In January elevated levels of the radionuclide tritium were detected in monitoring wells at the nuclear power plant.
Entergy said the leakage came from two separate pipes inside a concrete tunnel. A floor drain that normally would have taken the water from the Entergy tunnel for normal processing was clogged with debris and mud. This allowed the tritiated water to seep through an unsealed joint in the tunnel wall to the soil and eventually the groundwater.
The pipes, which drain moisture from the plant’s Advanced Off Gas (AOG) system, have since been rerouted. After identifying where the leakage to the soil occurred, workers continued efforts to identify other such pathways to the soil and found none.
Entergy’s Executive Vice President, Operations Mark Savoff said the company has embarked on a fleet-wide initiative related to tritium leak prevention, detection and mitigation. Initiative includes benchmarking industry best practices, prioritizing structures, systems and components, improved inspection techniques and improved strategies for leakage prevention, monitoring and mitigation.
Groundwater remediation to remove tritium will include pumping shallow groundwater into above-ground containers for processing and reuse in the plant. Also, planning is underway to remove about 150 cubic feet of soil that contains small amounts of other contaminants such as manganese and cobalt. The soil will be disposed of at a federally licensed disposal facility.
Entergy said no detectable tritium level has been found found in any drinking water well samples at the Vermont Yankee site or in the Connecticut River. Both the U.S. Nuclear Regulatory Commission and the Vermont Dept. of Health have said that the tritium in the groundwater at Vermont Yankee has not been a threat to public health and safety. The company said tritium is a radioactive form of hydrogen that occurs naturally and is also a byproduct of nuclear plant operations.
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