Harmful consequences of a nuclear accident can be reduced by timely application of the countermeasures. Those measures can be divided into urgent (the ones applied in early phases of accidents) and long-term (applied in later phases, once the direct influence of the radioactive cloud has passed away). The most important urgent countermeasures are:

	sheltering (instructing of the population to take cover inside the buildings);
	evacuation (urgent moving of the population from the endangered area);
	iodine prophylaxis (saturating of the thyroid gland with stable iodine in order to prevent the radioactive iodine from being taken in).

Among the most significant long-term countermeasures are:

	temporary relocation (relocation of the population from the endangered area for a period of two years);
	permanent relocation;
	agricultural countermeasures (measures for reduction of the degree of contamination and measures of limitation or prohibition on consuming water and food).

The procedure of decision making about the application of the countermeasures is very complex. Namely, each of the countermeasures beside the useful effects (reduction of introduced radiation doses), causes major or minor side effects.

Sheltering is a countermeasure consisting of retaining the population in closed spaces. Those closed spaces can be flats and rooms within tenements and family houses, basement spaces or spaces in objects specially built for that purpose - shelters with ventilation and air-filtering systems. This countermeasure provides protection from radiation coming from the radioactive cloud or the deposited radioactive material and prevents entering of radionuclides into the body by way of inhaling. In case of proclaiming this countermeasure it is necessary to remain in a closed space or reach it as soon as possible and wait for further instructions which will be announced by the media (radio and television).

Evacuation belongs in the group of preventive or urgent protection and rescue countermeasures depending on the moment of it's announcing. Evacuation means transfer of the population from endangered areas in order to avoid short-term exposure to high radiation doses. It is the only countermeasure with the potential of complete prevention of exposure to radiation caused by emission of radioactivity from nuclear facilities. Of course, complete prevention can only be expected if evacuation has been completed before the arrival of the radioactive cloud. Evacuation is a countermeasure within which absence of the inhabitants from the endangered areas does not last longer than a week. If radiological parameter measurements in the endangered area show that such quick return is not possible, a measure called temporary relocation is being applied.
According to our nuclear emergency response preparedness system evacution is envisaged only for areas within the 25 kilometer radius from Krško NPP, i.e. areas within the urgent protective planning zone (zones). Implementation of this countermeasure, if it turns out necessary, will proceed according to ready made and practiced plans. Civil service, military and other special units are in charge of this countermeasure implementation.

Iodine prophylaxis, i.e. prophylaxis of the thyroid gland with stable iodine is one of the added urgent countermeasures. The purpose of this countermeasure is to saturate the thyroid gland with stable iodine, preventing settling of radioactive iodine which can enter the thyroid gland by inhalation of contaminated air or ingestion of contaminated food. The countermeasure itself is implemented in a simple way, by consuming a corresponding dose, i.e. a tablet of stable iodine, which can be in form of potassium iodide (KI) or potassium iodate (KIO3).
The efficacy of stable iodine tablets depends on the time of consumption in relation to the duration of exposure to radioactive iodine. Tablets reach the highest level of effectiveness if consumed immediately before or one to two hours after the exposure to radioactive iodine. In that case the efficacy of radioactive iodine input blockade for the thyroid gland is more than 90%.

Temporary relocation is a countermeasure that includes transfer of the inhabitants from the indangered area to temporary evacuation centers for a period from several months to several years. This countermeasure is applied in case of a high level of radionuclide deposition in the endangered area. The length of inhabitants' absence from the contaminated area is determined by the dose avoided by implementation of this countermeasure. The temporary relocation countermeasure is implemented during the first week or the first month after the nuclear accident. Beside relocation of people, this countermeasure also includes relocation of movable properties and domestic animals from the endangered area.

Permanent relocation is a countermeasure implemented when an area is so contaminated that its decontamination cannot be technically or financially justified. Resources needed for its implementation are different from the ones needed for the implementation of temporary relocation or evacuation countermeasures. In fact, beside the organized transport of people and goods and the appropriate accommodation, permanently relocated inhabitants from endangered areas need to have secured existential conditions in the new environment.

Countermeasures connected with food products are based on the amount of the radionuclides deposition. The amount of radionuclides that will be deposited depends on their composition inside the radioactive cloud and the weather conditions during the nuclear accident. Radionuclides enter the human food chain by way of deposition from the cloud. Besides, they get into the surface - and ground waters. Therefore restriction, i.e. inhibition of using certain food products is undertaken immediately after the expected contamination level of a certain area has been assessed. Restriction of using food products (fresh fruit and vegetables, especially lettuce, as well as meat and milk coming from the contaminated area, and drinking water usage) reduces considerably the input of radionuclides into the human body, lessening health risks.