FEATURE ARTICLE
Managing the Environmental Legacy of U.S. Nuclear-Weapons Production
Although the waste from America's arms buildup will never be "cleaned up," human and environmental risks can be reduced and managed
Kevin Crowley, John F. Ahearne
From Production to "Cleanup"
The decline of large-scale nuclear-weapons production began in the late 1970s and accelerated through the 1980s, coinciding with the thaw in Cold War relations that culminated in the Strategic Arms Reduction Treaty (START) and the breakup of the Soviet Union, both in 1991. At the same time, the reactor accidents at Three Mile Island in 1979 and Chernobyl in 1986 raised public concerns about the continuing operations of U.S. production reactors. In May 1986, Energy Secretary John Harrington asked the National Academy of Sciences and National Academy of Engineering to review the safety of the government's production and research reactors. He also commissioned a group of experts to review the operation of the N-Reactor at Hanford. Based on that review, he shut down the reactor in 1987, commenting that the United States had no need for it because the country was "awash in plutonium."
During this same period states also were beginning to assert their authority to regulate environmental releases at the sites, prompted by a 1984 federal court ruling that the Y-12 site at Oak Ridge was subject to state regulation under the Resource Conservation and Recovery Act. Complaints from Colorado led to the June 1989 Federal Bureau of Investigation raid and closure of the Rocky Flats site, a 1951-vintage weapons-component manufacturing facility near Denver, for violations of federal environmental laws. Five months later, Energy Secretary James Watkins announced the creation of the Office of Environmental Restoration and Waste Management (now the Office of Environmental Management) and declared a new mission for weapons sites: environmental cleanup. The era of large-scale nuclear-weapons production had ended.
The new cleanup program contrasted, in many respects, with the production operations. From the earliest days of the Manhattan Project, weapons production had been conducted with scientific and technical rigor and a strong focus on meeting production goals that were noticeably lacking in the early years of the cleanup effort. One of the first actions taken by the new program, before it had developed an adequate understanding of the environmental insults at its sites or its scientific and technical capabilities to address them, was to negotiate legally enforceable cleanup agreements with states and regulators. Many of these original agreements had to be renegotiated after the problems were more fully understood. At present, the cleanup program is operating under some 70 separate agreements that contain more than 7,000 schedule milestones, many of which are potentially enforceable via court action.
Although the cleanup program has been in operation for over a decade, it has, until recently, accomplished relatively little actual cleanup. To be sure, DOE has had some important recent successes, both in site remediation and waste disposal. Perhaps its most notable waste disposal success was the 1999 opening of the Waste Isolation Pilot Plant near Carlsbad, New Mexico. This deep geologic repository will eventually be used to dispose of up to about 175,000 cubic meters of defense-generated transuranic waste (mainly plutonium-contaminated debris, clothing and tools, and the like) from nuclear weapons sites. Additionally, DOE has recommended Yucca Mountain, Nevada as the site for a deep geologic repository for spent fuel and high-level waste and is now in the process of developing an application for a construction license, which it plans to submit to the Nuclear Regulatory Commission in 2004. If constructed, this repository will be used to dispose of the immobilized high-level waste and spent fuel from nuclear weapons sites along with commercial spent fuel.
The notable remediation successes include the stabilization and capping of mill tailings piles and the cleanup of some Manhattan-era sites, the latter of which is presently being carried out by the Army Corps of Engineers. Also, successful efforts are being mounted at many sites to characterize the nature and extent of environmental contamination, halt the spread of contaminated groundwater, and cap waste burial sites to retard water infiltration and contaminant leakage. Work also is proceeding to decontaminate and demolish buildings and clean up contaminated soil and groundwater at some of the smaller sites (such as Fernald and Mound) so that they can be declared closed around 2006.
