More should be known this year about the extent of the radioactive contamination in soil within 400 yards of the Columbia River, the result of water that leaked or was disposed of from the K East Basin.
It’s one of the remaining pieces of the puzzle of what lies beneath the ground near the former K East and K West Reactors. Much of the soil cleanup work has been finished near Hanford’s other plutonium-production reactors.
CH2M Hill Plateau Remediation Co. workers will drill a borehole within 15 feet of the K East Reactor to assess the contamination that resulted from leaks from the reactor’s basin that once was used to hold irradiated fuel. The soil there is expected to be highly contaminated with cesium and strontium.
To prepare for drilling that borehole, CH2M Hill workers will start with a second borehole about 100 feet away between the reactor and the Columbia River. It is the site of an open-bottomed waste disposal crib where overflow water from the K East Basin was dumped into the ground.
CH2M Hill workers have not drilled into soil with highly radioactive contamination for several years, said Mark Cherry, CH2M Hill deputy vice president of soil and groundwater cleanup. The initial drilling will provide needed data about radioactive contamination in the soil there and also allow workers to practice using the same procedures needed for the higher-risk borehole at the reactor.
The contamination near the reactor came from a construction joint between the K East Reactor and its adjoining basin. Concrete was poured there to build the fuel discharge chute for dropping fuel from the reactor to the cooling basin. More than 15 million gallons of contaminated water is believed to have leaked there.
After the Cold War, about 2,300 tons of fuel irradiated at another reactor, N Reactor, was left in the K East Basin and nearby K West Basin after processing was no longer being done at Hanford to remove plutonium from the fuel for the nation’s nuclear weapons program.
As the unprocessed fuel corroded, highly radioactive sludge collected in the the basins. The fuel has since been removed from the basins and the sludge vacuumed up and consolidated in the nearby K West Reactor. It remains in underwater containers while DOE prepares to transfer it to central Hanford, where it will be treated for disposal.
At least two boreholes will be needed for the next step of cleanup, assessing the level of soil contamination from K East Reactor activities, said Jon Peschong, Department of Energy deputy assistant manager for cleanup in central Hanford and near the Columbia River. Soil sampling already has been done and data has been collected from monitoring wells, but more complete information from the boreholes will be used to make decisions on soil cleanup.
Temporary structures have gone up over the initial two borehole sites, with drilling to be done through openings in the top of the structures. A ventilation system will help with contamination control in the areas where potentially radioactive soil is handled and packaged. It also will help keep workers in protective gear cooler this summer.
The disposal crib was dug up earlier and a layer of clean soil laid over the site. The drill at the crib site was expected to finish digging through the clean soil and start on the soil beneath late last week, according to CH2M Hill.
“I’m excited to get going,” Cherry said.
The drill will go down to groundwater, believed to be about 100 feet deep, with samples collected every two feet to provide information about the extent and concentration of contamination.
DOE and CH2M Hill are calling the initial drilling a mockup. Workers are wearing the same anti-contamination coveralls, gloves and powered air purifying respirator hoods they will need when they drill in the soil closer to the reactor that’s expected to be more contaminated.
Both boreholes are expected to be completed before October, with the second borehole planned to be about 120 feet deep. The casings for the boreholes may be left in place to be used for monitoring wells.
Much of the contaminated soil near the K East and K West Reactors already has been dug up. But some of it Hanford workers cannot go after because it is near facilities that are needed until the radioactive sludge is out of the K West Basin, Peschong said.
The K East and K West Reactors are the last two Hanford reactors awaiting final cleanup. The K East Reactor has been in surveillance mode since 2013, with much of it torn down and openings sealed up.
When the K West Reactor also is ready to be put into long-term storage, a new form of “cocooning” is expected to be used at the same time for both. A steel shell is proposed to be built around each, topped with an angled roof to direct rainwater runoff away from adjacent soil waste sites.
Six other Hanford plutonium production reactors along the Columbia River already have been cocooned, or put into storage in place for 75 years to allow radiation in the cores to decay to more manageable levels.