As an ever-growing number of nuclear power plants reach the end of their lifetime, their decommissioning is increasingly being brought into focus. Additionally, political programmes, such as the nuclear phase-out in Germany that will be completed by the end of 2022, are increasing the number of nuclear power plants that require dismantling. Germany’s phase-out programme affects 23 nuclear power plants in total, with the decommissioning of 17 of them already underway1. Worldwide there are 442 active nuclear power plants, while an additional 54 are under construction and 119 more are planned2. Taking into account these numbers, the dismantling of nuclear power plants will clearly continue to be a topic of concern for the foreseeable future. Therefore, with the increasing number of facilities requiring dismantlement, the need for optimised deconstruction technologies arises. In nuclear decommissioning, dismantlement often takes place as soon as a plant shuts down to reduce any risk of contamination. Separation work takes place in the remaining cooling water of the reactor. Several tools and processes such as saw cutting, water jet cutting or plasma cutting are currently used in this field, with each of them having their own advantages and disadvantages. The main disadvantage of these existing methods, especially saw and water jet cutting, is the generation of secondary waste that then needs to be filtered out of the water. In addition, in the case of water jet cutting, a considerable amount of abrasive material is added, which must also be stored. To overcome this drawback, a project has been carried out at the Laser Zentrum Hannover (LZH) to study the feasibility of using laser cutting under water to minimise secondary waste production.