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Periods Detected During Analysis of Radioactivity Measurements Data

Analysis results of data of long-term radioactivity measurements of 3H, 56Mn, 32Si, 36Cl, 60Co, 137Cs, 90Sr-90Y, 226Ra, 238Pu and 239Pu sources are presented. For beta-radioactive sources, their activity in addition to the exponential drop is characterized by rhythmic variations with a period of 1 year and magnitude of 0.1-0.35% from the average value. These oscillations attain maximum values between January and March, with corresponding minimum values occurring from July to September. Spectral analysis of 7-year long measurements of count rates of beta-radioactive sources 90Sr-90Y as well as 15-year long measurements of beta-gamma radiation of 226Ra revealed presence of rhythmic variations with a period of about a month and magnitude 0.01%. Magnitude of diurnal oscillations did not exceed 0.003%. Analysis of measurements data for alpha radioactive sources 238Pu and 239Pu did not reveal any statistically reliable periodic patterns. Possible factors underlying these rhythmic oscillations in beta-radioactivity are discussed.