Removal of surface layer of concrete by a pulse-periodical discharge

To clean concrete (e.g., floor) contaminated by hazardous chemicals or radionuclides, its surface layer has to be removed. In our experiments and large area trials, 0.5 cm to 3 cm thick concrete layers have been removed either by the shock waves and cavitation initiated in water by a discharge or by a direct breakdown through concrete. The discharge mode is defined by the PFN design and operation parameters. In both cases, the spark discharge took place between two parallel linear electrodes. Concrete is crushed and spalled by a series of tens or hundreds of pulses following at 2 to 20 Hz frequency. Discharge through water follows breakdown at 20-30 kV, and effective concrete layer removal takes place for 30-50 kA, 20-40 /spl mu/s current pulses. Consumption of capacitance-stored energy is about 1.5 kJ per 1 cm/sup 3/ of concrete. Discharge through concrete requires much higher (100-150 kV) voltage, but only a few kA current amplitude of a 3 to 5 /spl mu/s pulse is required. In this case, energy consumption is lower-about 0.8 kJ/cm/sup 3/. The presentation provides a description of the prototype industrial unit, results of trial runs, energetic characteristics and decontamination quality.