When Problems Are a Sign of Success
by Moderator
Chris Allen
Project Manager
Division of Spent Fuel Storage and Transportation
![Spent fuel dry casks]()
Can a problem show that our regulatory system works? If you don’t think so, read on.
Two weeks ago, the NRC published an “information notice”
about moisture causing problems for dry spent fuel storage casks.
Information notices are one way the NRC communicates formally with
licensees. We send these notices when we want all licensees to be aware
of a particular problem found with just one or only a handful of
licensed facilities or equipment so they can prevent similar problems.
Spent fuel dry casks
The problem in this case centers on dry spent fuel storage casks that
store used nuclear fuel after it’s been cooled for several years in
spent fuel pools. The NRC reviews the designs of these casks to make
sure they will safely cool the fuel and contain the radiation it emits.
In
this case, two different sites using two different storage designs had
unanticipated problems on the outside of the system caused by moisture.
The structural integrity of the systems was never compromised and the
radiation levels at both sites remained very low.
The
first problem dates to 2007 at a facility in Idaho that stores spent
fuel debris from the damaged Three Mile Island reactor. The system uses
thick concrete for shielding and protection from earthquakes and other
natural forces. The operator saw that cracks in the concrete—originally
thought to be cosmetic and trivial—were spreading. The licensee’s
evaluation found water had entered bolt holes on top of the casks,
froze, thawed and cracked the concrete. The evaluation also identified
repairs, ways to prevent more water from getting in and a program for
monitoring cracking.
The
second problem, at the Peach Bottom reactor site in Pennsylvania, was
identified on October 11, 2010, when an alarm sounded. That alarm was
designed to be an early warning that the helium inside might be leaking.
On examination, the licensee found rust beneath a metal weather cover
and moisture around the bolts holding the cask lid in place. An outer
lid seal was leaking more helium than the NRC license allowed. An inner
seal kept the spent fuel and radioactivity confined inside the cask.
From
the time these issues were discovered, we made information available
through licensee event reports, NRC inspection reports, letters and
other communications with licensees. Our licensees and some trade
publications that follow NRC activities closely knew of the issues.
The
licensees talked with one another as well at industry-wide workshops
and conferences. And our inspectors, who also talk with one another,
always look for evidence that dry storage casks are in good condition.
So how does this mean the process worked?
Alarms
like the one at Peach Bottom and follow-up evaluations like the one in
Idaho are examples of the monitoring and periodic examinations that the
NRC requires all cask users to perform. These provide warnings long
before a problem could develop that might affect public health and
safety or the environment. We also require periodic examinations of dry
storage casks so any potential issues can be identified early.
The
NRC stayed up-to-date as the licensees learned more about the cause of
their problems, how to prevent such problems in the future, and how to
fix the problems on their existing systems. In this case, the NRC took
the extra step of issuing the information notice even though
communication between the NRC and licensees as well as among licensees
meant that, when the information notice came out last week, it was
actually “old news.”
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