Federal regulators have put off a decision on whether blended radioactive waste can be buried in Utah.
The Nuclear Regulatory Commission decided this week to develop a new set of rules assessing the dangers of blended waste based on the risks at individual disposal sites.
Utah regulators hailed the broader approach as smarter but are drafting their own standards in the meantime.
"It's not stopping Utah from going ahead and doing what's best for Utah," Utah Radiation Control Board Chairman Peter Jenkins, a health physicist, told The Associated Press on Friday.
The state board has issued draft regulations that require an operator to prove that mixing hotter but less concentrated wastes won't create an accidental danger hundreds or thousands of years in the future if somebody stumbles across the waste or digs it up.
State officials have questioned the practice even as the Utah Radiation Control Division moves forward with regulations that could allow Salt Lake City-based EnergySolutions to mix hotter wastes at a dump in Utah's west desert that's licensed to take only low-level radioactive waste.
The NRC said its own review could take years to produce a new set of regulations.
"The sense of the Commission is that entities wishing to pursue large scale blending should be encouraged to wait," NRC commissioners told staff scientists in a memorandum on Wednesday.
Jenkins said nothing in the decision, first reported by The Salt Lake Tribune, prevents Utah from adopting its own rules.
EnergySolutions said it welcomed the NRC's decision to take a wider look at blended wastes.
"This decision does not affect our operations at this time because we are not doing large-scale blending," company spokesman Mark Walker said in a statement provided Friday. "If large-scale blending were to become a part of our business model, we would operate in compliance with NRC rules."
The decades-old federal system for handling radioactive waste didn't anticipate new types of waste such as depleted uranium or blending.
Blending involves mixing higher- and lower-concentrated wastes, and it is seen by the nuclear industry as a solution to the closing of a South Carolina landfill in 2008 that took the hottest forms of waste.
EnergySolutions is licensed to take waste that can be dangerously radioactive for 100 years. The South Carolina site took one type of waste that remains hazardous for up to 300 years and another that's considered a risk for up to 500 years.
By mixing hotter wastes with larger volumes of inert material, EnergySolutions could keep overall hazard levels in check _ the issue is under study by federal and state regulators.
Jenkins said the assessments should take into account that EnergySolution's dump in Tooele County was covered by an ice-age lake 10,000 years ago that could reappear.
"Nobody has considered how this dump would contain wastes" if a new lake washed over it, he said.
The Healthy Environment Alliance of Utah has challenged the idea of blending wastes to get around limits at the Utah site and urged state authorities to prohibit it.