Laser-Based Cutting of Contaminated Concrete

A number of laser-based techniques applicable to nuclear decontamination and decommissioning have emerged from LPRC-UMIST and BNFL research projects. The most recent process is deep-section concrete cutting, which promises to yield cutting depths of 1 m and beyond, and which affords very easy waste containment. This paper reports work in deep-section concrete cutting effected by layer-by-layer laser melting of the concrete with mechanical removal of the vitrified dross between passes. It is particularly suited to radioactive substrates where containment of the waste stream is imperative. Slightly higher power densities than e.g. for laser scabbling are required for this application. A comparison of experimental results using high-power CO₂ (10.6 μm) and diode (0.808 + 0.940 μm ) lasers under roughly equivalent experimental conditions, cutting to depths of >100 mm, is presented. A marked improvement in cutting depth per pass is observed for the case of the diode laser. The increased cutting rate is rationalised in terms of the combined effects of coupling efficiency and beam shape. Pertinent features of the effluent are discussed.