Laser decontamination of epoxy painted concrete surfaces in nuclear plants

Laser technology offers an efficient decontamination of surfaces contaminated by polychlorinated biphenyls (PCB) by precise application of highly focused laser beam power. In the context of nuclear decommissioning all walls and floors of a reactor building have to be cleaned from chemical-toxic substances. State of the art is a manual and mechanic ablation and a subsequent treatment in a hazardous waste incinerator. In this study, alternatively, a laser-based system exhibiting, decontamination rates of up to 6.4 m(2)/h has been operated using a 10 kW diode laser in continuous wave (CW) mode with a spot size of 45 x 10 mm(2) and a wavelength of 980-1030 nm. The system allows a rapid heating of the surfaces up to temperatures of more than 1000 degrees C leading to ablation and thermal decomposition of PCB in one process step. Thermal quenching prevents formation of polychlorinated dioxines (PCDD) and polychlorinate furans (PCDF) in the flue gas. Additionally, an in situ measurement system based on laser induced fluorescence (LIF) is developed to monitor the thermal decomposition of PCB. For initial experiments samples covered with epoxy paint were used to evaluate the process and to carry out finite element based simulations. In this paper, experimental results of ablation tests by laser irradiation of epoxy painted concrete are presented and discussed. (C) 2013 Elsevier Ltd. All rights reserved.