Workers have entered an airlock at the Hanford Site’s 324 Building for the first time in 15 years. It marks the restart of significant hands-on work to demolish the building, after careful planning and practice at a mockup facility built outside of the Department of Energy facility in Washington state.
“There really is progress being made,” said Bryan Foley, DOE project director.
The 324 Building, also known as the Chemical Materials Engineering Laboratory, is one of the few remaining structures in Hanford’s 300 Area, after more than 170 buildings were demolished over the last decade.
Preparations for demolishing 324 stopped in 2010 after a highly radioactive spill of cesium and strontium was found beneath the building. The spill is significant, both because it is highly radioactive and is within 1,000 feet of the Columbia River and just 1 mile north of the city of Richland.
Employees with cleanup contractor CH2M Hill Plateau Remediation Co. have begun cleaning out the airlock, which serves the 324 Building’s B Cell and other hot cells; work is expected to continue through the summer.
Based in part on historical information, Hanford officials suspect the spill was produced fabrication in the 1980s of cesium and strontium into heat sources ordered by Germany to test a repository for radioactive waste. The radioactive material apparently leaked through the cracked lining at the bottom of the B Cell and seeped into the soil beneath the building along the edges of the hot cell floor.
The Tri-Party Agreement governing cleanup at Hanford was revised after the spill was discovered to extend the milestone for demolishing the 324 Building to September 2021. A September 2019 milestone also was added for completion of remote excavation of the worst of the spill.
Remediation plans, which were initially developed by former Hanford river corridor cleanup contractor Washington Closure Hanford, call for leaving the building standing to shield against radiation and prevent precipitation from driving contamination deeper into the soil.
An excavator arm will be installed on the 30-foot-high walls of B Cell. It will be remotely operated to break up a layer of grout on the floor of the hot cell. A remotely controlled saw will then cut a 3-foot-wide trench through the stainless steel and concrete floor. The trench will form a square around the perimeter of the hot cell, which measures 22 feet by 22 feet. Contaminated soil will be dug up about 10 feet deep from the trench using the excavator arm, and then the trench would be filled with grout to stabilize the building. The most contaminated soil will be stored in boxes in at least one adjacent hot cell. The waste will be grouted and removed when the building is demolished.
The airlock will be the hub of the project’s activity. The equipment that will be used in B Cell will pass through to be installed in the hot cell and contaminated soil will be loaded out through the airlock.
This will require a clean space. The airlock is currently cluttered with debris and old equipment, including a cable reel and televator, that must be removed. Workers practiced for the entry at a mockup of the 324 Building’s B Cell built near Hanford.
“Mockups have proved extremely valuable in performing dry runs on the work,” said Bill Kirby, CH2M vice president for the Hanford 300 Area. Workers have practiced putting on multiple layers of protective clothing and removing them without spreading contamination at the mockup. The practice in entering the mockup airlock helped “to learn the steps, figure out what we need to do first to get somebody in there and get them back out safely,” said Tim Renz, a radiological control technician. Workers are wearing powered air-purifying respirators in the airlock.
Testing also is underway on a prototype saw at the Hanford Maintenance and Storage Facility, which CH2M has used for other mockup and testing projects. A steel-reinforced, concrete pad was constructed in the building to replicate the B Cell floor and test the remote-controlled saw. “We need to be very confident when it goes in the cell that it is going to do its full job and we don’t have any questions to resolve,” said Mike Thien, CH2M technology testing manager.
More construction is expected this year on the mockup of the 324 Building’s B Cell, preparing it for practice and testing in 2018 of equipment now being purchased. An excavator arm, lights, and cameras needed for digging up the soil will be installed at the mockup facility.
