POWER November 2014 - 43

NUCLEAR FUEL
From Wet to Dry Storage
About a third of the nuclear fuel in a civilian
power reactor gets replaced at each refueling,
and is placed in deep pools at the
facility, where it can shed both thermal
heat and radiation. Originally, the idea in
the industry was that when the spent fuel
was cool enough to handle, it would be
shipped to commercial sites for reprocessing.
Commercial reprocessing failed in the
U.S., and the government abandoned recycling
technology.
In the early 1980s, utilities began to
fear that their fuel pools were filling up
and could not be easily enlarged, although
they can be " re-racked " to accommodate
more fuel assemblies in the pools. That's
a temporary fix, and utilities soon began
looking at ways to safely store used fuel
outside of the pool but still on the reactor
site, freeing up pool space for recently
replaced fuel rods.
Dry casks, according to the Nuclear
Regulatory Commission (NRC), " typically
have a sealed metal cylinder to contain
the spent fuel enclosed within a metal or
concrete outer shell to provide radiation
shielding. In some designs, casks are set
vertically on a concrete pad; in others,
they are placed horizontally. " The NRC licenses
dry cask storage, giving utilities a
pair of options. They can choose either a
site-specific storage cask design, with an
opportunity for a public hearing, or they
can choose a " general license, " allowing
use of any cask the agency has certified.
The certification process is also open to
public comment. To date, according to the
Electric Power Research Institute (EPRI),
there are nearly 2,000 canisters in use in
the U.S. (Figure 1).
Some anti-nuclear groups have claimed
that the casks are, in the words of Arnie
Gundersen of Vermont's Fairewinds Energy
Education, " sitting ducks for terrorist targets,
easily penetrated by armor-piercing
equipment terrorists have. " The NRC restored
in tank farms and largely forgotten.
Much of this dangerous liquid waste remains
in place today at DOE weapons sites, defying
decades of failed promises of cleanup.
When the U.S. created a quasi-civilian
agency after the war-the Atomic Energy
Commission (AEC)-to take over management
of the atom from the Army, the AEC's
November 2014 | POWER
1. Casket for spent nuclear fuel.
This schematic shows a vertical storage
canister (blue) inside a concrete cask (gray)
with inlet and outlet access vents. Courtesy:
EPRI
DOE history of nuclear waste management
described the Wolman report as finding that
the government waste program was " negligent. "
Shortly after that report, the AEC
began taking on waste management as an important
task and appointed Gorman to run the
agency's waste program.
But Wolman and Gorman got pushback
from AEC scientists and encountered the
often byzantine politics of the AEC. At the
AEC meeting where Wolman's report was
unveiled, noted and controversial physicist
Robert Oppenheimer dismissed waste disposal
as " unimportant. " NRC official historian
Samuel Walker said Oppenheimer's view
was " a prevalent judgment among physicists
and other scientists who held influential
posts with the AEC. " The next 15 years saw
little progress in cleaning up the waste tanks
the bomb makers left in their wake.
The arrival of civilian nuclear power
sponds, in typically low-key fashion, that
such a scenario has a " very low probability
of a successful attack. " According to the
NRC, " Since the first casks were loaded in
1986, dry storage has released no radiation
that affected the public or contaminated
the environment. There have been
no known or suspected attempts to sabotage
cask storage facilities. "
As the use of the on-site dry storage
technology spreads, as appears certain,
there will also be research and development
efforts to improve the technology.
EPRI is looking at technical issues associated
with dry cask storage. One problem
that has cropped up is that some canisters
may develop stress-corrosion cracking
(tiny cracks in the metal) as a result of
chlorine. This appears to be more common
in marine environments.
EPRI says it is " identifying promising
nondestructive evaluation technologies,
investigating robotic delivery systems,
and building representative mockups of
canister designs for testing and demonstration. "
first
head, David Lilienthal, named a Johns
Hopkins University sanitary engineering
professor, Abel Wolman, to an AEC advisory
committee on safety and industrial health.
After visiting AEC's labs and facilities in
1947, Wolman and a colleague, Arthur Gorman,
produced a damning 1948 report on the
state of nuclear waste management. A 1997
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plants in the 1960s and 1970s complicated
the AEC's waste management responsibilities
by adding SNF to the equation. The civilian
plants became an AEC priority after
President Dwight D. Eisenhower gave his famous
" Atoms for Peace " speech at the United
Nations in 1954 and Congress responded
with the 1954 Atomic Energy Act. By 1955,
the AEC's Glenn Seaborg warned that radioactive
waste " may well be a limiting factor "
in the development of civilian nuclear power
plants. The next year, a National Academy of
Sciences panel that Wolman chaired called
radioactive waste " an unparalleled problem. "
Plan A: Custom Burial
The AEC's response was a 1970 program to
develop waste storage in deep salt beds located
in Kansas. The national academy had
highlighted salt beds as favorable for underground
storage, because they tend to be dry.
Cracks and fissures are self-sealing because
salt has plasticity. Kansas looked good because
it was located in the central U.S., largely
equidistant from possible reactor sites.
There was a problem. It turned out the
AEC did a poor job of reconnoitering the site
it chose near Lyons, Kansas. After investing
much money and scientific credibility in the
site, it became clear that the government had
failed to account for many oil and gas wells
that had been drilled into the Kansas salt deposit,
leaving multiple pathways for corrosive
water to attack the metal canisters that the
agency planned to use to store the waste. That
project collapsed and the AEC was back to the
beginning on how to store nuclear waste.
Up until the mid-1970s, the industry expected
that it would recycle reactor fuel,
chopping it up, dissolving it in chemicals and
extracting plutonium for new reactor fuel.
That had two drawbacks: It was a nasty pro43
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POWER November 2014

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