Division of Spent Fuel Storage and Transportation
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.”