ABSTRACT
Four methods are presented to estimate contaminant concentration profiles in soil from the intensities of neutron-induced capture-gamma photon intensities measured at the soil surface. In particular, the method of linear regularization with and without an iterative positivity constraint, the Backus-Gilbert method, and the maximum entropy method are applied to the soil contamination problem. Example results obtained with the four methods are given for photon intensities calculated for idealized test contaminant profiles in soil irradiated by neutron sources above the surface.
Subject(s)
Neutron Activation Analysis/methods , Soil Pollutants, Radioactive/analysis , Gamma Rays , Models, Theoretical , Neutron Activation Analysis/statistics & numerical data , Neutrons , PhotonsABSTRACT
Four methods are presented to estimate contaminant concentration profiles in soil from the intensities of neutron-induced capture-gamma photon intensities measured at the soil surface. In particular, the method of linear regularization with and without an iterative positivity constraint, the Backus-Gilbert method, and the maximum entropy method are applied to the soil contamination problem. Example results obtained with the four methods are given for photon intensities calculated for idealized test contaminant profiles in soil irradiated by neutron sources above the surface.
Subject(s)
Neutron Activation Analysis/methods , Soil Pollutants, Radioactive/analysis , Gamma Rays , Models, Theoretical , Neutron Activation Analysis/statistics & numerical data , Neutrons , PhotonsABSTRACT
Geometry factors are derived for source and target regions consisting of concentric circular cylinders and cylindrical shells. Line-source kernels are derived from point kernels for monoenergetic electrons and photons. The geometry factors and line-source kernels are then combined to yield electron and photon absorbed fractions that, in turn, are used to calculate conversion factors for dose rates in blood vessel walls from radionuclides in the blood. Example calculations are presented for selected radionuclides and for blood vessels of three representative sizes.
