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A simple method for determining the lower limit of detection (LLD) for personnel dosimetry systems is described. The method relies on the definition of a critical level and a detection level. The critical level is the signal level above which a result has a small probability of being due to a fluctuation of the background. All results below the critical level should not be reported as an indication of a positive result. The detection level is the net signal level (i.e., dose received) above which there is a high confidence that a true reading will be detected and reported as a qualitatively positive result. The detection level may be identified as the LLD. A simple formula is derived to allow the calculation of the LLD under various conditions. This type of formula is being used by the Department of Energy Laboratory Accreditation Program (DOELAP) for personnel dosimetry. Participants in either the National Voluntary Laboratory Accreditation Program (NVLAP) for personnel dosimetry or DOELAP can use performance test results along with a measurement of background levels to estimate the LLDs for their dosimetry system. As long as they maintain their dosimetry system such that the LLDs are less than half the lower limit of the NVLAP or DOELAP test exposure ranges, dosimetry laboratories can avoid testing failures due to poor performance at very low exposures.

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FOREWORDResponse characteristics of selected personnel neutron dosimeters in current use at Department of Energy (DOE) facilities were determined as part of the DOE Personnel Neutron Dosimeter Upgrade Program. This determination is important to achieving the overall objectives of the program for several reasons, including:• providing a uniform assessment of performance characteristics for personnel neutron dosimeters in routine use by several DOE 1 aboratori es• measuring the accuracy and reproducibility of personnel neutron dosimeter dose evaluations in known radiation fields• establishing a basis for comparison of prototype personnel neutron dosimeters currently under development• comparing current personnel neutron dosimetry performance with existing and proposed dose limits• identifying any current personnel neutron dosimeter concepts which are superior in performance.It is important to point out at the outset that the data contained herein may not be totally indicative of the accuracy of occupational doses determined routinely by the respective laboratories. Several laboratories utilize supporting field instrument data, such as measurements using rem meters, tissue equivalent proportional counters, and/or 3-inch and 9-inch sphere measurements, in evaluating the occupational dose received. In addition, all results herein are strictly blind in that no laboratory·s data are explicitly identified.A series of personnel dosimeter neutron irradiations was carried out to determine certain performance characteristics of selected personnel neutron dosimeters that are in current use at Department of Energy (DOE) facilities . These irradiations were quite specialized since they employed only well defined beams and a few highly standardized neutron sources. Information obtained was not intended to directly evaluate any participating laboratory's ability to determine occupational dose. Many laboratories utilize additional information such as field measurements of neutron dose and spectra to arrive at actual personnel doses. Since the neutron sources were so highly standardized, they could be used to determine the inherent accuracy and precision, along with the lower detection limit and energy dependence of each type of dosimeter.This program was designed to provide a consistent evaluation of certain common characteristics of the different dosimeters in use by exposing all the types employed in this study to the same radiation fields. The processing and read-out of the dosimeters was carried out by the participating laboratories.The results of this study form a useful data base which should provide valuable information to the participants. They may determine their performance relative to the range of other participants from the information in this report. This information is available to the participants, although the results are presented in this report in a strictly blind manner. In addition, since there were some neutron fields used in this study which may not have been previously encountered by the participants, they ...