The Department of Energy (DOE) has ruled that all sealed
radioactive sources, even those considered exempt under Nuclear
Regulatory Commission regulations, are subject to radioactive
material controls. However, sources based on the primordial isotope
40K are not subject to these restrictions. 40K's beta and gamma
emissions could be used to produce x-rays in a high-Z metal and
provide a second photon peak. A gamma ray calibration source is
proposed that uses potassium chloride salt and a high-Z metal to
create a two-point calibration for a sodium iodide field gamma
Two methods of x-ray production were explored. First, a thin
high-Z layer (HZL) was interposed between the detector and the
potassium chloride-urethane source matrix. Second, bismuth metal
powder was homogeneously mixed with a urethane binding agent to
form a potassium chloride-bismuth matrix (KBM). The bismuth-based
source was selected as the development model because it is cheap,
nontoxic, and outperformed the HZL method in simulation. The
potassium chloride-bismuth-based calibration source would serve as
a light, cheap, field calibration source that is not subject to DOE
- J.L. Rogers, C.M. Marianno, G. Kallenbach, J.F. Trevino ,
"Modeling Study of a Proposed Field Calibration Source Using K-40 And High-Z Targets for Sodium Iodide Detectors,"
Journal of Health Physics 10:6 (2016).
- J. Rogers, C.M. Marianno, G. Kallenbach,
"Proposed Field Calibration Source for NaI(Tl) Detector Using K-40 and High-Z Targets,"
The 57th Annual Meeting of the Health Physics Society, Sacramento, CA, 22-26 July 2012.