NukeWorker Forum
Career Path => Radiation Safety => Topic started by: Gracie J on May 07, 2023, 10:41
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I'm trying to convert what would be equivalent to 0.4bq into CPS on the Ludlum 3277/1 with 43-92 scintillator that has an efficiency of 25.5%..
everyone around me is getting differing answers,
the calibration unit has set the alarm to 10CPS but I don't think this is correct? can someone break this down for me?
Source: Pu-239, 4337
Activity: 30972.44 dpm
Meter reading: 7960,7873,7780
count time: 1 min
Distance source to detector: surface
average efficiency 25.5% 4pi
?? would an alarm at 10CPS be equivalent to 0.4Bq?
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Pu-239 is a straight alpha emitter, emitting one alpha per decay. So should be a 1 to 1 relationship for a standard efficiency conversion.
Average meter reading of 7871 cpm?
Average 4pi efficiency of 0.255
7871 / 0.255 = 30,867 dpm.
You state an activity of 30,972.44 dpm
That's a difference of 0.3% so I'd say your calibration is pretty spot on.
Knowing that you can apply the same logic to your alarm setpoint.
10 cps / 0.255 = 39.2 dps
If you're trying to set the alarm setpoint at 0.4 Bq = 0.4 dps then you'd do
0.4 * 0.255 = 0.102 cps
I dont think that instrument is capable of setting an alarm setpoint that low, is it?