Operator related attenuation effects in radiometric surveys. (March 2016)

• Record Type: Journal Article
• Authors: Buchanan, E.; Cresswell, A.J.; Seitz, B.; Sanderson, D.C.W.
• Is Part Of: Radiation measurements. Volume 86(2016:Mar.)
• Page Start: 24
• Page End: 31
• Publication Date: 2016-03
• Subjects: Environmental radioactivity -- Gamma ray survey -- Attenuation by human operator; Nuclear emulsions -- Periodicals; Particle tracks (Nuclear physics) -- Periodicals; Thermoluminescence -- Periodicals; Cosmic rays -- Periodicals; Radiation -- Measurement -- Periodicals; Radiometry -- Periodicals; Radiation Monitoring -- Periodicals; Émulsions nucléaires -- Périodiques; Particules (Physique nucléaire) -- Traces -- Périodiques; Thermoluminescence -- Périodiques; Rayonnement cosmique -- Périodiques; Radiométrie -- Périodiques; 539.77
• DOI: 10.1016/j.radmeas.2015.12.029
• Languages: English
• ISSNs: 1350-4487

Abstract

Abstract: Radiometric surveys using airborne, vehicular mounted or backpack detector systems are increasingly used to identify and evaluate complex distributions of radioactivity in the environment. The signals detected depend on the energy and spatial distribution of radioactive sources, the material properties of the environment and the specific properties of the detector systems employed. Materials in close vicinity to the detector such as housings, and intermediate materials may have a critical impact on detection efficiency, and must therefore be taken into account in calibration. This study evaluates the effect of shielding by the body of the operator in backpack surveys. Controlled experiments using point sources and absorbers, chosen to represent the form and composition of human tissue, were conducted, and coupled to an analytical radiation transport model to estimate attenuation factors for mapping of 137 Cs. In this way generic factors to correct for this effect using portable spectrometers have been determined. The results compare well with observations at sampled calibration sites in Fukushima and the Solway area in Scotland. Reductions of the 137 Cs full-energy peak intensity between 20% and 30% may be expected depending on operator stature and the offset position of backpack systems. Similar effects may be present for other radiometric systems carried by a human operator. Highlights: Evaluation of operator effects on radiometric measurements with backpack systems. Potential for similar effects with other radiometric systems. Count rates for radiocaesium full energy peaks are reduced by 20–30%. Count rates for >450 keV, scaling to dose rate, are reduced by approximately 15%.