Potential Burnup Indicator Identification Based on Power History Decomposition

The burnup prediction capability of commonly measured nuclides is investigated. Accuracy of different burnup indicator groups (categorized based on typical measurement uncertainties) are also estimated. Specifically, category 1 comprises 11 isotopes, including the traditional burnup indicators such as neodymium isotopes. Notably, the typical burnup indicator ¹³⁷Cs is not included here because a sensitivity study shows that it can be sensitive to a linear ramp rate of power. However, this does not preclude ¹³⁷Cs from being used as a burnup indicator in practice. The selection of burnup indicators must also consider factors such as measurement cost, uncertainty, and availability; ¹³⁷Cs, for instance, is easily measured using gamma spectrometry and can be combined with other burnup indicators to infer and calibrate burnup values. Category 2 includes 14 isotopes with higher measurement uncertainty, which should be used in conjunction with other indicator isotopes to provide accurate burnup information. Future work will involve applying these analyses to a real-scale assembly model, using both simulation and experimental data to validate the burnup indicator list, and assessing their performance in burnup inference. The next phase of this study will also focus on predicting the power history of fuel samples. Similar work on void fraction history is also being conducted [7].