The determination of the depth of localised radioactive contamination by 137Cs and 60Co in sand with principal component analysis

Adams, Jamie and Mellor, Matthew and Joyce, Malcolm (2011) The determination of the depth of localised radioactive contamination by 137Cs and 60Co in sand with principal component analysis. Environmental Science and Technology, 45 (19). pp. 8262-8267. ISSN 0013-936X

Abstract

A method to determine the depth of buried localized radioactive contamination nonintrusively and nondestructively using principal component analysis is described. The γ-ray spectra from two radionuclides, cesium-137 and cobalt-60, have been analyzed to derive the two principal components that change most significantly as a result of varying the depth of the sources in a bespoke sand-filled phantom. The relationship between depth (d) and the angle (θ) between the first two principal component coefficients has been derived for both cases, viz.where x and y are constants dependent on the shielding material and the γ-ray energy spectrum of the radioactivity in question, and φ is a function of θ. The technique enables the depth of a localized radioactive source to be determined nonintrusively in the range 5 to 50 mm with an accuracy of ±1 mm.