Cord decontamination process

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... 

The required volume of ion exchange resins depends strongly on the concentrations of chelate-forming chemicals (dicarboxylic acids) still present in the solution. The most efficient way of minimizing these residual concentrations is oxy-pho-tolytic decomposition, as it is performed in the Cord/UV process (Bertholdt and Wille, 1994), in which the spent decontamination solution is irradiated by an intense UV source. With this technique, the volume of consumed resins is considerably smaller than it is in processes employing chemical decomposition techniques. 

Bertholdt, H.-O., Wille, H. Field experience with full system decontamination at Oskars-hamn 1 and Loviisa 2 with the Cord/UV process. Paper presented at the Suppliers Seminar during the European Nuclear Conf. ENC 94, Lyon, France, 1994... 

Figure 4.54. Amda installation for decontamination of sub-systems using the Cord process (By courtesy of Siemens/KWU)...

As an example of the decontamination of subsystems, the treatment of a BWR recirculation loop and, in addition, parts of the residual heat removal system and the reactor water cleanup system, by using the Cord process in parallel to the... 

Table 4.15. BWR reactor water cleanup system decontaminations using the Cord process (1990-1993)...

The Cord process is especially suited for the decontamination of PWR and BWR full primary systems. Detailed investigations (Wille and Bertholdt, 1989) have shown optimum materials compatibility with the solvents to be applied. Calculations showed that using the volume control system of the plant and the connected auxiliary systems, the time required for one decontamination cycle depends on the capacity of the purification system at a purification rate of 15% of the primary loop volume per hour, 24 hours are required. Heating of the entire loop can be achieved by running the main coolant pumps. As the reagents used for the oxidation step are chemically reduced, no time is lost with ion exchange, and a purification step by ion exchange is required only at the end of the decontamination step. For the decontamination of Siemens PWR primary loops, no external equipment is required while the installed capacities in other PWRs and BWRs are... 

Wille, H., Sato, Y. Field experience of chemical decontamination and waste reduction with the Cord process. Paper presented at the Intemat. Conf. Chemistry in Water Reactors — Operating Experience and New Developments. Nice, France, 1994... 

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