A couple could turn into showstoppers if critics are able to convince NRC reviewers that the Department of Energy's calculations about the repository's performance are off-base, he said.

"You end up getting it down to a few issues," Kraft said during a briefing at the institute's Henderson office that was held in anticipation that DOE will submit its license application in June.

Those issues include the estimated rate at which nuclear waste canisters will corrode once placed inside the mountain, and the amount of longer-lived radionuclides in tens of thousands of tons of used reactor fuel that will dissolve and be carried off into the environment at higher concentrations than project scientists calculate.

"What if solubility is way higher? That increases dose rates," Kraft said, referring to isotopes of technetium, iodine and neptunium.

As for corrosion of the canisters, he said a successful attempt by Nevada opponents to prove that the metal alloy will corrode "far faster" than DOE predicts could raise doubts with a licensing panel.

"I am willing to bet that performance of solubility and corrosion rates are going to be the big ones," he said.

Bob Loux, the Nevada official who coordinates opposition to the Yucca plan, agreed that corrosion and the movement of radioactive particles through the mountain will be major issues.

But Loux said he would expand the list of potential showstoppers that probably will be aired.

"Clearly the fitness of DOE as an applicant will also be one," said Loux, executive director of the Nevada Agency for Nuclear Projects.

Loux said the state believes it can make a strong case that shortcomings in Energy Department quality controls that have been documented over the years by DOE and congressional auditors should raise questions about its ability to manage the project.

Nevada also believes that potential for volcanic activity in the vicinity of the proposed repository, 100 miles northwest of Las Vegas, might resonate with the NRC, Loux said.

Last year, state scientists raised concerns for earthquake faults, particularly the Bow Ridge Fault, in the vicinity of concrete storage pads that DOE wants to build near the mountain.

That's where thousands of tons of highly radioactive spent fuel would sit to cool off before disposal in tunnels inside the mountain.

Kraft said it could take "a couple decades before it gets to the right heat load" for underground storage.

He expects Nevada will challenge the design for above-ground storage as having the perception of an interim storage site, which by law is not allowed in the state that hosts the permanent repository.

"While it looks like it is interim storage, it is not interim storage," he said.

Contact reporter Keith Rogers at krogers @reviewjournal.com or 702-383-0308. Contact Stephens Washington Bureau Chief Steve Tetreault at stetreault@ stephensmedia.com or 202-783-1760.