Standardisation of Sr-90, Ni-63 and Fe-55 by the 4 pi beta liquid scintillation spectrometry method with H-3-standard efficiency tracing

The 4 pi beta efficiency tracing liquid scintillation spectrometry method w as applied with success, at ENEA, to the activity measurement of pure beta- emitters (Sr-90 and Ni-63) and electron-capturing nuclides (Fe-55), using H -3 as tracer nuclide, The agreement of these measurements in comparison to other national metrology institutes was checked by means of two comparisons , carried out in 1996-1997. Furthermore a study of the stability of the pre pared sources was performed and the dependence of the measured activity con centration on the quenching level was analysed. The radionuclides were stan dardised to a combined standard uncertainty of 0.14% for Sr-90, 0.55% for N i-63 and 1.18% for Fe-55. (C) 1999 Elsevier Science Ltd. All rights reserve d.