Conceptual Design for an Epithermal-Neutron Beam for Boron Neutron Capture Therapy at the Georgia Institute of Technology Research Reactor

Abstract

Exceptional beam quality is very important to the success of Boron Neutron Capture Therapy (BNCT). In this work we completed a conceptual filter design which provides an epi-thermal neutron beam at the Georgia Tech Research Reactor (GTRR) suitable for BNCT application. Both Monte Carlo (MCNP) and discrete ordinate (ANISN, DORT) based computer codes were used in the filter design and parameter optimization process. The in-vessel portion of this filter, located between the core and the bio-medical facility port, is composed of a series of circular aluminum plates in D₂O surrounded by air-filled toroidal aluminum tubing. The tubing increases the buoyancy of the filter structure, reducing the stress placed on the reactor vessel. The ex-vessel filter, located in the existing bio-medical facility port, consists of a series of dry aluminum plates, lithiated aluminum plates, a plate of titanium and a bismuth lead gamma shield in a cadmium housing. The remainder of the cone is void, increasing beam collimation. The integrated epi-thermal neutron flux of 2.5×10⁹ n/cm²/s will keep treatment fractions less than 30 minutes. Both the fast neutron and gamma KERMAs are less than 2×10⁻¹¹ cGy/n/cm², allowing the therapeutic dose to be reached before the healthy tissue tolerance is exceeded from background radiations. The current to flux ratio of 0.86 is also excellent for BNCT application. The results show that the GTRR is capable of producing one of the best neutron sources for BNCT application in the United States. Plans to install the filter in the GTRR continue to move forward.