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

The 4πβ efficiency tracing liquid scintillation spectrometry method was applied with success, at ENEA, to the activity measurement of pure β-emitters (90Sr and 63Ni) and electron-capturing nuclides (55Fe), using 3H 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 prepared sources was performed and the dependence of the measured activity concentration on the quenching level was analysed. The radionuclides were standardised to a combined standard uncertainty of 0.14% for 90Sr, 0.55% for 63Ni and 1.18% for 55Fe.