Hydrogen evolution and corrosion rates for an Alloy 800H flow‐through reactor operating under supercritical water conditions were determined. Experiments were performed in the temperature range of 650 to 750 °C both with deoxygenated feed water, with an O2 concentration of less than 10 μg L−1 (ppb), and with a high oxygen concentration of around 20 mg L−1 (ppm). Effective rate constants for hydrogen evolution during the corrosion of an Alloy 800H were calculated to be 2.52×10−11, 2.88×10−11 and 4.30×10−11 mol cm−2 s−1, for the reactor temperatures of 650, 700 and 750 °C, respectively.

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Trace impurity patterns are important nuclear forensic signatures in uranium ore concentrates (UOCs) and Certified Reference Materials (CRMs) are used to validate the analysis methods employed by end users. Herein, we discuss the certification campaign for three new UOC CRMs from the National Research Council Canada: UCLO-1 (https://doi.org/10.4224/crm.2020.uclo-1), UCHI-1 (https://doi.org/10.4224/crm.2020.uchi-1), and UPER-1 (https://doi.org/10.4224/crm.2020.uper-1). This study involved 15 laboratories from 10 countries, using sector-field and (triple) quadrupole inductively-coupled plasma mass spectrometry to analyze 64 trace element impurities. We discuss the importance of the acids used for sample digestion, difficulties analyzing in a high uranium matrix, and data combination and uncertainty evaluation for this large dataset.