Spent Resin Hot Compaction at Tihange NPP

Spent ion exchange media are considered to be problematic waste that, in many cases, requires special approaches and precautions during their immobilization to meet acceptance criteria for disposal. Waste acceptance criteria define, among others, the quality of waste forms for disposal and therefore, will sometimes define appropriate treatment options. Furthermore, the Volume Reduction Factor is a key criterion in Belgium. A technical and economical comparison of industrially available systems, was performed by Tractebel Engineering, and led to decide the installation of a spent resin hot compaction unit at Tihange NPP. Tractebel Engineering is in charge of the project management and takes an active part in the process optimization. The Resin Hot Compaction Process mainly consists of the following steps: wet resin beads filling into a dryer – dewatering – mixing with a binding additive – drying under deep vacuum, until a residual water content of 4% – discharge of the dried waste into compactable drums – drum lid positioning – supercompaction at 1000 tons. In order to avoid cracks on the compacted drum, and surface external contamination from resin leaks, some optimization has been made about additive selection and drum design. Powdered cation exchange resins (as used for BWR condensate polishing) were found to be less compressible than common polymer powders, and to minimize springback as well as crack risks of the drum walls. Placing the compactable drum inside a second, slightly larger drum, also guarantees clean and reproducible pellets with a powder additive proportion limited to 25% of the total waste volume. Without this safety wrapping, the additive proportion must be raised to at least 30%. The obtained matrix inside pellets is a water free, solid but somewhat brittle block. Volume reduction factors between 1.8 and 1.9 are achieved. Special care must be taken about the mortar quality if pellets are to be grouted. This paper describes the Resin Hot Compaction Process application at Tihange NPP.