In six years, the reactors at Browns Ferry Nuclear Plant could begin burning mixed-oxide pellets, a controversial fuel source that could save the Tennessee Valley Authority money while reducing the nation’s supply of weapons-grade plutonium.

TVA’s decision, however, may be determined by a mix of public comments and findings from an environmental impact statement being prepared by the U.S. Department of Energy. The EIS will appear as a draft this week in the Federal Register.

A 60-day written public comment period is expected to begin Friday, to be followed on Sept. 13 with a meeting at Calhoun Community College to gather public input. TVA spokesman Ray Golden said a link to public comment information would be posted to TVA’s website.

“We want to make sure people know (TVA) has made no decision on whether to use MOX. We’re just a cooperating agency in a DOE evaluation process,” he said, adding the fuel would not be used at the Browns Ferry or Sequoyah nuclear plants prior to 2018. “TVA would be willing to use the materials, provided it’s operationally and environmentally safe, economically beneficial to the customers and can be licensed by the NRC.”

TVA speculates the fully implemented use of MOX could supply low-cost fuel for two decades.

TVA has been discussing the possibility of using the fuel since 2009 and had public meetings on the idea in 2010.

Nuclear Regulatory Commission spokesman Dave McIntyre said TVA must apply for license amendments at the Sequoyah and Browns Ferry plants to use the MOX fuel, but those applications have not yet been made. McIntyre said the review process would take one to two years.

What is MOX

MOX fuel is created by combining Uranium 235 pellets with Plutonium 239 pellets into a fuel assembly that would be shipped to the nuclear plants ready to insert in the reactor. A TVA fact sheet said rendering plutonium inaccessible for use in nuclear weapons supports nonproliferation while creating electricity.

Using the fuel, TVA says, supports an agreement between the U.S. and Russia in which the countries committed to disposing of no less than 34 metric tons of weapons-grade plutonium through its use in nuclear reactors.

MOX is a mixture of 95 percent non-fissionable U-238 uranium oxide and 5 percent plutonium oxide that replaces the fissionable U-235 typically found in commercial nuclear fuel. Plutonium is a byproduct of the uranium fission process in nuclear reactors and remains within the fuel pellets where it helps produce electricity.

TVA says the fuel was used in testing programs in the 1970s and 1980s at several plants, where it was confirmed it performs in a comparable manner to uranium fuel.

In February of last year, TVA signed a letter of intent with AREVA expressing the utility’s mutual desire to begin discussions concerning the potential use of mixed-oxide fuel in TVA nuclear plants. The fuel would originate from a $5 million fabrication facility under construction at the U.S. Department of Energy’s Savannah River site in Aiken, S.C.

While the letter acknowledged TVA’s role in the Department of Energy’s evaluation of surplus nuclear weapons, it did not commit the utility to use MOX. If TVA decides to begin using MOX, the materials would be shipped from the South Carolina location.

Risks of MOX

Some critics of the MOX fuel, which is a hotter fuel blend, say it makes reactors harder to control.

“The use of this experimental fuel in TVA’s aging reactors could have negative safety reactions,” said Tom Clements, an environmental advocate for the Alliance for Nuclear Accountability.

The Washington, D.C.-based Union of Concerned Scientists also sees hazards with the use of MOX in nuclear reactors.

A report issued in April of last year said safety implications differ depending on the amount of MOX fuel that is used. The group said reactor three at the Dai-Ichi plant in Fukushima, Japan, used 6 percent MOX fuel, an amount small enough that it would make no significant impact on the environment.

The UCS said increased safety issues arise when a larger amount (30 percent or more) is used, which could increase the likelihood of accidents and public health consequences should an accident occur.

The UCS believes the manufacture, transportation and storage of MOX fuel also increases the risk of nuclear terrorism. MOX does not contain highly radioactive components that make spent fuel dangerous, and plutonium can be separated from uranium by a straightforward chemical process.

— The Associated Press contributed to this story.