Temporal Fluctuations in Indoor Background Gamma Radiation Using NaI(Tl)

Health Phys. 2018 Mar;114(3):360-372. doi: 10.1097/HP.0000000000000813.


An enhanced understanding of background gamma radiation is necessary for accurate radionuclide activity quantification. Background spectra are routinely subtracted from spectra of samples prepared in known geometries, with data collection time chosen to optimize statistics for counting uncertainties. The work presents measured background spectra collected inside and outside shields of varying geometry and composition, showing the effects of these on background. Gamma background measurements with and without blank samples are included along with spectra from different sizes and shapes of NaI(Tl) detectors. If the environment is being monitored for quick and confident detection of recently appearing radiation sources, a thorough knowledge of the background radiation and its temporal variation is essential. To study the requirements of such background measurements, sequential background gamma radiation collections were obtained on an hourly basis for a total of 316 h from an unshielded 5.5 × 11 × 40 cm NaI(Tl) detector located inside a laboratory setting where small sources are routinely stored and used. Finally, a strategy for optimizing data collection times and analyzing background gamma radiation spectra for long-term radionuclide monitoring is presented.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Air Pollutants, Radioactive / analysis*
  • Air Pollution, Indoor / analysis*
  • Background Radiation*
  • Gamma Rays*
  • Iodides / analysis*
  • Iodides / radiation effects
  • Radiation Dosage
  • Radiation Monitoring / instrumentation*
  • Radiation Monitoring / methods
  • Sodium / analysis*
  • Sodium / radiation effects
  • Thallium / analysis*
  • Thallium / radiation effects


  • Air Pollutants, Radioactive
  • Iodides
  • thallium-doped sodium iodide
  • Sodium
  • Thallium