Monte Carlo Determination of Gamma Ray Exposure from a Homogeneous Ground Plane
Abstract
The purpose of this study was to evaluate the gamma ray dose rate from an infinite homogeneous ground plane source of fission products from U-235, U-238, and Pu-239. In this study a Monte Carlo method was used to model the contribution to dose resulting from gamma scatter in the air and in the ground. This was accomplished by using the MORSE code. Two intermediate parameters which were used to determine the dose rate are the Source Conversion Coefficient (SCC) and Source Normalization Constant (K). The mono-energetic SCC was calculated from morse and then used to determine the time dependent SCC for a variety of spectra. Both the energy spectra and the gamma emission rates which were used in this study were determined by DKPOWR. The time dependent SCC's and K values are presented for the three fuels. The K values at one hour after burst were 8064 (rads-tissue/hr) (kt/sq km) for U-235 fission products, 8467 (rads-tissue/hr)/ (kt/sq km) for U-238 fission products, and 7666 (rads-tissue/hr)/(kt/sq km) for Pu-239 fission products. The values of K as a function of time was compared to the WAY-Wigner approximation, t to the 1.2 power and found to differ by as much as 94% within 6 months. In addition to these results, the MORSE code was also used to compute a transport matrix which will permit the use of any other source spectrum and any other response function to be converted to a ground dose rate. This transport matrix is also presented.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1990
- Accession Number
- ADA220111
Entities
People
- Michael R. Howard
Organizations
- Air Force Institute of Technology