A new approach to assessment and management of the impact from medical liquid radioactive waste

The Swedish regulations concerning disposal of clinical radioactive waste are currently under revision and a graded approach is proposed for risk limitation purposes. To assist the revision procedures, a screening study was performed to estimate public exposures from liquid releases from hospitals to public sewers. The results showed that doses to sewage workers were above the dose constraint of 100 μSv a−1 especially for 131I and 99mTc. Hence, a dynamic model, LUCIA, was developed for realistic assessments in which radionuclide transportation in sewers was modelled. Probabilistic simulations were performed to obtain probability distributions of radionuclide concentrations in sludge. Concurrently, estimates of the effective doses to sewage workers decreased significantly and were below 10 μSv a−1 except for 111In and 131I. However, the Kd-coefficients representing the partition of radioactivity between water and sludge in sewers are highly uncertain for 111In. As shown by sensitivity studies, these values are the major determinant of the exposures in sewers.