GammaVision
®
v7 (A66-BW) 783620H / 1013
where A
<i
and A
>i
are the lower and upper activity limit of the i
th
qualifying peak calculated from
Eqs. 156 and 157, respectively.
6.17.6.8. Total Reported Activity
Total reported activity represents the summed activity calculated for all nuclides found in the sample. It is calculated as follows and printed in the analysis report immediately after the
Summary of Nuclides table, or the Summary of Nuclides (ISO NORM) table if the ISO NORM
report checkbox is marked on the Report tab.
(196)
where A
An
is the calculated nuclide activity for the n-th nuclide (see Eq. 189).
Note that if an MDA is reported for A
An
for a particular nuclide, that nuclide’s contribution is not included in A
tot
. In addition, any nuclide with the “Activity Not In Total” flag set is always excluded. Also note that this total activity is typically different from the total activity calculated for the standard GammaVision report. This is because the MDA values (which in turn might be used as the nuclide activity values) are calculated differently in ISO NORM due to the differences in background variance calculations.
6.17.7. GammaVision / ISO NORM Unique Calculations
6.17.7.1. Special Background Variance Calculations
In some special cases, Eq. 145 will yield a zero background variance due to zero peak background or zero peak background width. However, it is known that the background variance should not be zero. Thus special care must be taken to calculate a sensible background variance.
Zero Background Width
If the background widths L
Lo
and L
Hi are both zero (typically due to peak overlapping), then the first attempt is to calculate the background variance as:
(197)
Narrow Peak Width
When the number of channels in the background is greater than the number of channels in the peak, Eq. 145 can yield an unrealistically small background variance. In such cases, Gamma-
Vision calculates the background variance as follows:
326
