Pumps in the nuclear auxiliary systems of nuclear power stations, i. e. pumps used in the process-linked circuits of the primary circulation and which are therefore radioactive to a greater or lesser degree, e.g. in the radioactive effluent treatment system. Typical examples: dosing pumps, resin flush pumps, pH metering pumps, vaporizer feed pumps, filling and circulation pumps, flood pumps, flood filter feed pumps, sludge pumps, circulation and discharge pumps, concentrate pumps, and MB filter pumps. Special note must be given to the so-called "fundamentally safe systems" such as the recooling circuit with recooling pumps, well cooling pumps, well cleaning pumps, safety feed pumps, HP feed pumps, and nuclear intermediate cooling circuit pumps. As far as possible, double or tandem mechanical seals are used in these pumps in order to prevent the escape of radioactive leakage.