ingredients of the curry. The cooked pieces retained, on average, 38.5% of the radioactivity present in the raw dressed pieces. Among the ingredients, the gravy was found to contain an average of 34.8% of the activity of the dressed fish. The activity in greens and vegetables was found to vary from 4.0% (in cauliflower) to 7.2% (in potatoes). It may be concluded that normal home preparation and culinary processes removed much of the radioactivity from the fish.

Large-scale purification of 90Sr from nuclear waste materials for production of 90Y, a therapeutic medical radioisotope

A major limitation on the supply of the short-lived medical isotope 90Y (t1/2 = 64 h) is the available quantity of highly purified 90Sr generator material. A radiochemical production campaign was therefore undertaken to purify 1,500 Ci of 90Sr that had been isolated from fission waste materials. A series of alkaline precipitation steps removed all detectable traces of 137Cs, alpha emitters, and uranium and transuranic elements. Technical obstacles such as the buildup of gas pressure generated upon mixing large quantities of acid with solid 90Sr carbonate were overcome through safety features incorporated into the custom-built equipment used for 90Sr purification. Methods are described for analyzing the chemical and radiochemical purity of the final product and for accurately determining by gravimetry the quantities of 90Sr immobilized on stainless steel filters for future use.

Retardation capacity of organophilic bentonite for anionic fission products

Sorption and diffusivity of iodide and pertechnetate (I- and TcO4-) on MX-80 bentonite with different hexadecylpyridinium (HDPy+) loadings were studied using equilibrium solutions of different ionic strengths. In HDPy(+)-modified bentonite, iodide and pertechnetate ions exhibited increasing sorption (characterized by the distribution ratio, Rd), while Cs+ and Sr2+ showed decreasing sorption with increasing organophilicity. In case of medium-loading levels, the simultaneous sorption of anions (I- and TcO4-) and cations (Cs+ and Sr2+) was observed. Sorption of ions was influenced by the composition of the electrolytes employed. It decreased gradually with increasing ionic strength of the electrolyte solutions. The experiments revealed the general tendency that the diffusivity (Da [cm2.s-1]) for iodide and pertechnetate decreases with increasing organophilicity and increases with increasing ionic strength of the equilibrium solutions, confirming the results of the sorption experiments. Additionally, some mineralogical and chemical investigations, like IR spectral analysis of the organo-bentonite samples and exchange behavior of HDPy+, were performed. On the basis of these analyses, it was concluded that the alkylammonium ions are sorbed as (1) HDPy+ cations, (2) HDPyCl molecules and (3) micelles with decreasing binding intensities in this order.

The use of clinoptilolite and its sodium form for removal of radioactive cesium, and strontium from nuclear wastewater and Pb2+, Ni2+, Cd2+, Ba2+ from municipal wastewater

Three different samples of Iranian natural zeolites (clinoptilolite) and its sodium exchanged forms have been investigated for uptaking several different cations. Ion-exchange isotherms, have been given and discussed.

Hemodialysis as a potential method for the decontamination of persons exposed to radiocesium

Radiocesium may be deposited in the environment as a result of accidents in nuclear installations, for example, as in Chernobyl. Significant internal contamination with radiocesium poses a serious risk to human health, and, therefore, expedient removal is essential to reduce the radiation body burden. In vitro hemodialysis was tested as a potential method to remove radiocesium from a pasteurized plasma solution of bovine or human blood. Clearance values were calculated by a flow independent method. Hemodialysis appears to be a good method to remove radiocesium from blood: within 4 h more than 90% of the administered radiocesium is removed from blood or plasma. Radiocesium in dialysis fluid can be concentrated on Prussian Blue coated columns that were tested previously for hemoperfusion. Radioactive waste disposal problems can be solved by concentration of radiocesium on these columns. In vivo experiments are necessary to confirm these in vitro results.

[The use of ferrocyanides for obtaining pure meat production in contaminated areas following the accident at the Chernobyl Atomic Electric Power Station]

The paper reports a new technique of obtaining radioactive Cs-free meat in the regions contaminated with radionuclides as a result of Chernobyl accident. The method is based on specific digestion features of ruminant animals. Ferriferrocyanide compounds are proposed as sorbents. Ferrocene is most efficient when introduced into mixed feed (1-3 g/day for sheep, 3-5 g/day for calves and young bulls) once a day. After that the animals can be fed radioactively contaminated forage and graze on contaminated land.

[The effect of the method of treating samples of dried fungi on the process of extracting cesium radionuclides]

Most effective extraction of Cesium-137 radionuclide (near 100%) is produced by water during 48 h. The addition of salt (20 g/l) is not effective in this process.