F3 – Setup Menu
Gem-5 User’s Manual 119
preferable to leave the shield factor at 1.0 and relocate the monitor to a low
background area, build a shield wall, or install shielding at the source to reduce
background levels. While operating in “Walk-Through” mode self shielding
adjustment should be disabled, i.e. leave the Self Shield Factor – Occupied set at
1.0. See Footnote 13 on page 215 for the special case for gamma detectors.
Alarm Activity: This is the same item as described in the F5 – Group Settings
screen on page 127 but applies to the selected zone only. This is the alarm level at
which the unit is monitoring, i.e. the alarm release limit for clean/contaminated
decisions. The text displayed for this item reflects the F1 – Common Values screen
on page 103. The factory defaults are 2775 Bq.
Cold Alarm Activity: This is the same item as described in the F5 – Group Settings
on page 127 screen but applies to the selected zone only. This will only appear if
Cold to Hot setting in the F4 – Access Configuration screen on page 28 is set to
“Monitor”. Default value is the same as Alarm Activity. It is the release limit or
alarm set point for the Clean/Contaminated decision. The factory defaults are 2775
Bq for all Gamma detectors
The text and default values displayed for this item as well as the units for activity
reflect the units set in the Common Values screen.
High Alarm Activity: This is the same item as described in the F5 – Group Settings
screen on page 127 but applies to the selected zone only. This will only appear if
High Contamination Alarm is set to “High Count Rate (High Alarm Activity x
Efficiency)” on the F1 – Common Values screen on page 103. The setting defaults
are 7400 Bq for Gamma. Note that the High Alarm Activity can not be set lower
than Alarm Activity. The text and default values displayed for this item reflect the
units set in the F1 – Common Values screen on page 103.
Alarm Activity Dimension: This is the same item as described in the F5 – Group
Settings screen on page 127 but applies to the selected zone only. The range is from
0 cm to 100 cm. This item is used to convert alarm activity values expressed in
Bq/cm² (or dpm/cm² or nCi/cm² or pCi/cm² or µCi/cm
2
) to Bq (or dpm or nCi or pCi
or µCi as appropriate). It only appears if a “…/cm²” unit is chosen in the Activity
Units setting in the F1 – Common Values screen on page 103.
Measurement Process: Intended to account for occupant positioning uncertainty but
can include other applicable uncertainties. Default is “0” %.
Valued % displayed is u
ru
×100% ×k
c.
Applied via revised equation (8) of Supplementary Bayesian Methodology Users
Manual.
Alarm Test Source: This is the same item as described in the F5 – Group Settings
screen on page 127 but applies to the selected zone only. This allows the source that
is intended to be used for alarm testing to be specified. It is optional for Alarm Test
Type settings of “Alarm Test” and “Coverage Test” but is required for “Verification
Test”.
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