Perhaps the most significant technical success in the remediation program to date has been the construction and successful operation of a $2.5 billion plant at Savannah River for immobilizing high-level waste, which went into production in 1996 and has to date produced more than 1,200 canisters of borosilicate waste glass. At Hanford, work also has begun to cocoon the nine production reactors, remediate contaminated soil and groundwater along the Columbia River, and stabilize corroding spent fuel from the N-Reactor that has been stored for over decade in two unlined water basins next to the river, one of which is leaking. This fuel is being dried, canned and placed into temporary storage away from the river. With the notable exception of the immobilization program at Savannah River, however, none of these remediation actions has been technically demanding. In fact, attempts to undertake the technically demanding tasks have failed, due largely to inadequate scientific and technical understanding. Three examples serve to illustrate this point.
In the early 1990s, the Idaho laboratory began a project to excavate and treat waste and contaminated soil from a 1-acre site known as "Pit 9," one of a series of pits and trenches used for disposal of low-level and transuranic radioactive waste. Pit 9 is thought to contain about 7,000 cubic meters of sludge and other solids contaminated with plutonium from Rocky Flats, and the remediation effort was designed to demonstrate retrieval and processing technologies that could be applied elsewhere on the site. The DOE awarded a $200 million contract for this work in late 1994, but the project fell behind schedule, and costs exceeded the contract price before any waste had been retrieved or processed. The contract has been canceled, and the contractor has alleged that inadequate characterization of the waste in the pit contributed to this failure. Excavation of waste from this pit may not take place until 2004, fully a decade after the initial contract was awarded.
Efforts are now under way at Savannah River to develop a chemical process to remove radionuclides, principally cesium, strontium and plutonium, from the nonsludge fraction of its high-level waste for immobilization in glass. Savannah River contractors spent 10 years and almost $500 million to develop an in-tank precipitation process for removing cesium, but when this process was placed in production in one of the underground storage tanks, large quantities of benzene, an explosive hazard, were generated. Subsequent investigations and experiments failed to positively identify the benzene-generation mechanism, although a catalytic reaction involving trace elements in the waste was thought to be responsible.
DOE–funded scientists are now developing a solvent-extraction process that has a high selectivity for cesium. This process looks promising, but the schedule for waste retrieval and processing has been set back several years. The delay would likely have been much longer if not for the foresight of the department's research and development organizations, which funded research on alternative separation processes before the problems became evident.
There have been several attempts at Hanford, starting in the early 1990s, to begin retrieving and immobilizing high-level waste from its tanks using approaches similar to those at Savannah River. Construction of a facility to immobilize about 10 percent by volume and 25 percent by radioactivity of the liquid high-level waste finally began this year with the start of construction of a waste treatment and immobilization facility. This phase-1 project is slated to last until 2018 and cost about $15 billion. Hanford has not yet determined how it will process the remaining waste, or how it will retrieve the solid or semi-solid wastes from its single-containment tanks to meet the 99 percent removal milestone required by its compliance agreement with the State of Washington. Retrieval of this waste without damaging the tanks and releasing contaminants to the environment may be difficult using currently available technologies.
To be fair, the DOE has tried several times in recent years to improve the effectiveness of the cleanup effort. In 1995, the assistant secretary for environmental management announced a "10-year plan" for reducing the high annual carrying costs of the sites by accelerating the closure of smaller sites. Several sites, including the Mound (Ohio) and Rocky Flats sites, are now slated to be closed by 2006. The current administration is developing a plan to "accelerate cleanup" by focusing on risk reduction and negotiating with site regulators to shorten cleanup schedules. The objective is to reduce the current $220 billion to $300 billion estimated life-cycle cost of the cleanup program by $100 billion and 40 years.
Although these goals strike us as sensible, the success of this effort will hinge on several factors. Will regulators be willing to modify their compliance agreements with the DOE? Will state and local authorities and the site administrators themselves allow reallocation of budgets so that high-risk projects can be funded on an accelerated schedule—or conversely, will Congress allocate additional funds for this purpose? Will the DOE and contractors exercise good judgment in developing and applying remediation plans and, especially, learn from past experiences at the sites to avoid repeats of some of the problems described previously? Can DOE-funded investigators come up with timely solutions when new problems are identified, as they did for the cesium-separation problem at Savannah River?
» Post Comment