1. Goran Kolarević,
Republic of Srpska, Bosnia and Herzegovina
2. Dražan Jaroš, Centar za radioterapiju, Republic of Srpska, Bosnia and Herzegovina
3. Dragoljub Mirjanić, Akademija nauka i umjetnosti Republike Srpske, Bana Lazarevića 1, Banja Luka, Republic of Srpska, Bosnia and Herzegovina
Abstract: Orthovoltage units are used in the treatment of shallow benign and malignant lesions. The high voltage in the X-ray tube is 100-300 kV (half value layer 0.5-4 mm of copper).
This type of units requires construction protection against ionizing radiation. The protection requirements should be based on the highest energies the appliances have. In this energy range, the effective scattering cross section for photon removal from the beam for photoelectric effect will be large in materials with high atomic numbers. Therefore, a thin layer of lead will be equivalent to a thick layer of concrete, of which barriers (walls) are usually made, which is the cheapest solution. The purpose of radiation protection is to limit the radiation exposure of the general population and employees (persons professionally exposed to ionizing radiation) to a legally acceptable level of 1 mSv/year, i.e. 20 mSv/year. The aim of the study is to calculate the values of primary barrier thicknesses (towards the control panel and exterior wall) for concrete and lead in the case of 250 kV devices, based on IAEA recommendations, as well as the thickness of the safety doors when the beam cannot be directed directly at them (secondary barrier). The calculation is based on the average workload. The thickness of the barrier to the control panel for concrete is 431.9 mm and 12.3 mm for lead. For the outer walls of the bunker, 333.9 mm of concrete or 9.5 mm of lead is appropriate. The security door requires a lead plate 6.28 mm thick. Ambient measurements (on the outer surfaces of all barriers) check the degree of protection achieved and detect any errors.