Monte Carlo and deterministic analysis of a University of Virginia BNCT facility

A comprehensive effort is underway to design a high- performance BNCT facility at the 2 MW University of Virginia research reactor. This endeavor includes detailed core criticality and leakage calculations, coupled neutron/photon transport analyses, and dosimetry computations. Detailed geometries are modeled with MCNP for both the core and filter, as well as for phantom dosimetry studies, whereas the symmetric and deep-penetration problem of the filter/collimeter design is solved with the DORT code. Final filter configurations are evaluated with both stochastic and deterministic methods, and the results are compared and synthesized. The complementary use of these two computational methods yields a broader insight into the problem than can be achieved by using either method alone. Calculations show that certain adjustments to the core configuration increase the leakage to the filter thereby improving beam performance. Increased performance is also achieved by strategic shaping, placement, and optimization of neutral reflectors and filtering materials in the beam tube. Results of numerous optimization studies, which led to the final beam design, are presented. Ongoing work includes integration of recently developed treatment planning codes from INEL into the dosimetry analyses. New methods of coupling discrete ordinates and adjoint Monte Carlo calculations for medical applications are also under development.