Mixing it up: American nuclear power gets a lesson in MOX

Kathleen Davis, Associate Editor

Raise your hand if you know what MOX is. Go ahead. Don’t be shy. (No one’s probably in your office anyway.)

Don’t worry. I didn’t know either. But, you see, there was this article from The Moscow Times that I was reading–an editorial, really–discussing the pros and cons (mostly cons) of shipping Russian plutonium to the U.S. for use in nuclear power plants.

Yeah. I made the same confused face. So, I went looking for answers. And, when it comes to MOX in the U.S., those answers lie in one place: Duke Energy.

In March 1999, the Department of Energy (DOE) signed a contract with a consortium comprised of Duke Energy, COGEMA and Stone & Webster (DCS) to design, construct, operate and deactivate (eventually) a MOX fuel fabrication facility; design the commercial MOX fuel; and use MOX fuel in commercial nuclear power plants.

Duke Power, a business unit of Duke Energy, operates three nuclear generating stations. The MOX fuel will be used at two of those: McGuire and Catawba.

“Here at Duke we’ve been operating seven nuclear reactors since the early 1970s,” said Steve Nesbit, project manager of Duke Power’s mixed oxide fuel project. “And we are proud to be a part of this program.

“In addition to supporting an important national security initiative, MOX fuel will provide McGuire and Catawba with a long-term, economical supply of nuclear fuel.”

What is MOX, and why should I care?

The acronym “MOX” is short for mixed oxide, and it breaks down like this: Traditional nuclear fuel is 100 percent enriched uranium oxide, but MOX nuclear fuel is around 95 percent enriched uranium oxide and less than five percent plutonium oxide–hence, the “mixed” title. (In fact, it is very similar to the conventional uranium fuel currently used in nuclear plants, and would be used alongside that fuel.)

So, why bother, if the two are so very similar? Why not just stick with our original fuel and call the whole thing good? Well, that does little to help solve the problem of massive weapons stockpiles, which abound from thirty years of a “mine is bigger than yours” stand-off that is no longer relevant. And the U.S. MOX program is all about making a dent in that mound of nukes.

“The genesis of this program was the end of the Cold War back in the early 1990s,” Nesbit stated. “As Russia and the U.S. moved from an adversarial posture to a more cooperative posture, people in both countries recognized that the existence of extensive nuclear material for weapons posed a security threat for their countries and the world in general.”

In 1992, General Brent Scowcroft, then national security advisor to President George Bush, requested that the National Academy of

Sciences study the management and disposal options for surplus weapons-usable plutonium to reduce the “clear and present danger” of theft of nuclear materials. The Academy recommended that the two countries pursue disposition options that result in a form of plutonium which would be difficult to recover for weapons use. One recommended approach was the fabrication and use of MOX in reactors.

So, in 1999, with the permission and approval of the DOE, in comes DCS. With their MOX program, a few fuel assemblies will be produced and run in their Duke Power reactors for a few years as a sort of “test” of the program–no jumping in with both feet and without a lifeguard. Instead, their progress will be slow and steady.

“We’re a conservative lot here in the nuclear industry,” Nesbit stated. “We like to make sure we do things right. So, when we do shake things up a bit–like with this MOX program–we are extremely careful about it.”

“Assuming a 40/60 MOX/tra-ditional mix in our reactors, we should use approximately 2 tons of plutonium per year,” he added. And it sounds like an enormous amount of plutonium, until you figure in that the original agreement with Russia called for the disposal of 34 tons. And, of course, more will probably become available in the future.

Still, as with all journeys, we have to start somewhere.

How it will work

In the case of DCS’ program, we actually start with the DOE. (See flow chart.) Neither Duke, nor the DOE, is taking the disposal of that plutonium lightly. Every safety precaution has been thought through, examined, played out, and reconfigured to ensure both the protection of the public, and the protection of the plutonium itself.

Plutonium stored in Pantex, Texas will be shipped by the DOE to a disassembly and conversion facility. (See sidebar.) From there, the plutonium oxide powder created from that process will be moved to the MOX fuel fabrication facility to be built by DCS and the DOE (and based on a similar French facility COGEMA owns). Once converted into MOX, the fuel will be pressed into pellets and formed into fuel assemblies, in much the traditional fashion for the nuclear industry. At this point, the MOX assemblies will be ready to use at McGuire and Catawba.

The mixed oxide fuel fabrication facility will be built at the Savannah River Site (SRS) near Aiken, S.C. It will be located in F Area in the center of the 311-square-mile DOE reservation.

Construction of the facility will begin in early 2004. Operation of the facility is planned to begin in 2007, with the first batch of MOX fuel scheduled to be ready for transportation in 2008, according to Nesbit.

“I’m responsible for getting our plants ready for that day,” Nesbit added. “And what we’re doing here is working on getting approval from the Nuclear Regulatory Commission to use MOX and making small modifications to the plants to efficiently use the MOX fuel. These aren’t gigantic modifications, but there are a few pieces of hardware that we’re going to change.”

The work that Nesbit and his team are doing to convert the plants, as well as the work to construct and operate the fuel fabrication facility will be paid for by the government under a cost-reimbursable contract. So, the financial investment in this MOX program is being borne by the government, to the tune of $50 or $60 million for just the two plants to be converted.

