The feasibility of underwater cutting with a CO2 laser has been demonstrated under 0.5 m of water, using a pressurized oxygene jet to eliminate the water between focusing nozzle and the piece to be cut. The laser beam can therefore interact with the piece without obstruction. The research work aims at demonstrating this technique under 10 m of water with a view to its application for PWRs.
The work includes the determination and optimization of the relevant cutting parameters (eg, power, maximum cutting depth, cutting speed) under various water depth on nonactive stainless steel components and the establishment of a data base specific to underwater cutting.
CEA developed laser systems for dismantling tasks in the framework of the previous Community research programme (contract FI1D-0013). Radius Engineering is working on powerful laser systems (up to 5 kW).
As laser cutting gives very small and proper kerves, a substantial reduction of swarfs and aerosols can be expected compared with other thermal cutting techniques.
The feasibility of underwater cutting with a carbon dioxide laser has been demonstrated under 0.5 m of water, using a pressurized oxygen jet to eliminate the water between focusing nozzle and the piece to be cut. The laser beam can therefore interact with the piece without obstruction. The research work aims at demonstrating this technique under 10 m of water with a view to its application for pressurized water reactors (PWR).
The experimental setup for underwater cutting must correspond to the criteria of pression (10 metres water column) and distance from the cutting head to the laser source. To meet these boundary conditions, the experiment was set up across different floors of the building. The 500 W carbon dioxide laser is installed on the second floor. The experimentation vessel and control cabinet of the laser are located on ground level. The first tests have run with this configuration.
Initially, the work mainly involved mechanical design problems:
preparing the experimental site;
designing the watertight cutting head;
installing these devices on site.
Preliminary cutting test have been run under 0.5 m water and have been compared with cuts realized under ambient conditions on thin plates of stainless steel.
1. Conception of an underwater laser head able to cut up to 10 mm of stainless steel and being easily replaceable
2. Manufacturing of a 3 kW CO2 laser head specified in 1.
3. Mechanical and optical testing of the laser head in air up to 1.5 kW with subsequent conceptual adaptations, if any.
4. Manufacturing of the experimental device including water basin of 10 m depth and aerosol recuperation
5. Functional underwater cutting tests (little water depth)
6. Cutting under 10 m water (same programme as in 5.)
7. Development of the remote system to control the alignment between laser head and piece to be cut.
8. Computer-assisted optimization tests with respect to main cutting parameters (eg, laser power, cutting speed, gas pressure and quantity, kerf width, effluent generation) for stainless steel plates of 5 to 40 mm thickness
9. Evaluation of effluent generation with respect to the tests in 8
10. Establishment of a specification document for the laser system as well as for the cutting technique
11. Evaluation of the safety, costs and radiological impact of the technique including cost of equipment and cost per one meter of cut work.
Funding SchemeCSC - Cost-sharing contracts