The Nuclear Regulatory Commission's decision classifying depleted uranium as the least hazardous type of radioactive material is "unsupportable," the chairman of the House Environment and Energy Subcommittee said yesterday.

Chairman Ed Markey (D-Mass.) and subcommittee member Jim Matheson (D-Utah) told the NRC in a letter (pdf): "The arbitrary and capricious mischaracterization of depleted uranium as Class A waste will undermine public confidence in the waste classification system, may increase risks to public health and safety and raises the possibility that additional, uncharacterized and possibly even more dangerous materials could be similarly treated in the future."

At issue is a 3-1 NRC vote on Wednesday deciding that depleted uranium be classified as a Class A low-level waste, with the caveat that additional disposal restrictions might be needed for large quantities of it.

Commissioner Gregory Jaczko cast the dissenting vote, saying depleted uranium is low-level waste but not Class A. "I do not believe that it is logical to argue that waste that requires additional requirements for disposal -- similar to those required for Class C waste -- can still be labeled as Class A waste," Jaczko said. Class C waste is hazardous for up to 500 years, whereas Class A waste is hazardous for up to 100 years.

Markey and Matheson demand that the NRC explain its decision in writing and provide records and communications that led to the vote. "The subcommittee intends to carefully review the basis for this action," they wrote.

Depleted uranium is mainly a byproduct from uranium enrichment facilities. It is a unique waste stream as it actually gets more radioactive the longer it sits -- unlike most radioactive materials, which become less hazardous as they decay.

Depleted uranium has a concentration that exceeds by 10 times the Class A waste limit of 0.05 microcuries per cubic centimeter recommended by NRC staff in a 1981 draft environmental impact statement, according to the Institute for Energy and Environmental Research, a nuclear watchdog group.

Until recently, the NRC hasn't had to regulate depleted uranium. The NRC decided not to classify it along with other wastes in the 1980s because there wasn't enough volume to regulate it; the only source for it was Department of Energy enrichment facilities.

But the issue arose during 2006 license proceedings for Louisiana Energy Services' uranium enrichment facility in New Mexico, the first private U.S. facility. The commission determined then that depleted uranium was low-level waste, but it directed staff to study and recommend further actions. There is concern that if depleted uranium is not classified as Class A waste it may become orphaned waste.

Legislation

Low-level waste has been on Congress' radar since a nuclear waste management company, EnergySolutions, applied for a license to import Italian low-level waste for recycling in Tennessee and disposal in Utah. Matheson and Rep. Bart Gordon (D-Tenn.) have introduced legislation to ban the importation of foreign nuclear waste to preserve domestic disposal areas for low-level waste space.

There are four U.S. uranium enrichment plants, including the LES plant, either licensed and being constructed or undergoing NRC review.

NRC's decision on depleted uranium would provide a future revenue stream for EnergySolutions -- which can take Class A waste from all states and the government -- and two other sites that can take waste only from designated states or the federal government.

NRC staff assumes that between existing stocks and depleted uranium from new plants there will be 1.4 million tons of depleted uranium that will eventually need disposal, the Institute for Energy and Environmental Research said.

Click here (pdf) to view the letter.