New determination of the half-life of 121Te

After complete decay of the 123I activity of an aqueous solution, the γ-emissions from the long-lived contaminating radionuclides 121Tem and 121Te were followed simultaneously over a period of about 120 days. A revised value for the half-life image days is deduced which differs appreciably from the value of 16.8 days adopted in the literature. The special influence of 121Tem nuclei in the decay chain 121Tem→121Te→121Sb on the evaluation procedure is discussed in detail.