Three Mile Island: How a Nuclear Reactor Works
At the heart of every nuclear power plant lies the radioactive core. The
core is a nuclear furnace, generating heat as its atoms split during a
controlled chain reaction. At Three Mile Island, the core stands 12 feet high
and weighs 100 tons.
Control rods are lowered into or raised out of the core to control the
rate at which the atoms split, and therefore the amount of heat generated by
the core. Lowering the rods slows down the reaction; raising the rods increases
Water in the primary loop flows around the core, absorbing the heat
generated. Because it comes in contact with the core, the water in the primary
loop is radioactive. Pumps move the water through the primary loop. The
PORV is a pressure release valve. The EIW, or Emergency Injection
Water, allows water to enter the system in the event of a "loss of coolant."
Heat transfers from the water in the primary loop to water in the secondary
loop. The water in the secondary loop turns to steam. The steam powers a
turbine, which is connected to a generator.The generator produces
electricity. Pumps move the water through the secondary loop and back to
where the heat is exchanged. Water in the secondary loop does not mingle with
the water in the primary loop and therefore is not radioactive.
Surrounding the core and much of the primary loop is a four-foot-thick,
concrete containment structure.
What Happened: Step-by-Step (Shockwave activity)
Text version of "What Happened: Step-by-Step