Denise Chancellor and Jim Soper, assistant attorneys general, asked the board to reverse its Feb. 25 ruling that there was less than one chance in 1 million that an F-16 could crash into the nuclear dump, which cleared the way for the Nuclear Regulatory Commission to issue a license for the facility.

Private Fuel Storage, a coalition of electric utilities, wants to store 44,000 tons of nuclear fuel on the Skull Valley Goshute Indian Reservation about 50 miles southwest of Salt Lake City.

"By the technical standards, the legal standards and the test data, PFS has failed to meet the criteria," Chancellor said.

Paul Turk, the staff attorney for the licensing board, urged the judges to reject each of the state's contentions.

"You don't give yourself enough credit. Your decision is correct," Turk told the judges. "The state wants you to set that aside, but they're wrong."

The licensing board could reverse its earlier opinion, or decide another hearing is needed to explore potential radiation exposures related to accidents at the site.

It is possible, though unlikely, that the six-hour hearing before the three judges could be the state's last chance to make its case before the Nuclear Regulatory Commission rules on PFS' license.

"The project is safe. It complies with every standard for storing spent fuel," said John Parkyn, chief executive officer of PFS. "These casks are designed to withstand [a jet crash], so whether they're standing in Utah or Wisconsin, they'll withstand it."

Margene Bullcreek, a member of the Skull Valley Goshute tribe, said she remains hopeful the board will not endanger members of the tribe by allowing the waste to be stored on the reservation.

The state argued that:

l The board failed to hold PFS to the Energy Department standard in determining the strength of the casks.

l The board failed to adequately consider the damage that could be done by an F-16 clipping the top of one of the fuel casks.

l The state should be entitled to another hearing before the board to present data on radiation that might seep from a cask if it is damaged internally without puncturing its exterior.

l The board built its risk assessment of an F-16 crash on models extrapolated from inadequate data, building on the key point in Judge Peter Lam's February dissent.

"It seems to me that this data is so frail . . . it's now reduced to the point where it means nothing," Soper said.

The board did not rule on the state's arguments and could take a month to do so.

Lam appeared most amenable to the state's arguments, while Judge Paul Abramson peppered the Utah attorneys with skeptical questions and, at times, snippy barbs.

Judge Michael Farrar sought middle ground, floating hypotheticals and potential solutions, including possibly having both sides submit new evidence on whether enough radiation could escape from a damaged but unruptured cask to warrant consideration.

PFS' attorney, Paul Gaukler, argued against further delays, saying the state hadn't raised the cask issue during earlier hearings and "justice delayed is justice denied" for PFS.

The NRC could grant a license, then withdraw it if the state's objections are upheld, although it is likely the NRC will wait until the state's objections have been fully aired.

The state has appealed the F-16 crash issues to the NRC and has asked the commission for a hearing on the merits of licensing the PFS site.