Non-dependence of nuclear decay rates of 123I and 99mTc on Earth-Sun distance.

Recently published studies have suggested an annual fluctuation of the decay rate of several radionuclides, in particular 32Si and 226Ra. Variation of solar neutrino flux caused by variation of Earth-Sun distance has been proposed as the mechanism of this fluctuation. In this study we prospectively look at two radionuclides which have not previously been studied for annual variation, 123I and 99mTc. Half-lives of samples of these radionuclides were measured approximately weekly and semiweekly respectively over a period of 2 years. Spectral analysis using the Lomb-Scargle method demonstrated no significant periodicity, and in particular, no evidence for a period of 1 year.