Wet sieving and magnetic separation of grain mixtures to minimize secondary waste in the decommissioning of nuclear facilities Subproject: Experiments with non-radioactive materials (NaMaSK)
One method for the deconstruction of a reactor pressure vessel and its internals is the Water Abrasive Suspension Cutting (WASS) process, in which steel materials are cut with a special high-pressure water jet. This process offers many technical advantages but it has a major disadvantage as additional secondary waste arises. Due to the addition of abrasive, the WASS process produces a waste mixture of inactive abrasive particles and radioactive steel particles (activated by neutron radiation) when dismantling steel components of nuclear facilities. However, the amounts of secondary waste generated in this way are considerable.
The NaMaSK system invented by Karlsruhe Institute of Technology (KIT) intends to separate the WASS cut waste mixture of inactive abrasive particles and radioactive steel particles by sieving, removing the small particles and then treating the resulting coarse fraction in the sieve with a magnetic filter. This treatment creates a selected abrasive which can be reused in the WASS process for a new cut. The reuse of the abrasive should reduce the secondary waste by 50-75%. The proposed research project of KIT will also test the application of corrosion inhibitors with subsequent processing of the grain mixtures, thus enabling the cutting of ferritic steels. For testing the NaMaSK method, WASS cuts with selected nonradioactive austenitic and ferritic steel grades will be performed. Thereafter, the individual process steps, such as sieving, filtration and magnetic separation have to be improved. Then all process steps will be carried out together to determine which percentage of reuse can be achieved. In addition, experiments with radioactive samples are planned in the controlled area of KIT´s Institute for Nuclear Waste Disposal (INE).
The radioactive samples will be produced in the nuclear plant in Philippsburg (KKP) and the Orano GmbH will be responsible for production, packaging and transport of the radioactive samples.