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Title: Modeling study of a proposed field calibration source using K-40 and high-Z targets for sodium iodide detectors

Calibration sources based on the primordial isotope potassium-40 (40K) have reduced controls on the source’s activity due to its terrestrial ubiquity and very low specific activity. Potassium–40’s beta emissions and 1,460.8 keV gamma ray can be used to induce K-shell fluorescence x rays in high-Z metals between 60 and 80 keV. A gamma ray calibration source that uses potassium chloride salt and a high-Z metal to create a two-point calibration for a sodium iodide field gamma spectroscopy instrument is thus proposed. The calibration source was designed in collaboration with the Sandia National Laboratory using the Monte Carlo N-Particle eXtended (MCNPX) transport code. 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 inexpensive, nontoxic, and outperforms the high-Z layer method in simulation. As a result, based on the MCNPX studies, sealing a mixture of bismuth powder and potassium chloride into a thin plastic case could provide a light, inexpensive field calibration source.
Authors:
 [1] ;  [2] ;  [3] ;  [2]
  1. Remote Sensing Lab. (United States)
  2. Texas A & M Univ., College Station, TX (United States)
  3. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Publication Date:
OSTI Identifier:
1333863
Report Number(s):
SAND--2015-2204J
Journal ID: ISSN 0017-9078; 579556
Grant/Contract Number:
AC04-94AL85000
Type:
Accepted Manuscript
Journal Name:
Health Physics
Additional Journal Information:
Journal Volume: 110; Journal Issue: 6; Journal ID: ISSN 0017-9078
Publisher:
Health Physics Society
Research Org:
Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY 40K; Monte Carlo; calibration; x rays