Retention of 137cesium in acid sulphate soils of South Central Thailand

Adsorption and desorption of ¹³⁷Cs by acid sulphate soils from the Nakhon Nayok province, South Central Plain of Thailand located near the Ongkarak Nuclear Research Center (ONRC) were investigated using a batch equilibration technique. The influence of added limestone (12 and 18 tons ha^?1) on ¹³⁷Cs adsorption–desorption was studied. Based on Freundlich isotherms, both adsorption and desorption of ¹³⁷Cs were nonlinear. A large portion (98.26–99.97%) of added ¹³⁷Cs (3.7?×?10³?7.03?×?10⁵ Bq l^?1) was sorbed by the soils with or without added lime. The higher lime treatments, however, favoured stronger adsorption of ¹³⁷Cs as compared with soil with no lime, which was supported by higher K _ads values. The addition of lime, the cation exchange capacity and pH of the soil increased and hence favoured the stronger adsorption of ¹³⁷Cs. Acid sulphate soils with a high clay content, medium to high organic matter, high CEC, and predominant clay types consisting of a mixture of illite, kaolinite, and montmorillonite were the main soil factors contributing to the high ¹³⁷Cs adsorption capacity. Competing cations such as NH₄ ⁺, K⁺, Na⁺, Ca²⁺, and Mg²⁺ had little influence on ¹³⁷Cs adsorption as compared with liming, where a significant positive correlation between K _ads and soil pH was observed. The ¹³⁷Cs adsorption–desorption characteristics of the acid sulphate soils studied exhibited a very strong irreversible sorption pattern. Only a small portion (0.09–0.58%) of ¹³⁷Cs adsorbed at the highest added initial ¹³⁷Cs concentration was desorbed by four successive soil extractions. Results clearly demonstrated that Nakhon Nayok province acid sulphate soils have a high ¹³⁷Cs adsorption capacity, which limits the ¹³⁷Cs bioavailability.     

Total immobilization of soil heavy metals with nano-Fe/Ca/CaO dispersion mixtures

This report shows that soil heavy metals can be totally immobilized by grinding with nano-Fe/Ca/CaO. Remediation of soils contaminated by heavy metals is a critical issue in Japan. Indeed, contaminated soils are notoriously difficult to remediate using available technologies. Major setbacks in typical immobilization techniques for heavy metals are wet conditions, forming secondary effluents and further treatment for effluents. Solidification with nano-Fe/Ca/CaO dispersion mixture is a promising treatment for the total immobilization of soil heavy metals As, Cd, Cr, Pb, and separation in dry conditions. Here, we studied the heavy metal immobilization by simple grinding with the addition of three mixtures: nano-Fe/CaO, nano-Fe/Ca/CaO, and nano-Fe/Ca/CaO/PO₄. Samples were analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES) and scanning electron microscopy combined with electron dispersive spectroscopy (SEM–EDS). Results show that the addition of nano-Fe/Ca/CaO immobilized 95–99 % of heavy metals, versus 65–80 % by simple grinding. After treatment, 36–45 wt% of magnetic and 64–55 wt% of nonmagnetic fractions of soil were separated. Their condensed heavy metal concentration was 85–95 % and 10–20 %, respectively. Nano-Fe/Ca/CaO treatment reduced the concentration of leachates heavy metals to values lower than the Japan soil elution standard regulatory threshold of 0.01 mg/l for As, Cd, and Pb; and 0.05 mg/l for Cr. This technology can therefore immobilize totally soil heavy metals and reduce heavy metal by separation.     

Cäsium-137 in Böden saarländischer Waldökosysteme

Scopes and main features

In order to explain the behaviour of the artificial radioisotope¹³⁷Cs towards landscape resources in the Saar-Lor-Lux-Region, the cross-border region between southwestern Germany/ Saarland, France/Lorraine and Luxembourg, regional distribution as well as downward translocation and depth functions of¹³⁷Cs in the main soil substrates of forest ecosystems in the Saarland were investigated.

