S

• Safeguards (International)

  Term used to include the measures established to prevent failure to comply with a law or agreement that bans the use of nuclear materials or facilities with non-peaceful aims. It is usually used in the plural.

• Safety barrier

  A set of components, systems or administrative regulations used at nuclear or radioactive sites to prevent accidents. At a nuclear power plant there are usually three 3 safety barriers: the fuel rod cladding, the reactor vessel (the primary circuit) and the reactor containment. The fuel pellet itself is sometimes added as a first barrier, since under normal operating conditions its treatment enables it to retain a large part of the generated fission products.

• Salem

  Emergency room of the Spanish Nuclear Safety Council.

• Screen

  1. Fluorescent screen: Surface covered with a fluorescent substance that emits light when it receives an ionising radiation. 2. Reinforcement screen: Sheet which under the action of X-rays emits a secondary radiation that contributes to the printing of the plate. 3. Radiation-absorbing device that blocks its path in order to intercept radiation totally or partially.

• Semi-decay period

  Time interval needed for the number of atoms in a radioactive nuclide to be reduced by half through spontaneous decay.

• Semi-reduction thickness

  Thickness of a given substance that reduces by half the intensity of a certain type of radiation, when it is interposed in its path.

• Shield (biological)

  Material placed between a source of radiation and personnel in order to minimise the number of particles and radiation, and protect personnel from the effects of such radiation.

• Shielding factor

  Correction factor owing to radiation attenuation.

• Sievert (Sv)

  Unit of equivalent and effective radiation dose in the International System of Units: 1 Sv = 1 J/kg. The old unit is the REM. 1Sv = 100 REM.

• Single exposure

  Brief external exposure or internal exposure resulting from radionuclide intake during a short period of time.

• Source (of radiation)

  Device or substance capable of emitting ionising radiation.

• Stop

  In reactor technology, synonymous with shutdown. When following a nuclear reactor's stop the coolant temperature remains high, this is known as a hot shutdown. If the coolant temperature falls, the term used is "cold shutdown".

• Supervisor

  Person authorised by the Spanish Nuclear Safety Council and in charge of directing the operation of a nuclear or radioactive facility and the work of the operators and, where applicable, of replacing the operators.