Process Control Plan for Tank 241-SY-101 Surface Level Rise Remediation

The tank 241-SY-101 transfer system was conceived and designed to address the immediate needs presented by rapidly changing waste conditions in tank 241-SY-101. Within approximately the last year, the waste in this tank has exhibited unexpected behavior (Rassat et al. 1999) in the form of rapidly increasing crust growth. This growth has been brought about by a rapidly increasing rate of gas entrapment within the crust. It has been conceived that the lack of crust agitation beginning upon the advent of mixer pump operations may have set-up a more consolidated, gas impermeable barrier when compared to a crust regularly broken up by the prior buoyant displacement events within the tank. The interim goals of the project are to: (1) protect the mixer pump operability (2) begin releasing gas from the crust, and (3) begin dissolving the crust and solids in the slurry layer. The final goals of the project (Final State) are to solve both the level growth and BD-GRE safety issues in this tank by achieving a condition of the waste such that no active measures are required to safely store the waste, i.e., crust and non convective layer are mostly dissolved, and therefore the mixer pump will no longer be needed to prevent BD-GREs in excess of 100% LFL. Transfers (which are designed to create space in the tank) and dilution (which will dissolve the solids) will accomplish this. Dissolution of solids will result in a release of gas retained by those solids and remove that volume of solids as a future retention site