Nuclear 101: How Does a Nuclear Reactor Work?

Introduction

• Nuclear reactors are essential components of nuclear power plants.
• They control nuclear chain reactions to produce heat through a process called fission.
• The heat generated is used to create steam that spins a turbine to produce electricity.
• Nuclear power is a significant source of reliable carbon-free electricity with over 400 commercial reactors worldwide, including 94 in the US.

Nuclear Fission

• Definition: A process where atoms are split to release energy.
• Fuel: Uranium is used as nuclear fuel.
  • Processed into ceramic pellets and stacked into fuel rods.
  • Fuel rods are grouped into fuel assemblies, hundreds of which form the reactor core.
• Reactor Core: Contains fuel rods immersed in water acting as a coolant and moderator.
  • Coolant: Cools the core.
  • Moderator: Slows down neutrons to sustain the chain reaction.
• Control Rods: Inserted or withdrawn from the core to control the reaction rate.
• The heat from fission turns water into steam, driving turbines for electricity generation.

Types of Light-Water Reactors

• All US commercial nuclear reactors are light-water reactors.
• Function: Use normal water as both coolant and neutron moderator.

Pressurized Water Reactors (PWRs)

• More than 65% of US reactors.
• Feature high-pressure water in the core to prevent boiling.
• Heat from the core water is transferred to a secondary water source in a heat exchanger, producing steam.
• The steam spins the generator, and core water cycles back for reheating.

Boiling Water Reactors (BWRs)

• Approximately a third of US reactors.
• Produce steam directly within the reactor vessel through heated water from fission.
• Steam directly powers the turbine; unused steam is condensed and recycled.

Conclusion

• Nuclear reactors play a pivotal role in generating carbon-free electricity.
• Understanding reactor types helps in appreciating their operational and environmental significance.