There have been a number of investigators who have reported time-dependent radioactive decay rates—sinusoidal annual variations—for several different radioactive isotopes (see Table 2 of first article by O’Keefe et al., 2013). Most of these studies are based on the actual measurement of decay over a time period of a few decades. Others refute these conclusions, usually claiming that temperature variations in these experiments have not been properly accounted for.
The second article (Hutchin) reports on experimental results of an extremely high-precision electron tunneling experiment that accounts for temperature variations, and supports a non-constant radioactive decay rate. The common link between radioactive decay and electron tunneling is Planck’s “Constant”…, which also appears to vary with time! Furthermore, this experiment found the sinusoidal variations due to a “cosmic lock” onto Betelgeuse in the Orion constellation. So maybe there’s something to this astrological thingy after all!
Lastly, the reported variations in the radioactive decay rate are almost exclusively associated with Beta decay. Interestingly, radiocarbon dating is based on the beta decay of 14C. Something to think about…