Results

The study shows that the highest¹³⁷Cs activities are found in the north of the Saarland, whereas the south and south-eastern regions show distinctly lower concentrations of¹³⁷Cs. Migration rates range between 0.25 cm/a and 1.0 cm/a. On an average, the highest migration rates were found in the clayey-silty substrates of the lime stone areas in theMuschelkalk regions (Middle Triassic) (0.66 cm/a), followed by the loamy substrates of Lower Permian clastic sediments (Unterrotliegendes) (0.53 cm/a) and the sandy substrates of theBuntsandstein areas (Lower Triassic sandstone) (0.41 cm/a). 90 to 95% of the¹³⁷Cs activities in the clay-poor soils of the Unterrotliegendes and the Buntsandstein were traced in the upper 10 cm of the humus topsoil. The substrates of the lime stone areas (Muschelkalk), in contrast to this, reveal a¹³⁷Cs activity of only 70–76% at the same depth.

Conclusions

Due to the fact that the primary and secondary pores of the soil pore system, in their function as translocation pathways, decrease with increasing soil depth, a significant reduction in the migration rates of¹³⁷Cs can be expected with increasing soil depth. On the other hand, the maximal migration depth of 40 cm found in shallow soils on jointed parent material, as well as on sites with high groundwater tables, implies a possible contamination of near-surface groundwater.

Future outlook

Based on the results of this study, a permanent monitoring of¹³⁷Cs was added to the long-term Soil Monitoring Program run by the Federal Administrative Office of Environment of the Saarland (Landesamt für Umweltschutz des Saarlandes)     

A model of radiocesium cycling in a sand hills—Turkey Oak (Quercus laevis) ecosystem

Digital simulation models of radiocesium cycling in Turkey Oaks were developed from in situ ¹³⁴Cs tagging studies. Predictions of ¹³⁴Cs steady-state distribution for 3-, 4- and 5-compartment, donor-controlled models were compared with the estimated fallout ¹³⁷Cs distribution as a measure of model validation; output from the 5-compartment model compared best. Sensitivity analysis demonstrated that Turkey Oak burden of ¹³⁴Cs was equally sensitive to the output rate from the tree compartment and the availability of ¹³⁴Cs for uptake (i.e., presence in the root zone) but not the rate of uptake by Turkey Oaks. Observed distribution and model predictions indicate that radiocesium is readily bioaccumulated by Turkey Oaks (～13% of the ecosystem burden) from the soil and is cycled within the sand hills—Turkey Oak ecosystem.     

Sediment accumulation and bio-diffusion mixing rates derived from excess <Superscript>210</Superscript>Pb and <Superscript>137</Superscript>Cs profiles in sediment cores of Mumbai Harbor Bay

Bio-diffusion mixing rates (D_b) were estimated from depth profiles of excess ²¹⁰Pb and ¹³⁷Cs in three sediment cores collected from Mumbai Harbour Bay (MHB) using a steady state vertical advection - diffusion model. The mean of ²¹⁰Pb and ¹³⁷Cs derived D_b values along the studied area were obtained to be about 23 and 36 cm²y^?1 respectively. These derived values were within the range of literature values reported for other equivalent environment internationally. The relatively higher D_b values for ¹³⁷Cs profiles demonstrated that particles have diffused more intensely within the surface layer of sediments over 1 year. Conversely, low D_b values for ²¹⁰Pb indicate slow mixing rates in the sediment profile which might be resulted from low ²¹⁰Pb flux and diffusion of ²²²Rn to the seafloor. The significant differences between ²¹⁰Pb and ¹³⁷Cs derived D_b values among cores indicate that there appeared to be as regional differences in sediment properties and local variability in the intensity of seafloor mixing. Furthermore, D_b values also depend on differences in characteristic time and depth scales of radionuclides in cores, benthic fauna abundances, organic carbon flux to the sediments and primary production in overlying surface waters. Comparison of ²¹⁰Pb derived D_b values with those calculated from ¹³⁷Cs distributions reveals better agreement for core 2 than core 1 and 3. The agreement may be fortuitous because ¹³⁷Cs appears significantly deeper than ²¹⁰Pb in all cores. It was also observed that D_b values increases as sediment accumulation rate increases for both radionuclide.     

