Concerns were raised last year that the steel-and-concrete casks, in use at several nuclear sites, were flawed. Under plans put forth by the consortium called Private Fuel Storage (PFS), the casks would hold up to 44,000 tons of spent nuclear reactor fuel at the Skull Valley site, 45 miles southwest of Salt Lake City.

Bringing the charge was a former quality assurance auditor, Oscar Shirani, who warned of faulty welding and other safety shortcomings in the casks, which are designed by New Jersey-based Holtec International and fabricated by U.S. Tool and Die. Shirani also claimed that the NRC staff ignored his warnings.

Investigators agreed to review the allegations after requests were made by two public-interest watchdog groups. But in a 20-page report this week, the inspector general concluded that the NRC provided adequate oversight of Holtec and U.S. Tool and Die's quality assurance programs.

The NRC, the inspector general's report said, conducted yearly inspections from 1999-2002, and audits in 1996, 1999, 2000 and 2002. Deficiencies were revealed, but investigators concluded that the quality assurance programs at both companies met all requirements.

"The NRC inspection into Shirani's concerns found no violations of NRC regulations or significant safety deficiencies," the inspector general's report said.

PFS spokeswoman Sue Martin said Friday that the inspector general's report upheld the consortium's long-standing belief that the casks met NRC safety requirements.

"We're pleased but not surprised by the results," she said. "We've always thought that the Holtec casks were performing well in all of the places that they're being used."

But the casks' durability have likely come into question again this week as the NRC's licensing board held another round of closed-door hearings on the PFS proposal in Washington - centering on the potential effects of a fighter jet crash into the Goshute storage facility, where the casks would be stored above ground.

In March 2003, the Atomic Safety and Licensing Board stalled PFS's efforts to get a license and begin construction at the Utah site by ruling that the chances of such a crash - military jets fly over the area between Hill Air Force Base and the Utah Test and Training Range - exceeded the allowable risk.

Martin said the NRC's licensing board has two more days of hearings scheduled next month on the PFS proposal. A licensing decision is expected early next year.

jbaird@sltrib.com