High Level Waste Tank

Liquid high-level waste (HLW) processing has been completed.  The underground waste tanks will be closed following decisions on long-term site management. Greater than 97 percent of the long-live radioactivity has been removed and vitrified from the tanks.  In 2000, efforts quantified (characterized) the amount of long-lived radioactivity remaining in the tanks and commenced cleaning activities such that the remaining activity was of sufficiently low concentration so that closure of the Waste Tank Farm could commence.

Liquid HLW Residual Characterization
Characterization sampling activities included the use of several technologies to get an accurate picture of what was remaining in the tank.

Technologies used included:
1. Deployment of a special camera within the tank measured two dimensional
    spatial mapping of gamma ray emitting radiation in real time;
2. Deployment of neutron track recorders within the tank measured neutron
    fluxes from many reactions within the tank down to the levels of 
    cosmic ray-induced background.
3. Deployment of a burnishing sampler within the tank allowed in-tank fixed
    waste scrape samples to be collected from the walls, columns,
     and other vertical and horizontal surfaces of the tank for radiochemical analysis.

The approach for characterization of the waste in Tank 8D-2 used direct measurement techniques (i.e., burnishing samples) in combination with indirect technologies such as the gamma camera and neutron track recorders.  Data resulting from the tank characterization activities was evaluated and used to update the radioactive quantification inventory for Tank 8D-2 in late summer 2001.
 

Liquid HLW Residual Removal
Following characterization activities, preparations were made to help remove the fixed radioactivity that was bound to the wall of Tank 8D-2.  In March 2001, two mechanical sluicer's (high-pressure sprayers) were deployed in the tank.  The sluicer's existed in opposite riser's and a submersible pump was employed to force liquid from the bottom of the tank to the spray assembly where it was directed at tank surface locations at a force of 100 pounds per square inch.  The liquid sprayed from the sluicer removed fixed radioactivity on the surface of the tank walls.

High Pressure Sluicer

HLW Tank Closure Project
All retrievable HLW has been removed from the tank and sodium-bearing wastewater has been concentrated.  In 2004 treatment of the low activity sodium-bearing wastewater was completed. The the HLW Tanks (8D-1 and 8D-2) have been placed into a safe surveillance and maintenance mode. This meant placing the tanks in a mode where the active continuing tank operation was ventilation. 


Tasks which were completed (July 2003) to achieve this interim closure mode included:
1. Deactivation of the Supernatant Treatment System which has
    its major components within Tank 8D-1.
2. Installing cut-off jumpers between Tank 7D-2 and the Liquid Waste
    Treatment System to prevent further waste additions to Tanks 8D-1
    and 8D-2.
3. Isolating remaining pathways for wastes to enter Tanks 8D-1 and 8D-2.
4. Managing of the groundwater inflow into the Tank 8D-2 vault.

A Record of Decision for site closure of the West Valley Demonstration Project is not expected for several years.  However, DOE is pursuing methods to ensure safe lay-up of the tanks pending final decision on closure.

 

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WVES