The development and construction of the first nuclear power plants became the basis for the emergence of a new branch of the economy, an economy based on the use of radioactive means. Threats of a radiological nature generated by this new qualitative branch of the economy are not related solely to the operation of the nuclear power plant. Transport, decontamination or the process of recovering spent nuclear fuel for reuse in special reactors are also a source of potential threats. And these hazards do not only apply to persons working in nuclear power plants or having contact with nuclear fuel. They also affect the security of the population in a wider scope, becoming the subject of interest for specialists dealing with common security. The aim of the article is an attempt to systematize and approximate the issue of radiation hazards related to the construction and operation of nuclear power plants. The tragedies of 1986 in the USSR and 2011 in Japan show the magnitude of losses and human suffering in the event of a radiation event with signs of a catastrophe. In article, author explained the concept and the essence of radiation hazards, including the risk assessment of this type of threats in Poland, presented the general principles of employee protection and defense against failures used in nuclear power plants, as well as the concept of the so-called defense in depth.