Compliance assessment when radioactive discharges are close to exemption levels in nuclear medicine facilities

Nuclear Medicine has applied radiopharmaceuticals to diagnose and treat several diseases for decades. The decay of the radionuclide inserted in the drug needs to be monitored and controlled to avoid unnecessary impact on the environment, as well as on the general public. Gamma-ray spectrometry is the technique usually selected to identify and quantify these gamma emitters radionuclides. When radionuclides' active concentrations are close to upper limit specifications, doubts are raised about whether they meet the regulatory body's definitions. A different and innovative approach to assessing compliance in these situations is the use of guard band, interval between the boundary and the end of the acceptance zone. The study presented aimed the evaluation of the guard bands' effect on the disposal limits of some radionuclides commonly used in a medical facility. A relatively small increase in the activity concentration could be observed when the guard bands approach was used for the detector's uncertainty. However, these values can be used when activity concentrations are on the boundary of the exemption level. According to the results achieved with this study, guard bands can be seen as an alternative approach to the current one that do not use an in-depth metrological study. For the biota study, and under the described conditions, it was verified that the guard band approach did not show significant damage.