When the Zion Nuclear Power Station in Illinois closed its doors in 1998, plant owner Commonwealth Edison, now part of Exelon, thought it would take more than two decades to clean up the site.
At the time, Zion needed repairs that exceeded the value of the 2,080-megawatt plant, and dismantling it was the better financial option, said Craig Nesbit, vice president of communications at Exelon. But when operations ceased, the flow of money from utility ratepayers also stopped, drying up the source of Zion's decommissioning funds.
The company opted to delay its cleanup plan. Aside from removing the main reactor components, Exelon would not begin the rest of the work until the 2020s, by which time the funds would have accumulated enough interest to cover the full decommissioning process.
Luckily for Exelon, though, another option presented itself when EnergySolutions, a nuclear waste managment company based in Salt Lake City, offered to take over the decommissioning plan. The company acquired the Zion plant in September 2010. According to EnergySolutions CEO Val Christensen, full decommissioning will cost about $1 billion dollars over the next 10 years.
EnergySolutions can expedite the cleanup because of its technical capacity, said Christensen. His company is currently decommissioning 18 reactors in England. They also own a low-level nuclear waste storage facility in Clive, Utah, which will speed up the waste disposal process.
The move has saved Exelon considerable headache and illuminates some of the unseen challenges of nuclear energy operation. Indeed, other plant operators haven't been as lucky when it came to decontaminating their nuclear reactor sites.
Although the usual critiques of nuclear generation revolve around safety risks and high construction fees, relatively little attention has been paid to what happens when a nuclear plant powers down for good.
Costs Can Reach Over $1 Billion
Every nuclear plant must be decommissioned at the end of its useful life, usually after it has been operating for 40-60 years. The costly, labor-intensive process involves two major actions: nuclear waste disposal and decontamination to reduce residual radioactivity.
The U.S. currently operates 104 commercial nuclear power plants. Most were built in the 1970s and are slated for decommissioning during the next three decades. As of April 2011, there were 23 nuclear units in various stages of decommissioning. Ten out of the 23 have been completely cleaned up.
According to Paul Genoa, director of policy development of the Nuclear Energy Institute, a trade group for the nuclear power industry, decommissioning costs typically run at $500 million per unit. But actual costs vary based on the plant's size and design, and some have reached over $1 billion — between 10 percent and 25 percent of the cost of constructing a nuclear reactor today.
Projects can run over budget if the plant is more contaminated than previously thought, said David Lochbaum, director of the Nuclear Safety Project at the Union of Concerned Scientists.
Industry Learns from Mistakes
A decommissioned plant creates several different streams of waste. For one, spent nuclear fuel rods are kept in dry storage at the reactor sites. According to the Nuclear Energy Institute, an average nuclear plant generates 20 metric tons of used nuclear fuel annually, or 1,200 metric tons over a plant's 60-year lifespan — an amount equivalent to the size and weight of about 1,200 SUVs.
Two, anything contaminated with small levels of radiation — pipes, tools, workers' clothing — are sent to special low-level nuclear waste facilities around the country. The remaining non-radiated waste can be disposed of in regular landfills.
Human error can complicate the cleanup process.
When Connecticut's Haddam Neck plant was dismantled in 1996, for instance, some contaminated materials were mistakenly sent to municipal landfills. They were later dug up and moved to nuclear waste facilities, a mistake that cost the company millions. The original decommissioning cost was estimated at $719 million; the company spent nearly $1.2 billion in the end.
"We've learned from those lessons," said Genoa of the Nuclear Energy Institute. Early plants like Haddam Neck were built in the 1960s "at a time when radiation detection monitoring is worse than it is today." The Nuclear Regulatory Commission has since strengthened safety regulations. Today's plants, for instance, closely monitor radiation levels in the building and surrounding land to ensure that contaminated materials are disposed of in the proper facilities.
Lochbaum agreed that there is "better tracking today." He also predicted that the process would improve with time, as the industry gains more experience decommissioning plants.
SAFSTOR'S Safety Advantages
The Nuclear Regulatory Commission offers three pathways to decommissioning. The first involves immediate cleanup after the plant shuts down. Genoa said this is the fastest method to return the site back to the public for beneficial use.
