Highly radioactive spill near Columbia River in E. Washington worse than expected

The leak of highly radioactive waste under a building on the Hanford Nuclear Preserve north of Richland and near the Columbia River is deeper and wider than expected.

In a statement Thursday, the Energy Department said the soil contamination at the Hanford 324 Building 1,000 feet from the Columbia River and one mile north of Richland is much larger than previously identified.

Now the Energy Department is rethinking the cleanup plan for the spill discovered 13 years ago, with work crews preparing to excavate the radioactive material for the past six years.

The cesium-strontium leak in the ground under Building 324 is so radioactively hot it would be lethal to a worker in direct contact within two minutes, the DOE previously said.

Radioactivity in contaminated soil was measured at 8,900 rads per hour.

The plan has been to leave Building 324 standing to act as a barrier to keep precipitation from reaching underground contamination and bringing it closer to the aquifer, which moves toward the Columbia River.

Workers began preparing to clean up a highly radioactive spill under the Hanford Site Building 324 near Richland and the Columbia River in 2017. The spill was recently found to be much larger than anticipated.

Workers began preparing to clean up a highly radioactive spill under the Hanford Site Building 324 near Richland and the Columbia River in 2017. The spill was recently found to be much larger than anticipated.

Work began in 2017 to stabilize the building and the ground underneath so that a remote-controlled excavator could be used inside the building to excavate the highly contaminated soil underneath.

Now DOE is considering a more expensive and time-consuming cleanup plan that involves tearing down the approximately 58-year-old building and building a retaining superstructure above the waste site and then excavating the ground. contaminated. Details of the new plan have not been worked out.

DOE is discussing the possible new cleanup plan with its project regulator, the Environmental Protection Agency.

The spill did not reach groundwater, where it would travel the short distance underground to the Columbia River, based on well monitoring data, the DOE said Thursday.

324 Building used for research

The building at the south end of the 580-square-mile Hanford Nuclear Reservation in Eastern Washington is located in the 300 Sites area, where the uranium fuel for the Hanford reactors that produced plutonium for the nuclear weapons program was manufactured of the nation from World War II until the Cold War.

The Hanford 300 area was also used for research, and the 102,000 square foot Building 324 was used for research and other projects involving highly radioactive material from 1966 to 1996.

Building 324 is one of the last structures still standing in Area 300 of the Hanford Nuclear Preserve, just north of Richland.

Building 324 is one of the last structures still standing in Area 300 of the Hanford Nuclear Reserves, just north of Richland.

It was expected to be demolished by the statutory deadline of September 2015, but while preparations for the demolition were underway in 2010 the spill was discovered under the building.

In the 1980s one of the building’s six hot cells was used to prepare concentrated radioactive cesium and strontium from the wastes of Hanford’s plutonium production for Germany for use in testing a radioactive waste repository.

Hanford workers stood outside the hot cell and used controls to operate manipulators inside the 30-foot-high hot cell with 5-foot-thick walls as they gazed through leaded glass windows.

At the time of construction for Germany, the stainless steel cladding on the floor of the hot cell was damaged, allowing concentrated high-level waste to escape into the ground beneath the building.

The bottom of the cell is about 42 feet above the water table.

Hanford was used to produce plutonium for the nation's nuclear weapons program during World War II and the Cold War.  Environmental remediation is underway now.

Hanford was used to produce plutonium for the nation’s nuclear weapons program during World War II and the Cold War. Environmental remediation is underway now.

DOE planned to recommission the hot cell to mount an excavator arm inside it. The floor of the hot cell would be cut away with a remotely operated saw and then the excavator would lift the contaminated soil through the hot cell.

The use of the hot cell was intended to protect Hanford workers in the project from radiation in the waste.

Excavating the contaminated soil with the building standing required the installation of 13 structural supports, called micropiles, into the soil beneath the building to stabilize its foundation.

Radioactive leak discovered

After it was completed in the fall of 2022, the next step for DOE contractor Central Plateau Cleanup Co. was to install underground horizontal supports into the ground outside the building’s footprint by injecting cement mortar into the ground to form blocks. The intent was to help prevent soil flaking when excavating the contamination.

As construction began, contaminated soil was discovered in a larger area underneath the building, where it was not expected.

DOE suspended work in April, and Pacific Northwest National Laboratory, DOE’s national laboratory in Richland, was called in to help Hanford officials understand the extent of the underground contamination.

PNNL confirmed the Hanford contractors’ findings that the spill was both wider and deeper than thought when the plan to excavate it from inside the hot cell was developed.

Work on that floor was initially undertaken by previous DOE contractor CH2M Hill Plateau Remediation Co. before the contract expired. Central Plateau Cleanup Co. took over the work in early 2021.

A much larger volume of contaminated soil would need to be removed than initially anticipated, the PNNL concluded. The excavator arm to be mounted in the hot cell for excavation could not reach all of the contaminated soil, with some of it deeper than it could reach.

Hanford workers have been preparing to clean up a highly radioactive spill under the 324 building for six years.  It has recently been discovered that the contamination of the spill is significantly higher than expected.

Hanford workers have been preparing to clean up a highly radioactive spill under the 324 building for six years. Spill contamination has recently been discovered to be significantly greater than expected.

DOE has begun to rethink its remediation plan for the spill not only due to the larger excavations required, but also due to concerns about the aging building.

Equipment failures highlighted the condition of the building and the cost of continuing to maintain and repair it while using one of its hot cells to excavate waste.

However, the DOE said the building is currently in a safe and stable configuration. Contaminated soils have been stable for decades, he said.

New plan for the Hanford spill

The new plan that DOE is considering is meant to be safer for the workforce, protective of the environment and effective in accomplishing the mission, Hanford workers were told Thursday in a message to employees.

While this change in approach will take longer to complete, it represents a safer path to remediation and aligns with current budget profiles through fiscal year 2025, the message said.

As a precaution, two new monitoring wells will be installed to continue checking for any underground diffusion of cesium and strontium.

Workers practiced using remote-controlled equipment in a model of the 324 building in preparation for digging up highly radioactive waste.

Workers practiced using remote-controlled equipment in a model of the 324 building in preparation for digging up highly radioactive waste.

The proposed new cleanup plan would begin with decommissioning Building 324, including fogging ventilation systems to stabilize contamination, filling the building’s hot cells with grout, and turning off heat and electricity.

Then the building would be demolished to the foundations and the foundation slab eventually extended.

The extended slab would act as a larger barrier to protect it from rain and snowmelt that could push radioactive contamination deeper into groundwater.

Then a containment superstructure would be built over the waste site. The design of the superstructure has not started.

With it in place, the contaminated soil would then be dug up.

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