A sustainable use of nuclear energy?
Philip Finck talks about reprocessing nuclear fuel.
Phillip Finck is Deputy Associate Laboratory Director of Applied Science and Technology and National Security for Argonne National Laboratory, operated by the University of Chicago for the Department of Energy. Finck coordinates all nuclear energy related activities at Argonne, including the development of an experimental program that intends to safely recycle nuclear waste.
Dr. Finck spoke with Earth & Sky’s Jorge Salazar about his vision of sustainable use of nuclear energy through reprocessing spent nuclear fuel.
Salazar: Thank you for speaking with me today, Dr. Finck. Could you explain just how nuclear fuel recycling works?
Finck: Let me first explain what a nuclear fuel cycle is. Typically, we have about 400 reactors in the world, and most of them work with what’s called one full cycle. You put fresh fuel in the reactor, typically the fresh fuel contains mostly uranium 238 and a little bit, about 5% of uranium 235, and you burn it for some time. When you extract it, the spent fuel contains only a little bit of uranium 235, but it also contains fission products, plutonium, americium, neptunium, in small quantities.
Many countries right now are still working with what’s called the once–through cycle. Once you’ve irradiated the fuel for a while, for say three years, you take it out and store it for a while, and eventually you will send it to a geological repository such as the one that the U.S. is developing at Yucca Mountain.
One important consideration is to see how nuclear is going to develop for the world. It is clear to me, that with the growing energy problems that we’re seeing, the need for energy independence, plus the need for higher energy production in countries that are developing right now, nuclear is one of the key options. And the once–through cycle, in the long term, is probably not sustainable, for three reasons.
The first reason is that eventually, uranium supplies will run out. Now, that’s not for quite a while, we have time to get ready for this, but certainly we have to think about it.
The second reason that the once–through cycle just described is not sustainable is that we have to find a way to dispose of the irradiated nuclear fuel. The geologic repository approach we have adapted, for example, in the U.S. is a complex way of doing things. We are working on opening Yucca Mountain, but we already know that the capacity of Yucca Mountain, the legislative capacity of Yucca Mountain, will be reached by 2010, that’s in a few years. And the technical limit of Yucca Mountain will be reached by 2030, which is when the current fleet of reactors will be retired in the U.S. So certainly, we need to look at our long–term solution, maybe other repositories, maybe advanced fuel cycles to do the job. Our country is also looking into repositories. Nobody has yet opened one. There is, typically, quite a bit of public and political resistance to geological repositories.
One alternative solution that has been adopted in a few countries is what I call limited recycle. Limited recycle is something that has been implemented right now in France, Japan, the U.K., Russia to some extant. And the idea is to take the spent fuel, and instead of sending it to a repository, you send it to what is called a reprocessing process. What you do out of the reprocessing is that you separate the components of the spent fuel into groups of individual species that you dispose of in different ways.
The closed fuel cycle consists, right now, as implemented, for example, in France, of extracting the plutonium out of spent fuel. And typically, spent fuel contains about 1% plutonium, taking that plutonium and fabricating new fuel out of it, which is called mox fuel. That’s an industrial process that’s in existence in several countries and was developed a long time ago in the U.S. And, I think that most of the world technology is derived from U.S. technology. The idea is that once you have fabricated that mox fuel that contains the plutonium, you irradiate it again and you burn a fraction of the plutonium. Eventually, of course, you still will have some irradiated mox assemblies that you will need to dispose of. Again, going to a repository is a solution that is being looked at very strongly.
An alternate solution is to go to what we call a closed fuel cycle. In the closed fuel cycle, instead of only extracting plutonium, you would extract, together, all of the transuranic elements, plutonium, americium, neptunium, and curium, you would send them to a fast reactor, that’s a reactor where neutrons stay at high energy and are not motivated by water. The advantage of this is that the fast neutrons help you destroy these transuranic elements. What you do is that you add them into a fast reactor, you extract the spent fuel, and you recycle in the reactor.
And what we have shown, in many tests over the last 20 or 30 years is that you’re likely to be able to reduce the toxicity of the cycle of the nuclear waste by a factor of up to 100. What this translates to is that you could put 100 times more waste into a given repository. And we have to be careful to normalize that hundred times. Essentially, for the same repository, you could produce 100 times more electricity in your nuclear reactors, or you could have 100 times more reactors, or you would need 100 times less repositories. There are many ways to normalize that. But the idea of the closed fuel cycle is to extract out of the spent fuel these elements that could be a problem and destroy them for fission.
Where do we stand today? Some of the technologies have already been developed, and in some certain cases, deployed for the world. There exist today reprocessing plants in Russia, in France, in the U.K., there’s one that is under completion in Japan that actually takes the spent fuel from the conventional reactors and does the separation based on the PUREX process.
PUREX is a process that is very well known in industry, that existed in Europe and was developed in the U.S. many years ago. It has, in my mind, the disadvantage of separating pure plutonium, which raises proliferation issues. I believe that we should never separate pure plutonium, and that is also the U.S. policy. Separation of pure plutonium leads to possible build up of materials that can be misused.
So, we have been developing, at Argonne, with two other laboratories in Idaho and Oak Ridge National Lab, the process called UREX+ that would replace PUREX. And the main idea of UREX plus is that it would keep together all of the transuranics, that is the materials that are much less attractive for misuse, and then send that material directly to fast reactors in adequate fuel form, additional to what it would manage the other elements to separate, it would send various streams to various types of waste forms, and most importantly, it would not create any liquid waste, which to us is a key condition. We want to drive towards processes that are as “green” as possible, that are as clean as possible. Going from PUREX to UREX in U.S. industry is a process we have to go through, which is probably not too complex, but we still need to go through demonstration stages. UREX has been demonstrated at laboratory scales to kilogram quantities of spent fuel here at Argonne. And we met all of our expectations.
