Occupational internal monitoring in nuclear medicine service of Sainte-Anne military hospital: previous considerations and results.

The Nuclear Medicine Department of Sainte-Anne military hospital in Toulon uses 99mTc, 123I and 18F unsealed sources to provide therapeutic and diagnostic care. For a few years, only ambient air and surface monitoring were performed to check the absence of internal contamination risk for workers. To verify this risk assessment hypothesis, confirmatory monitoring programme including in vivo and in vitro measurements was performed by the French defence radiation protection service (SPRA, Clamart). Here, due to the short half-life of targeted radionuclides, the analytical sensitivity was determined with estimations of minimal detectable activities and derived recording levels. It was shown that sensitivity was sufficient to detect an internal contamination leading to an effective dose of 0.1 mSv for few days post intake. At the same time, around 20 whole-body countings were performed. Results were below minimal detectable activity and were confirmed by 24-hours urine analysis. So, actual working conditions do not lead to measurable internal contamination for nuclear medicine staff.

TRITIUM ANALYSIS IN URINE BY THE TRIPLE-TO-DOUBLE COINCIDENCE RATIO METHOD WITH THE HIDEX 300 SL LIQUID SCINTILLATION COUNTER.

The triple-to-double coincidence ratio (TDCR) method is a liquid scintillation primary method for the absolute activity measurement of pure ß- and pure electron capture emitters. This method requires specific three-photomultiplier liquid scintillation counters. The aim of the present work is to assess the TDCR method performance for routine tritium analysis in urine using an HIDEX 300 SL, the only three-photomultiplier liquid scintillation counter designed for routine laboratories. The physical parameters and the semi-empirical Birks parameter (kB) of the prepared liquid scintillation source were firstly determined. TDCR model equations solving and detection efficiencies calculations for measured samples were performed by TDCR07c computing program. Accuracy, uncertainties and detection limit of TDCR method were assessed through the tritium analysis of six intercomparison urine samples. The results demonstrate that the analytical performance of the TDCR method implemented on the HIDEX 300 SL is conform to the recommendations for the monitoring of workers exposed to tritium.