Reactor full systems, decontamination

Table 4.16. Summary of reactor full-system decontaminations (By courtesy of Siemens/KWU)...

Other full-system decontaminations (e. g. of the Steam Generating Heavy Water Reactor) have been performed using the Rjrco reagent or the Lomi process with and without the NP pretreatment step. The results of these operations were satisfactory as regards decontamination factors and materials compatibility at the circuit surfaces, as well as at the fuel assemblies. 

Although the results obtained in full-system decontaminations at Candu plants as well as at the SGHWR reactor proved to be encouraging, there are sufficient... 

Aspden, R. G., Grand, T. E PWR full-reactor coolant system decontamination. Materials evaluation after three cycles of exposure to the LOMI decontamination process. Report EPRI NP-75I2-M (1991)... 

O Boyle, D. R., Walschot, F. W., Ocken, H., Wood, C. J. Recent developments in full-system decontamination. Proc. 5. BNES Conf. Water Chemistry of Nuclear Reactor Systems, Bournemouth, UK, 1989, Vol. 1, p. 159-162... 

In the past years a large number of decontaminations have been carried out, most of them in nuclear power plants in the USA, with the fields of application ranging from components which have been removed from the primary circuit to subsystems and to full reactor primary systems. In the following section only a few examples will be cited with special respect to the procedures applied a more detailed survey of decontamination applications in water-cooled reactors was given by the IAEA (1994 a). 

One of many sequencing batch reactor (SBR) processes developed by Wang, Kurylko, and Wang in 1994 (125) is a physicochemical sequencing batch reactor adsorptive bubble separation (SBR-ABS) process, which can be used for potable water purification, industrial water treatment, wastewater effluent treatment, and groundwater decontamination (126). There are various types of SBR-ABS systems (a) physicochemical SBR flotation, (b) physicochemical SBR fractionation, (c) biological SBR flotation (2,3,4). The physicochemical SBR flotation has been used successfully in full-scale operation in Europe (123). 

A further development of the Mopac process led to the KWU Cord process (Chemical—Oxidation—Reduction-Decontamination), a multi-cycle, low-concentration process which proved to be especially suitable for the decontamination of subsystems and full reactor systems (Wille and Sato, 1994). The principles of this process are shown in Fig. 4.52. A CoRD decontamination cycle starts with an oxidation step, using a dilute solution of permanganic acid the excess Mn04 is then reduced by addition of a dicarboxylic acid, thereby generating CO2. By further addition of the dicarboxylic acid up to a concentration of about 0.2%, dissolution of the oxides starts and the metal ions are retained in the solution as complex compounds. The whole process is conducted at about 95 C it does not require a fixed number of cycles, but can be repeated according to the final radiation dose... 

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