Leveraging lasers9 January 2018
Laser cutting technologies offer huge potential for nuclear decommissioning. Work is currently underway to utilise the technique for cutting fuel debris at Fukushima Daiichi
ONET Technologies was chosen in 2011 by France’s Alternative Energies and Atomic Energy Commission (CEA) to design, build and operate the dismantling and waste treatment system used in decommissioning two fuel reprocessing dissolvers at Marcoule in France. The period is 2011 – 2022, requiring 15000 hours of engineering studies to manage 11t of primary waste and 60t of secondary waste. This project involves deploying remote equipment and tools, including laser cutting (CEA patented technology), to decommission two highly radioactive dissolvers and treat all the resulting waste.
In December 2016, ONET Technologies started operations ahead of schedule, using the Cybernetix Maestro manipulator (also developed by CEA). It used laser cutting of the dissolvers. The cutting phase is now reaching its end, with the final elements of the dissolvers finished at the end of July. These operations are increasing ONET’s field experience in complex remote handling with the constraints of maintenance, management of contamination and fumes, safety etc.
When the cutting phase is finished, the cut pieces will be removed. Every single piece of waste will be characterised, prior to being packed into concrete boxes. Decontamination tasks will then be implemented in the cell (still by remote means) prior to the final stage of decommissioning, when person-access will be permitted. In parallel with these final tasks, preparatory works will start on the second dissolver, to enable decommissioning to begin using the same system of a remote manipulator, laser, tools and waste treatment system. This should start in 2019.
Mitsubishi Research Institute selected its first project in 2014, which was in the fuel debris retrieval project at Fukushima Daiichi. It was based on R&D developments led by CEA in dismantling and severe accident simulation, on IRSN skills in airborne measurement and on the experience of ONET Technologies. This project is now in its third phase, and it is part of the Japanese national project for development of new technologies in the following topics:
- Laser cutting performance on simulated fuel debris in air and underwater,
- Fuel debris simulants development, production and characterisation,
- Dust and fumes measurement, characterisation and collection in air and underwater.
Following the positive results obtained in 2016, the French team led by ONET started a third phase of the project in April 2017. It is planned to run until March 2019. The main objectives are:
- Increase the level of maturity of underwater cutting technology (up to 5m depth) and non-emerging cutting technology (as massive blocks of fuel debris are expected to be found),
- Develop dust and fume collection technologies to recover secondary outlets that will be generated during laser cutting in air or underwater and enable them to be treated.