During the decommissioning of a nuclear facility, dismantling of the reactor pressure vessel and its internal components poses a major challenge. Due to the effects of neutron radiation, the activated components can only be dismantled using remote handling techniques. One of the cutting method for dismantling the reactor pressure vessel and its internals, which offers many technical advantages, is the water abrasive suspension cutting (WAS). This cutting technique uses a high-pressure water jet mixed with abrasive particles to cut through materials. This allows even complex structures (e.g. internals) and components under mechanical stress to be dismantled safely, remotely and quickly. The cutting process produces a mixture of abrasive and radioactive steel particles, which must be disposed of as radioactive waste. This results in a considerable amount of additional radioactive waste and increases the cost of the process. This secondary waste makes the cutting process unattractive despite its several technical advantages.

In order to reduce the amount of secondary waste, a separation process for the steel/abrasive particle mixture has been developed at KIT and funded by the Federal Ministry of Research, Technology and Space (BMFTR). A reusable abrasive is obtained, that can be used directly for further cutting. This reuse of abrasive benefits to reduce the amount of secondary waste. In the separation process, the abrasive waste is sieved immediately after cutting and then treated with a magnetic filter. The sieving removes abrasive fragments and small steel particles. The fraction of large, intact abrasive particles that can be used for further cutting is then treated with a magnetic filter to separate any remaining steel particles.

To demonstrate and investigate the process, a prototype separation plant was first developed using a batch process. Further analysis of the process highlighted that a continuously operated plant must be developed to address the shortcomings and enable upscaling for industrial use. The plant will be designed with the support of Iqony GmbH to meet the requirements for operation in the nuclear sector. The separation tests with the plant are promising. Depending on the operating parameters, the combination of the magnetic filter and the continuously operated sieve allows between 50-70% of the abrasive to be reused, which significantly reduces secondary waste.

A key component of the separation plant is the innovative magnetic filter. This filter uses permanent magnets and is able to be operated continuously, without interruptions for cleaning cycles. It is a closed system and due to its simple geometry it is easy to clean and decontaminate, which is an important factor for the use in the nuclear industry. The operating principle is shown in the Figure. The magnetic filter can also be applied to many different use cases with similar criteria, for example in oil refinery, waste water treatment, lithium-ion cell recycling, etc.