Friday, April 1, 2011

Post # 36: More on "Beyond Design Basis" Accidents In Spent Fuel Pools

I provided a short bibliography of documents detailing research that has been done on "beyond design basis" accidents in BWR refueling / spent fuel pools in Post # 33.

Subsequent to that posting I ran across a couple of outstanding documents on the subject that I had overlooked.  They are included in the amended bibliography below as References 3 and 4. 

1. NUREG/CR-0649, "Spent Fuel Heatup Following Loss of Water During Storage,"Allan S. Benjamin, David J. McCloskey, Dana A. Powers, Stephen A. Dupree, March 1979.

2. NUREG/CR-4982, "Severe Accidents in Spent Fuel Pools in Support of Generic Safety Issue 82," V. L. Sailer, K. R. Perkins, J. R. Weeks, H. R. Connell, July 1987.  

3. E. D. Throm, "Regulatory Analysis for the Resolution of Generic Issue 82, Beyond Design Basis Accidents in Spent-Fuel Pools," NUREG-1353, U.S. Nuclear Regulatory Commission, April 1989.

4. Edward D. Throm, "Beyond design basis accidents in spent-fuel pools – Generic Issue 82,", Nuclear Engineering and Design 126 (1991) 333-359.

5. Robvert Alvarez, Jan Beyea, Klaus Janberg, et. al., "Reducing the Hazards from Stored Spent Power-Reactor Fuel in the United States," Science and Gobal Security 11: 1-51, 2003

6. Mihaly Kunstar, Lajos Matus, Nora Ver, et al., "Experimental investigation of the late phase of spent fuel pool accidents," Int. J. Nuclear Energy Science and Technology, Vol. 3, No. 3, 2007, page. 287-301

As one would expect, the NRC as spent a great deal of time on this issue.  The following URL relates to NRC's work on Generic Issue 82, cited in References 3 and 4 above:

Finally, a quick quote from Reference 4 above, that actually summarizes the conclusions of many that have looked at the issue before:

"Although these studies conclude that most of the spent-fuel pool risk is derived from beyond design basis earthquakes, this risk is not greater than the risk form core damage accidents due to these beyond design basis earthquakes.  Therefore, reducing the risk from spent-fuel pools due of events beyond the safe shutdown earthquake would still leave a comparable risk due to core damage accidents. The risk due to beyond design basis accidents in spent-fuel pools, while not negligible, is sufficiently low that the added cost involved with further risk reduction is not warranted." (italics added by me).

Basically, the conclusions were that any earthquake strong enough to lead to a severe accident in a spent fuel pool would probably also pose a significant threat to the reactor.  Given the low probably of such events, it made little sense to focus on the spent fuel pool when the reactor would normally pose the more significant challenge. These conclusions will almost certainly be revisited in light of recent events at Fukushima.  It will be interesting to track the dialog.

Just thinking...


  1. There is also discussion of this issue in the 2006 Safety and Security of Commercial Spent Nuclear Fuel Storage

    Loss of pool coolant event consequences were discussed. The main threat was stated to be a beyond design basis seismic event. The word tsunami does not appear. It was recommended that cheap to implement common sense measures might be implemented such as rearranging rods in the pools to reduce the possibility of a propagating zirconium cladding fire should the pool go dry or even should it lose some water, also beef up the ability to restore water in an emergency. Moving more rods more quickly to dry casks was not recommended.

  2. PS. the chapter on Spent Fuel Pool Storage, i.e. this page discusses the existing previous literature on the subject that this NRC panel thought worth of mention and study.

    The panel was created to assess "conflicting public claims" about what would happen if a loss of pool coolant event was ever created by a terrorist attack, but the discussion is relevant in the light of events at Fukushima.

  3. David,

    Yes, the Academy report is an excellent resource and one I should have included in my listing.

    Fukushima will catalyze a re-look at many nuclear power safety issues. Clearly, the design and operations practice of storing spent fuel for extended periods in close proximity to the reactor will be one of the issues that will be revisited. This topic is coupled to the overall spent fuel management issue, Yucca Mountain, interim repositories and "away-from-reactor" spent/used fuel storage.

    Interesting days ahead...

    Thanks for the comments!

  4. I think it will be increasingly perceived to be unethical to oppose any method of dealing with nuclear waste after this. When Nader was leading the anti nuke movement a strategy to "constipate" the industry was conceived, and it is simply unethical now that the danger of waste in pools that don't have containments is a bigger issue.

    I wrote a post: Dysfunctional Anti Nuke Waste Strategy Increases Nuclear Risk

  5. You are correct, David. One of the lessons of Fukushima will be that it is unwise to hold used/spent nuclear fuel in close physical proximity to the reactor any longer than required for it to cool sufficiently to be moved. If one works backwards from the endpoint on this train of thought, the availability of a safe, secure, off-site storage depot for spent fuel is essential to facilitate this transition in operating practice.

    Thanks for your comment,