Staff Reports
WC Monitor
9/11/2015
External events and natural phenomena, including severe earthquakes, fires, and extended loss of power, pose some of the greatest risk at the Hanford Site, according to an interim report on a risk review project for the site. The interim report, prepared by the Consortium for Risk Evaluation with Stakeholder Participation (CRESP), also rated as high risk tank wastes and dependence on active controls to maintain safety for facilities with large inventories of radionuclides.
The Department of Energy commissioned the $4 million study to identify and characterize potential risks at Hanford. The review is intended to provide information to help guide decisions about the sequencing of the remaining cleanup work at the site. The interim report considers about half of the remaining cleanup, with an additional interim report planned to cover the rest. Risk analysis completed by the CRESP review team to date covers the tank farms and contaminated groundwater plumes, along with some of the processing canyons, waste disposal areas, and operating facilities.
The interim report concluded that members of the public, outside the boundary of the site or in areas of controlled access such as on the Columbia River, now usually face low to no risk of harm from radiological exposure, even through events that would release radioactive contaminants. But the events could put people on site at risk of radioactive exposure, whether they are workers or people visiting Hanford.
The interim report cited three areas of particular concern due to external events and natural phenomena.
- A severe earthquake could lead to the total structural failure of the 202-A Building and both tunnels at the Plutonium and Uranium Extraction, or PUREX, facility, according to the document. The plant reprocessed almost 70 percent of irradiated fuel at Hanford between the 1950s and 1990 to remove plutonium, uranium, and neptunium. The tunnels were used for waste disposal, with the newer of the tunnels containing 28 railcars of waste. People located 100 meters away could be exposed to at least 25 rems of radiation in several scenarios, including a collapse of structures or a fire in particular areas, including the oldest tunnel, which was constructed almost entirely of railroad ties.
- The Central Waste Complex, where solid waste is stored, could put people there and nearby at risk in the event of a fire involving drums of waste, the interim report said. The risk might increase because the complex continues to receive wastes, but currently is unable to ship waste off-site for disposal because the Waste Isolation Pilot Plant is closed and funding has not covered repackaging of wastes, the interim report said.
- The third facility among those at the greatest risk from external events is the Waste Encapsulation and Storage Facility, where cesium and strontium capsules are stored in pools of water that provide cooling and radiation shielding. The storage pools currently are safe, but the structure’s long-term integrity is uncertain, the interim report said.
Risks at the tank farms include hydrogen gas generation, the interim report said. If the hydrogen caught fire, waste could be released from the tanks into the atmosphere or the ground. Risks posed by hydrogen gas generation can be somewhat reduced through removal of water-soluble cesium 137, the interim report said. Groundwater threats could be substantially reduced by removal of water-soluble constituents from a selected set of tanks. The interim review includes a tank-by-tank look at risk, including which of Hanford’s 177 waste storage tanks pose the greatest risk to groundwater.
CRESP reviewers were concerned over dependence on active controls, such as power, cooling water, and active ventilation, at the K Basins and at the Waste Encapsulation and Storage Facility. Safe storage at the K Basins relies on keeping the sludge submerged in water to reduce radiation exposure to workers and prevent fires of reactive metal fragments. Safe processing of K Basin sludge also requires keeping it wet during retrieval, transfer, interim storage, and processing, the interim report said. At the Waste Encapsulation and Storage Facility, the concern is related to a severe earthquake that could damage hot cell and ventilation equipment, potentially exposing people at the facility and in the area to contaminants.
The interim report rated rather than ranked risks, said David Kosson, the review’s principal investigator. “Risk management is the purview of the Tri-Party agencies,” he said. Many factors in addition to risk must be considered when cleanup decisions are made, including legal obligations, input from stakeholders, community values, whether disposition pathways are available, the available workforce, and continuity of the workforce, he said.
When plans to conduct the review were announced, the Hanford Advisory Board criticized the project, fearing DOE could use the results to reduce cleanup efforts. Kosson acknowledged that much remediation has been done at Hanford, particularly in the river corridor, but that remaining cleanup is expected to take 50 more years and cost more than $100 billion. The review should help provide the basis for understanding why Hanford cleanup is so complex and so costly, he said. “It’s important to take a step back periodically to assess what is remaining and how to think about the challenges ahead,” Kosson said. He stressed that the Hanford risk review should not be confused with a recently released report to Congress that analyzed how effectively DOE addresses risk across the environmental management complex. That report was criticized by the governors of Washington and Oregon, who said it instead focused on ways to reduce costs of cleanup. CRESP was asked to organize the committee that prepared that report, but did not write it. Comments may be made on the interim risk report prepared by CRESP for Hanford at www.cresp.org/hanford until Oct. 30.
