How A Nuclear Reactor Works



How A Nuclear Reactor Works
Nuclear Power Plant
How A Nuclear Reactor Works
Pressurized Water Reactor - Nuclear Power Plant
A. Main Parts of a Nuclear Reactor
1. Fuel
Pellets stacked in long metal tubes (fuel rods). These are
arranged in bundles in the reactor with space between them
for control rods.
2. Moderator
Slows down neutrons so they have a greater probability of
colliding with another uranium atom. Usually water or
A. Main Parts of a Nuclear Reactor (continued)
3. Control System
Control rods are filled with substances that absorb neutrons
(boron or cadmium). These help control the rate of the
4. Heat Removal System
The reactor must be cooled to prevent overheating and
melting of the core. Heat is carried away by water and
used for steam production.
5. Radiation Shield
Thermal (steel) shield protects the walls of the reactor
vessel from radiation damage. A concrete shield protects
the workers from radiation.
B. Disposal Of Nuclear Waste
1. When most usable uranium has fissioned, the “spent” fuel
assembly is removed from the reactor.
2. Until a long term storage facility is operational (Yucca Mountain,
NV?), “spent” fuel is stored in water pools at the reactor site.
3. Water removes leftover heat and serves as a radiation shield.
Underground disposal
of radioactive waste
(in Finland)
Typical water pools for
nuclear waste storage
C. Nuclear Meltdown
1. Refers to melting fuel in a reactor when there is an inability to
remove heat effectively.
2. Causes include a loss of coolant in the system and/or failure of
the reactor to shut down when faulty.
3. If a meltdown does occur, a release of radiation occurs only if
there is a major failure in the containment structure (pressure,
fire, explosion).
C. Nuclear Meltdown (continued)
Chernobyl disaster
• Ukraine (Soviet Union), 1986
• Worst nuclear power plant accident in history
• 31 peopled during the accident itself, but more people
suffered long-term effects like cancer and deformities
C. Nuclear Meltdown (continued)
Japan, March 2011
Occurred after the power plant was hit by a tsunami
Although no fatalities were reported after the incident, over
300,000 people had to evacuate the area

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