A year after the partial collapse of a tunnel used to store highly radioactively contaminated equipment at the Hanford Site in Washington state, the Department of Energy is examining risks at the facility and across its cleanup complex. Work also continues to stabilize a second and larger tunnel at Hanford, which a structural analysis also determined to be at risk of collapse.
On May 9, 2017, workers discovered a breach in the smaller of two PUREX Plant tunnels, which together hold 36 railcars loaded with waste. Off-site emergency response centers were activated and thousands of workers were ordered to take cover indoors until it was determined that no radioactive material had become airborne. The 8 feet of soil above the tunnel had fallen on top of the waste when a section of the tunnel roof gave way, effectively containing the waste.
The incident prompted DOE’s Office of Environmental Management to assemble a team to perform a complex-wide extent of condition review of risk at other excess facilities considered to be high hazard, the department said. The team visited three environmental cleanup sites – Hanford, Oak Ridge in Tennessee, and Savannah River in South Carolina – and determined the properties were generally appropriately managing the risks of aging high-hazard facilities. The team’s report is still in draft form and not yet publicly available.
Two weeks after the tunnel collapse, Sen. Maria Cantwell (D-Wash.) and six other members of Congress asked the Government Accountability Office to specifically examine Hanford’s aging facilities to determine how they are monitored and maintained. The GAO has not yet released a report on its findings.
The two DOE offices that oversee remediation at Hanford, the Richland Operations Office and the Office of River Protection, have launched their own initiative. They have been collaborating over the last year to draw up a site-wide list of cleanup priorities for discussion with the facility’s regulators: the Washington state Department of Ecology and the U.S. Environmental Protection Agency.
Such a joint assessment by the two DOE offices would have been unlikely two years ago, said Alex Smith, Nuclear Waste Program manager for the Department of Ecology. The priority list being developed is in addition to priority lists for contractors and for the individual DOE projects. A final joint-office list has yet to be released, but it could lead to changes in the Tri-Party Agreement that governs cleanup at Hanford, with some projects being moved forward in the schedule and others delayed.
“It’s a continual job for us to evaluate risk and work on those things that we feel are the more imminent risks,” said Doug Shoop, manager of the Richland Operations Office.
Hanford stakeholders had been aware of the risk the PUREX tunnels presented before May 2017. The Hanford Advisory Board in early 2016 advised DOE and its regulators to “expeditiously investigate potential risks posed by the PUREX tunnels.” The board’s thoughts about the tunnels were covered in just two sentences in a wide-ranging, seven-page letter on proposed changes to Tri-Party Agreement milestones for central Hanford. The Energy Department and its regulators agreed with the advice and said they would submit a report on assessing structural integrity of the tunnels by September 2017, which turned out to be four months after the partial collapse.
The multi-university Consortium for Risk Evaluation with Stakeholder Participation (CRESP) also identified the tunnels as a potential risk as part of a Hanford risk review project commissioned by DOE. A September 2015 update on the project said a collapse of the tunnels following an event such as an earthquake could expose workers within 100 yards to radiation.
However, DOE, its regulators, and some key stakeholders were more concerned about other risks at the former plutonium production complex. The tunnels “weren’t really considered to be the big risk. There are a lot of them out there,” said David Reeploeg, vice president for federal projects at the Tri-City Development Council (TRIDEC).
Among the focuses of the Richland Operations Office at the time were demolition of the highly contaminated Plutonium Finishing Plant; preparing to dig up a highly radioactive spill beneath the 324 Building near the Columbia River; moving radioactive sludge out of underwater storage near the Columbia River; and moving cesium and strontium capsules out of a concrete basin that is at risk in a severe earthquake.
In addition, much of the attention and the majority of spending at Hanford goes to the Office of River Protection’s work to manage and then treat 56 million gallons of radioactive waste stored in underground tanks. Some 67 of 149 single-shell waste tanks are suspected of having leaked or spilled waste in the past, and one is known to be actively leaking. In addition, the oldest of 28 double-shell tanks was taken out of service after it sprang a leak between its shells.
Hanford Challenge, a Seattle-based watchdog, is more critical of the Energy Department for allowing the tunnel collapse than most Hanford-area stakeholders, such as TRIDEC. Hanford Challenge Executive Director Tom Carpenter said DOE has a dismissive attitude toward risk, which contributed both to the tunnel collapse and the spread of radioactive contamination later in the year during demolition of the Plutonium Finishing Plant.
After the partial tunnel collapse, DOE moved quickly to stabilize the older of the two PUREX Plant tunnels, which holds eight railcars. It had contractor CH2M Hill Plateau Remediation Co. immediately fill the breach with soil. By November the tunnel had been filled with concrete-like grout to prevent further collapse. Permanent plans for cleaning up the tunnel and the waste now grouted in place within have not been made. The Energy Department also has settled on grouting as its preferred plan for stabilizing the second tunnel, which holds 28 railcars loaded with waste. Work could start as soon as this summer.
