Yankee leaks on track for repair next month
VERNON — The two leaking radioactive steam drain lines, believed to be a source of a plume of radioactive tritium contamination at the site of the Vermont Yankee nuclear reactor, will be rerouted until a more permanent redesign can be built when the reactor shuts down next month for its regular refueling and maintenance outage, the company said Thursday.
Entergy Nuclear spokesman Larry Smith said one of the two drain lines in the advanced off-gas underground pipe tunnel was still leaking 100 gallons of radioactive water a day and couldn't be accessed, unlike its leaking twin, which was plugged on Feb. 14.
But he said that while tritium levels continue to drop in several monitoring wells near the excavation pit at the Vernon reactor, the company was not ready to say it had found all the sources of the tritium leak.
"We will say we have found the source when we are confident we have," said Smith, noting that Entergy Nuclear engineers are checking on other potential problem sources, including the 500,000-gallon condensate storage tank, which holds radioactive reactor water. The tank is being checked for a third time, the state Health Department said.
"Everything needs to be thoroughly checked so it is not a source," said Smith, noting that several groundwater monitoring wells were "trending" downward since the leaks were found in the steam drain lines and either plugged or diverted. However, at least one well shows measurements in excess of 1 million picocuries per liter, and several are around 500,000 picocuries. The EPA standard for drinking water is 20,000 picocuries per liter.
While the steam line is still leaking about 100 gallons a day from a hole about the size of a quarter, it is being drained off into a system where it is treated and reused, he said, and is not escaping into the environment.
In addition, two other underground pipes underneath the foundation of the advanced off-gas building will be tested for their structural integrity and those pipes may be rerouted during the refueling outage, the Health Department said.
According to the daily Department of Health update on the tritium investigation, the inspection of the advanced off-gas pipe tunnel by remote-controlled robots has been completed and those robots are now being removed.
Entergy has determined that only the two steam trap drain lines are leaking inside the tunnel, which carries dozens of pipes. The company has said while the steam drain lines were leaking, the drain in the bottom of the tunnel became plugged with debris, and standing water accumulated and then found its way out into the environment through two cracked pipes.
Soil tests near those two cracked pipes have revealed other radioactive materials, such as cobalt-60 and cesium-137, among other radioisotopes.
