HPA-RPD-032 - GRANIS: A Model for the Assessment of External Photon Irradiation from Contaminated Media of Infinite Lateral Extent

Synopsis

GRANIS ( Gamma Radiation Above Nuclides In Soil) is a model developed at HPA-RPD to calculate the external photon dose from layers of contaminated material which have finite thickness yet are effectively infinite in horizontal extent. The model allows different vertical activity profiles to be considered, so has particular application for the prediction of external gamma irradiation following the deposition of radionuclides to ground following short or continuous releases of radionuclides to the environment. GRANIS calculates effective dose and equivalent dose for four tissues. This report describes the theory behind the GRANIS version 3 (v3) model and includes results calculated by GRANIS v3 for a set of typical cases. The report describes intercomparisons made of the results of GRANIS v3 with standard theoretical methods, published papers and other radiation transport codes. GRANIS v3 was found to agree well with other results, particularly for photon energies in the range 0.1 to 4 MeV, which is of interest for exposure assessments.

Last reviewed: 17 July 2009