Sediment environmental capacity of 137Cs in Daya Bay

Sediment environmental capacity of pollutants is very important for marine environmental management. Based on the methodology of a study on water, soil environmental capacity, and mass conservation theory in a system, the concept and model on sediment environmental capacity for ¹³⁷Cs in Daya Bay were developed. The static capacity for ¹³⁷Cs in the upper sediment near the shore at a shallow area was calculated, and the annual dynamic capacity and total dynamic capacity were also calculated through determination of the typical biomass in the sediment. The results showed that the estimated environmental capacity for ¹³⁷Cs in sediments was approximately equal to the current input of ¹³⁷Cs into the sediments. Controlling the input of ¹³⁷Cs in the sediments within the environmental capacity guarantees the sustainability of the current situation of the Daya Bay ecosystem and avoidance of a significant degradation of the system.     

Use of zeolitized coal fly ash in the simultaneous removal of ammonium and phosphate from aqueous solution

Discharge of wastewater containing nitrogen and phosphate can cause eutrophication. Therefore, the development of an efficient material for the immobilization of the nutrients is important. In this study, a low calcium fly ash and high calcium fly ash were converted into zeolite using the hydrothermal method. The removal of ammonium and phosphate that coexist in aqueous solution by the synthesized zeolites were studied. The results showed that zeolitized fly ash could efficiently eliminate ammonium and phosphate at the same time. Saturation of zeolite with Ca²⁺ rather than Na⁺ favored the removal of both ammonium and phosphate because the cation exchange reaction by the NH₄ ⁺ resulted in the release of Ca²⁺ into the solution and precipitation of Ca²⁺ with PO₄ ^3? followed. An increase in the temperature elevated the immobilization of phosphate whereas it abated the removal of ammonium. Nearly 60% removal efficiency for ammonium was achieved in the neutral pH range from 5.5 to 10.5, while the increase or decrease in pH out of the neutral range lowered the adsorption. In contrast, the removal of phosphate approached 100% at a pH lower than 5.0 or higher than 9.0, and less phosphate was immobilized at neutral pH. However, there was still a narrow pH range from 9.0 to 10.5 favoring the removal of both ammonium and phosphate. It was concluded that the removal of ammonium was caused by cation exchange; the contribution of NH₃ volatilization to immobilization at alkaline conditions (up to pH level of 11.4) was limited. With respect to phosphate immobilization, the mechanism was mainly the formation of precipitate as Ca₃(PO₄)₂ within the basic pH range or as FePO₄ and AlPO₄ within acidic pH range.     

Temperature effects on accumulation and retention of radionuclides in the sea star,Asterias forbesi: implications for contaminated northern waters

Radioactive waste disposal and nuclear testing concentrated in high latitudes in the northern hemisphere have resulted in the accumulation of radionuclides in Arctic marine ecosystems, but little is known of the consequences for marine biota in these waters. Under controlled laboratory conditions in May through September 1994, we examined the bioaccumulation in sea stars, Asterias forbesi (Desor), or the radionuclides ²⁴¹Am, ⁵⁷Co and ¹³⁷Cs, all of which are important components of disposed radioactive wastes. Experiments at 2 and 12°C determined the relative importance of food (the bivalve, Macoma balthica) and water as sources of radionuclides and assessed the influence of temperature on radionuclide influx and efflux rates. The lower temperature greatly increased the retention of radionuclides ingested with food; for instance, the biological half-life (tb _1/2) of ²⁴¹Am in the sea stars was 31 d at 12°C, but was virtually infinite at 2°C. Retention of ingested ⁵⁷Co was also increased at 2°C (tb _1/2=41 d). ¹³⁷Cs was not accumulated from food. Low temperature significantly reduced net influx rates of ¹³⁷Cs from water, but did not affect net uptake of ²⁴¹Am or ⁵⁷Co. Temperature had little effect on the retention of all three isotopes obtained from the dissolved phase. These experiments suggest that extrapolation of results of previous radioecological studies, conducted at warmer temperatures, to polar or temperate winter environments may be problematic, and that nuclear waste isotopes obtained through trophic transfer may be retained far more efficiently in high latitude marine biota than by fauna from warmer ecosystems.     

Uptake of 137Cs in cultured fresh water fish (Cyprinus carpio): Physiological and histological effects

An experiment was conducted in fresh‐water fish (Cyprinus carpio) cultured, in small water tanks, artificially contaminated with radioactive ¹³⁷Cs (3000 Bq/1) to determine the uptake of ¹³⁷Cs and its physiological and histological effects in different fish organs.

