Sproat urged them to step up lobbying for Congress to pass a bill that would loosen the strings on the fund earmarked to pay for the repository.
Ratepayers for nuclear utilities are charged a fraction of a penny per kilowatt hour of electricity they consume, a rate that has built the fund to a $21 billion balance.
In time, more than $1 billion will be needed annually for construction, DOE officials say. Budget caps in Congress, plus the efforts of repository opponents such as Senate Majority Leader Harry Reid, D-Nev., have limited annual payouts to about $400 million.
"Until we get this issue fixed I can't, nor can anyone else, tell you with any degree of certainty when the repository is going to open," Sproat said. "This is the single biggest issue we as a country need to address so this repository can go forward."
At $400 million a year, "we are never, ever going to build this repository with that kind of cash flow funding; it just ain't going to happen," he said.
The longer a repository goes unopened, the more taxpayers will pay to utilities who have sued the Energy Department for delays, Sproat said.
If Yucca were to open by 2017, the liability would be some $7 billion, he said. A 2020 opening would cost $11 billion in settlements and judgments.
Sproat said those numbers are getting the attention of lawmakers.
"We are talking big bucks," he said. "It is one of the levers that gets people interested and gets them to understand we just can't leave things the way they are."
In the near term, Sproat said, DOE plans to file a repository license application "sometime this summer" with the Nuclear Regulatory Commission.
Spending limits engineered by Reid in this year's budget caused DOE to push back a June 30 target.
Contact Stephens Washington Bureau Chief Steve Tetreault at stetreault@stephensmedia.com or (202) 783-1760.