DESIGN AND CONSTRUCTION OF THE WEST VALLEY SUPERNATANT TREATMENT SYSTEM

After just six years, the West Valley Demonstra- tion Project (WVDP) is in the final stages of test- ing in preparation for pretreatment and volume reduction of some 2120 m3 (560,000 gallons) of highly radioactive liquid waste. The primary ob- jective of the WVDP is to solidify the high-level waste and transport it to a federal repository. This waste will be solidified in borosilicate glass begin- ning in the fall of 1992. Project engineers have designed and constructed the Supernatant Treat- ment System (STS) to decant the liquid from an underground high-level waste storage tank and concentrate radioactive cesium from the liquid onto an inorganic zeolite ion exchange medium. Four ion exchange columns [6096 mm (20 ft) high and 914.4 mm (3 ft) in diameter] will be used to move liquid sequentially through three columns while the fourth column is off-line having its loaded zeolite replaced. This process will reduce the volume of the final waste form by a factor of six. The STS has been installed within a spare un- derground high-level waste tank which saved the Project construction costs and improved project schedule. This paper discusses the history of the STS design and the challenges presented by its construction.