Isotopic Measurement of HTR-10 Irradiated Fuels Based on Anti-Compton Gamma Spectroscopic Method

Abstract Accurate determination of isotopic compositions of irradiated fuel elements plays a critical role in assessing fuel burnup, optimizing reactor performance, and ensuring safe operations. Spherical fuel elements are used in pebble-bed HTGRs (High Temperature Gas-cooled Reactors) such as HTR-10 and HTR-PM. However, there is almost no isotopic measurement of such fuels in the open literature, which has seriously limited the optimization of fuel management practices for HTGR systems. Recently, an isotopic measurement experiment of two irradiated HTR-10 fuels is carried out in China using gamma spectroscopic method. The analysis results are presented in this paper. We identified 9 fission products in the measured gamma spectra, and the measurement uncertainty are smaller than 5% for most isotopes. Furthermore, the correctness of the detection efficiency curve is stressed in this work. Multiple validation methods are employed, including standard source measurement, linear attenuation model, and self-calibration method, to ensure the accuracy and reliability of this work. Finally, sources of uncertainties are discussed and methods for accuracy improvement are proposed accordingly.