It was found that ¹³⁷Cs was located in muscular tissues, gills, head muscles, liver and kidneys. Moderate amounts were found in spleen, eyes, gonads, intestine and urinary bladder. It seems that sorption was of much less importance than ingestion in the uptake of ¹³⁷Cs. The histological examination in musculature tissue, revealed an acute hyperemia with focal hemorrages which may be due to allergic effects of ¹³⁷Cs. Hyperemia and focal fatty degeneration of hepatic cells was also noted in the liver which may be due to toxic effects of ¹³⁷Cs diffused hyperemia has also occurred in the brain and focal degeneration of epithelial cells of renal tubules.     

Decrease of Pb bioavailability in solis by addition of phosphate ions

Bioavailability of Pb in contaminated soils can be highly decreased by conversion of labile Pb species into pyromorphite Pb₅(PO₄)₃Cl, induced by amendment with a phosphate source. However, PO₄ ³⁻ can be specifically adsorbed on goethite α-Fe(OH)₃ present in soils. We demonstrate that despite the stability of phosphate ions adsorbed on goethite surface, the reaction between goethite-adsorbed phosphates and aqueous lead in the presence of Cl⁻ results in crystallization of pyromorphite. Two morphological forms of pyromorphite formed on goethite were observed: 1) incrustations, indicating direct reaction of Pb and Cl ions with PO₄ ³⁻ adsorbed on goethite surface, and 2) aggregates of pyromorphite crystals indicating that the reaction with PO₄ ³⁻ ions took place in the volume of the solution. This suggests that precipitation of pyromorphite is faster than desorption of phosphates and that aqueous Pb may serve as a sink for phosphate ions by shifting the equilibrium and inducing PO₄ ³⁻ desorption.     

Influence of fertilizer and sewage sludge compost on yield and heavy metal accumulation by lettuce grown in urban soils

Previous research has demonstrated that many urban soils are enriched in Pb, Cd and Zn. Culture of vegetable crops in these soils could allow transfer of potentially toxic metals to foods. Tanya lettuce (Lactuca sativa L.) was grown in pots of five urban garden soils and one control agricultural soil to assess the effect of urban-soil metal enrichment, and the effect of soil amendments, on heavy metal uptake by garden vegetables. The amendments included NPK fertilizer, limestone, Ca(H₂PO₄)₂, and two rates of limed sewage sludge compost. Soil Cd ranged from 0.08 to 9.6 mg kg^–1; soil Zn from 38 to 3490 mg kg^–1; and soil Pb from 12 to 5210 mg kg^–1. Lettuce yield on the urban garden soils was as great as or greater than that on the control soil. Lettuce Cd, Zn and Pb concentrations increased from 0.65, 23, and 2.2 mg kg^–1 dry matter in the control soil to as high as 3.53, 422 and 37.0 mg kg^–1 on the metal-rich urban garden soils. Adding limestone or limed sewage sludge compost raised soil pH and significantly reduced lettuce Cd and Zn, while phosphate fertilizer lowered soil pH and had little effect on Zn but increased Cd concentration in lettuce. Urban garden soils caused a significant increase in lettuce leaf Pb concentration, especially on the highest Pb soil. Adding NPK fertilizer, phosphate, or sludge compost to two high Pb soils lowered lettuce Pb concentration, but adding limestone generally did not. On normally fertilized soils, Pb uptake by lettuce was not exceptionally high until soil Pb substantially exceeded 500 mg kg^–1. Comparing garden vegetables and soil as potential sources of Pb risk to children, it is clear that the risk is greater through ingestion of soil or dust than through ingestion of garden vegetables grown on the soil. Urban dwellers should obtain soil metal analyses before selecting garden locations to reduce Pb risk to their children.     

