Oct 14 2019

Recycling Nuclear Fuel

Evaluating the risks and benefits of nuclear fission is a bit of a moving target as the technology develops. Even with established nuclear power plant designs and management technology, I think the benefits outweigh the risks when you compare it to the alternatives and factor global warming into the mix. (I discussed this before and won’t go over all the points again here.)

However, we are not stuck with the current nuclear technology. We are on the brink of developing so-called Generation IV reactors that have a number of advantages. They are safer, smaller, more efficient, and generate significantly less waste (used nuclear fuel – UNF). Scientists, however, have now reported an advance that can potentially significantly reduce UNF, with or without Gen IV reactors.

Closing the Nuclear Fuel Cycle with a Simplified Minor Actinide Lanthanide Separation Process (ALSEP) and Additive Manufacturing.

This is a process for separating various components of the UNF, specifically removing the actinide lanthanide elements. The targets are long-lived isotopes of americium (Am) and curium (Cm) and also neptunium (Np). These are called minor actinides (MA) in the paper. Why is it important to separate out these elements from the UNF? There are two potential reasons.

First, these are the highly toxic and very long-lived radioactive elements in UNF. If you separate them out, the rest of the nuclear waste can be stored much easier and the time it would take for the half-life to decrease the radioactivity down to the level of uranium ore would be reduced from hundreds of thousands of years to just hundreds of years. It’s also easier to store because it will not get as hot.

That alone is an amazing breakthrough. It makes the remaining nuclear waste much easier to deal with, because the main problem with this UNF is the small portion of the long-lived MAs.

But then what do we do with the MAs? There are two options. With current reactor technology we still cannot burn them as fuel. But because they are now purified out of the UNF, and are only a small fraction of the total waste, this long-lived portion can be stored in compact safe long-term form in appropriate facilities. So in other words – we don’t have to store all nuclear waste to accommodate the small fraction that includes long-lived toxic elements. We can separate them out, store the bulk much more easily, and then relegate only the long-lived fraction to long-term storage.

However, with Gen IV nuclear reactors we can actually burn the MAs as fuel. This has multiple advantages. First, this will allow for the recovery of 95% of the fissionable material from the spent nuclear fuel, greatly extending the energy that we can get out of any unit of mined ore. This will extend our supply of nuclear fuel and reduce the need for uranium mining. Further, the process will convert the MAs into short half-life isotopes. This will significantly reduce the amount of long-lived UNF that would have to be stored.

We could even use this process on existing UNF, much of which is still being stored on site at nuclear reactors. We could fuel the new Gen IV reactors entirely from the waste of older reactors for decades, perhaps centuries, while getting rid of all the troublesome waste.

You can read the technical details in the original paper, but here is a summary:

For the MA recovery, the following design criteria were selected for developing a robust and cost-effective process: (1) a single extraction cycle, (2) minimal aqueous feed adjustment for the PUREX raffinate, (3) using conventional industrial chemicals in both the aqueous and organic phases, and (4) radiolytic and hydrolytic stability of the solvent components. Based on these criteria, we have developed the Actinide Lanthanide SEParation (ALSEP) concept.

The authors claim the process was tested on actual waste, and that it is scalable to industrial levels (always an important detail often neglected in reporting). They also report that the process works to >99% purity – so essentially it removes virtually all of the MAs from the UNF.

With or without Gen IV reactors, we can start using this process to separate out our nuclear waste. But there isn’t much of a reason to do it unless we do at least one of two things – build Gen IV reactors or approve a long term storage facility for the MAs. I would prefer that we build Gen IV nuclear reactors. They were already a good idea, and now they just became much better. We should focus on the reactor designs that can entirely use recycled fuel from older reactors. It’s a win-win.

I try to anticipate points on the other side, but I am having trouble seeing any downside. Opponents of nuclear energy could argue that the Gen IV plants are unproven, and that they are too expensive. We would be better off spending that money on renewable energy. That, I would argue, is a false choice. We could use both. Renewables are not a panacea. They have limitations which get increasingly difficult as we try to increase penetration. Having 20-30% baseload of nuclear power (or more) is a great option, primarily to displace coal-fired and natural gas plants.

Further – we now have to consider the cost of building Gen IV plants against the cost of dealing with all the existing nuclear waste. Building these plants just to deal with nuclear waste is not a bad idea, and we get electricity out of it.

The final objection I hear is that there isn’t enough time, which I think is just silly. There is no expiration date on mitigating global warming. In 10-20 years when these plants can potentially come online, we will still be in desperate need of low carbon electricity.

This development is good news. I hope that it pans out when the industry takes a look at it and tries to implement the process.


No responses yet