1/f fluctuations in beta- decay of y-90

The decay statistics of Y-90 have been studied from the count data collected during the radioactive beta- decay from a carrier-free isotope of Sr-90-Y-90. The values of the relative Allan variance exceeded those predicted for a simple Poissonian process for counting times longer than 10 min and reached a limiting value called the flicker floor attributed to 1/f fluctuations. This study was extended for various energies of the Y-90 spectrum.