The safe enclosure of the radioactive inventory of a nuclear plant is structured according to the multiple barrier principle, i.e. radioactive substances must pass these multiple different barriers connected in series before they are released. Barriers of a nuclear reactor:

  • Retention of the fission products in the nuclear fuel itself,
  • Enclosure of the nuclear fuel in cladding tubes,
  • Enclosure of the fuel elements in the reactor pressure vessel and primary coolant system,
  • Gas-tight containment around the reactor pressure vessel.