Rock Doc: Waste meets fate in salty tomb

Mon., Aug. 27, 2012

The next time you have a salt shaker handy, remove a few grains. If you have a magnifying glass, you’ll see the salt is really tiny cubes. Salt is a mineral and each grain is a well-formed crystal that breaks into cubic shapes.

Salt in your salt shaker looks like a simple solid. But salt far enough underground behaves like Silly Putty, oozing and flowing over time. Salt has been on my mind recently because I’ve been reading about nuclear energy. Bear with me and I’ll explain.

Nuclear plants give us a fifth of the electrical power that we use in the grid each day. Even some environmental activists think highly of nuclear energy because it gives us power without producing greenhouse gases.

But our use of nuclear plants also demands that we address the question of burying radioactive waste. The good news is that we’ve started to do exactly that in New Mexico and so far things are going just as planned. I’ve been reading recently about that and related matters in a book called “Power to Save the World” by Gwyneth Cravens.

The 4-square-mile Waste Isolation Pilot Plant is in the Chihuahuan Desert. It makes use of one small part of an enormous salt bed.

In many parts of the world, circulating groundwater could move nuclear waste after it’s buried. Happily, the salt formation at WIPP is quite dry, with only a little water in it. Best of all, the water does not move to any appreciable extent from the salt to the surrounding rocks.

“Movement of groundwater from or through the salt formation to rocks nearby is essentially nonexistent,” Dr. Don Wall of Washington State University told me. Wall is the director of the nuclear reactor at WSU and he used to work on the WIPP project.

WIPP’s storage “rooms” for nuclear waste are more than 2,000 feet underground in the salt bed. For me, part of the magic of WIPP is that salt that deep underground deforms like plastic, flowing about three inches per year. That’s a helpful feature for the isolation of the nuclear waste because it means the salt will flow around the casks of waste, enveloping them in earth material and sealing them in place as time unfolds.

Alert readers may remember that concentrated, high-level nuclear waste was slated to go to the Yucca Mountain site in Nevada. We spent billions of dollars researching and building that repository. But Yucca Mountain was ultimately nixed because people in Nevada didn’t want the waste in their state.

Many in New Mexico feel differently about WIPP and its successful operations are converting some skeptics, one by one.

Nuclear energy is part of our daily electrical power supply. No matter your feelings about that, we’ve got nuclear waste on our hands. For my part, I’m glad WIPP is putting waste into a salty tomb.

E. Kirsten Peters, a native of the rural Northwest, was trained as a geologist at Princeton and Harvard. Questions for future Rock Docs can be sent to epeters@wsu.edu. This column is a service of the College of Agricultural, Human and Natural Resource Sciences at Washington State University.