The tritium discovered last month in groundwater in Genoa was not the first radioactive material released in the decommissioning of the former Dairyland Power nuclear plant.
LaCrosseSolutions, the company in charge of the $85 million project, accidentally spilled 400 gallons of radioactive water into the Mississippi River last year, though the Nuclear Regulatory Commission says there was little risk to public health.
The NRC last month determined that the spill was a violation of federal regulations, one of three low-level violations identified in the annual inspection of the decommissioning operations at the La Crosse Boiling Water Reactor. None of the violations resulted in a citation.
On Feb. 23, 2017, a radiation protection technician discovered that a garden hose attached to a sump pump had been left overnight in a 20,000-gallon tank of waste water collected in the course of dismantling the reactor containment building, according to reports filed with state and federal regulators.
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The hose, intended to return water to the tank from a surrounding containment area, siphoned contaminated water back out of the tank, and some of the water spilled over the top of a berm and into a storm sewer that drains into the nearby river, according to the reports.
An analysis found cesium-137 in water samples at concentrations of 0.000001 to 0.00000286 microcuries per milliliter, which exceed the federal limits for effluent. That translates to a potential dose of 0.005 to 0.01 milirem for a person who drank the contaminated water for a year.
Professor Jeff Bryan, who teaches nuclear chemistry at the University of Wisconsin-La Crosse, said the potential exposure to ionizing radiation was very low, about 1/100th the exposure for an hour on a commercial flight, and the levels would need to be about 1 million times higher to cause noticeable adverse health effects.
“This was a really dumb accident,” Bryan said. “Stupid, but not hazardous.”
The analysis results were confirmed by an NRC inspector who was on site that day.
The NRC did not issue a citation but found LaCrosseSolutions violated policies that say any radioactive releases must be planned and controlled to keep the levels as low “as reasonably achievable.”
“The bottom line is this — this was an unplanned release and it was unmonitored,” said NRC spokeswoman Viktoria Mitlyng. “This isn’t something we want to see happen.”
Mark Walker, vice president of marketing and communications for EnergySolutions, said Friday he didn’t have enough information to comment on the incident.
The NRC identified two other level-four violations during the annual survey, neither of which resulted in a citation.
In June the company disabled the five on-site fire hydrants after a leak but decided the Genoa Fire Department could provide water from the Mississippi River in the event of a fire. NRC inspectors said that could possibly reduce the effectiveness of the fire protection program which LaCrosseSolutions had not evaluated.
In another instance, an equipment operator failed to remove all the concrete during the initial demolition, which was initially overlooked because the company didn’t perform the necessary soil surveys.
The NRC determined the violations created a low public safety risk and the company took corrective measures.
“It’s not just that they took the hose out of the tank this particular time, but they took action to make sure this kind of thing doesn’t happen again,” Mitlyng said.
Last week LaCrosseSolutions announced that it had found elevated levels of tritium in groundwater near the former reactor building.
An environmental consultant hired by LaCrosseSolutions has asked the Wisconsin Department of Natural Resources for permission to inject non-toxic dye into the soil in an effort to determine the source of the tritium, groundwater flow patterns, and the potential for tritium to reach the Mississippi River.
The test is expected to take four to six weeks, according to the application by Haley and Aldrich.
Tritium levels found in a monitoring well about 25 feet below ground were 24,200 picocuries per liter. The Environmental Protection Agency’s safe limit for drinking water is 20,000 picocuries per liter. Staff at the adjacent Genoa power station were advised to stop drinking well water as a precaution.
Dairyland Power Cooperative operated the 50-megawatt plant, built by the U.S. government, from 1967 until 1987. The reactor vessel was removed in 2007 and taken to a disposal site in South Carolina, and the uranium fuel rods were encased in dry storage casks that will remain on site until the federal government opens a long-term storage facility.
LaCrosseSolutions, a subsidiary of EnergySolutions, took over the site license in 2016 to complete the decommissioning process.
Under the agreement, LaCrosseSolutions will remove everything down to three feet below ground and return the clean site to the La Crosse-based utility. Physical demolition is expected to be completed by the end of 2018.
Note: This story was updated. An earlier version incorrectly stated the EPA limit for the safe level of tritium in drinking water.