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Improving spent-fuel safety at our nuclear plants

“Trouble with a capital T and rhymes with P and stands for pool” is how Elliott Negin and David Lochbaum, of the Union of Concerned Scientists, describe the current, spent-fuel holding practice at most of the nation’s nuclear power plants.
The “depleted” fuel assemblies, inefficient for energy generation after a few years in a reactor, remain dangerously radioactive for tens of thousands of years. They must be strictly isolated from the environment and the radiation blocked.
For more than 54,000 tons of them, this is accomplished by placing them immediately in “wet pools,” under 45 feet of water.
Following a roughly five-year cooling-off period, they can be shipped offsite, this having been the owners’ plan when the nuclear power plants were built, decades ago.
Serious safety problems bedevil the current situation, as nuclear engineer Lochbaum explains.
For one, the pools are outside the reactor containment structure, typically “in buildings with sheet metal siding like that in a Sears storage shed.”
Their vulnerability to natural disasters or deliberate disabling is high.
Worse, the pools are dangerously overcrowded, some holding five times the spent fuel they were designed to accommodate. Unfortunately, in the 50 years since electricity generation via atom splitting began, no safe geologic storage site, nor a way to recycle and reduce the radioactive waste has been found.
Should a malfunction in keeping the fuel stacks under deep water layers occur for any reason, exposing them to air, vast radiation releases would be the likely, if not inevitable, consequence.
Fortunately, a way to reduce the high risks associated with the overcrowded pools exists.
The spent fuel can be kept in appropriately engineered, “hardened” dry casks, after its initial cooling in underwater storage.
The National Academy of Sciences had recommended this method, as having “inherent security advantages,” six years ago.
As of now, the U.S. nuclear plants use it for only a fourth of the accumulated spent fuel, it being more expensive than the current, wet-pool method.
Two recent events demonstrate the great safety advantages of dry-cask over the predominant, current storage. Japan, before March last year, planned to develop a nuclear waste reprocessing facility. Awaiting shipment to that, a portion of the Fukushima plant’s spent fuel was stored in dry casks.
Despite jarring in the magnitude-nine earthquake and immersion in the tsunami that caused massive radiation releases from the reactor meltdowns, the dry casks went unscathed.
When a much milder quake hit the U.S. east coast last August, stronger nevertheless than the North Anna nuclear plant near Richmond was designed for, almost all the steel casks holding most of its spent fuel were shifted on their pads.
But they remained undamaged and their radiation fully contained.
In light of the Fukushima disaster, a bipartisan team in the U.S. Senate, including Lamar Alexander, is looking to develop legislation toward upgrading safety at our nuclear plants.
Expediting the transfer of spent fuel to hardened dry casks is one step toward that, which, one hopes, he will help to have included in the legislation.