Phosphate-induced differences in stabilization efficiency for soils contaminated with lead,zinc, and cadmium

Phosphates can cost-effectively decrease the mobility of Pb in contaminated soils. However, Pb always coexists with other metals in soil, their competitive reactions with phosphates have not been tested. In this study, the abilities of KH₂PO₄, K₂HPO₄, and K₃PO₄ to stabilize Pb, Zn, and Cd in soils contaminated with a single metal or a ternary metal for different phosphorus/metal molar ratios were investigated. Results indicated that the stabilization efficiency of KH₂PO₄, K₂HPO₄, and K₃PO₄ for Pb, Zn, and Cd in single metal contaminated soil (P/M ratio 0.6) was 96.00%–98.74%, 33.76%–47.81%, and 9.50%–55.79%, respectively. Competitive stabilization occurred in the ternary system, Pb exhibited a strong competition, the stabilization efficiency of Zn and Cd reduced by 23.50%–31.64%, and 7.10%–39.26%, respectively. Pyromorphite and amorphous lead phosphate formed with excess KH₂PO₄ or K₂HPO₄ addition, while K₃PO₄ resulted in the formation of a hydroxypyromorphite precipitate. Amorphous Zn and Cd phosphates and hydroxides were the primary products. The immobilization rate of Zn and Cd depends on pH, and increased significantly in response to the excess phosphate application. This approach provides insight into phosphate-induced differences in stabilization efficiency in soils contaminated with multiple metals, which is of theoretical and engineering significance.

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Modelling of leachates from dolomitic mine tailings

The REDEQL.EPAK computer model was used to study speciation of Pb, Cd, Zn, and Ca in leachates from dolomitic Pb mine tailings. By allowing or disallowing precipitation of solids and equilibration of the modelled leachate with atmospheric C0₂, comparison of fresh and aged leachates was made. The effects of treatment of the tailings with phosphate containing fertilizer were studied through addition of P0₄ ^3– to the modelled solution. Equilibrium constants pertaining to metal ion-humic acid complexation were added to the thermodynamic data base of the model in order to study the effects of decaying plant material on tailings leachate.Initial leachate of the tailings is found to be supersaturated with Cd and Zn. Non-complexed (free) Cd²⁺ and Zn²⁺ is predicted to comprise most of the soluble form of these metals in the leachate; Pb is predicted to be present largely as PbCO₃ ion pair. Equilibration of the leachate with the atmosphere is predicted to lead to extensive precipitation of CdCO₃ and ZnSiO₃. Precipitation of Pb₅(PO₄)₃Cl is predicted at high PO₄ ^3– concentration and at low pH. Complexation by the humic acid is predicted to compete effectively with other ligands in the leachate for the metal ions. The results are compared with experimental findings.     

Distribution and behaviour of radiocaesium in Scottish freshwater loch sediments

The distribution and behaviour of radiocaesium have been studied in the sediments of two contrasting freshwater lochs: Round Loch of Glenhead, an acidified loch in south-west Scotland, with organic-rich sediments (≈20%C) and Loch Lomond, 35 km north-west of Glasgow, where sediments are low in organic matter (1–6%C, southern basin), but with a relatively high clay content. In the sediments of Scottish freshwater lochs,¹³⁷Cs [half life (t_1/2) = 30.23 yr] originates from fallout from nuclear weapons’ testing (1950s and 1960s) and from the Chernobyl reactor accident in 1986, which is also the source of the shorter-lived¹³⁴Cs [half life (t_1/2) = 2.05 yr]. Use of the characteristic¹³⁴Cs/¹³⁷Cs activity ratio of radiocaesium emitted from Chernobyl enables resolution of sedimentary radiocaesium profiles into the two component sources. In the organic-rich sediment of Round Loch, downward diffusion of radiocaesium in porewaters obscures its pattern of input to the loch. In the more clay-rich sediments of Loch Lomond, separate radiocaesium concentration peaks, related to atmospheric deposition maxima, are clearly discernible, although an influence of partial mixing is apparent. While the derived Chernobyl fallout inventory of radiocaesium in Round Loch sediments is broadly comparable with that for Loch Lomond, the corresponding weapons testing inventory is an order of magnitude lower than in Loch Lomond. Although Round Loch is situated in an area of known elevated Chernobyl deposition, the inventory is much lower than literature values of atmospheric deposition, indicating significant loss of radiocaesium from this loch. The weapons testing inventory in Round Loch is also lower than reported estimates, whereas in Loch Lomond the established inventories from both sources are similar to, or greater than, fallout deposition. The differences between the distribution and inventories in the two lakes confirms that radiocaesium is much less efficiently bound and is correspondingly much more mobile in the organic sediments of Round Loch of Glenhead than in the more clay-rich sediments of Loch Lomond.     

