The federal Nuclear Regulatory Commission, as part of a "long-term" comprehensive study of its radioactive waste classification system, will consider reclassifying depleted uranium as high-level waste. Meanwhile, it will develop site-specific disposal criteria to help determine which landfills can safely accept large quantities of the radioactive material -- 11 tons or more.

File that under better late than never, because EnergySolutions has already accepted 49 tons of depleted uranium at its low-level nuclear waste disposal facility at Clive in Tooele County, including more than 5,000 55-gallon drums since last October.

But a lot more depleted uranium could be on the way, as new uranium enrichment facilities ramp up to fuel a nuclear energy renaissance, and the federal Department of Energy prepares to transfer approximately 700,000 tons of the material from temporary storage sites to permanent disposal facilities. And the depleted uranium, the refuse from the process in which natural uranium is enriched to create fuel for nuclear power plants, poses unique disposal challenges.

Regular Class A, low-level waste comes and goes -- after 100 years it has decayed to the point where it is no longer considered a hazard. But depleted uranium, while relatively benign at first, keeps getting hotter and hotter for a million years as it breaks down into more radioactive and easily-dispersed elements.

For decades, depleted uranium disposal wasn't an issue because there wasn't a lot of depleted uranium to dispose of. The material was never specifically categorized when NRC classification guidelines were developed in the 1980s, and depleted uranium was treated as Class A waste by default.

But as government stockpiles grew and applications for new uranium enrichment facilities were received and the need for disposal of large amounts of depleted uranium became apparent, the NRC formally classified the material as low-level waste this year after a cursory review.

The decision stunned Rep. Jim Matheson, D-Utah, and Rep. Edward Markey, D-Mass, members of the House Energy and Environment subcommittee, which oversees the NRC. The congressmen termed the ruling "an arbitrary and capricious mischaracterization" of depleted uranium, and demanded answers. The NRC responded by announcing it would study the issue, but it has yet to set a timetable for its review, and the depleted uranium keeps pouring into Utah.

The NRC needs to stop this madness. Federal regulators need to establish a moratorium on the disposal of depleted uranium until the study is complete.