Safely drying and cementation of ion-exchange resins

The nuclear industry uses a lot of water which inevitably becomes contaminated. This contamination is removed mainly using ion-exchange resins. These polluted resins have to be handled and safely stored because of the levels of radiation involved. Hosokawa Micron has developed two methods of handling the polluted ion exchange resins prior to long term waste storage.

  1. Drying of resins prior to cementation
    The waste water/resin mixture is collected prior to drying to reduce its volume and it is this product that is fed to a specially modified Nauta® vacuum dryer. Near to the base of the dryer special filter elements are incorporated into the vessel wall to take away as much water as possible, thus concentrating the polluted resin. When the fill level is reached vacuum and heat are applied to dry the product from an initial moisture content of about 50 - 55% (wt) to a final moisture content of approximately 4%. The final product temperature is approximately 100°C.

    This hot dry product is discharged from the dryer into special drums which are then immediately reduced in volume to under 30% of their original volume using a special press. Four to five of the press reduced drums are then transferred to another drum which is filled with cement and sealed for long term safe storage.

    Safely drying and cementation of ion-exchange resins

  2. Cementation of wet resins
    In this process the waste resin/water mixture is collected and dried in a filter press before storage procedure starts. The filter press material is then mixed with cement in a special drum type mixer which is then sealed ready for storage the contaminated mixing rotor being stored in the last drum of the cleaning campaign.

    The loss of the rotor after each campaign adds significant cost to the operation and Hosokawa Micron have worked with specific customers to develop a new technique that operates without losing the mixing rotor. After several tests based on the well known Flexomix high impact mixer, a special design was developed having two inlets. One for contaminated pressed resin and one for cement. Water is added during mixing and the collection drums are pressed to the bottom of the Flexomix unit. The drum fill level being controlled using special radar detection and a camera mounted inside the Flexomix housing. The Flexomix has a stainless steel mixing chamber and an integrated vibrator to avoid sticky product on the mixing chamber.

The method using the vacuum dryer has reduced the number of contained drums per campaign. The method using a Flexomix has the big advantage that rotor disposal is eliminated.