Optimization of the epithermal neutronic beam for BNCT at a 22 MW MTR reactor

Highlights: • A BNCT facility model is added to a 22-MW MTR previousely modelled reactor using the MCNP-4C Code. • A special design of a BNCT epithermal neutron beam is suggested. • No Thermal Column is required for irradiation. • All materials used in the design are simple and cheap. The design of an Epithermal Neutronic Beam (ENB) at a 22 MW MTR reactor for the Boron Neutron Capture Therapy (BNCT) is discussed in this paper(Calculations were made for the ETRR-2 reactor). Along the beam a moderator made from the materials: Pb + Al + Cd + Al + FLUENTAL + Al + FLUENTAl + Air + Cd + Bi with Pb was used as reflector. Following the moderator is air + Pb + Air with Bi lined collimator and Li₂CO₃-Polyethelene at the beam exit. The collimator is surrounded by layers of water, heavy concrete and Pb. The calculated values of the beam at the head phantom were: _epith = 2.402 10⁹ n/cm².s, D_f/_epith = 1.724 10⁻¹¹ cGy cm²/n and D_γ/_epith = 0.196 10⁻¹¹ cGy cm²/n, where the head phantom was placed at 5 cm from the beam exit. The obtained values by using the MCNP code of the Advantage Depth (AD), the Advantage Ratio (AR), the Advantage Depth Dose Ratio (ADDR), the treatment time and the therapeutic ratio were: 8.75 cm, 5.62, 36.37 cGy/min, 34.37 and 5.62, respectively. The MCNP geometry plotting resources were used to plot all geometrical cross sections of the simulated reactor.