Spent 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 US nuclear power plants now.
Spent fuel pools contain more highly radioactive fuel than the reactor cores.
And the spent fuel pools at all US 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. The photograph at left shows a
boiling water reactor under construction. The steel foundation for the spent
fuel pool’s floor and walls is being erected. The large hole in the center of
the photograph allows personnel to access equipment inside the reactor
containment structure. A smaller hole in the lower left of the photograph,
partially obstructed by reinforcing bar for an upcoming concrete pour, allows
spent fuel assemblies to pass underwater from the reactor core to the fuel pool.
As can be seen, the reactor containment structure is a steel-lined, reinforced
concrete building whereas the spent fuel pool building is simplymade of
reinforced concrete.
The picture below shows the spent fuel pool in the
completely constructed plant. The racks visible in the bottom of the pool store
the spent fuel assemblies. The gap in the concrete wall in the lower right
connects the spent fuel pool to the transfer area. Fuel assemblies are lowered
from the vertical position to the horizontal position in the transfer area for
transport through the small containment hole to the reactor core.
The concrete wall on the far side of the
picture, behind the railing and traversed by sheet-metal ventilation ductwork,
is an outside wall. In the construction picture, this wall is represented by the
reinforcing bars for the 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.
Some of the nuclear power plants with boiling
water reactors are even more vulnerable. For example, the spent fuel pool is in
the taller building on the left side of the nuclear plant shown below. The
longer, shorter building on the right houses the turbine/generator. The
photograph on the right shows the platform used to move fuel within the spent
fuel pool. It rides on rails and spans the width of the spent fuel pool. The
dark wall in the background is the blue panel shown in the picture on the left.
It is corrugated metal siding that would hardly stop a Cessna from penetrating,
yet alone a fully loaded commercial jet. As suggested from the photographs, the
spent fuel pool at this plant is as high above ground as possible. About the
only way to elevate it further would be to balance it on top of the red and
white striped chimney in the background.
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 as shown below.
Weapons available on the black market, and even some that can be legitimately
purchased in the US, 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?