Phantom studies of Cd, Hg and Cl by prompt gamma neutron activation analysis using a 238Pu–Be neutron source

Prompt gamma neutron activation analysis is a means of non-invasive monitoring for occupational exposure to toxic heavy metals such as Cd and Hg. Preliminary kidney detection limits from previous phantom studies at McMaster were 13.6±0.2ppm for Cd (125mL phantom) and 315±24ppm for Hg (125mL phantom) using the 238Pu–Be neutron source and 0.88±0.01ppm for Cd (125mL phantom) and 16.91±0.05ppm for Hg (30mL phantom) using the thermal neutron beam port at the McMaster Nuclear Reactor. The detection limits vary greatly between the two methods due to differences in experimental set-up, neutron energy spectra and a difference in dose by more than a factor of 100. The Hg detection limit from preliminary data is much higher than expected for both neutron source types. In order to explain the apparent detection limit discrepancy, measurements of Hg and Cd phantoms were performed using the 238Pu–Be neutron source. The results were compared to phantom measurements of Cl, a well-known neutron activation element.