[en] This paper presents the part of PhD work performed at the TRIGA Mark II Vienna. A detailed three dimensional MCNP model of the reactor was developed. The neutronics library JEFF3.1 was applied to this model. The model was completed by employing the fresh fuel composition experiments and was confirmed by the initial criticality, reactivity distribution and thermal flux distribution performed in 1962. To analyse the current burned core, burn up and its relevant material composition was calculated by ORIGEN2 and confirmed by gamma spectroscopy of six spent Fuel Elements FE(s). This new material composition of the current core was incorporated into the already developed MCNP model. This paper presents the current core calculations employing MCNP5 and its experimental validation through criticality and reactivity distribution experiments, performed at the TRIGA Mark II research reactor Vienna. The MCNP predicts the criticality of the current core on loading of 78th FE in the core which is also confirmed experimentally. Five FE(s) were calculated and measured for their reactivity worths. The deviations between theoretical results and experimental observations were in range from 3% to 17%. (author)