Defense-in-Depth

The defense-in-depth approach ensures that any release of hazardous amounts of radioactive materials will be extremely unlikely.

This approach uses three barriers to prevent the release of fission products from the reactor core to the environment. These consist of the following:

  1. Fuel rods (fuel pellet and fuel cladding)
  2. Reactor vessel and primary coolant system
  3. Containment building

The chance of any single barrier failing is unlikely. The chance of all three failing simultaneously is, therefore, extremely remote.

Fission product barriers: fission products surrounded by fuel and fuel cladding, which is surrounded by the reactor vessel, which is surrounded by containment.