"It was used for two operating cycles and we made a decision that an additional cycle is not required," said Rita Sipe, a nuclear media relations spokeswoman for Duke Energy.
The reason, she said, is that the first two cycles provided sufficient data that will be analyzed as part of the evaluation process for MOX, which is made by blending plutonium from dismantled nuclear bombs with conventional reactor fuels.
Duke has a pending "expression of interest" with the National Nuclear Security Administration in using MOX fuels that will be made at the $4.86 billion facility under construction at SRS.
The decision not to conduct a third test cycle at Catawba 1, she added, should not be construed as a lack of interest. "Duke remains very much interested in MOX."
Tom Clements, the Southeast nuclear campaign coordinator for Friends of the Earth, said, however, that Duke's decision appears to indicate an intent to abandon its interest.
"It is my feeling that Duke is trying to step politely and silently away from this troubled MOX test and will be glad to be rid of involvement in the whole program," he said.
The U.S. Nuclear Regulatory Commission, he said, might be unwilling to license the fuel for commercial use without a more substantial series of tests.
Jennifer Wagner, a spokeswoman for the National Nuclear Security Administration, said, however, that the two cycles already completed will satisfy the federal requirements.
"Irradiation of the MOX lead test assemblies for two 18-month cycles was successfully completed as required by the Nuclear Regulatory Commission," she said in an e-mail. "After a post-irradiation examination of five rods from the LTAs is completed next year, sufficient data will exist from the two cycles of irradiation to demonstrate that MOX fuel performs satisfactorily."
The most recent testing cycle ended in May 2008, after which some abnormalities were noted in the fuel rods. Ms. Sipe said some of the rods were sent to Oak Ridge National Laboratory for further evaluation, and the results remain incomplete.
Those abnormalities included unexpected expansion of the rods and some bowing. Ms. Wagner said the conditions had nothing to do with the fuel being MOX and conventional uranium fuels are known to have similar conditions.
NRC spokesman Roger Hannah said licensing authorities were made aware of the abnormalities.
"In talking with our experts this is something that happens from time to time," he said. "It does not appear to be MOX-related but they want to fully understand it before they go any farther."
The plant under construction at SRS is designed to dispose of 34 metric tons of weapons grade plutonium. The main process building is about 21 percent complete, and the overall project is 38 percent complete. It is scheduled to open in 2016, with fuel delivery to clients two years later.
In addition to Duke Energy, other potential users of the MOX fuels include Tennessee Valley Authority and at least one other entity the Energy Department has not publicly identified.
Jim Giusti, an Energy Department spokesman at SRS, said federal authorities remain confident there will be ample clients to use the MOX fuels.
"There are plenty of reactors interested but they have to know ahead of time when it will be available," he said, predicting there will be more clients formally involved as the project moves closer to actual fuel delivery.
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MOX PLANT TIMETABLE
2011: Structural completion
2014 : Facilities ready for testing
2016: First plutonium fuel produced
2018: Actual fuel delivery to clients
In addition to Duke Energy, other potential users of the MOX fuels include Tennessee Valley Authority and at least one other entity whom the Energy Department has not publicly identified.
Source: U.S. Energy Department