Energy Absorption Buildup Factors and Energy Conservation

Abstract

The ANSI/ANS energy absorption buildup factors (ANSI/ANS-6.4.3–1991) were used to determine if they conserve absorbed energy from a point source of monoenergetic photons in an infinite, absorbing medium. Air, water, concrete, iron, lead, and uranium were considered for photon energies ranging from 0.015 to 15 MeV. The primary calculations were based on fitting natural cubic splines to the energy absorption buildup factors and analytical integration of the energy absorbed using the cubic spline curve fit. This method was supplemented by linear spline interpolation. For air, water, concrete, and iron, the ANSI/ANS energy absorption buildup factors were determined using the method of moments with theenergy attenuation and deposition coefficients of Hubbell (NSRDS-NBS 29). The results of this study essentially confirmed energy conservation for these four materials using the energy attenuation and deposition coefficients of Hubbell. For lead and uranium, the ANSI/ANS energy absorption buildup factors were determined using the discrete ordinates-integral transport method with PHOTX energy attenuation and deposition coefficients that are essentially the same as those in the ANSI/ANS report. The calculations in this study could not confirm energy conservation for these two materials.