Optimization study for BNCT facility based on a DT neutron generator

Background: A Boron Neutron Capture Therapy (BNCT) facility, based on a DT neutron generator, with the final goal to find out a potential, alternative, solution to existing BNCT treatment facilities which are based on nuclear reactors is examined. Materials and Methods: With the aim of the MCNP4B Monte Carlo code different beam-shaping assembly (BSA) configurations were considered. Lead was selected as reflector material while CF2, D2O, Fluental, PbF4, PbF2, BiF3, BiF5, MgF2, Al2O3, AlF3, TiF3, BeD2, CaF2 and 7LiF were examined as spectrum shifters. In order to improve the quality of the beam titanium, nickel-60, iron and titanium alloy (Ti6Al14V) were simulated as fast neutrons filters while lead and bismuth were considered as gamma filters. Results: An extensive set of calculations performed with MCNP4B Monte Carlo code have shown that the combination of 7LiF which accommodates a conic part made of D2O, then followed by a TiF3 layer is the optimum moderator design. The use of three different materials for further reduction of fast neutrons, thermal neutrons and gamma rays is necessary. 60Ni, Cd and Bi were chosen respectively for these purposes. The epithermal neutron flux obtained at the beam exit window turned out to be 3.94×109 n cm-2 s-1 while fulfilling all the recommended IAEA in-air Figure Of Merit (FOM) criteria. The assessment of the dose profiles in head phantom and the in-phantom FOM are also presented. Conclusion: The proposed assembly configuration may provide an attractive option for centers wishing to install a BNCT facility.