Waste volume reduction using surface characterization and decontamination by laser ablation. 1998 annual progress report

'Much of the contaminated concrete from nuclear facilities contains radionuclides only in the near surface region. Removal of the contaminated layer would greatly reduce the volume of waste requiring storage. The objectives of this research are to understand the depth-dependent concentration and chemistry of radionuclide-contaminated concrete surfaces, to determine the mechanism and efficacy of laser ablation in removing contaminated surface layers, and to chemically and physically characterize the captured ablation effluent which would become the stored waste. This report summarizes work from the first eight months of a three-year project. Samples consisted of specimens of non-contaminated high density concrete from the Experimental Boiling Water Reactor at Argonne National Laboratory (sectioned into small coupons) and samples cast in the laboratory using Type 1 Portland cement and either silica, alumina, or sand. Some samples of concrete and cement were doped with Cs-133. Ablation experiments were done with a 1.6 kW pulsed Nd:YAG laser. The beam was delivered via a fiber optic cable, focused to a 0.5 \265m spot, and rastered across the surface. The ablated material was collected with a vacuum shroud system and captured on a 0.2 micron filter. Virgin and ablated surfaces were chemically analyzed with laser desorption surface mass spectrometry.