The University of Arizona

Is the ‘Problem’ of Nuclear Waste Solved?

March 9, 2012
Author Profile: 

“The nuclear waste problem is solved; we just have to do something about it.”

So said Mark Lynas, a controversial and award-winning writer from the UK who visited the University of Arizona last week and talked about his new book, The God Species: How the Planet Can Survive the Age of Humans. He was listing his solutions to “the challenge of 9.5 billion people living at western levels of consumption by 2050, within planetary boundaries.” Solution number 4: Recycle nuclear waste.

Lynas’s idea piqued my interest: Can we recycle nuclear waste efficiently? Is switching from coal-powered energy to nuclear-powered energy a logical and viable option? I decided to delve deeper.

How exactly does Lynas suggest we recycle nuclear waste such as plutonium and uranium? He says the most sensible and sustainable option is to use the waste in what is known as an ‘integral fast reactor,’ or IFR. Instead of being cooled by water, as the currently used light-water reactors are, the IFR is cooled by liquid sodium or lead and is fueled by plutonium and uranium waste (see diagram). The efficiency of the IFR—which can produce 60 times more energy than current water-cooled reactors using the same amount of uranium fuel—prompted the U.S. government to research them for many decades before 1994, when Congress canceled all nuclear power research, including fast reactor projects (The Independent; The Guardian).Diagram of a fast reactor cooled by liquid sodium. Image from The Guardian, February 2, 2012.

Lynas also argues that IFRs are safer than current plants, since “steam explosions due to overheating or containment failures are not a problem” because IFRs use molten sodium circulating at atmospheric pressure, not water at high pressure (Lynas July 2011 blog). This passive safety feature ensures that a meltdown such as last year’s accident at Fukushima won’t occur since the reactor won’t go into meltdown if its power source is cut off (The Guardian).

The most recent buzz surrounds GE Hitachi’s version of the fast reactor described above that uses sodium as its coolant, called the “PRISM Sodium-Cooled Reactor” (Lynas March 2012 blog). According to The Guardian, Britain’s Department of Energy and Climate Change and the Nuclear Decommissioning Authority think it “is an interesting design,” but believe it is too far from commercial viability—even though GE Hitachi believes it could construct the reactor in a few years—because “the technology maturity for the fuel, reactor and recycling plant are considered to all be low” (The Guardian, February and January 2012). What I found most incredible is that according to the February Guardian report, these reactors, given enough of them, could “produce enough low-carbon electricity from Britain’s waste stockpile to supply the UK at current rates of demand for more than 500 years” (Britain’s waste includes more than 100 tons of plutonium and 35,000 tons of depleted uranium)!

Where’s the U.S. in this? GE Hitachi and a partnership of other companies signed a memorandum of understanding in 2010 allowing the companies to begin building a prototype unit at the U.S. Department of Energy’s Savannah River site in South Carolina before completing the U.S. Nuclear Regulatory Commission’s licensing procedures (World Nuclear News). It is not clear what became of this project, but it seems that GE Hitachi has instead begun directly marketing utilities with the pitch that the design can recycle excess plutonium (World Nuclear Association).

Lynas and UK media make these reactors sound like a gift from God…so what’s the catch? The biggest downside is that sodium has high chemical reactivity with air and water, with the potential for explosion and fire (and hence, sodium leaks) if it comes into contact with either element (Department of Energy). Current designs claim to lessen the risk of fire reaching the reactor by including an intermediate coolant loop between the reactor and steam turbines.

Another issue is that nuclear plants already in use can’t be retrofitted with this new design. However, GE claims that the cost of the new plants should be competitive but depend on unknown quantities, such as installation costs and licensing requirements, and the risk of going over budget is always high with a new design (The Guardian).

And don’t forget that even with the new design, some waste is still created, albeit a lot less than current light-water reactors. According to the UK government, the plutonium waste that would be used to fuel the reactor is currently in oxide form, and would have to be converted to metal form before it can be used by the PRISM reactor (The Guardian). They say this conversion would result in plutonium contaminated salt waste that would need to be dealt with. The government is also worried of a security risk because metal plutonium is easier to make into bombs.

So is the nuclear waste problem ‘solved’ as Lynas claims? The idea certainly sounds enticing: a reactor that not only uses nuclear waste, but does so in a low-carbon and safer way? And living in the Southwest, I especially like the idea of a reactor that doesn’t use water as a coolant (see previous blog). What’s not to like?

The risk of explosion is of course worrisome, especially in light of Fukushima. And I also worry that maybe there are unknown risks since the design hasn’t been well tested at all. I can say, however, that I would like to see more research into this design, and maybe the U.S. can take a lesson from the UK, who seems to be looking into the design more thoroughly.

What do you think?