Date of Award
Master of Science
Department of Engineering Physics
Charles J. Bridgman, PhD.
Five assumptions regarding a first order model developed to calculate dose rate at a detector above a fallout field are analyzed. The omission of scattering is relaxed by the method of successive scatters resulting in a build up factor of 1.1. The use of a single average photon energy to represent a fallout distribution is analyzed using the Oak Ridge National Laboratory Isotope Generator (ORIGEN) Fallout Analysis Tool. An average photon energy of 0.81MeV is calculated and shown to be an accurate approximation of the fallout field energy distribution. A Gaussian distribution is used to calculate the minimal impact of non-uniform activity density on the source normalization constant (SNC). The effects of time on the SNC are also examined by the ORIGEN Fallout Analysis Tool and shown to warrant an additional time correction factor. Finally, previous research accomplished by Herte reveals 2-5% self-shielding from terrain roughness. These findings are incorporated into an updated SNC value that is 25% greater than the value found from the first order model.
DTIC Accession Number
Smith, Justin M., "Source Normalization Constants for Ground Distributed Fallout Fields" (2011). Theses and Dissertations. 1472.