Porosity of a two-phase system can be determined by a statistical method that fits a composite function to the histogram of X-ray computed tomography data (Clausnitzer, 1999). This method was applied to neutron computed tomography (N-CT) data sets taken before and after a recently completed hardware and software upgrade at the McClellan Nuclear Radiation Center’s (MNRC) N-CT system. The net effect of the improvements was a decrease in both pixel size and system noise. Results show that this technique cannot be used to accurately determine phase fractions of glass beads with air-filled void space with either the old or new neutron tomography system due to a low attenuation contrast between quartz glass and air. However, when deuterium water is substituted for air, corrected volume fractions are calculated due to increased attenuation contrast. Attenuation contrast of phases, sample size, and system noise are important to successful use of this method, especially in low-resolution systems (>150microns/pixel).
Porosity of a two-phase system can be determined by a statistical method that fits a composite function to the histogram of X-ray computed tomography data (Clausnitzer, 1999). This method was applied to neutron computed tomography (N-CT) data sets taken before and after a recently completed hardware and software upgrade at the 
