While the Department of Energy recently celebrated the beginning of hot commissioning of the Hanford Site's Waste Treatment and Immobilization Plant (WTP), which has begun immobilizing the site's radioactive tank waste in glass through vitrification, the Defense Nuclear Facilities Safety Board has reported a possible bottleneck in waste processing. According to the DNFSB, unless current systems run efficiently, the issue could result in the interruption of operations at the WTP's Low-Activity Waste Facility, where waste vitrification takes place.

During operations, the LAW Facility will process an average of 5,300 gallons of tank waste per day, according to Bechtel, the contractor leading design, construction, and commissioning of the WTP. That waste is piped to the facility after being treated by Hanford's Tanks Side Cesium Removal (TSCR) system, which filters undissolved solid material and removes cesium from liquid waste.

According to a November 7 activity report by the DNFSB, the TSCR system may not be able to produce waste feed fast enough to keep up with the LAW Facility's vitrification rate.

Tank backlog: Hanford Tank Waste Operations and Closure (H2C), the DOE contractor responsible for managing Hanford's tank waste, announced on November 24 that the TSCR system had started a weeks-long waste treatment campaign, during which it will treat about 240,000 gallons of tank waste. The treated waste is stored in Hanford's AP-106 underground tank before being sent to the LAW Facility as needed.

According to the DNFSB report, while the AP-106 tank had a backlog of 800,000 gallons of waste, the TSCR system will have to operate efficiently if it is to supply the LAW Facility without interruption.

"DOE and H2C are exploring operational improvements that might increase TSCR system production rates. If feasible, these actions would help reduce the risk of interrupted LAW Facility operation caused by treated waste feed shortages," the report states.

To help increase the feed of low-activity waste, Hanford is installing an additional treatment system called the Advanced Modular Pretreatment System. The DOE in November approved Critical Decision 3A for the system, authorizing its construction.

About 36,000 gallons of Hanford's tank waste, the result of defense-related plutonium processing, had been vitrified as of December 9, according to the DOE's Office of Environmental Management.