Iodine-129 in Thyroids and Tellurium Isotopes in Meteorites by Neutron Activation Analysis

摘要

A combination of neutron activation and mass spectrometry has been used to determine the concentration of fissiogenic exp 129 I and the value of the exp 129 I/ exp 127 I ratio in thyroids of man, cow, and deer from Missouri. Deer thyroids show an average value of exp 129 I/ exp 127 I = 1.8 x 10 exp -8 and an average concentration of 3 x 10 exp -3 pCi exp 129 I per gram of thyroid (wet weight). Thyroids of cows and humans show successively lower values for the exp 129 I/ exp 127 I ratio and the exp 129 I content because their diets dilute fission-produced exp 129 I in the natural iodine cycle with mineral iodine. The results of analyses on a few thyroids from other geographic areas are also reported. The isotopic compositions of tellurium, krypton, and xenon were determined in acid-resistant residues of the Allende meteorite. Neutron activation and gamma -counting were used to determine the relative abundances of six tellurium isotopes, and mass spectrometry was used to determine the isotopic compositions of krypton and xenon in aliquots of the same residues. Nucleogenetic anomalies were observed in the isotopic compositions of these three elements. The presence of isotopically distinct components of tellurium, krypton, and xenon in these residues provides strong support for the suggestion that our solar system formed directly from the debris of a supernova. (ERA citation 04:028097)