Washington state is giving the Department of Energy more time to figure out how it will safely store radioactive waste in two Hanford nuclear reservation tunnels.
The state also is amending its legal order to make clear that DOE must provide plans to stabilize a 1,700-foot-long tunnel storing 28 rail cars loaded with highly radioactive equipment. The tunnel is at serious risk of collapse, according to a DOE analysis.
“We don’t want to delay urgent work on the tunnel, but it’s important stabilization plans are developed for both tunnels,” said Stephanie Schleif, facility transition project manager for the state Department of Ecology’s nuclear waste program.
The Washington State Department of Ecology issued a legal order May 10, a day after the shorter of two waste-storage tunnels at Hanford’s PUREX processing plant was discovered to be partially collapsed.
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The initial order required a proposal for ensuring the waste be safely stored by Oct. 2.
On Friday the state notified DOE that it was extending the deadline to Dec. 8, and was adding language to its legal order to make clear that the longer tunnel must be stabilized.
DOE said in a statement that it “appreciates the additional time to complete the corrective actions under the administrative order.”
The older and shorter of the two PUREX tunnels has been partially stabilized.
8 rail cars with waste in Tunnel 1
28 rail cars with waste in Tunnel 2
360 feet length of Tunnel 1
1,700 feet length of Tunnel 2
The hole discovered in its top has been filled with sand and soil and its 360-foot length has been covered with a sheet of heavy plastic.
Work is expected to start soon to fill the tunnel with concrete-like grout to further stabilize it.
But DOE is taking more time to determine the best way to stabilize the second PUREX waste tunnel.
It met the first requirement of the state’s legal order by a July 1 deadline, conducting a required structural analysis that determined the second tunnel was at serious risk of collapse.
On the second deadline of Aug. 1, it was required to detail actions it would take to ensure the safe storage of the waste in the second tunnel.
Rather than telling the Department of Ecology how it planned to stabilize the tunnel, DOE told the state it planned to step up monitoring while it convened an expert panel to consider the best option for stabilization.
That did not meet requirements of the order, the state said in a statement on Aug 1.
But it also said that DOE’s “proposal to convene a panel of experts to analyze options to stabilize Tunnel 2 and the waste in it has merit, especially if it results in a robust solution that all agree will be adequately protective.”
It noted that it would be difficult for DOE to meet the Oct. 2 deadline after not supplying compete information for the Aug. 1 deadline.
Among the proposals DOE has said are on the table for stabilizing the longer tunnel is covering it with a tent or pre-engineered building.
DOE also is considering filling the tunnel with expanding foam or with sand or clay, an option it put on the list after it was suggested at the public meeting.
A controlled collapse of the tunnel is being evaluated, although it could be difficult to keep contamination from spreading and protect workers.
DOE also is considering whether to go ahead and retrieve the stored waste. It would be a permanent solution, but would take more time than other solutions to plan and carry out.
The older tunnel, built in 1956, was constructed mostly of timbers. A second tunnel, built in 1964, had state and concrete used in its construction.
Options are being evaluated on factors including cost, the level of protection offered and whether the proposed fix would interfere with eventual permanent cleanup of the tunnel. DOE also is considering how long options would take to complete as the threat of a collapse looms.
The expert review proposed by DOE is consider the tunnel design, operating history and waste inventory. Information will be used for a detailed analysis for Tunnel 2 and then a decision on which option would be best for stabilization of the tunnel.
The tunnel that partially collapsed was built of timbers in 1956 and had a flat roof. Eight rail cars loaded with highly radioactive waste from operations at the PUREX plant were pushed into the tunnel.
No worker was injured in the May 9 partial collapse of the tunnel, and no spread of radioactive contamination was found.
The second tunnel, built in 1964, was built in the shape of a Quonset hut, with steel ribs supporting corrugated steel plate roof panels.
After two collapses during construction, it was re-engineered to add steel I-beams and reinforced, arched concrete girders over the top.