The effect of heat flux on fume generation in laser cutting for nuclear decommissioning

Laser cutting offers unique productivity improvements to the demanding environment of nuclear decommissioning compared to typical industry applications. However, the aerosols generated through liquid breakdown and evaporation present a challenge to in-situ extraction and filtering processes. This paper analyses the influence of heat flux within the cut-front on the quantity and distribution of fume produced. Two methods of altering the heat input have been investigated: the reactivity of the cutting assist gas and the rate of beam progression within the cut. Quantification of these interactions is, so far, lacking in the scientific literature. 3 mm 304 Stainless Steel samples were cut using a 1 kW Fibre laser. The fume was captured using a bespoke extraction system designed to ensure reliable fume sampling. A Static Light Scattering approach, using a TSI OPS 3330, was then used for concentration and dimensional fume quantification. As expected, there is a larger concentration of fume when cutting with oxygen compared to nitrogen. The influence of increased heat flux was also observed by changing the beam progression rate, which additionally altered the particle size distribution of the fume. The results demonstrate how the net heat flux from these two factors can influence the conditions within the kerf, such as melt-thickness and edge profile, which subsequently affect the particle generation processes. Further research on these preliminary findings is needed to understand the role of evaporative and liquid-atomization processes in fume generation.