CALIBRATION OF THE NPL SECONDARY STANDARD RADIONUCLIDE CALIBRATOR FOR(32)P, SR-89 AND Y-90

Pure beta particle emitting radionuclides have many therapeutic applic ations in nuclear medicine. The response of the NPL secondary standard radionuclide calibrator to P-32, Sr-89 and Y-90 has been measured usi ng accurately calibrated solutions. For this purpose, high efficiency solid sources were prepared gravimetrically from dilute solutions of e ach radionuclide and assayed in a 4 pi proportional counter; the sourc e activities were determined using known detection efficiency factors. Measurements were made of the current response (pA/MBq) of the NPL se condary standard radionuclide calibrator using the original concentrat ed solutions. Calibration figures have been derived for 2 and 5 ml Bri tish Standard glass ampoules and Amersham International pie P6 vials. Volume correction factors have also been determined. Gamma-ray emittin g contaminants can have a disproportionate effect on the calibrator re sponse and particular attention has been paid to this.