Local Shielding of Target for Production of 18F – Numerical Optimization – A. Demerdjiev, K. Shegunov, G. Asova, D.T. Dimitrov, N. Goutev, D. Tonev

The results presented in the current paper are part of the studies which we are conducting in regards with the
radiological characterization of the cyclotron facility that is currently being built by the Institute for Nuclear Research and
Nuclear Energy at the Bulgarian Academy of Sciences. The facility is going to be dedicated to research and development of
radiopharmaceuticals, and 18F is of primary interest.
Adding a local shielding around the target will be useful in limiting the spatial distribution of the emitted secondary neutrons
(during the target irradiation) and the activation of the bunker walls. The effect of adding a layer of borated polyethylene is
studied. We are considering a simplified spherical geometry, divided into spherical shells, of the bunker walls. By employing
the FLUKA Monte-Carlo transport code we obtained results for the distribution of the fluence of the secondary neutrons and
the activated radionuclides in the spherical shells.

Keywords: FLUKA simulations, 18O target, borated polyethylene.