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3.6.4 Limitations to non-destructive methods

Non-intrusive radiological surveys are limited in their applicability by three main issues:

  • The type of radionuclides present. In general the equipment used by a non-intrusive field survey detects and quantifies mainly high-energy beta and gamma emissions. This limitation is due to the varying detection geometry. At this moment, new methods are under development, which make use of the variation of the low-energy gamma emission flux. This flux indicates qualitatively the presence of radionuclides.
  • The depth of burial/shielding of the radioactivity. Burial/shielding of the radioactivity will influence the detection limit of radionuclides.
  • ‘Radiation’ emitted from nearby buildings/facilities/pavement. This radiation influences the background by non-intrusive radioactivity surveys by giving rise to elevated levels of radiation in an area that is being surveyed for radioactive contamination. In this case, in the survey design, this has to be taken into account by increased measuring times, or increased shielding on the detector (with consequent weight increase) or samples would have to be removed to a low radiation area for monitoring or analysis.