Detection limits for radioisotopic counting techniques

The method of defining detection limits which has been adopted by the 222-S Analytical Laboratory counting room is described. The system for reporting limits defines two levels of detection limits: the critical level (L/sub c/) which must be exceeded before a sample can be said to contain any material above the background level and a detection limit (L/sub D/) at which we can be 95% sure that we will detect material. The common method of using twice the standard deviation of the background as a lower detection limit was found to lead to erroneous results. Equations relating L/sub c/ and L/sub D/ to the magnitude and standard deviation of the background were derived. Two examples illustrate the use of these levels. (auth