Backfill refers to both the procedure and the material (filling material) for the backfilling of the still existing cavities or residual cavities during the final sealing phase in the post-closure phase of a repository mine.

Intact state of barriers in which they fulfil their function.

Geological conditions or technical/geotechnical measures to impede or prevent the release of harmful substances from the waste into the biosphere.

Geological conditions to prevent inadmissible releases of radioactive materials (such as repository formation, adjoining rock or overburden).

The radioactive inventory of a nuclear facility is safely enclosed with the help of the multi-barrier system, i. e. in order to be released, radioactive substances have to pass several different barriers one after the other. The radiological barriers of a nuclear reactor consist of: 1. the retention of the fission products in the nuclear fuel itself, 2. the enclosure of the nuclear fuel in hull pipes, 3. the enclosure of the fuel elements in the reactor pressure vessel, and 4. the gas-tight containment around the reactor pressure vessel.

Technical measures to prevent inadmissible releases of radioactive materials (such as waste product, package, stowage or shaft sealing).

The Becquerel (short form: Bq) is the measuring unit of the "activity" of a radioactive substance and indicates how many nuclear disintegrations per second occur.

Bed separators are pieces of rock separating from the roof of a mine opening which may fall down or have already fallen down.

Particle radiation consisting of electrons which are emitted by atomic nuclei during radioactive decay. The energy distribution of the beta particles is continuous (beta spectrum) and has a sharp upper limit (so-called end energy).

Particles produced through radioactive decay, consisting of electrons or respectively positrons.

Collective term (used in Germany) for equivalent dose and effective dose. The body dose for a reference period (e. g. calendar year, month) is the sum of the dose received by external radiation exposure during this reference period and the committed dose received by internal radiation exposure which is due to an activity intake during this reference period. The unit of the body dose is J/kg with the special name Sievert (Sv).

Power reactor at which (in contrast to the pressurised water reactor, german: Druckwasserreaktor DWR) a part of the cooling water boils inside the reactor and the heat is discharged as steam. The wet steam or saturated steam generated in this way is directly used for driving the turbine and the generator to produce electric current. German: Siedewasserreaktor, SWR.

Management of liquids existing in the mine, e.g. collection and transport of influent saline solutions.