Half-life measurement of 126Sn isolated from Hanford nuclear defense waste

Long-term risk assessment of residual and disposed nuclear fuel reprocessing waste requires good knowledge of component isotopes with long half-lives. For example, the accuracy of the accepted Sn-126 half-life of approximately 100,000 years is insufficient for desired risk assessments. From modeling and sampling, Sn-126 is known to exist in Hanford nuclear waste. Excess portions of waste characterization samples were used to isolate Sn-126 for measurement of its half-life. Isolation was performed with ion-exchange resins. The resulting Sn-126 was gamma-assayed with a hyperpure germanium spectrometer for decay photon identification and activity values. An inductively coupled plasma/mass spectrometer was used to measure the atom quantity of the isolated Sn-126. The separation chemistry, observed gamma energies, and calculated half-life are presented. The half-life of Sn-126 estimated in this work is (2.33 +/- 0.10)(.)10(5) years.