The Department of Energy has provided Washington state with a proposed plan requiring up to seven years of work to close the Hanford Site’s 324 Building, which sits above a highly radioactive spill. The plan was required to meet a Tri-Party Agreement milestone at the end of June to include the building in the Hanford dangerous waste permit and provide a schedule for completing closure activities.
The proposed schedule is based on CH2M Plateau Remediation Co.’s initial review of work after it took over the building’s cleanup from Washington Closure Hanford as its river corridor contract nears expiration in September. “This is an important project,” said Stephanie Schleif, facility transition project manager for the Washington state Department of Ecology. “Ecology is pleased to see DOE moving forward on the 324 Building.”
The 324 Building, also known as the Chemical Materials Engineering Laboratory, housed radiological and other laboratories, support facilities, and administrative areas.
The first of four phases of closure activities for the building includes installing remotely operated equipment into B Cell, the hot cell where radioactive material spilled through a crack into the soil beneath the building. The hot cell would provide shielding as equipment is used to first remove the cell liner and floor slab and then excavate the contaminated soil down to about 13 feet deep below the floor.
The debris and the soil would be either shipped to the Environmental Restoration Disposal Facility in central Hanford or transferred to the nearby A, C, or D cells in the 324 Building, based on levels of radioactivity. Materials with a higher dose rate would be given preference for storage in the limited space in adjacent cells. After soil excavation is completed, the hole at the bottom of the hot cell would be filled with grout and any void spaces in the adjacent hot cells also would be grouted. The first phase is projected to require 22 months.
During Phase 2, projected to take 30 months, the outer portions of the building would be demolished, leaving hot cells and underground vaults intact. The vaults, which had tanks used to temporarily store high-level and low-level radioactive waste, have been cleaned out and grouted. A stack also would have to be removed, although it could be done with or after Phase 3.
In Phase 3, which could take 19 months, the hot cells and vaults would be cut out and removed as monoliths, including the concrete cell walls, which are up to 6 feet thick. The heaviest cell would be the A Cell, which could weigh 2,000 tons when filled with grout and waste. The cells and vaults are expected to be hauled to the central Hanford landfill. The remaining foundation and excavation of residual contaminated soils would be done in Phase 4, which could overlap with Phase 3, according to the proposed plan. The work, which would include backfilling the remaining excavation from demolition and remediation will be backfilled to grade and revegetated, is tentatively scheduled to take 15 months.
A public comment period is planned from this week through Sept. 9, focusing primarily on the cleanup regulated by the state, which has authority over the chemical contamination within the building rather than the radioactive contamination underneath. The Department of Energy initially had a Tri-Party Agreement milestone to tear down the building torn in fiscal 2013. But during preparations for that in 2010, the spill beneath B Cell was discovered. The most recent milestone requires cleanup of the 324 Building to be completed in fiscal 2021; whether that milestone is achievable may be addressed during the public comment period. DOE information prepared for budget hearings indicated that removal of soil from beneath the building might not start until after fiscal 2018. Comments may be sent to [email protected].
