Elevated levels of radioactive tritium were found in groundwater samples taken early last year from the La Crosse Boiling Water Reactor in Wisconsin, produced during demolition of the reactor building, according to a site investigation report submitted to the state in November.
However, subsequent sampling through much of the year showed tritium release into groundwater had stopped, the environmental consulting firm Haley & Aldrich said in a report to decommissioning contractor LaCrosseSolutions that was forwarded to the Wisconsin Department of Natural Resources.
“No remedial activities are warranted. No further action is necessary,” the consultant said.
Built in 1967, the reactor near Genoa, Wis., operated for 19 years before the Dairyland Power Cooperative shut it down in 1987. In subsequent years it was partly decommissioned, with EnergySolutions subsidiary LaCrosseSolutions in 2016 assuming its operations license to complete the job. Decommissioning was largely complete by October 2018, with only two support structures remaining, Dairyland spokeswoman Katie Thomson said last week by email.
Groundwater samples taken in December 2017 from a monitoring well at the site showed a tritium concentration of 13,000 picocuries per liter. While that did not reach the U.S. Environmental Protection Agency’s maximum contaminant level of 20,000 picocuries per liter, it was high enough for further checks. Samples were taken from three wells in February 2018, with one showing a tritium concentration of 24,200 picocuries per liter. Further sampling from April to September showed tritium was not entering the groundwater.
The contamination originated withexhaust from the ventilation system for the reactor building demolition that contained a gas form of tritium and merged with water and ice melt runoff. LaCrosseSolutions fixed the source problem and has been monitoring for further contamination, Thomson said.
As of last fall, decommissioning operations at La Crosse were scheduled to end by the second quarter of this year. Certain proceedings have been paused by the partial shutdown of the federal government, Thomson said: “We do not have an updated schedule at this time.”