A new internal pair production branching ratio of 90Y: The development of a non-destructive assay for 90Y and 90Sr

90Y is utilized as a therapeutic radioisotope in radiolabeled monoclonal antibodies and in microspheres for targeted radiation therapy of the liver. Currently, the widely used dose calibrator assay of 90Y can have uncertainties exceeding ±10%. A non-destructive assay using spectroscopy is possible by reducing the currently published uncertainty (±12%) in the internal pair production branching ratio for the 0+–0+ transition of 90Zr. A high-purity germanium detector was used to determine the branching ratio to be (31.86±0.47)×10−6.