A Model For Absorption-Modified Multiplication Effects in the Assay of HEU-Containing Powders in a Random Driver

A model has been developed which describes the enhancement of the response, in a random driver, of a "stack" of highly enriched uranium of arbitrary height over the integral of the response of infinitessimal layers that would be produced solely by the interrogating sources which are external to the stack. The model has not yet been applied to containers filled to varying heights with powders, for which it was developed, but it has been used successfully to describe the response from stacks of uranium plates of varying heights and from a set of containers filled to a constant height with varying amounts of UCL in an Al~0 3 matrix.