Determination of 235U/238U ratio by low energy gamma rays. An experimental evaluation

Determination of the 235U/238U atom ratio is required for various applications. Thermal ionization mass spectrometry (TIMS) is generally used for this purpose since the method gives most precise results. However, the method has limitations like elaborate sample preparation and high cost. Thus, an alternative methodology based on low energy photon spectrometry (LEPS) was developed and tested using routine samples. It involves the determination of gamma (γ) activity at gamma energies of 63.3, 92.8, 143.6, and 185.7 keV in isotopic standard solutions of uranium and different enriched uranium sample solutions. The method is fast as it does not involve chemical treatment as in TIMS. In this paper, a comparative evaluation of thermal ionization mass spectrometry and low energy photon spectrometry is reported for the determination of the 235U/238U atom ratio. The results obtained by the two systems compare well with each other within the statistical uncertainties of each system. Between the two, low energy photon spectrometry will be useful for rapid analysis of routine samples of enriched uranium. (orig.)