What is the Reactor Core?

• A. The part of a nuclear reactor where the heat is generated and includes fuel, cladding, fuel assemblies, moderator/coolant and control rods
• B. The outer containment building that prevents release of radioactivity
• C. The turbine section where steam is expanded to perform work
• D. The structure housing the cooling towers and condensers

Answer: (A)

The region where fission heat is produced is the reactor core. It contains the fuel elements (the fuel rods grouped into fuel assemblies) and their cladding, all of which are the parts that actually sustain the nuclear chain reaction. Surrounding and interacting with the fuel are the moderator and the coolant; in many reactors these are the same medium (water) that slows neutrons to sustain fission and also removes the generated heat. Control rods, made of neutron-absorbing material, sit in this same region to regulate reactivity by absorbing neutrons when needed. Everything inside this core region is focused on producing and managing the heat from fission. The outer containment building, the turbine section, and the cooling towers are separate systems that provide safety containment, convert heat to electricity, and reject heat, respectively, but they are not part of the core where the fission reactions and heat generation occur.