California's last nuclear power plant is closing down.
The Diablo Canyon nuclear facility, located in central California, has been churning out electricity for about three decades, providing enough power for around 1.7 million homes. But utility provider PG&E announced Tuesday that they will not be renewing licenses with the Nuclear Regulatory Commission. Instead, the company plans to focus on renewable energy sources.
The last of Diablo's permits expire in 2025.
California is no stranger to shuttering plants. The San Onofre facility, situated just south of Orange County, was permanently retired in 2013. So it should come as no surprise that decommissioning Diablo will be no small feat. One of the biggest hurdles? Storing thousands of tons of nuclear waste.
Where does it all go?
Take Two put that question to Daniel Kammen, professor of energy at UC Berkeley.
What type of nuclear waste are we looking at? What causes it?
What causes it is where we start. It’s caused by the radioactive decay of the uranium — the fuel itself. It decays over a very complex set of pathways into daughter molecules that ultimately end up with molecules that are about half the weight of the initial uranium. And that’s basically different forms of lead. But getting there takes everything from fractions of a second to tens of thousands to millions of years. That material is called the high-level waste.
Then there’s what’s called low-level waste, and that is the metals, the materials, the cooling fluids in the plant that get somewhat radioactive and are much less of a problem, but they’re also material that has to be stored in a careful way. There’s really two flavors of waste.
We throw around the word ‘radioactive’ a lot when we talk about nuclear energy, but in layman’s terms, what are we actually talking about when we say radioactive?
You’re talking about the decay products: neutrons, part of the center of atoms that come off and make metals brittle and affect tissue in various ways; also, high energy particles, both electrons from atoms and energy and light that comes off, as well. You get this mixture of different materials, largely metals, giving off radioactive particles and energy as they decay over this very long process to their final state.
How effective are our methods of storage? Do we have an effective way to keep that waste safe in the long term?
A tough question, because we have good methods to manage it, in the sense that we know what is going to come out in terms of radioactive materials, heat, corrosion of the metals, but the long-term story [is that] humans aren't good at storing things and managing things for thousands to millions of years.
The casks themselves are designed to decay, but they’re designed to be put into holes that we drill into rock, and as the casks decay, it’s the rock that provides the secure storage... It is a good storage system if all the parameters work out well — and that "if" is complicated, because the science is good, but you simply have a hard time thinking, "Can we really guarantee this for tens to hundreds of thousands of years or millions of years?"
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(Answers have been edited for clarity.)