It is a textbook and manual of a training course held at the Budapest Technical University for operators of irradiation devices. Calculation methods of radiation technology (estimation of activity variation, space dependence of dose rates, shielding, efficiency) are presented. Instructions for laboratory exercises (dose and dose rate measurements, sterilization by irradiation, handling of irradiation devices) involved in the course given. Two laboratory irradiation devices (RH-GAMMA-30, produced in the Soviet Union and the K-120-type semi-large scale device of the Isotope Institute of the Hungarian Academy of Sciences are described in detail. Handling instructions for the two devices and radiation protection regulations are given. A brief glossary in the field of radiation technology is added.