The next stage is to irradiate this in a fast reactor. The first reactor that ever produced electricity in the world was a reactor that we designed at Argonne and built in Idaho in the early 1950s, before I was born, actually. Reactors like that have been built in various countries throughout the world. We have built some, the Russians and Japanese, the British, the French, the Germans, currently the Chinese and the Indians are each building one. It’s a technology that’s relatively well–known. We have some operational experience, typically you learn from having difficulties, and we have solved those difficulties, so we think that reactor technology is ready to go. And we at Argonne are certainly more interested in designing and building one. There are some remaining issues that need to be resolved. We need to make sure that we know to fabricate fuels that contain a significant amount of transuranic elements, and we have done some of that. We are not totally finished. We are collaborating with foreign countries and doing that. We need, also, for that very special fast reactor fuel, we need to make sure that we have a process to recycle it. Special process has been developed at Argonne for the last 20 years. Again, we are collaborating with foreign countries. And there are still a couple of issues that we believe we can solve, but we need to finish the R&D process.
Many of the technologies exist, there are still some R&D to be completed, and then some large–scale demonstrations are needed.
Salazar: Elaborate a little more on the UREX and PUREX reprocessing method.
Finck: I ‘m really talking about two different processes. There is one that is used to reprocess the spent fuel from current commercial reactors. That’s called UREX. And then there is a process that will be used to reprocess the fast reactor fuel. That’s pyro–processing.
UREX is essentially a process where you dissolve the spent fuel in a nitric acid solution, and then you do a successive operation to extract first the transuranic elements. You also extract the fission products, you also extract the uranium in a very clean form. And then you use the various products for different applications. Uranium would probably be kept for future operations in fuel. The Trans–uranics are used to fabricate fuel for a fast reactor. The fission products are extracted and stored in a very stable waste form for disposal.
The big different in the pyro–processing scheme that we are talking about is that pyro–processing is not a scheme based on dissolution in aqueous solution. It’s essentially, electrolysis of fuel in molten salt. The advantage of this is that it does group separation of the transuranics, all the transuranics stay together in it. It works very well for fuel that is very hot. It works very well for fuel that is very hot. It also doesn’t have critical limits, typically when you mix fuel an water, critical limits are low, whereas with pyro–processing there is no water, and criticality limits are higher. But the main advantage is that it works very easily with hot fuel. Pyro–processing is not new. None of the processes that I’m talking about have been invented recently. PUREX is about 50 years old. Pyroprocessing has been used in other industries, for example aluminum industry for many years. So, in a sense, we have just adapted these industrial processes to our use. And that’s what we’ve been doing the R&D on for the last many years.
Salazar: So is the reprocessing of spent nuclear fuels safe?
Finck: Let me talk quickly about safety. One point I want to make is that Argonne doesn’t work alone. We are always collaborating with most of the other laboratories. There is actually a very good collaboration, it’s a very good spirit right now. Argonne pioneered, about 20 years ago, a concept called passive safety. We developed a reactor design, that based on physical principles shuts itself down if anything abnormal occurs. It was not only developed on paper, it was actually demonstrated physically in a reactor called EVR–2 that existed in Idaho at a time, and we demonstrated through various events, unexpected events, the reactor based on pure physical principles would go back to a safe mode. And we believe, I believe strongly that this is probably one of the biggest progress in nuclear energy in the last 20 years is to go to passive safety for a reactor. And this concept is being applied more and more to other designs of reactors that we see emerging right now.
In general, as far as I know, in civilian applications, there has been no accidents related to our reprocessing plants. We are essentially working on very sound safety principles. We plan to have no effluence to the public, and the basis of the design, we guarantee ourselves against any abnormal event by design. It’s just a very low probability, a nonexistent probability of accident. The plant that has operated in France and the U.K. have had no accidents. It’s been a very safe operation, and a very good industrial experience there.
Salazar: Thank you for speaking with me today, Dr. Finck. Is there anything else you’d like to share with the public today?
Finck: I think that, the bottom line is that today, the nuclear option is really necessary to ensure our energy security for the long term. Mixed with our technology, I think that we should develop not only nuclear, but we should develop all forms of energy, and nuclear is very important to that mix. The fact of going to advance fuel cycle will provide us the benefit of long–term sustainability in the sense that it will significantly reduce the amount of waste produced. We will actually significantly insure long–term supply of energy. We will also, by using this closed fuel cycle, reduce the global risk of buildup of special nuclear materials by burning them.
Salazar: So what lies in the development of reprocessing spent nuclear fuel?
Finck: The technology is beyond the laboratory scale, all are either fully implemented, and we need to go, I would say, worldwide, with demonstration of these technologies. We need to build plants of a pilot scale size to really show that they are working at real scale. We need to also build an international consensus to develop these things. I think that international collaboration is very important in these matters to move forward. The step is to move to a demonstration stage, and then, when we are done with a demonstration, there comes the time to decide where to implement them commercially, or not.
In the U.S., we used to have reprocessing plants, we don’t have any anymore. Any process of deployment of the technology would have to go through some pilot–scale and then commercial plant. Rough timeline to go to a commercial plant is roughly 20 years. In France, U.K., and Russia, they have plants operating right now that are operating on the PUREX technology, not on the UREX technology. The Japanese, I believe, have been building one for a few years and are very close to opening it (Rokkasho).
Salazar: Thank you again for your time today.
Finck: Thank you very much. I think this is very important for our future. we need to get these technologies going. It’s important for our energy security and it’s important for our global world stability.
