Laser cutting of steel plates up to 100 mm in thickness with a 6-kW fiber laser for application to dismantling of nuclear facilities

•A cutting study with a high power ytterbium-doped fiber laser was conducted for application to dismantling of nuclear facilities.•Stainless steel and carbon steel plates of various thicknesses were cut at a laser power of 6-kW.•Despite the use of a low output of 6-kW, the cutting was successful for both stainless steel and carbon steel plates up to 100 mm in thickness.•The cutting capability was ∼16.7 mm by kW which is much higher than commonly known value, and the maximum cutting speeds were faster for the same thicknesses than those from other groups.