Deep gouging development of deep blind kerf laser cutting technology for FUKUSHIMA fuel debris retrieval
Résumé
As a part of international calls for projects for Fukushima for fuels debris retrieval (Request For Proposal (RFP) for Conceptual Study of Innovative Approach for Fuel Debris Retrieval and Feasibility Study of Essential Technologies), the Japanese government is funding projects led by industrial companies it has selected. In this frame and since 2014, CEA, in collaboration with ONET Technologies and IRSN has performed several assessments on laser cutting process feasibility and performances for dismantling and FUKUSHIMA fuel debris retrieval. The applicability of laser process cutting to corium has been assessed under several conditions, namely in air, under water, in through-thickness-cutting conditions and gouging conditions. Indeed, in through-thickness conditions a fibre laser beam affects the work piece surface with sufficient energy to melt the material, which is ejected through the kerf from a gas-jet coaxial to the laser beam. When the piece is too thick or when it lays on a support which can not be cut, molten material can not be ejected through the kerf in the laser beam direction and special tools and cutting strategies must be employed. Specific tools and strategies have been developed, optimized (e.g. in terms of robustness and reliability) and implemented at CEA in order to adapt laser cutting process to FUKUSHIMA fuel debris retrieval specificities. This paper presents proposed solutions and main cutting results obtained in conditions representative of in site conditions deep gouging (more than 40 mm thickness in one pass), edge or bulk (in the middle of the work piece) start/stop cutting, not plane surface (relief variation) cutting, sensitivity to position, inclination,