Fast Neutron Computed Tomography Resolution Study

Abstract

There has been a continued desire to include more physical phenomena and mechanistic treatment in the prediction of Critical Heat Flux (CHF). A major impediment to these efforts is the lack of local void measurements, as typical instrumentation employed usually involve only a few point measurements of void fraction and hence spatial distribution of phase is often lacking or non-existent. Fast neutron sources are particularly advantageous for imaging void fraction distributions since the interaction cross sections for fast neutrons with structural materials is small and scattering cross sections with liquid water are substantial. We have performed MCNP neutron transport calculations which demonstrate that there is a strong potential for measuring subchannel level void fraction within an acceptable time frame. This work will present the design and MCNP simulation results for void fraction measurements in a CANDU bundle.