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Screening Internal Contamination of Inhaled and Ingested Radionuclides with Hand-held Survey Meters

Adams, Tim G.; Casagrande, Rocco*

doi: 10.1097/HP.0000000000000756
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During the aftermath of a radiological accident or attack, the rapid identification of individuals who have internalized medically significant amounts of material is paramount to guide medical and public health decisions. This paper explores the utility of hand-held, pancake GM detectors to determine if an individual has inhaled 90Sr, 137Cs, 238Pu, 239Pu, or 241Am in quantities requiring treatment. Additionally, ingestion of 90Sr or 137Cs was considered. Both 90Sr and 137Cs were modeled in equilibrium with their progeny, but the progeny of 238Pu, 239Pu, and 241Am were excluded. Treatment thresholds are defined using the National Council on Radiation Protection & Measurements’ (NCRP) clinical decision guides (CDGs). Using Monte Carlo N-Particle (MCNP) modeling software, a human phantom and detector were modeled to determine the activity required to achieve a detector reading of twice background 1, 7, or 30 d post-ingestion or post-inhalation. Modeling found that inhaled 238Pu, 239Pu, and 241Am are detectable only if the contaminated individual inhaled thousands-fold more material than the CDG. This lack of detectability means that hand-held GM detectors are inappropriate for initial screening for americium or plutonium and that more intensive screening is necessary to confirm suspected contamination. Cesium-137, by contrast, could be detected at levels 10‐ to 100‐fold lower than the amount requiring treatment, allowing quick differentiation between contaminated and uncontaminated individuals. Surprisingly, 90Sr was detectable within a factor of 2 of the amount requiring treatment. Detection of 90Sr was due primarily to bremsstrahlung radiation from beta interactions with calcium in bone. While rapid screening could identify individuals contaminated by 137Cs and possibly with 90Sr, further screening of identified individuals is necessary to establish medical need. However, these contaminated individuals could still be prioritized for further testing and possible presumptive treatment. Based on the findings of this study, concepts of operation for the use of hand-held survey meters should be developed for the screening of individuals potentially internally contaminated with 137Cs and 90Sr.

*Gryphon Scientific, LLC, Takoma Park, MD.

The authors declare no conflicts of interest.

For correspondence contact: Tim G. Adams, 6930 Carroll Ave, #810, Takoma Park, MD 20912, or email at tadams@gryphonscientific.com.

(Manuscript accepted 21 August 2017)

© 2018 by the Health Physics Society