Washington River Protection Solutions had removed well over a third of the sludge in the Hanford Site double-shell tank with an interior leak by midday Thursday. About 61,000 gallons of radioactive sludge had been retrieved, with an estimated 90,000 gallons remaining. Sludge retrieval got off to a slow start last month, with the Department of Energy facing a March 4, 2017, deadline to have waste removed from Tank AY-102, the first of 28 double-shell tanks to be built at Hanford. The deadline was established in a settlement agreement with the state. At least 60 gallons of waste is believed to have leaked from the inner shell into three places within the space between the inner and outer shells. Retrieving the waste is expected to help DOE discover what caused the leak.
Washington River Protection Solutions began pumping sludge late last week from Tank AY-102. It was the fourth time that WRPS attempted to start emptying sludge after workers left the site for the customary Friday through Sunday weekends, with initial work planned when few employees would be on-site. On the earlier weekends workers contended with equipment issues, including problems with a flow meter, software, and the slurry pump in Tank AP-102, which will store sludge removed from Tank AY-102. “This is not uncommon when we start up retrieval with new equipment,” said Jerry Holloway, WRPS spokesman. “A certain amount of troubleshooting is common.”
Workers made good progress once sludge retrieval began last week. By the end of the weekend about 52,000 gallons of sludge had been removed from the tank using a sluicing retrieval system. WRPS stopped work then to evaluate chemical vapor control data and make possible changes to protective measures before resuming sludge retrieval. Vapors are more likely to be present during sludge retrieval than the earlier liquid waste retrieval from the tank. More than 2,000 data points were collected over the weekend from the exhauster stacks and direct reading instruments during sludge retrieval as part of the industrial hygiene plan. After WRPS reviewed the data this week, chief operating officer Rob Gregory told employees that all readings were below action levels.
Sludge retrieval started up again Wednesday night, with 9,000 additional gallons of waste removed by midday Thursday. “While vapor levels have been well below action levels, we will maintain the current respiratory protection and industrial hygiene monitoring requirements with one exception – the traffic access restrictions put in place during previous retrieval periods will no longer be used,” Gregory said in a message to employees. Sludge retrieval is planned to continue through Sunday, when work is expected to stop again for vapor data analysis. WRPS originally had planned to switch retrieval methods in late spring or early summer, and that still may be required despite initial progress on retrieval. The current sluicers would be replaced with extended-reach sluicers that can reach deeper into the tank and fold out to reach more areas. A high-pressure water system may also be needed to break up any hardened waste at the bottom of the tank.
WRPS was required to start waste retrieval in Tank AY-102 by March 4, a deadline it met by pumping out 550,000 gallons of liquid waste, which sat on top of the sludge, between March 3 and March 9. The liquid waste had been left in place until near the start of sludge retrieval to help cool the sludge, which generates heat. Some additional liquid waste was removed over the past weekends as attempts were made to start the sludge retrieval. Before sludge retrieval resumed Wednesday night, Gregory told workers that approximately 87 percent of the tank’s total waste volume had been retrieved within a month. “It’s exciting to see the progress we’re making on this critical project,” he said.
