Activation evaluation of Siemens linear accelerator using Monte Carlo simulation

In this study, the components of the linear accelerator parts discarded to prepare regulations for the disposal of the linear accelerator, and based on these data, radionuclide and radioactivity concentrations over time were evaluated using Monte Carlo codes, that is, PHITS code and DCHAIN. The Siemens Oncor Expression linear accelerator was simulated using data provided by the manufacturer such as target, primary collimator, absorber, flattening filter, ion chamber, mirror, secondary collimator (Y-jaw), and MLC(X-jaw). The results of the Monte Carlo simulation confirmed that the major radionuclides for each part of the Siemens linear accelerator changed from short-half-life nuclides to long-half-life nuclides over time after the shutdown of the equipment, resulting in a decrease in the radioactivity concentration over time. When a Monte Carlo simulation was performed considering the measured impurities, it was confirmed that additional nuclides were generated such as were 50 V, 183m W, 94m Nb, 100 Mo, and 101 Tc in addition to the radionuclides calculated using the data provided by the manufacturer. As a result, it was confirmed that radionuclides with a long half-life were produced by impurities, so it is considered that the effect of impurities in the parts should be considered when dismantling and discarding.