Year
1975
Abstract
The neutrons produced from the ( a,n ) reaction on fluorine have been used to measure the U isotopic abundance in UF. samples. A 411 detector consisting of 14 He counters embedded in a polyethylene anulus was specifically designed to receive standard IS (high-enriched) and 2S (low-enriched) UF, sample IT.*. ° cylinders. The U isotopic abundances of the 19 2S and 5 IS samples studied range from 0.30 to 4.0% (wt) and 80.0 to 97.71 (wt) respectively. A typical net weight for the UF,. in the IS cylinders is 800 g and in 2S cylinders is 1700g. For counting times of 10 sec and for U concentrations over a range of 0.001 to 1.0% (wt), the neutron method will achieve accuracies better than 2.5% (la) for the depleted and low-enriched UF& and approximately 0.5% (la) for the high-enriched UF,- when compared with the 234U isotopic abundances obtained using a high precision, two-stage mass spectrometer. Extension of the 234U neutron assay method to samples containing 232U is now being investigated. From these preliminary results it appears that the isotope separation plant operator and the safeguards inspector should be able to use this new non-destructive assay technique for precision 734 measurements of the isotopic abundance of U. In addition, the method could be useful as an indirect field method for U assay where gamma techniques give inconclusive results and where the *? \"Z. C *7 T A U/ U ratio can be assumed or has been previously established either by measurement or calculation.