Assessment of the expected induced radioactivity in the bunker walls at the inrne-bas cyclotron facility

The Institute for Nuclear Research and Nuclear Energy at the Bulgarian Academy of Sciences is working on the construction of a cyclotron centre. Оne of the challenges in designing the radiation protection of a cyclotron centre is the preliminary assessment of the expected amounts of radioactive waste that will be generated during the lifetime of the facility. Our aim in this paper is to make an estimation of the expected induced radioactivity in the cyclotron bunker walls after the 20 year operational period of the facility. For this purpose, Monte Carlo simulations with the code FLUKA were performed. The distributions of the specific activity of the generated radionuclides in the concrete walls and of the residual dose rates inside the bunker are obtained. The specific activity of the most important long-lived radionuclides in the concrete walls of the bunker, namely 154Eu, 152Eu, 134Cs, 60Co, 54Mn is estimated. On the basis of these results an optimization of the shielding design is proposed in order to decrease the amount of radioactive waste which will be generated during the facility lifetime.