Neutron transport analysis of McMaster nuclear reactor advanced dynamic neutron imaging facility

An advanced dynamic neutron imaging facility is being commissioned in the McMaster Nuclear Reactor (MNR) for non-destructive testing and multi-phase flow studies in energy and environmental research and development. The facility is required to produce a high quality thermal neutron flux of 10 ⁷-10⁸ n/cm²-s with a collimation ratio of 120 at image plane to promote high-speed neutron imaging up to 2000 frames per second. Neutron source strength and neutron transport have been experimentally and numerically determined. Neutron source strength at the beam tube entrance was evaluated by experimentally measuring the thermal and fast neutron fluxes, and simple analytical neutron transport calculations were performed based upon these measured neutron fluxes to predict facility components in accordance with high-speed dynamic neutron imaging and operation safety requirements. Monte-Carlo simulations (MCNP-4B) with multi-group neutron energy have also been used to validate neutron beam parameters and to ensure shielding capabilities of facility shutter and cave walls. The facility requirements such as neutron flux, image size, beam quality as well as the prediction of neutron transport through facility components; beam tube, beam shutter and radiography cave were described in details. Results obtained from numerical simulations show that an average thermal flux of 1.11×10⁷ n/cm²-s is obtained over an imaging area with 20.0 cm in diameter.