Since 1965, the Savannah River Site (SRS) has conducted deer hunts which are open to the general public. SRS performs field monitoring for cesium-137 (Cs-137) of each harvested animal to determine whether the animal may be released to the hunter. A new field system for measuring Cs-137 in the harvested animals has been developed. The system incorporates numerous enhancements compared to the original system. The original system was composed of two Ludlum Measurements scalar-driven 2 inch x 2

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... sodium iodide counters, while the new system is based on a single Ametek Ortec Digibase-driven 2 inch x 4 inch x 16 inch sodium iodide gamma spectrometer. The new system includes a series of easy-to-assemble stainless steel encapsulated lead shields. The combination of the larger detector size and lead shielding improved the detection limit of the new system by a factor of approximately three compared to the original system. This lower detection limit allows for a larger number of measurements to be directly compared to the laboratory results, in cases where animal portions have been sampled. The new system eliminates the need for manual transcription of data from the scalar readout to paper and then to the Hunter Dose Tracking System (HDTS). An easy-to-use graphical user interface to control the system was designed, built, and adjusted with feedback from field personnel. Information on the specific animal/hunter is input into the computer and analysis results are now automatically sent from the spectrometer, combined with the animal specific information and loaded into the HDTS database. The new system provides immediate feedback to field personnel on whether to release or retain the animal. The new system also eliminates the cumbersome manual calibration protocols of the original system. On the morning of the hunt, the system's calibration routines automatically adjust the system gain with a check source measurement. The calibration is then verified against a NISTtraceable standard. Each subsequent animal measurement is validated with a simultaneous measurement of an on-board quality assurance check source. There is a significant improvement over the quality assurance (QA) of the original system where system drift was not tracked, and QA hinged on periodic measurements of a check source after a set number of animal counts. The system reports activity within the whole animal based on an innovative Monte-Carlo N-Particle (MCNP) model which scales the dimensions of the animal being measured to the animal type and weight. In addition, all spectra are stored for later retrieval, if necessary, whereas in the original system the data was not retrievable. For each measurement, the reported activity is also accompanied with the uncertainty of the measurement as well as the caveat as to whether the returned value is below the system's detection limit. The results from developing and using this system are presented as well as recommendations on improvements to the overall field monitoring of the SRS hunts. It is important to note that any errors with the sampling method and uncertainty in the activity measurements result in small changes to calculated dose and are well below any limits.