The Tennessee Valley Authority this week said it was beginning an evaluation of the environmental impact of using mixed oxide fuel (MOX) made from surplus nuclear weapons to power nuclear plants.

MOX is made of a combination of plutonium and uranium. The draft environmental impact statement is expected to be posted in the Federal Register this week, said Ray Golden, TVA spokesman.

The Sequoyah and Browns Ferry plants are looking to use the fuel. TVA is tentatively testing a kind of MOX fuel made from old nuclear weapons at its Soddy-Daisy, Tenn., and Athens, Ala., reactors. This kind of MOX has never been used anywhere else before, TVA and nuclear experts said.

Golden said TVA is willing to consider using MOX fuel if it meets three criteria: It is operationally and environmentally safe, economically beneficial to TVA customers, and licensed by the Nuclear Regulatory Commission.

Opponents of the fuel say it makes reactors more difficult to control because it is a hotter blend of fuel.

"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.

MOX was used in Japan's Fukushima Daiichi reactor, which experienced a meltdown last year after an earthquake and tsunami.

According to Golden, MOX made from a combination of spent nuclear fuel and fresh uranium has been tested in Europe and for a short time by a Duke Energy Corp. commercial reactor, before Duke dropped the trial. It remains unknown whether that drop was due to abnormal performance, as early Duke and NRC documents say, or whether Duke stopped because it had already collected all the data and technical information it needed (Pam Sohn, Chattanooga Times Free Press, July 25). -- HP