Validation of an innovative separation plant consisting of a sieve and magnetic filter for the reduction of radioactive waste for interim storage

Various cutting methods are available for dismantling the reactor pressure vessel and its internals. One process that offers many technical advantages is the water-abrasive suspension cutting process. In this cold cutting process, a high-pressure water jet mixed with abrasive particles is used for cutting. This way, even complex structures (e.g. fixtures) and components can be cut safely, remotely and quickly under mechanical tension. During cutting, a mixture of used abrasive and radioactive steel particles is produced, which must be disposed of as radioactive waste. This additional secondary waste to be disposed of increases with every cut and, in turn, increases the overall cost of the process. It makes the cutting technique unattractive despite its many technical advantages.

In order to reduce the amount of secondary waste, a separation process for the treatment of steel/abrasive particle mixture was developed. The process employed sieving and magnetic filtration to separate abrasive particles from the particle mixture. Firstly, the homogenous mixture of steel and abrasive particles is sieved, which removes the fine particles containing broken abrasive and small steel particles. In the next step, the sieved fraction is treated through a magnetic filter, removing bigger steel particles. The separation process aimed to reduce secondary waste by reusing abrasive particles for further WAS cutting.

In this regard, a prototype separation system with a sieve and magnetic filter was built and tested in a batch process. The shortcomings of the procedure related to the handling of material and upscalling the process so that it can be introduced to the market, suggested to develop a continuously operated separation plant that can be employed in nuclear facilities. To cope with these limitations, a continuously operated sieving mechanism and a magnetic filter were developed. The preliminary results of the continuously operated sieve have shown impressive results in terms of sieving error, but there is still room for improvement in terms of steady operation. Similarly, the innovative and patented magnetic filter exhibited quite exciting early results, but the process still requires a lot of improvement in terms of process control and measuring methodology.

In the ongoing research project, the continuous sieve and the magnetic filter will be validated under variable conditions and parameters. The improvements to the filter will be developed through simulations and experimental validation using 3D prints of new filter geometries, which can make the filter viable for other separation applications. The aim is to design and build a system with both components that can be used for abrasive treatment in nuclear facilities. Furthermore, the separation plant will be designed for use in nuclear facilities. In this regard, the project is supported in an advisory capacity by Iqony gmbh. They will provide expertise related to the special requirements for the nuclear sector right from the start of development. In the presentation, the preliminary results of the continuous sieve and magnetic filter will be presented.