Synthetischer Crandallit

Crandallite (Ca,Sr) Al₃ (PO₄)₂ (OH)₅ · H₂O crystallizes in the alunitecrystal lattice. Because of its open structure, the cations Ca²⁺, Sr²⁺, and Al³⁺ can be replaced by various elements depending on their diadochial properties; the element entering into the crystal network thus becomes immobilized. Artificial amorphous crandallite has been shown to eliminate the heavy metal ions: Pb²⁺>>Cu²⁺>Hg²⁺>>Cd²⁺ from contamined water in the presence of lateritic phosphates. Pb²⁺ could be removed nearly quantitatively in all cases.     

Geochemical Associations of Sellafield-Derived Radionuclides in Saltmarsh Deposits of the Solway Firth

This paper describes a study of the geochemical associations of Sellafield waste radionuclides in saltmarsh sediments from south-west s]Scotland. The contaminant radionuclides are transported to this environment in association with particulate material and ¹³⁷Cs was found to be predominantly (80-98%) non-extractable. In the case of ^239+240Pu there was a redistribution from the oxalate extractable oxide fraction to the pyrophosphate extractable organic fraction as a consequence of on-shore transfer of contaminated sediment. The relatively aggressive nature of the chemical extractants required to remove the radionuclides from the sediments suggests that they were in a form which was unlikely to result in their being released into the aquatic environment or taken up by plants. Plutonium had a greater potential mobility or bioavailability than Cs. Values of K^D for the desorption of ¹³⁷Cs from the sediment by freshwater, groundwater and seawater were all approximately 10⁵ L kg^-1, confirming its immobility in this environment. The desorption K_D values for stable ¹³³Cs were all approximately 10⁶ L kg^-1, so the stable Cs did not have a significant influence on the radiocaesium in this sediment.     

Cs-137 contamination in forest ecosystems in southwest Rila Mountain, Bulgaria

We studied Cs-137 contamination and radionuclide transfer in mountain forest ecosystems from Bulgaria. Here we show the first analyses of Cs-137 soil-to-plant transfer and we assess that it depends on the soil organic matter content and the specifics of the tree species. The forest litter is strong polluted with Cs-137 and is a barrier for its migration. In the upper 0-5 cm of the soil the Cs content ranges from 52 to 81 Bq kg^–1 then decreases in deeper layers. The 1-year-old needles of spruce, fir, and Scots pine accumulate more cesium than the fine roots. The values of the needles transfer factor range between 0.3 and 0.58. The fine roots transfer factor varies between 0.1 and 0.32.     

Etude de la décontamination d'Arenicola marina (annélide,polychète) après contamination expérimentale par le caesium 137 ou le cobalt 60

From a nuclear protection standpoint, problems of decontamination are of great interest. In Arenicola marina L. a comparative study has been made on the elimination of two radionuclides, the metabolic functions of which are very different: ¹³⁷Cs and ⁶⁰Co. After experimental contamination with ¹³⁷Cs, significant decontamination is possible; however, elimination of ¹³⁷Cs accumulated in muscles is very slow. The elimination of ⁶⁰Co is very slow; its biological half-life in A. marina is about 3 months.     

Release,deposition and elimination of radiocesium (137Cs) in the terrestrial environment

Radionuclide contamination in terrestrial ecosystems has reached a dangerous level. The major artificial radionuclide present in the environment is ¹³⁷Cs, which is released as a result of weapon production related to atomic projects, accidental explosions of nuclear power plants and other sources, such as reactors, evaporation ponds, liquid storage tanks, and burial grounds. The release of potentially hazardous radionuclides (radiocesium) in recent years has provided the opportunity to conduct multidisciplinary studies on their fate and transport. Radiocesium’s high fission yield and ease of detection made it a prime candidate for early radio-ecological investigations. The facility setting provides a diverse background for the improved understanding of various factors that contribute toward the fate and transfer of radionuclides in the terrestrial ecosystem. In this review, we summarize the significant environmental radiocesium transfer factors to determine the damaging effects of radiocesium on terrestrial ecosystem. It has been found that ¹³⁷Cs can trace the transport of other radionuclides that have a high affinity for binding to soil particles (silts and clays). Possible remedial methods are also discussed for contaminated terrestrial systems. This review will serve as a guideline for future studies of the fate and transport of ¹³⁷Cs in terrestrial environments in the wake of the Fukushima Nuclear Power Plant disaster in 2011.