The emergency plan is considered the last barrier available to protect people against the harmful effects of radiation coming from the liberated radionuclides. It demands a substantial national administrative and techni­cal infrastructure which is reflected in the corresponding emergency plan. The site characteristics require that there should be an efficient way of communicating the situation to the affected people. Among the emergency procedures, in order of increasing importance, it will be necessary to remain indoors, ingest potassium iodide to protect the thyroid, and evacuate people to safer places. Among the long-term measures it is necessary to monitor water and food, to confiscate crops and other products and to establish a decontamination programme. Large population densities, intensive indus­trial and agricultural development, complicated topography and lack of evacuation routes are impediments to an efficient emergency plan.

The principle on the ultimate heat sink provisions is defined as given below:

Principle 4: The site selected for a nuclear power plant has a reliable long-term sink that can remove energy generated in the plant after shutdown, both imme­diately after shutdown and over the longer term.

The generation of residual energy after reactor shutdown due to the disin­tegration of the radioactive fission and activation products, the so-called decay heat, is a specific property of nuclear power. The impossibility of removing such energy causes the heating up of the core, the loss of fuel integrity and its potential meltdown and the release of radionuclides. Therefore the availability of an ultimate heat sink is an unavoidable require­ment. This ultimate heat sink could be the same as the sink receiving the heat rejected from the thermodynamic circuit, but under accidental condi­tions the decay heat can be released to the atmosphere providing that such systems will withstand all foreseeable extreme circumstances.