engleski

Characterization of In-Drum Drying Products

A few years ago Krsko NPP has decided to introduce In-Drum Drying technology for treatment and conditioning of evaporator concentrates and spent ion resins. The main reason for such decision was the need for waste volume reduction and experience with solidification techniques in vermiculite-cement matrix that have been proven as inadequate solution in the Krsko circumstances. Mentioned decision has been encouraged by good experience in the field in some German and Spanish NPP’s. In the paper, solidification techniques in vermiculite-cement matrix and In-Drum Drying System are described briefly. The resulting waste forms (so called solidification and drying products) and containers that are used for interim storage of these waste forms are described as well. A comparison of the drying and solidification technology is performed and advantages as well as disadvantages are underlined. Experience gained during almost seven years of system operation has showed that drying technology resulted in volume reduction by factor of 30 for evaporator concentrates, and by factor of 2 for spent ion resins. Special consideration is paid on characterization of drying products. In case of evaporator concentrates the resulting waste form is a solid salt block with up to 5% bound water. It is conditioned in stainless steel drums (net volume of 200 l) with bolts and lifting rings. The fluidized spent ion resins (primary and blow-down) are filled into spent resin drying tank, dewatered and dried by electrical jacket heaters. The resulting waste form i.e. fine granulates are directly discharged into a shielded stainless steel drum (net volume of 150 l) with bolts and lifting rings as well. Characterization of both waste forms has performed in accordance with recommendations given in Characterization of Radioactive Waste Forms and Packages issued by International Atomic Energy Agency, 1997. It means that radiological, chemical, physical, mechanical, biological and thermal properties of the waste forms have been taken into consideration. In the paper, the main results of the analysis are presented. The results show that satisfying the waste acceptance criteria for waste disposal will require additional conditioning probably. It applies on fine granulates in particular. It is concluded that installation and usage of In-Drum Drying System resulted in a significant reduction of waste volume. By this way the capacity problem of interim storage at the site has been solved temporarily. On the other hand, raised the problem of satisfying waste acceptance criteria for disposal. This problem is taken into consideration in the paper, and few possible options are discussed.

radioactive waste characterization, solidification, segregation, In-Drum Drying products

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