How do we define the concepts specific activity, radioactive concentration, carrier, carrier-free and no-carrier-added?
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The fission of highly enriched uranium (HEU) by thermal neutrons creates dozens of isotopic products. The Isotope and Nuclear Chemistry Group participates in programs that involve analysis of “fresh' fission products by beta counting following radiochemical separations. This is a laborious and time-consuming process that can take several days to generate results. Gamma-spectroscopy can provide a more immediate path to isotopic activities, however, short-lived, high-yield isotopes can swamp a gamma-spectrum, making difficult the identification and quantification of isotopes on the wings and valley of the fission yield curve. The gamma-spectrum of a sample of newly produced fission products is dominated by the many emissions of a very few high-yield isotopes. Specifically, <Superscript>132</Superscript>Te (<Emphasis Type=”Italic”>T<Subscript>1/2</Subscript></Emphasis> = 3.2 d), its daughter, <Superscript>132</Superscript>I (<Emphasis Type=”Italic”>T<Subscript>1/2</Subscript></Emphasis> = 2.28 h), <Superscript>140</Superscript>Ba (<Emphasis Type=”Italic”>T<Subscript>1/2</Subscript></Emphasis> = 12.75 d), and its daughter <Superscript>140</Superscript>La (<Emphasis Type=”Italic”>T<Subscript>1/2</Subscript></Emphasis> = 1.68 d) emit at least 18 gamma-rays above 100 keV that are greater than 5% abundance. Additionally, the 1596 keV emission from <Superscript>140</Superscript>La imposes a Compton background that hinders the detection of isotopes that are neither subject to matrix dependent fractionation nor gaseous or volatile precursors. Some of these isotopes of interest are <Superscript>111</Superscript>Ag, <Superscript>115</Superscript>Cd, and the rare earths, <Superscript>153</Superscript>Sm, <Superscript>154</Superscript>Eu, <Superscript>156</Superscript>Eu, and <Superscript>160</Superscript>Tb. C-INC has performed an HEU irradiation and also “cold' carrier analyses by ICP-AES to determine methods for rapid and reliable separations that may be used to detect and quantify low-yield fission products by gamma-spectroscopy. Results and progress are presented.
KeywordsUranium Fission Product Radioactive Concentration Radiochemical Separation Enrich Uranium
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