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Answer to Question #2452 Submitted to "Ask the Experts"Category: Instrumentation and Measurements — Instrument Calibration (IC) The following question was answered by an expert in the appropriate field: Q
Is there a reference document that states a requirement for the length of time background measurements are to be made for a gamma spectroscopy system? In a recent audit I was informed that for statistical purposes it was necessary to run the weekly background for 1,000 minutes.
A
You're obviously looking for certain minimum detectable activity levels and want a good handle on background. I'm not aware of any "requirement" for a weekly 1,000-minute check on background for gamma spectroscopy. This sounds like a significant period of the available counting time in a seven-day week. Depending on sample workload it should be possible to do this 1,000-minute count over a weekend, setting up to run at the end of the day on Friday. Once you have documented a stable background on a particular system, it would not be unreasonable to do monthly or quarterly 1,000-minute background counts, with shorter-duration weekly quality-control background checks. I'd check your background control charts for stability, look at the government protocols referenced in this topical area of ATE, and contact other gamma-counting labs. If you need contacts, let me know.
David J. Allard, CHP
Answer posted on 9 April 2003. The information and material posted on this Web site is intended as general reference information only. Specific facts and circumstances may alter the concepts and applications of materials and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice specific to whatever facts and circumstances are presented in any given situation. Answers are correct at the time they are posted on the Web site. Be advised that over time, some requirements could change, new data could be made available, or Internet links could change. For answers that have been posted for several months or longer, please check the current status of the posted information prior to using the responses for specific applications.
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