Closing the San Onofre nuclear plant in Southern California was supposed to cost $3.9 billion.
It turns out that estimate may be too low. Now, Southern California Edison estimates the tab will be closer to $4.4 billion.
David Lockbaum is a nuclear engineer who once worked for the Nuclear Regulatory Commission. He's now the director of the nuclear safety program for the Union of Concerned Scientists.
The major reason for the huge price tag for dismantling the plant is that they're dealing with radioactive material and toxic chemicals that need to be treated extremely carefully, Lockbaum said. That extra care comes at a price.
Since the federal government has not provided a storage site for the nuclear waste that will be removed from the San Onofre plant — a site they began looking for decades ago — part of the plan had to include on-site storage for the waste.
"The continued storage on site for decades into the future...is built into the cost structure," says Lockbaum.
And, storing waste that remains radioactive for at least 10,000 years can be tricky.
"That's really the prime reason why the federal government hasn't been able to find a repository," Lockbaum says. "That location must be secure and contain the material from the environment for at least 10,000 years."
"For a country that's about 300 years old, projecting into the future 10,000 years is a daunting challenge," he said.