How A Nuclear Reactor Works

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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
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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
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Slows down neutrons so they have a greater probability of
colliding with another uranium atom. Usually water or
graphite.
A. Main Parts of a Nuclear Reactor (continued)
3. Control System
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Control rods are filled with substances that absorb neutrons
(boron or cadmium). These help control the rate of the
reaction.
4. Heat Removal System
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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
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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)
•
Fukushima
•
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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