Nuclear power plants have engineered safety features at their disposal as well as pre-planned measures which in combination should practically rule out a severe accident happening in a nuclear power plant. A number of active and passive systems ensure the safe operation of the plant. In the case of undesired operating conditions, for example, systems will automatically switch off the reactor without requiring staff to take action. In Germany, high maintenance standards and strict regulatory requirements are continuously surveyed by authorities and their entrusted experts.

A severe accident can only happen if the numerous existing graded levels of safety measures have failed and if the additional measures for the prevention of severe damage to the reactor core and for the mitigation of radiological consequences were unsuccessful.

Even though the probability of such an accident happening in Germany is extremely low, certain dangers may exist during the operation or after the shut-down of a nuclear power plant. This is due to the fact that heat is created as a result of the radioactive decay of the fission products in the reactor core, which only cools down slowly, even after the power plant has been shut down. Should this heat not be dissipated safely, the power plant’s safety features may be threatened or even destroyed. For this reason, the reactor core of a nuclear power plant is located in a pressure-vessel with a closed cycle cooling system behind thick concrete walls. Additionally, staff is trained in the implementation of ad hoc measures to create a temporary cooling system in order to avoid or at least minimise the release of radioactive material into the environment.