To date, all 10 of the fully decommissioned plants have met the NRC requirements for unrestricted use, which means the sites are safe enough to be reclaimed for any purpose including agriculture, housing or green space.
In the second option, called SAFSTOR, the plant is closed and awaits cleanup at a later time, offering plants like Zion extra time to increase their decommissioning funds. The NRC gives utilities up to 60 years to complete decommissioning.
This waiting period adds flexibility for plant owners with multiple reactors. The Illinois Dresden plant in Morris, Ill., for example, has three units. The first was shut down in the late 1970s, but units 2 and 3 are still running. Once they cease operation all three units will be decommissioned together to save money and resources.
Because radioactivity decays over time, SAFSTOR has some safety advantages as well, explained Genoa. Isotopes with short half-lives, like cobalt-60 (5 years), will be easier to clean up if the plant remains in stasis for decades.
Of the 13 reactors currently being decommissioned, six chose immediate decontamination and seven remain in SAFSTOR conditions.
The ENTOMB Option
No U.S. plant has ever chosen the third decommissioning option, called ENTOMB. Genoa said the name brings up unfortunate images of Chernobyl, but the comparison is not a fair one.
"In Chernobyl, the radiation was uncontained, so they built an enclosure over it to protect the public," he said. By contrast, the ENTOMB option is much more controlled.
Workers would begin by moving the fuel rods into dry storage casks. That first step removes 99.9 percent of the plant's radiation. Next, they use solvents and filters to clean up other contaminated surfaces. The radioactive material is sent to low-level waste facilities, and the plant is left to sit for decades.
Genoa said that with ENTOMB there is no need to build extra containment buildings because most of the radiation is already gone, though plant operators would continue to monitor the site for security. "It might need some waterproofing or coats of paint, but other than water or [unauthorized] people getting in, there's very little risk."
After 80 to 100 years, the plant would be safe enough to enter while wearing street clothes, said Genoa, and workers could dismantle the plant with just "a plasma torch and dust mask."
But despite the safety advantages, Genoa said utilities don't like the ENTOMB option because they don't want to deal with the long-term liability. And most nuclear plants are built on valuable waterfront property, so the public generally wants to reclaim the sites as soon as possible.
Zion First to Transfer License
Zion's decommissioning has drawn its fair share of attention. While nuclear operators often hire contractors for the cleanup work, Exelon is the first company to transfer its nuclear operating license for the purposes of decommissioning.
Christensen, the CEO of EnergySolutions, said they acquired the license to speed up the cleanup process. "By owning the site ... we can manage our own destiny, keep on schedule and make changes the split second they need to be made.
"It is also a profitable venture for EnergySolutions," Christensen added. For example, as operators of the Clive nuclear waste facility in Clive, Utah, EnergySolutions will make money from the disposal fees.
About 30 percent of the cost of decommissioning goes towards waste disposal, said Christensen.
EnergySolutions now has total stewardship over the project. They're also legally responsible for anything that might go wrong, but Christensen was confident in his company's abilities.
Trading Radioactivity for Volume
Low-level radiation waste comes in three varieties: Class A, B and C. The facility at Clive only takes Class A waste, which contains the lowest levels of radiation.
In addition to Clive, there are two other low-level nuclear waste facilities in the United States — in Barnwell, South Carolina and Hanford, Washington. Both sites accept Class B and C waste but only from select northwestern and eastern states. Similarly, a new low-level waste facility under construction in Andrews County, Texas will limit its intake to nuclear waste from Texas and Vermont.
When Barnwell and Hanford started restricting their operations, nuclear plants learned to adjust their practices, said Genoa. Operators began changing filters more often to selectively create Class A waste that could be sent to Clive. As a result, Class B and C now make up less than 15 percent of low-level nuclear waste.
In decommissioning Zion, EnergySolutions will store its Class B and C waste on-site and rely on the Clive facility for disposal of Class A material, while the industry watches the Zion plant's experience.
For his part, Genoa is supportive of the company's unique decommissioning approach, calling the license transfer at Zion an "interesting" model for the future. The NRC will be keeping close tabs on the project, he said, in hopes that "the new approach can lead to a cheaper, more efficient [decommissioning] process."