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Suggested Citation:"4.2.3 Discussion." National Research Council. 2006. Safety and Security of Commercial Spent Nuclear Fuel Storage: Public Report. Washington, DC: The National Academies Press. doi: 10.17226/11263.

site that currently stores the most spent fuel in that cask type.13 Site conditions differed for each cask.

The effects of jet fuel fires also were not considered in the analyses. Based on an analysis of actual aircraft accidents, Sandia determined that jet fuel would likely be dispersed over a large area in a low-angle impact. Consequently, the resulting petroleum fire would likely be of short duration (generally less than 15 minutes according to Sandia researchers). Long-duration fires that could damage the casks or even ignite the cladding of the spent fuel were not seen to be credible for the aircraft impact scenarios considered by Sandia.14

The results of these analyses, which are considered by the Nuclear Regulatory Commission to be classified or safeguards information, are detailed in the classified report. In general, the analyses show that some types of impacts will damage some types of casks. For some scenarios there could be substantial cask-to-cask interactions, including collisions and partial tip-overs.

Nevertheless, predicted releases of radioactive material from the casks, mainly noble gases, were relatively small for all of the scenarios considered by Sandia. The analyses show that the releases were governed by design-specific features of the casks Sandia noted that the modeling of such releases is difficult and requires expert judgment for several elements of the calculation. Detailed calculations of the consequences were still in progress when the committee was briefed on these analyses.

4.2.2 Other Assaults

Analyses are also being carried out to understand the consequences of other types of assaults on the cask designs shown in FIGURE 4.3. These include assaults using explosives and certain types of high-energy devices. The analyses were still underway when the committee was briefed on these analyses, and the results were characterized by the Nuclear Regulatory Commission as preliminary. Details are provided in the classified report.

4.2.3 Discussion

As noted previously, the dry cask vulnerability analyses were still underway when the committee’s classified study was completed. Based on the analyses it did receive, the committee judges that no cask provides complete protection against all types of terrorist attacks. The committee judges that releases of radioactive material from dry casks are low for the scenarios it examined with one possible exception as discussed in the classified report. It is not clear to the committee whether it is credible to assume that this “exceptional” scenario could actually be carried out.


As noted in Chapter 1, the committee did not concern itself with how radioactive materials would be transported through the environment once they were released from a dry cask. Rather, the committee confined its examination to whether and how much radioactive material might be released from a dry cask in the event of a terrorist attack.


The committee subgroup that visited Germany was briefed on a fire test on the Castor cask that involved a fully engulfing one-hour petroleum fire. The cask maintained its integrity during and after this test. See Appendix C. The results of this test do not necessarily translate to casks having other designs.

Suggested Citation:"4.2.3 Discussion." National Research Council. 2006. Safety and Security of Commercial Spent Nuclear Fuel Storage: Public Report. Washington, DC: The National Academies Press. doi: 10.17226/11263.
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In response to a request from Congress, the Nuclear Regulatory Commission and the Department of Homeland Security sponsored a National Academies study to assess the safety and security risks of spent nuclear fuel stored in cooling pools and dry casks at commercial nuclear power plants. The information provided in this book examines the risks of terrorist attacks using these materials for a radiological dispersal device. Safety and Security of Commercial Spent Nuclear Fuel is an unclassified public summary of a more detailed classified book. The book finds that successful terrorist attacks on spent fuel pools, though difficult, are possible. A propagating fire in a pool could release large amounts of radioactive material, but rearranging spent fuel in the pool during storage and providing emergency water spray systems would reduce the likelihood of a propagating fire even under severe damage conditions. The book suggests that additional studies are needed to better understand these risks. Although dry casks have advantages over cooling pools, pools are necessary at all operating nuclear power plants to store at least the recently discharged fuel. The book explains it would be difficult for terrorists to steal enough spent fuel to construct a significant radiological dispersal device.

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