Thermo Scientific SAM12, Manual

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Technical Description - Physics Issue: 1.0
6-8 SAM12 User Manual Thermo Fisher Scientific
N
sl
is the Changing Conditions variable (see Params 1 (page 5-8) ).
It is not recommended that N
sl
should be set below 3.0
σ
.
The first Changing Conditions check will take place after 2T
sl
and then after every second within the monitoring cycle.
where T
sl
is the Changing Conditions period (time slice) variable (see
Params 1 (page 5-8) ).
After monitoring an article for the prescribed monitoring time
(T
mon
), the effective contamination alarm level (C
effect
) is
calculated as follows:
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
+
⎟⎟
⎠
⎞
⎜⎜
⎝
⎛
+ − =
MON
cps
MON B
eff
cps
effect
T
C
T t
B P C C
1 1
The total system background count rate B
eff
is then subtracted
from the total system gross contamination count rate (C
gross
),
and the remaining (net) contamination count rate compared
with the alarm level. So an alarm condition exists if:
( )
effect eff gross
C B C
≥ −
The system will display both the activity of contamination
on/in the article, and its associated uncertainty. Both of these
options may be enabled from the Options sub-menu (see
Options (page 5-6) ). The Activity may be displayed after any
measurement, as long as the evaluated activity is greater than
the MDA.
The activity is calculated using the following formula:
mix
eff gross
Act Act
E
B C
Z R
−
=
.
where R
Act
refers to the activity in the selected unit.
le nuclide mix, E
mix
= E
nuc
. However where the user has
created a mix with multiple nuclides:
∑
=
nuc nuc mix
P E E
.
where E
nuc
is the efficiency of the system to a specific nuclide
P
nuc
is the proportion of the specific nuclide within the total mix.
The uncertainty of the activity measurement is calculated as
follows:
⎟⎟
⎠
⎞
⎜⎜
⎝
⎛
+
mon
gross
B
eff
mix
conf Act
T
C
t
B
E
N R
.
where N
conf
is the number of confidence levels.
Contamination Alarm
Calculation of Activity and
Uncertainty