By Jo Ann Hustis -
[email protected]
Exelon Nuclear is digging deep today for the source of a tritiated water leak at Dresden Generating Station at Morris.
The incident – discovered via a monitoring well on Tuesday, June 2, and officially confirmed Thursday, June 4 – is confined within the station site. This is the second incident of its kind for Dresden, which successfully capped off and replaced a leaking pipe in December 2006.
Other monitoring wells at the plant indicate no tritiated water beyond the plant site, Dresden spokesman Bob Osgood noted today.
“We took immediate action to verify what we found as part of our regular environmental monitoring program,” he said. “Nothing has left the property, testing at the mouth of the river and perimeter of the plant property shows.”
The monitoring well sample tested at tritum levels of 3.2 million picocuries per liter of water, and 17,500 picocuries per liter in adjacent monitoring wells, indicating virtually no spread of tritiated water underground, he said.
“We said, ‘Oh, oh, something’s wrong here,” he said of the monitoring well sample. “So, we did more sampling. The 3.2 million reading we got from a monitoring point that’s tested twice a year. Based on that, we knew this is where we should dig.”
Tritium is a naturally occurring isotope of hydrogen that emits a very low level of radiation, and is found in more-concentrated levels in water used in nuclear generating stations.
Both the Nuclear Regulatory Commission and Exelon have gone on record stating public health and safety have not been jeopardized by the release, nor are the safety and welfare of Dresden employees at risk.
The leak is in an area outside the reactor building and near the administration building, where several pipes are located six to seven feet underground. The pipes move tritiated water from the reactor to large condensate storage tanks.
The well was routinely tested about a month ago, and it was fine, Osgood said. These wells are sampled on a monthly basis.
Osgood said not much tritiated water is in the excavation around the pipes. What’s there is being removed.
“We’re sucking out the water in the excavation and holding that in storage tanks,” he said. “We will process this water like we do all other water. We haven’t yet been able to quantify the amount of water involved, but we know its not too much.”
The discovery is not affecting operation of the station.
Osgood said work crews have excavated the pipes today and are going about two feet deeper into the ground to attach an ultrasound device to detect any leaks and thinning of the pipe walls.
He did not term the leak as a major incident, saying it is probably smaller than similar leaks in 2004 and 2006, when Exelon replaced a length of pipe in the same general location.
“But, we take all leaks seriously,” he said, noting some media coverage to date is indicating this is not a major incident.
Viktoria Mytling, spokesman for Region 3, Nuclear Regulatory Commission in Lisle, said today the present leak is in about the same location as the previous incidents.
“They are now trying to identify the source of the leak,” she said. “They’re taking readings in other monitoring wells, and there is no indication of any kind of movement of tritium levels.”
Mytling said there is no underground course for elevated tritium levels to move offsite from Dresden Station.
She said other monitoring wells, which would show any movement of groundwater, are located between the well where the discovery was made and the outer regions of the property.
Cleanup of the tritiated water site depends on where the leak originated.
“I cannot tell you how they will remediate the tritium leak,” she said. “It’s something you have to talk to the utility about.”
Exelon spokesman Craig Nesbit said the leak was found fairly quickly, confined to the center plant site, and is being characterized at this time.
“The tritium wasn’t there the last time we checked,” he said. “We’re confident we can fix it pretty quickly. There are a lot of pipes in that area we have to excavate and check.”
Dresden is reworking the station’s underground pipe program, which is designed to find leaks and potential problems – finding deterioration before a leak starts.
Nesbit said the material in the underground pipes should last as long as that in the rest of the station’s equipment.
“Underground pipes are something we don’t expect to replace,” he said. “Otherwise, they wouldn’t be underground.”
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