Starting this week, Ameren will have a new way to store radioactive waste at its Callaway nuclear power plant near Fulton.
It’s called dry cask storage.
Since Callaway began operations in 1984, Ameren has kept spent fuel inside the plant, submerged in a pool containing 413 gallons of borated (or acidic) water.
As of now, that pool contains about 1,800 used fuel assemblies — bundles of 12-foot-long rods filled with uranium pellets. The pool’s total capacity is just over 2,300 assemblies.
Every 18 months, Callaway shuts down so that about third of its 193 operating fuel assemblies can be replaced; the used ones — 60 or so of them — are added to the pool. Ameren’s director of engineering projects, Shannon Able, said that means by 2020, the pool will run out of room. “We’re not at capacity, but we’re getting close,” Able said.
Now some of the spent fuel assemblies will be transferred from the pool to 17-foot-tall stainless steel canisters and then moved outdoors, to an underground concrete storage pad. The goal is not to shut down the pool; newly generated waste will still need to spend about five years under water so that it cools down enough to be ready for dry storage.
Able said the dry storage method is as safe as the spent fuel pool. "The expected dose that we're going to have from this facility is 0.2 millirems per hour," Able said. For comparison, Able said the radiation from a dental X-ray is equivalent to about 0.5 millirems per hour.
Able said the biggest advantage of dry storage is that, unlike the spent fuel pool, it doesn't need water or electricity. "We don’t have to maintain water levels, we don’t have to maintain cooling pumps for the water, which we do inside the building," Able said.
According to Ameren, dry cask systems are already in use at most nuclear power plants in the U.S.
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