Alexander P. Murray

A chemical decontamination process for decontaminating and decommissioning nuclear reactors

Five chemical decontamination processes have been developed for nuclear reactor applications. One of these processes is the cerium decontamination process (CDP). This method uses a cerium acid reagent to rapidly decontaminate surfaces, obtaining decontamination factors in excess of 300 in 6 h on pressurized water reactor specimens. Sound volume reduction and waste management techniques have been demonstrated, and solidified waste volume fractions as low as 9% experimentally obtained. The CDP method represents the hybrid decontamination technique often sought for component replacement and decommissioning operations: high effectiveness, rapid kinetics, simple waste treatment, and a low solidified waste volume.

Dilute Chemical Decontamination Process for Pressurized and Boiling Water Reactor Applications

Westinghouse Electric Corporation (WEC) has developed five chemical processes for nuclear decontamination, based on extensive experimental testing using radioactive pressurized water reactor (PWR) and boiling water reactor (BWR) samples. The dilute chemical decontamination process offers the best combination of effectiveness, low corrosion, low waste volume, and fast field implementation time. This is an alternating multistep process. For PWRs, an oxidation treatment is necessary. Projected contact decontamination factors (DFs) are about 50 on plant Inconel surfaces, with comparable results on stainless steel. Actual test DFs have exceeded 500 in the process test loop. For BWRs, an oxidation step is unnecessary, but very beneficial. DFs of 10 to 20 are achieved without an oxidation treatment. Full process DFs exceed 500 when the oxidation treatment is included. Low corrosion rates are observed, without any adverse effects. Only solid waste is produced by the process. WEC has fabricated a trailer-mounted application system for this process, and is offering it as a decontamination service to commercial customers.

Mathematical modeling of the chemical decontamination of boiling water reactor components

An analytical model has been derived for the chemical decontamination of boiling water reactor primary systems and components. The model results in a complex, hyperbolic function expression that simplifies to two limiting conditions: boundary layer mass transfer and oxide film reaction control. The latter produces an exponential activity decrease with time, in agreement with the presented data and a previous phenomenological model. Gross rate constants of 0.71 to 1.1 and 0.12 to 0.16 h/sup -1/ are calculated for the dilute chemical decontamination process at 121 and 95/sup 0/C, respectively, with an activation energy of 20 kcal/mol. The model indicates that flow effects are relatively unimportant. Other processes should follow this model, but have different rate constants. Future decontamination efforts should incorporate field/activity measurements with time and specimen surface area measurements into the experimental plan for model verification and a better elucidation of the decontamination phenomena.