And, once the project is up and running, the MOX fuel will come to Duke Power with a discount from the traditional enriched uranium price.

“We’ll actually get the fuel at a lower price than conventional fuel, and we’ll have cost savings as a result,” Nesbit added. “And the money we pay to the government for this fuel will go toward defraying the cost of making it in the first place.

Click here to enlarge image

“The amount that we will pay will not cover the government’s cost, however. But, keep these two things in mind. First, we are defraying a cost from having to store the plutonium, which we already do, and, additionally, the purpose of the program isn’t to make money. It’s to dispose of this material to keep the future a little safer for our children and their children.”

He concluded, “We spent trillions to make these weapons in the first place. I think the investment of a few billion to get rid of the material is probably well spent.”

It’s all the rage in France these days

If you raised your hand at the beginning of this article, you might have some idea of MOX from the European side of the power equation.

Catawba 1 & 2 (above) is a setting for Duke Power’s new MOX program. Catawba, located in South Carolina, is jointly owned by North Carolina Electric Membership Corp., North Carolina Municipal Agency Number One, Piedmont Municipal Power Agency, Duke Power and Saluda River Electric Cooperative.
Click here to enlarge image

“Mixed oxide fuel is not a new concept for the nuclear industry,” Nesbit said. “Overseas, various countries have been using MOX on an industrial scale since the late 1970s/early 1980s.”

McGuire 1 & 2 (above) is a setting for Duke Power’s new MOX program. McGuire is in North Carolina and is solely owned by Duke.
Click here to enlarge image

Currently, there are 35 reactors in Europe that use mixed oxide fuel. Not brought about by a weapons-reduction program like MOX here in the U.S., European MOX operates on a different kind of nuclear fuel cycle, giving them plutonium to use on a regular basis.

In the U.S., we dig uranium up, process it, and “enrich” it–increasing the amount of one uranium isotope (uranium 235) to around four percent. (It starts out around 0.7 percent.) Then that uranium is suitable for reactor fuel, and it’s made into fuel assemblies and such. Once used up, the waste material is stored.

In Europe, they start out in the same way: Digging up that uranium. They enrich it and use it in a reactor. But, instead of storing it afterward, as the U.S. does, a number of European countries take their spent fuel to reprocessing facilities and separate out the various elements of the spent fuel. After recovering the uranium and plutonium (which was created by the process in the reactor), they reuse it by creating a mixed oxide fuel. For them, it’s a form of recycling.

“I will point out that the plutonium that these European countries are creating in their reactors is known as ‘reactor-grade’ plutonium, which makes it not particularly attractive for use in nuclear weapons,” Nesbit said. “The isotopes aren’t really favorable for weapons use.”

“Here in the U.S., however, we have on our hands a surplus of weapons-grade plutonium from the defense industry, and what we’re going to do is apply the technology developed commercially in Europe to dispose of that more dangerous plutonium,” he added.

And, according to Nesbit, there will be no technical problems with converting the European commercial technology for reactor-grade plutonium to weapons-grade plutonium, as both are blended with much larger amounts of uranium to make MOX fuel. In fact, weapons-grade plutonium is so pure, that less plutonium must be blended in to make MOX.

“From a chemical standpoint, plutonium is plutonium. Reactor-grade plutonium and weapons-grade plutonium are chemically identical,” Nesbit pointed out. “So, the same knowledge base for how plutonium works with reactor-grade is very applicable to how MOX will work over here.”

And Duke Energy is more than ready to put that knowledge to the test.

But, according to Nesbit, there are no plans to ship plutonium from Russia to these local facilities for MOX processing. It appears that the author of that Moscow Times editorial was sorely misinformed.

Perhaps I should write a letter to the editor.

Nesbit is project manager, mixed oxide fuel project, for Duke Power. He is responsible for preparing the company’s McGuire and Catawba nuclear stations to use MOX fuel, beginning in 2008. Nesbit is a member of the American Nuclear Society and serves on that organization’s special committee on nuclear nonproliferation.

Aqueous polishing: Making MOX diamonds out of plutonium

Before surplus weapons-grade plutonium can be used in mixed oxide fuel (MOX), the plutonium must be purified. The purification process is a chemical process called aqueous polishing.

Aqueous polishing is accomplished in three basic steps and uses various chemicals to remove impurities such as gallium, americium and uranium. This process is conducted prior to the mechanical process of combining uranium and plutonium to produce MOX fuel rods.

Plutonium in the form of oxide is first dissolved in nitric oxide. In the second step, impurities are chemically removed with tributyl phosphate.

In the last step, the purified plutonium is converted back to plutonium oxide, packaged and stored in durable cans for future production of MOX fuel pellets.

Aqueous polishing is based on the same process the French nuclear industry has safely and successfully used for over 30 years. Much of the solid and liquid materials used during this process are recycled to reduce waste. The liquid waste contains radionuclides. This waste will be transferred from the MOX facility to locations on the Savannah River Site for treatment here in the U.S. elp

Source: Duke Cogema Stone & Webster (DCS).

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