Radioactive waste management of Y-90 microspheres used for radioembolization technique

Abstract

Introduction The radioembolization technique is used for the treatment of liver tumors, with the implantation of glass microspheres doped with yttrium-90 (Y-90). Specific radiation protection procedures, particularly those regarding radioactive waste managements are required. Several publications indicate the presence of radionuclidic impurities in those microspheres, resulting in additional radiation safety concerns, with possible impact on the minimum radioactive waste storage time. Purpose Determination of the effective half-life time of Y-90 radioactive waste samples, in order to establish a minimum storage time before discharge, and the identification of potential radionuclide impurities of Y-90. Materials and methods Exposure rate and surface contamination measurements were performed on plastic containers containing residues from Y-90 microsphere delivery procedures. The gamma energy spectrum analysis of the decayed Y-90 samples was also obtained using a NaI(Tl) detector. Results Waste emission values higher than those expected for a pure Y-90 decay were measured, even after 30 days after the procedure, suggesting the presence of impurities. An larger effective half-life time days was determined when compared with pure Y-90. Spectrum peaks were observed suggesting the presence of Y-88. Conclusion For samples decayed up to 3 months, these findings impose an increase of the waste decay time for Y-90 waste containers when compared with pure Y-90. Spectrum analysis suggests the presence of Y-88. Further analysis are being made in samples decayed greater than 6 months, that include the spectrum acquisition in order to assess the presence of other potential impurities. Disclosure The authors have noting to disclose.