A Chernobyl Lesson for FukushimaSteve Featherstone
The challenges for Japanese authorities at the Fukushima Dai-Ichi nuclear power station remain grave. With potentially fatal radioactive material leaking from the stricken plants, it will take weeks or months for workers to stabilize the facility and know how much nuclear fuel is damaged in the reactors and spent fuel pools. Only then can the cleanup begin.
"It isn't a week endeavor or a month endeavor, it's a years endeavor to do this work," says Kurt Kehler, vice-president of CH2M Hill, a company that decommissions and demolishes nuclear power plants around the world. CH2M Hill is mothballing the Hanford facility in Washington State, which produced plutonium for the Manhattan Project. The company was also among the bidders to build a steel hangar to contain radiation from Chernobyl, a project now being built by Novarka, a consortium of French contractors.
"There's two different things you're concerned with in the nuclear cleanup business," Kehler adds. "One is contamination and one is radiation, and they're completely different." Nuclear fuel rods emanate radiation; particles of fallout create radioactive contamination of land or objects.
Fukushima is unlikely to reach Chernobyl levels in either category, but the problems faced there still hold lessons. When the Chernobyl reactor blew, deadly radiation emanating from its smoldering core and radioactive fallout blanketed the site, thwarting attempts to seal it off. In a desperate measure, the Soviets entombed the reactor within a concrete shell, or sarcophagus, while they figured out a better way to dispose of the molten nuclear fuel deep inside. The sarcophagus was designed to last 10 years. That was 25 years ago. Now it's dangerously unstable.
"It was never a really well-put-together structure," says Laurin Dodd, a manager at the Chernobyl plant for the last five years. "There's large openings in it the size of picture windows with small mammals going in and out, and birds going in and out." As the managing director for the Shelter Implementation Plan, Dodd works for the Ukrainian government overseeing Novarka's construction of the New Safe Confinement (NSC), a 345-foot-high steel hangar that, when completed in 2015, will cover the crumbling sarcophagus. Radiation levels directly over the sarcophagus are too high for the arch to be built in place. Instead, it will be erected piecemeal in a nearby "assembly zone" and slid over the sarcophagus on rails.
While radiation levels are lower in the assembly zone, the ground around the plant is a radioactive minefield that sometimes brings work to a halt. Crews digging holes for concrete and steel pilings to anchor the rails have struck highly contaminated equipment buried by the Soviets. "Caterpillars, cranes, trucks, just about anything you can imagine," Dodd says. "Occasionally there are pieces of fuel that were blown out of the reactor during the accident."
With excavation work nearly finished, crews will soon begin pouring concrete platforms to hold the cranes that will eventually lift the arch segments into place. Blueprints for the arch have yet to be approved by Ukrainian regulators, and designing it "has been a bit painful, because it's the first of its kind, and it's unique and huge," says Sean Evans, operation leader for the €1.5 billion Chernobyl Shelter Fund at the European Bank for Reconstruction and Development (EBRD), the NSC plan's administrator. It's not only the massive size of the arch that makes it unique, or the fact that it's being assembled in one of the most contaminated places on the planet, but rather its purpose. It's much more complicated than an oversized steel barn. "Confinement is but one of its jobs," Evans says. "It's really an integrated decommissioning facility."
When EBRD eventually hands over the NSC's keys to Ukrainian authorities, workers will begin the monumental task of decommissioning Chernobyl. Remote-operated cranes attached to the underside of the arch will dismantle the leaky sarcophagus, block by block, revealing the scorched wreckage of the reactor building. At the time of the accident, about 200 tons of nuclear fuel melted straight through the building and flowed into the basement, forming blob-like configurations that Chernobyl technicians have given colorful names, such as "the elephant's foot." Ultimately the entire reactor building will be demolished, the elephant's foot chiseled away, and the whole radioactive mess carted off and buried. For the duration of this delicate operation, which could take decades, humidity inside the hangar must be maintained at a low 40 percent to prevent corrosion of its steel frame. The Ukrainians will have plenty of time to get the job done, since the container is designed to last 100 years.
Once the Japanese get the reactors at Fukushima under control, they will face many of the same challenges: keeping workers safe in a highly radioactive environment and preventing radioactive material from leaking into the water or atmosphere. Some problems will be unique to Fukushima. For instance, how will damaged fuel rods be extracted from the reactor vessels and spent fuel pools?
Kehler of CH2M Hill speculates that the Japanese won't require anything quite so big or complicated as Chernobyl's to shelter the reactor buildings while they're pulling the fuel out of them. "They would build another secondary containment," says Kehler, "a light steel shelter around the buildings." In other words, the reactor buildings may end up looking much the way they did almost three weeks ago, before the name Fukushima became synonymous with the phrase "nuclear disaster."
The bottom line: The ongoing containment challenges faced at Chernobyl may hold lessons for Japan's damaged Fukushima nuclear plant.