Concerning the time dependence of the decay rate of 137Cs

The decay rates of eight nuclides (85Kr, 90Sr, 108Ag, 133Ba, 137Cs, 152Eu, 154Eu, and 226Ra) were monitored by the standards group at the Physikalisch-Technische Bundesanstalt (PTB), Braunschweig, Germany, over the time frame June 1999 to November 2008. We find that the PTB measurements of the decay rate of 137Cs show no evidence of an annual oscillation, in agreement with the recent report by Bellotti et al. However, power spectrum analysis of PTB measurements of a 133Ba standard, measured in the same detector system, does show such evidence. This result is consistent with our finding that different nuclides have different sensitivities to whatever external influences are responsible for the observed periodic variations.

► Analysis of measured decay data for two isotopes measured on the same detector has been performed.
► The spectral analysis found periodicities for one isotope, 133Ba, but not the other, 137Cs.
► This supports an explanation not involving systematic/environmental causes.
► The results are consistent with others where periodicities have and have not been observed.
► Failure to observe periodicities in one isotope does not exclude their presence in others.