POWER February 2015 - 46

NUCLEAR FUEL LIFECYCLE
site dry storage has become the de facto next and final step in the U.S.
storage plan. The NRC formally recognized onsite dry cask storage
as safe from short to indefinite timeframes with its August 2014 Continued
Storage of Spent Nuclear Fuel Rule. And that is one reason the
market for onsite dry cask storage is sure to grow.
A report by authors from Oak Ridge National Laboratory projects
that the number of SNF canisters in dry storage will roughly double
in the next 10 years (from more than 1,850 in 2013) and will exceed
10,000 by 2050 in the U.S. alone. An October 2014 report by the U.S.
Government Accountability Office (GAO) found that in 2013, about
70% of SNF was stored in pools and the remaining 30% in dry storage.
As reactors reach the end of their operating licenses, the volume
of SNF will increase.
Cask designs vary by manufacturer, but some of the main variants
involve purpose (some designs can be used both for transportation and
storage), orientation (vertical or horizontal), materials (stainless steel is
most common, though cast iron is also used), and siting (above ground
on a cement pad or subsurface).
Dry cask storage has been used in North America, Europe, and
Asia. The first casks used in the U.S. were loaded in 1986 at the Surry
Nuclear Power Plant in Virginia. As of September 2014, the NRC,
which offers both a site-specific and a general license for dry storage
cask systems, said spent fuel was being housed in dry storage at more
than 50 sites under general licenses and at 15 sites with specific licenses.
However, Maureen Conley in the NRC's Office of Public Affairs
told POWER that the commission hasn't received a site-specific
license application " in many years. "
The NRC also licenses cask designs; not all vendors have applied for
or received NRC licenses. In addition to Holtec and AREVA TN, vendors
with currently approved designs are General Nuclear Systems Inc.
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(only used at Surry), NAC International Inc., and Energy Solutions Inc.
Conley confirmed that reactors with operating licenses may use any
of the dry storage systems certified by the NRC as long as they do an
analysis showing their site meets the parameters of the approval. Some
sites use casks of multiple designs or from multiple vendors.
Security Concerns Push Dry Cask Storage
In addition to the absence of permanent storage sites and crowded spent
fuel pools, two events within a decade underscored the need for more
secure " interim " storage options: the terrorist attacks of September 11,
2001, and the disaster at the Fukushima Daiichi power plant in 2011.
The NRC notes that after 9/11, it required plant operators to take
" several measures aimed at mitigating the effects of a large fire, explosion,
or accident that damages a spent fuel pool. These were meant
to deal with the aftermath of a terrorist attack or plane crash; however,
they would also be effective in responding to natural phenomena such
as tornadoes, earthquakes or tsunami. " These measures included:
■ Controlling the configuration of fuel assemblies in the pool to enhance
the ability to keep the fuel cool and recover from damage to
the pool.
■ Establishing emergency spent fuel cooling capability.
■ Staging emergency response equipment nearby so it can be deployed
quickly.
In December 2014, more than three years after the site experienced
catastrophic damage from the Great East Japan earthquake and tsunami,
Tokyo Electric Power Co. (Tepco), the plant's operator, finished
removing 1,331 spent fuel rods and 204 unused assemblies from Daiichi
Unit 4 and had placed them in a cask container for transportation
to an undamaged Unit 6 pool on the site. (Because Unit 4 had
been under routine maintenance at the time of the disaster, all 1,535
fuel assemblies were in the pool.) Tepco expects to remove fuel from
Units 1, 2, and 3 by fall of this year. It started with Unit 4 because
the hydrogen explosion that blew the roof off the reactor building
made that pool the most critical to remediate. (A video at http://on.fb.
me/1Drgd3M tracks the stages of the fuel removal process.)
In Japan, concern about the safety of SNF pools persists, especially
as onsite pools fill up and completion of a planned Japanese
fuel reprocessing center in Rokkasho is looking unlikely.
A June 2014 report in the Nikkei Asian Review noted that Japan's
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pools have been criticized as being vulnerable to natural disaster or
terrorist attack. The Japanese Economy, Trade and Industry Ministry,
the publication said, plans to provide incentives for using dry cask
storage as soon as after one year of in-pool cooling. In addition to
offering better safety in the event of a disaster, the story noted that
maintenance costs for dry cask storage are reportedly 60% lower than
for pool storage. Japan, the article said, currently has two dry cask
sites " storing 240 tons combined, or roughly 1% of the total amount
of spent fuel in the country. "
According to a paper by Xuegang Liu of the Division of Nuclear
Chemistry and Engineering, The Institute of Nuclear and New Energy
Technology, Tsinghua University, Beijing ( " Spent Nuclear Fuel
Management in China, " NAPSNet Special Reports, Aug. 5, 2014),
because China has chosen to use a closed-cycle fuel path, it has less
need for long-term SNF storage. The author notes that " Dry cask storage
has only been implemented for CANDU spent fuel at the Qinshan
Phase III NPP, because of the low thermal density of CANDU spent
fuel and the lack of plans to reprocess spent CANDU fuel, which is
made of natural uranium. Dry cask storage is also a possibility for use
in storing fuel from high temperature gas cooled pebble-bed reactors,
and dry casks are being designed for this purpose. "
In China, although the disposition of SNF varies based upon reac

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POWER February 2015

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