Comparison of NORM Surrogate with Bulk NORM for Detector Characterization

A study, funded by the Domestic Nuclear Detection Office, was conducted to investigate the similarities and differences between using a surrogate NORM (Normally Occuring Radioactive Material)source in place of actual bulk NORM to aid in the development of standards for radiation detection systems. The bulk NORM tested were floor tiles, fertilizer, Zircon sand and bulk KCl (water softner). The use of bulk NORM material in detector testing can be problematic, primarily because of the space and weight taken up by the material. A more portable source is very useful for this type of testing if it replicates the important characteristics of the material being simulated. The surrogate material was found to replicate all of the important features of the bulk NORM it was tested against for use in spectral masking scenarios. This paper describes the measurements collected and illustrates the differences and similarities between the bulk NORM and the surrogate.