Radioactive waste is stored in underground waste tanks at the Savannah River Site (SRS). Once the waste is removed, the residual waste in the tanks is immobilized in a grout form, while the high level fraction is immobilized in glass canisters and stored until disposal. Once there is mutual agreement to cease waste removal activities from the tanks and all regulatory approvals are received, these tanks are prepared for operational closure. Operational closure of the tanks consists of filling with grout for the purpose of stabilizing residual material, filling the tank void space for long-term structural stability, and discouraging future intrusion. Two of the old-style Type I tanks (Tanks 5F and 6F) at SRS have received regulatory approval confirming waste removal has been completed, and have been operationally closed. As part of the closure process for Tanks 5F and 6F, a first time process of adding grout to a tank annulus and internal cooling coils was performed. Consistent with state - approved closure plans, three types of grout were used to fill Tanks 5F and 6F. Reducing grout was used to fill the entire volume of Tanks 5F and 6F (bulk fill grout), and a less viscous grout was used to fill equipment that was left in the tank (equipment fill grout). A third type of grout, a slightly modified version of the equipment fill grout, was used to fill the cooling coils in the tank. The reducing grout (bulk fill) was added to the tanks using portable grout pumps filled from concrete trucks, and delivered through slick lines to multiple risers of each primary tank and annulus. Cooling coil and equipment filling grout was added by mixing dry material and water in the facility and then filling with a smaller grout pump or by hand. Filling of the two tanks, (including tank/annulus internals, remaining equipment, cooling coils, and tank/annulus access points (risers)) has been completed.
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