Robinson Response below. From: [email protected] [mailto:[email protected]] On Behalf Of Thomas J Vandermey Sent: Wednesday, July 06, 2011 11:41 AM To: [email protected] Cc: Jill Phebe Newton Subject: Powernet: Quick Benchmark on RP Instrument QC
Request benchmark on RP Instrument QC charts: 1. What type of QC limits do you use? Statistical limits or tolerance limits or both? both 2. What limiting values do you use, e.g. +/- 3 sigma of check source readings, +/- 3% of mean check source reading, variable limits depending on type of instrument, etc.? We normally apply the 3 sigma limits. However our Tennelecs are not setup in a laboratory setting (temperature is not carefully controlled for example) so our procedure will allow it to remain in service as long as source check results are within +/- 20%. This almost never comes into play however because we are typically successful at keeping the units well within the 3 sigma limits. 3. What basis do you cite for limits used, e.g. MARLAP, ANSI N42.23, etc.? We don’t use our Tennelecs for anything other than Occupational HP so it is our position that the portable instrument limit criteria are applicable (smears can be counted with frisker, fixed counters or Tennelec’s). Air samples can be counted with fixed counters or Tennelecs. 4. What is done if source check falls outside limits? Outside of +/- 20% procedure requires instrument to be taken OOS for repair/recalibration etc. Typically we take instrument OOS at the lower more conservative 3 sigma value. Thanks very much, Tom VanderMey, CHP Principal Radiological Engineer DTE Energy, Fermi 2 734-586-1539
