Cesium Decontamination

Keywords Cesium decontamination. Sea sludge. Microbial activity, Anaerobic condition... 

An anaerobic condition was unsuccessful for cesium decontamination fi om sea sludge. Microorganisms activation was seemingly realized, but expected decontaminating effects were not observed. A hypothesis for attaining the maximal decontamination based on microorganisms activator was thus dismissed. Since a similar experiment with use of micro-bubbles has been successfully carried out, an optimum aerobic condition is to be investigated with another hypothesis based on hydroxyl radical in consideration. 

Kaminski, M.D. Nunez, L. Cesium extraction from a novel chemical decontamination process solvent using magnetic microparticles, Sep. Sci. Technol. 37 (2002) 3703-3714. 

Bibler, J. P., Wallace, R. M., and Bray, L. A. Testing a New Cesium-Specific Ion Exchange Resin for Decontamination of Alkaline High-Activity Waste, Report WSRC-RP-89, Westinghouse Savannah River Co., Aiken, SC, 1989. 

Prussian blue Fe4[Fe(CN)6]3 can bind cesium therefore it is used in clinical practice as an antidote for the treatment of humans contaminated with radioactive cesium (see also Section 3.6.4). CUnical use of ferric ferrocyanide in doses up to 20 g d for decontaminations of persons exposed to radiocesium has not been associated with any reported toxicity [3.201]. 

The main contributors to the radioactivity of the effluent were Cs-137, Cs-134, and Ru-106. Most of the radioactivity from the low-level radioactive effluents could be removed by ED. Greater DF was achieved for cesium than for rathenium due to the nonionic nature of the latter [12]. The degree of decontamination increased with the number of electrodialysis stages performed. Salt content and radionuclide concentration did not have any marked influence on the decontamination factors of these nuclides [7]. The concentrate streams generated during electrodialysis contained 0.005-0.05 mCi/L of Cs-137, and the VRF achieved in the electrodialysis operation was ca. 10. 

In the nonradioactive studies, the decontamination factors for Na+, K+, and Rb+ increased with increasing cesium loading (Table III) for... 

The deposition of fission products on primary circuit surfaces and, in particular, on the reformer tube walls causes difficulties during maintenance and catalyst refilling procedures, if the activity is intolerably high. Cesium and silver isotopes released during reactor operation are of major concern. Particularly silver diffuses easily out of the fuel elements at operating temperature conditions into the coolant and migrates easily into metal surfaces and is difficult to remove in decontamination operations [32]. 

Examples of substances with significant potentiai for secondary contamination and requiring aggressive decontamination and protection of downstream personnel include potent organophosphoms insecticides, oily nitro compounds, and highly radioactive compounds such as cesium or plutonium. 

There are assessments predicting the use of RO for the processing of the wastes from medical application [48,49] and for the removal of cesium-137 from decontamination wastes after accident in the steel production factory [50], RO is considered as a method for removal of radioactive pollutants from contaminated water (removal of Cs and °Sr) in the vicinity of atomic power plants [51] as well as for removal of small quantities of radionuclides ( Rn, Ra)... 

L.N. Oji, K.B. Martin, D.T. Hobbs, Development of prototype titanate ion exchange loaded-membranes for strontium, cesium and actinide decontamination from aqueous media, J. Radioanal. Nucl. Chem. 279(3), 2009, 847-854. 

CEA Cadarache and seven European universities were involved in a research programme to synthesize and test new macrocyclic extractants (crown-ethers and calixarenes). The main aim of this study was to selectively remove caesium, strontium and actinides from medium level liquid waste (MLLW) to decontaminate them to the extent that they can be disposed of in a near surface site. A new calixarene has been synthesized by the University of Parma, which has a cesium/sodium selectivity 100 times higher than that of the best current extractant for cesium. The large selectivity of this molecule has been explained theoretically. The results obtained for cesium extraction from simulated MLLW have been confirmed with real HLLW. Finally, new functionalized calixarenes have been also synthesized, which are more selective to actinides and lanthanides than the best extractant available on the market. 

Kaneka Corp., a Japanese chemical company has established an efficient radioactive decontamination strategy by using their biosurfactant, called Kaneka Surfactin, which is composed of surfactin. They successfully carried out decontamination of areas affected by the Fukushima No. 1 nuclear power plant disaster. Efficient surface and detergent activity of surfactin make it eliminates radioactive cesium and other contaminants from the polluted area. Strategy adopted by Kaneka Corp. for radioactive decontamination of roads using surfactin solution is shown in Figure 14.8. 

In the case when defective fuel rods are present in the reactor core, the BWR reactor water contains the other fission products and the activation products released from the fuel in concentrations well below those of fission product iodine. This applies as well for fission product cesium, which is retained on the ion exchangers of the reactor water cleanup system with a decontamination factor of about 100. As far as it is known, cesium in the reactor water is present as the Cs ion, whereas large proportions of most of the polyvalent fission products and of the actinides are attached to the corrosion product particles suspended in the water as yet, there is no detailed knowledge on the chemical state of these elements (i. e., adsorbed to the surfaces or incorporated into the Fe203 lattice). It was reported that the strontium isotopes as well as Np appear in the reactor water in the dissolved cationic state, while Tc was found in the reactor water as a dissolved anionic species, most likely Tc04 (Lin and Holloway, 1972). According to James (1988), discrete fuel particles were not detected in the BWR reactor water. 

Vicens and coworkers (Chapter 26) report the use of novel calix-fcw-crown ether compounds as carriers in a supported liquid membrane system for the removal of cesium from nuclear waste water. Decontamination factors of greater than 20 are obtained in the treatment of synthetic acidic radioactive wastes. Very good stability (over 50 days) and high decontamination yields are achieved. 

Calix[4]-W5-crowns 1-7 are used as selective cesium-carriers in supported liquid membranes (SLMs). Application of the D esi diffusional model allows the transport isotherms of trace level Cs through SLMs (containing calix[4]-6/5-crowns) to be determined as a function of the ionic concentration of the aqueous feed solutions. Compound 5 appears to be much more efficient than mixtures of crown ethers and acidic exchangers, especially in very acidic media. Decontamination factors greater than 20 are obtained in the treatment of synthetic acidic radioactive wastes. Permeability coefficient measurements are conducted for repetitive transport experiments in order to determine the SMLs stability with time. Very good results (over 50 days of stability) and high decontamination yields are observed with l,3-calfac[4]-Aw-crowns 5 and 6. 

Decontamination of Radioactive Cesium from Sea Sludge Using Microbial Activity... 

Removal of cesium from seafloor sludge under anaerobic conditions was intended in the present study as a means of decontaminating the marine environment. The reason for the choice of anaerobic conditions was that purification of organic nutrient salts in sea sludge had been aerobically attained by activation of microorganisms in a previous study [2]. A new method of decontamination will be suggested here referring to two previous studies. 

The other one suggested potential of an aerobic decontamination for decontamination of cesium from sludge [4]. Three different experimental conditions were compared micro bubbles and water flow (Case 1), water flow only (Case 2) and neither (Case 3). The amount of cesium eluted from sludge was there estimated from the increase of the concentration of cesium in water. The best results were reported for Case 1 which decontaminated approximately 20% of cesium in sea sludge. Neither Case 2 nor Case 3 showed any decontamination of cesium. 

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