contain strontium.

If $^{90}$Sr were present in the rainwater samples then the chemistry performed to produce a Sr precipitate would break the secular equilibrium between the decays of $^{90}$Sr (t$_{1/2}$ = 28.8 years) and $^{90}$Y (t$_{1/2}$ = 2.67 days).The samples were immediately counted after preparation and again one week later on a planar HPGe detector equipped with a thin beryllium entrance window (0.254 mm), which allows for transmission of low energy gamma and x-rays. The efficiency of a thin planar detector drops off rapidly for higher energy gammas ($>$100 keV). Betas however, maintain a constant efficiency at these higher energies since they are absorbed over a short distance within the HPGe crystal, so a $\beta$ particle above an MeV would have a far greater efficiency compared to gammas in that energy region. The dimensions of the planar HPGe used in these measurements was 32 mm in diameter and 13 mm thick. We then compared a ratio of the counts in the 0-0.546 MeV energy interval (the $^{90}$Sr endpoint) to that in the 0.546-2 MeV interval (approximate $^{90}$Y endpoint) immediately after filtering and again after one week to search relative changes between the two energy regions, which would be expected if 