Nuclear Power Plant How A Nuclear Reactor Works
- Slides: 8
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 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 graphite.
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 reaction. 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 people died during the accident itself, but more people suffered long-term effects like cancer and deformities
C. Nuclear Meltdown (continued) • Fukushima Daini Nuclear Power Plant • 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, and almost 16, 000 died due to the earthquake and tsunami