More Sludge Sent to Perma-Fix
WC Monitor
5/9/2014
A second 5,000-gallon shipment of radioactive sludge has made its way from Oak Ridge to Richland, Wash.,for treatment and there could be another dozen or more as the Department of Energy works to clean up an Oak Ridge sewage-treatment facility that was contaminated by discharges of radioactive technetium during the late stages of demolition at the K-25 building. The hot sludges are being transported to the Perma-Fix Northwest treatment facility, and Mike Koentop, executive officer of DOE’s Environmental Management Office in Oak Ridge, said the Perma-Fix contract is valued at about $600,000 to $1.2 million, depending on how many sludge shipments are required.
The radioactive material was discovered in February in sewer lines at DOE’s East Tennessee Technology Park, where demolition of K-25 was nearing completion. The technetium was known to be present in several of K-25’s processing cells, and those cells were segregated during the multi-year demolition project and saved for last to prevent the spread of the radioactive hazard. After it was learned that the technetium infiltrated a sewer line near the demolition site and had reached the city’s treatment plant, steps were taken to plug the source. The line near the demolition area was disconnected from the main sewer line that crosses under the Clinch River and delivers sewage to the city’s treatment plant, which continued to receive some residual amounts of Tc-99 even after the source was sealed off.
Tc-99 Reduced to Background Levels
Gary Cinder, the city of Oak Ridge’s public works director, said this week that incoming levels of Tc-99 had essentially been reduced to background levels. The discharges at ETTP and the effluents at the sewage-treatment facility were reportedly within environmental standards. The highest concentrations (about 600,000 picocuries per liter) were found in the sewage plant’s “digester.” According to Cinder, the city’s plant uses microbes to treat the sewage, and that process generates sludge. The process also breeds more bugs, and when there are too many, some of the sludge is removed from the treatment system and placed in the digester. It remains there until more room is needed. Typically, the excess would be removed and dried, then used as fertilizer or disposed of locally. However, because of the elevated levels of radioactivity, DOE took ownership of the sludge and promised to take care of it.
DOE’s cleanup contractor, URS-CH2M Oak Ridge (UCOR), reached an agreement with PermaFix for removal of the hot sludge and treatment at its facility in Washington state. After being thermally treated there, the ashes will be sent to a Utah landfill for disposal. Cinder praised DOE for its handling of the problem. “The whole issue has been handled very well by DOE and UCOR and their contractors,” he said. “We weren’t thrilled or pleased that it happened, we’ve been very pleased with how they’ve responded.” The levels of radioactivity at the Oak Ridge treatment plant are gradually going down, and that’s expected to continue as more sludge is removed from the digester and replaced with sludge that’s not as contaminated.
