Electrochemical decontamination

DeFlaun, M. F. and Condee, C. W. (1997) Electrokinetic Transport of Bacteria f Journal of Hazardous Materials, Special Edition on Electrochemical Decontamination of Soil and Water, Edited by Yalcin B. Acar and AkramN. Alshawabkeh, pp. 263-278. 

Halogenated organics are usually toxic, and their electroreduction can make them easily biodegradable. This is also a common goal in the electrochemical decontamination of organic pollutants in wastewaters by anodic oxidation. Although modern processes have seriously reduced the operation... 

Boye, B., Brillas, E., Marselli, B., Michaud, P.-A., Comninellis, Ch. and Dieng, M.M. (2004) Electrochemical decontamination of waters by advanced oxidation processes (AOPS) Case of the mineralization of 2,4,5-T on BDD electrode. Bull. Chem. Soc. Ethiop. 18, 205-214. 

Porta, A. and Kulhanek, A. (1986) Process for the electrochemical decontamination of water polluted by pathogenic germs with peroxide formed in situ. US Patent No. 4.619.745. 

Haran BS, Zheng G, Popov BN, White RE. (1995). Electrochemical decontamination of soils development of a new electrochemical method for decontamination of hexavalent chromium from sand. Proceedings of the Electrochemical Society 12 227-251. 

As was described in the preceding section, the chemical decontamination processes result in a chemical dissolution of the oxide contamination layers present on the surfaces of the materials. In contrast, the electrochemical decontamination procedures are based on the anodic dissolution of a thin surface layer of the base material, as a consequence of which the oxide layer is peeled off from the surfaces of the materials. As a prerequisite for successful application, the electrolyte used has to be in electrical contact with the base material. Basically, the oxide layers are electrical insulators, but their porosity is usually large enough to ensure a sufficiently high electrical conductivity. On some occasions, very tight Fe203 layers have been observed in BWR circuits which rendered the direct application of the... 

Figure 4.53. Techniques of electrochemical decontamination (By courtesy of Siemens/KWU)...

In the practical application of electrochemical decontamination procedures, different electrode arrangements are possible, depending on the geometric form of the component to be treated. Two basic possibilities, namely the bath (or immersion) technique and the in-situ technique, are schematically shown in Fig. 4.53. When the bath technique is used, which is mainly applicable for disassembled parts with... 

Leuchte, H. W., Stenersen, F., Steringer, A. Development and optimization of an easy-to-process electrolyte for electrochemical decontamination of stainless steel components. Proc. CEC 3. Internat. Conf. on Decommissioning of Nuclear Installations, Luxembourg 1994, p. 312-324... 

Hungary Pavlik, 0. Institute of Isotopes of the Hungarian Academy of Sciences Electrochemical decontamination for the main pipeline of the primary circuit by movable cathode... 

ELECTROCHEMICAL DECONTAMINATION FOR THE MAIN PIPELINE OF THE PRIMARY CIRCUIT BY MOVABLE CATHODE... 

Electrochemical decontamination is the reverse procedure of electroplating. The upper oxide-layers containing the contaminants can be removed from the metal surface using a direct electric current between the workpiece and a cathode in an electrolyte. The method can be applied by immersing the workpiece to be decontaminated in an electrolyte tank as an anode. 

Electrochemical decontamination by movable cathode has been used since the beginning of the operation of the first reactor unit. 

Fig. 2. Electrochemical decontamination for the main circulating pump case... 

Fig.4 Electrochemical decontamination for the case of the main gate valve... 

The advantages of the remotely operated electrochemical decontamination procedure are as follows ... 

Considering the obtained results with the electrochemical decontamination technology, the development of the procedure has been extended for the decontamination of the main pipeline of the primary circuit. 

The electrochemical decontamination procedures developed so far use strong acides - pH l - as electrolytes, which would cause corrosion on the metal surface if they can not be removed in a short time. Therefore the following criteria were established. 

Decontamination during decommissioning of nuclear facility is used to minimize radiation exposure of personnel and public, to recover of metals and to reduction of radwaste amount to be disposed of. For obtaining of maximal benefits decontamination processes should be optimized. Results and activities related to development and optimization of chemical and electrochemical decontamination of metals from NPP A-1 are summarized in the paper. 

Laboratory experiments for preliminary selection of electrolytes (except H3PO4) and current flows (anodic, cathodic and alternating) for electrochemical decontamination of steels for unrestricted release. Verification of the process under pilot plant condition. 

Design, manufacturing and testing of appropriate equipment for pilot plant verification of the chemical decontamination combined with ultrasound and the electrochemical decontamination. 

The results of electrochemical decontamination of carbon steel proved that this type of decontamination can be effectively used to clean for free release chemically unsuccessfully decontaminated materials. Only small differences in time required for complete decontamination of material were observed by different polarisation of material. Efficiency of the process may be improved by short anodic polarization before the decontamination is completed. Combination of electrochemical decontamination and mechanical effect improves the efficiency of the process. 

Electrochemical decontamination of carbon steel in the electrolyte based on citric and sulphuric acids with additives... 

Solla-GuHon, J., Montiel, V., Aldaz, A. and Clavilier, J. (2003) Synthesis and electrochemical decontamination of platinum-palladium nanopartides prepared by water-in-oil microemulsion. Journal of the Electrochemical Society, 150, E104. 

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