GammaVision
®
v7 (A66-BW)
The averaged nuclide counting uncertainty
σ
avg
is calculated from:
783620H / 1013
(62)
The reported nuclide counting uncertainty is calculated at 1 sigma and reported at 1, 2, or 3 sigma, depending on the Confidence level setting on the Report tab. It is calculated as:
(63)
GammaVision compares the averaged peak counting uncertainty and the minimum peak counting uncertainty and reports the smaller value as the nuclide counting uncertainty.
6.8. Total Activity (ROI32 Analysis Engine Only)
Total activity represents the summed activity calculated for all nuclides found in the sample. It is calculated as follows and printed immediately after the Summary of ROI Nuclides table in the analysis report.
(64)
where A
avg
is calculated per Section 6.7.1. Note that if MDA is reported for A
avg
for a particular nuclide, that nuclide’s contribution is not included in A
tot
.
6.9. MDA
The Minimum Detectable Activity (MDA) is a measure of how small an activity could be present and not be detected by the analysis. There are many factors affecting the MDA, which is reported in activity units such as becquerels. The calibration geometry, the backgrounds (systemand source-induced), the detector resolution and the particular nuclide all substantially affect the
MDA reported.
In most instances, the MDA value is calculated based on the background value of the peak. If the peak area was not used in the activity calculation because it failed the sensitivity test, or a shape test, the peak area is added to the background for the MDA calculation unless the MDA defines the background separately. If the background is 0, it is set to 1 for the MDA calculation. The background will still be reported as 0 on the report. By reviewing the individual MDA values
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