Hey, there, Doc – I saw something in my feed today that seems up your alley. It was about the new Executive Orders about radiation and nuclear energy; the part I’m curious about said that, even though other countries recycle their reactor fuel to recycle the parts that are still good into new fuel rods, the US doesn’t – we just throw it away. Doesn’t it make sense to recycle what’s right there instead of throwing it away and then having to dig up and process more uranium?
Ah – if only it were that easy! But recycling nuclear reactor fuel isn’t as simple or as straightforward as recycling aluminum cans. It gets into domestic politics, international politics, and even nuclear non-proliferation. So (rubbing my hands together) – let’s get started!
How and why reactor fuel is recycled
It’s easier to start with the “why” part of this – reactor fuel is recycled because, even when it’s no longer useful for producing energy, it still has fissile material in it. Some of that is the U-235 that wasn’t fissioned, the rest is plutonium that was produced during the fission process. Where the plutonium comes from…if U-235 is enriched to 6% to make reactor fuel then 94% of the uranium atoms are U-238. There are a lot of neutrons flying around the reactor core and when one of them is captured by a U-238 atom it turns it into U-239. A few months and two beta decays later that U-239 atom has turned into an atom of Pu-239 – about as fissile as U-235 and some of the stuff they make nuclear weapons out of. But it also makes great reactor fuel – especially when mixed with some of the U-235 remaining in the spent fuel. The question is how to get it out of the fuel and into a new fuel rod.
It starts with putting the spent fuel into storage for a while to let the short-lived fission products decay away – there are enough of them to make the spent fuel lethally radioactive shortly after it’s removed from the core, but if they’re allowed to decay away for a while – usually anywhere from 1-3 years. After that the fuel can be removed from the storage pools, chopped up, dissolved in acid, and chemically processed to remove the uranium and plutonium. The uranium won’t have enough U-235 to be directly made into fuel so it will need to be put into a uranium enrichment cascade to get it back up to reactor-grade. The plutonium will contain more isotopes than just Pu-239, but there’s enough of that nuclide that the plutonium will add to the fission reaction. So the plutonium and uranium are blended to form a mixed-oxide (MOX) reactor fuel that can be made into new fuel rods and put into a reactor core to produce power.
Why the US stopped recycling reactor fuel
The US used to recycle fuel from commercial reactor plants. I saw evidence of this when I was reviewing an environmental monitoring report at one of our uranium enrichment plants – it reported the presence of U-236, which doesn’t occur in nature; U-236 is only formed when U-235 captures a neutron without fissioning. But during the Carter administration we stopped recycling in order to set a good example to the world – instead of removing Pu-239 from the spent fuel and (the thinking went) making a target for would-be nuclear terrorists or wanna-be nuclear states. Carter’s solution was to leave the plutonium locked up within the spent fuel. Of course, the plutonium is still there in the spent fuel and, although it’s not easy to remove, the process to do so is well-known and it’s very effective. The only way to keep the plutonium from ever being used to make a nuclear bomb is to make it no longer plutonium – to put it in a reactor and fission it. This is one of the nice things about MOX – not only does it get energy from the plutonium that would otherwise go unused, but it destroys the plutonium forever in the process.
Why other countries are recycling – and why we don’t (usually) get upset
Other nations “closed” the nuclear fuel cycle by recycling their spent reactor fuel and they’ve done so for decades. France and Japan reprocess a higher fraction of their spent reactor fuel than any other nation, but China, India, Russia, and the UK also recycle their spent reactor fuel and the Dutch send theirs to France for recycling. North Korea might or might not recycle fuel from power reactors, but they do have the technology to extract plutonium from spent fuel, as does (we suspect) Pakistan. Nuclear-armed states (UK, China, Russia, France, India, North Korea, and Pakistan) might well be recycling primarily to extract plutonium for nuclear weapons production, although Russia, France, and the UK don’t seem to be building up their nuclear weapons stockpiles at the moment…not to mention that they’re already nuclear powers.
Most of the time the recycling and/or plutonium extraction doesn’t bother us much because all but one (Japan) of the nations that are recycling already have nuclear weapons and a lot of them are nations that are our allies. That’s why we don’t complain about France, the UK, Japan, the UK, Russia, India, China, or Pakistan. But North Korea and Iran having that capability concerns us because they’re military and geopolitical wild cards. Iran is a particular concern because they don’t yet (as far as we know) have nuclear weapons and they support terrorist groups; North Korea is simply hard to predict and harder to try to influence.
And the US?
A half-century after shuttering our spent fuel recycling program the US is starting to show signs of interest – two companies informed the Nuclear Regulatory Commission of their interest to construct and operate recycling facilities in 2008, not much progress has been made and making their 2032 target date seems unlikely.
At present what we’re doing is pretty much the same thing we’ve been doing for the last 50 years or so – we’re taking spent fuel out of the reactors, putting it into swimming pools for several years to cool off, then moving it into dry cask storage on reactor plant sites to continue decaying. At some point the casks might be transferred to a permanent disposal facility such as Yucca Mountain, although the State of Nevada has strenuously objected and many senators and congressional representatives are supporting their objections. Another possible fate for these casks would be transfer to a newly opened reprocessing facility, although such facilities remain controversial and are likely to attract opposition as the licensing process gets closer to completion. Or the casks might simply continue to be stored on over 50 individual sites as they are now, patiently awaiting a resolution to decades of American irresolution on this topic.