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Spent Reactor Fuel Security

Much of the discussion since the September 11th attacks on the World Trade Center and the Pentagon has focused on the resistance of reactor containment structures to aircraft strikes. The Nuclear Regulatory Commission (NRC) needs to analyze this issue so that its answer is known rather than debated.

More importantly, the NRC must address the vulnerability of spent fuel storage at all U.S. nuclear power plants now. Spent fuel pools contain more highly radioactive fuel than the reactor cores. And the spent fuel pools at all U.S. nuclear plants are located outside the reactor containment structure. When the spent fuel pools fill up, spent fuel is stored in concrete casks outside the plant. Thus, spent fuel is a softer target that could yield graver consequences than an aircraft crashing through the reactor containment structure.

What is the spent fuel pool?

The spent fuel pool is a 45-feet deep concrete pit that stores highly radioactive fuel assemblies after their removal from the reactor core. Water storage is required because spent fuel assemblies continue to emit considerable amounts of both heat and radiation for many years. The fuel pool water is continuously cooled to remove the heat produced by the spent fuel assemblies. Without cooling, the fuel pool water will heat up and boil. If the water boils or drains away, the spent fuel assemblies will overheat and either melt or catch on fire. NRC studies have estimated that many thousands of people living within 50 miles could die from the radiation released when spent fuel assemblies melt or catch on fire.

Where are the spent fuel pools located?

The spent fuel pools at nuclear power plants with pressurized water reactors are located in buildings adjacent to the reactor containment structures. Typically called the Fuel Handling Buildings, these structures are designed to withstand nature (e.g. earthquakes, tornadoes, hurricanes, floods, and snow storms) but not man (e.g., sabotage and accidental or intentional aircraft strikes). The Fuel Handling Buildings are basically standard, industrial-grade buildings (much like K-Mart but without the neon signs). 

The spent fuel pools themselves are generally below ground level within the Fuel Handling Buildings.  Consequently, it is less likely for water to drain out of the spent fuel pool when its floor or walls are damaged than if it were located above ground.

 

The spent fuel pools for nuclear power plants with boiling water reactors are located above ground in the building surrounding the primary reactor containment structure.  This can make some boiling water reactors even more vulnerable.

The reactor containment structure is often a steel-lined, reinforced concrete building whereas the spent fuel pool building is usually made simply of reinforced concrete.

An aircraft—or missile—would not need to completely level the fuel building to cause harm. It would merely need to crack the concrete wall or floor of the spent fuel pool and drain the water out. The spent fuel pool is designed to remain intact following an earthquake, but it is not designed to withstand aircraft impacts and explosive forces.

What about spent fuel stored in dry casks?

When the spent fuel pool in the "attic" of the nuclear plant fills up, some of the highly radioactive fuel assemblies are loaded into large casks and stored outside on concrete pads.  Weapons available on the black market, and even some that can be legitimately purchased in the U.S., or explosives could cause the casks to be penetrated resulting in the release of large amounts of radiation. At some plants, the casks are line-of-sight visible from open access (i.e., unsecured) areas while other plants place casks inside unguarded chain-link fences.

What should the NRC do about spent fuel security?

As soon as it is safe to do so, most of the spent fuel at reactors should be put into dry casks. Fuel in dry casks is less likely to catch fire, and terrorists would have to break open many dry casks to release the same amount of radioactivity that a single wet pool could release.

To reduce the vulnerability of these dry casks, the NRC should adopt new "physical protection standards" that enhance the security requirements for dry cask storage so that the fuel will be protected against reasonably foreseeable threats that might emerge over several decades. The new standards should consider credible scenarios by which attackers could gain access to and release the radioactive material from the dry casks. Protection would involve a combination of operational measures and physical measures, such as putting spent fuel casks into enclosed buildings, using earthen berms, or erecting other barriers.

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