The primary impact of concern in the event of an accident or an intentional attack on a nuclear power plant is the same: major off-site releases of radioactive material. This section examines potential safety65 and security66 impacts arising from the operation of nuclear power plants in the United States. The following discussion is drawn from a recent National Research Council report on the safety and security of commercial spent nuclear fuel storage (NRC, 2006).

There are two potential sources for off-site radioactive releases: the nuclear fuel in the reactor core and in used fuel storage. An accident or terrorist attack that disrupts cooling of the fuel could damage the fuel and release radioactive material to the environment. The fuel in the reactor core of a nuclear plant generates substantial quantities of heat and radioactivity. The plant’s cooling system is designed to remove this heat from the core so it can be used for electricity generation. A loss of coolant would cause temperatures in the core to increase, even after the reactor is shut down.67 At about 1000°C, the fuel cladding68 would begin to oxidize rapidly in the presence of air or steam (if the core did not remain covered with water). This exothermic reaction releases large quantities of heat that would further raise temperatures. At about 1800°C, the cladding and fuel would begin to melt, releasing radioactive gases and aerosols into the core. These radioactive materials could be released to the surrounding environment if the reactor pressure vessel69 and the containment70 were to fail. Such releases could endanger local populations and contaminate the environment.

An accident or terrorist attack on a used-fuel pool could have similar con-


“Safety” is defined here as measures that would protect nuclear facilities against failure, damage, human error, or other accidents that would disperse radioactivity into the environment.


“Security” is defined here as measures to protect nuclear facilities against sabotage, attacks, or theft.


This “heat” is the product of radioactive decay in the fuel.


“Fuel cladding” is a thin-walled metal tube that forms the outer jacket of a nuclear fuel rod. It prevents corrosion of the nuclear fuel and the release of fission products into the coolant.


The “reactor pressure vessel” is a thick-walled cylindrical steel vessel enclosing the reactor core in a nuclear power plant.


A “containment building” is a steel or reinforced concrete structure enclosing a nuclear reactor. The containment building is typically an airtight steel structure enclosing the reactor, sealed off from the outside atmosphere and attached to a concrete shield. In the United States, the design and thickness of the containment and the shield are governed by federal regulations (10 CFR 50.55a).

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