Abstract. In cancer treatment, high energy X-rays are used which are produced by linear accelerators (LINACs). If the energy of these beams is over 8 MeV, photonuclear reactions occur between the bremsstrahlung photons and the metallic parts of the LINAC. As a result of these interactions, neutrons are also produced as secondary radiation products (Ȗ,n) which are called photoneutrons. The study aims to map the photoneutron flux distribution within the LINAC bunker via neutron activation analysis (NAA) using indium-cadmium foils. Irradiations made at different gantry angles (0°, 90°, 180° and 270°) with a total of 91 positions in the Philips SLI-25 linear accelerator treatment room and location-based distribution of thermal neutron flux was obtained. Gamma spectrum analysis was carried out with high purity germanium (HPGe) detector. Results of the analysis showed that the maximum neutron flux in the room occurred at just above of the LINAC head (1.2x10 5 neutrons/cm 2 .s) which is compatible with an americium-beryllium (Am-Be) neutron source. There was a 90% decrease of flux at the walls and at the start of the maze with respect to the maximum neutron flux. And, just in front of the LINAC door, inside the room, neutron flux was measured less than 1% of the maximum.

24 Na is a beta and gamma emitting radioisotope that is widely used in medical field as medical radiotracing. This radioisotope with a half-life of 14.977 hours is mostly produced in cyclotrons. The cross-section of a radioisotope is used to obtain various data about the production of that radioisotope. In cases where it is not possible to obtain experimental data, missing data can be completed with cross-section calculations and the obtained data can be compared with experimental, saving time, cost and effort. This study was carried out for detailed analysis of cross-section calculations for 24 Na isotope, which has a wide range of usage in medicine. In this direction, the cross-sections obtained from different computation programs were compared with literature data of the reactions. Production cross-sections of the 24 Na isotope were investigated in the 23 Na(d,p) 24 Na, 24 Mg(n,p) 24 Na, 25 Mg(n,n+p) 24 Na, 25 Mg(p,2p) 24 Na, 26 Mg(d,α) 24 Na and 27 Al(n,α) 24 Na reactions with the equilibrium and pre-equilibrium models of nuclear reaction codes of TALYS 1.95 and EMPIRE 3.2. Results were compared with experimental data from the EXFOR data library. The relevance of the models to the reactions was discussed and calculations were made using the relative variance analysis method to determine the most consistent model.

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