Feasibility of 106Ru Peak Measurement for MOX Fuel Burnup Analysis


Simulations were performed using ORIGEN-ARP to investigate ¹³⁷Cs and ¹⁰⁶Ru-¹⁰⁶Rh as suitable fission products for non-destructive analysis of irradiated MOX. The simulations confirm that both ¹³⁷Cs and ¹⁰⁶Ru will provide a linear correlation with burnup when exclusively applied to MOX fuel assemblies. Moreover, ¹⁰⁶Ru can also be used in conjunction with cesium to form a ratio almost independent of enrichment and power history. Simulations were conducted using three different uranium enrichments and one MOX enrichment over a burnup range of 20,000-60,000 MWD/MTHM. Comparison of the three uranium enrichments indicates the ¹⁰⁶Ru ratio is consistent in predicting burnup with a maximum standard deviation of 0.046. Two MOX cases were simulated confirming operational history independence of ¹⁰⁶Ru in predicting total burnup. The ¹⁰⁶Ru burnup ratio also has the benefit of enabling distinction between UO₂ and MOX fuel because of its significantly larger (~11 times) fission yield from ²³⁹Pu. To investigate the detectability of ¹⁰⁶Ru and other cesium peaks, data was collected using a HPGe detector at the Missouri S&T nuclear reactor (MS&TR) beam port. Gamma spectra were obtained immediately following reactor shutdown with the most promising spectrums obtained 3-5 h after shutdown. Even for relatively high enrichment (~20%) fuel at MS&TR, cesium peaks were prominent and easily discernable from the intense Compton continuum. The ¹⁰⁶Ru peak was weak, though still distinguishable from the background, suggesting that with an appropriately designed collimator, suitable detector and electronics it might be feasible to reliably measure ¹⁰⁶Ru in even UO₂ fuel. For MOX and LEU LWR fuels one would expect a more intense ¹⁰⁶Ru signature. © 2010 Elsevier B.V. All rights reserved.


Mining and Nuclear Engineering

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© 2010 Elsevier, All rights reserved.