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Conference Spotlight
2025 ANS Winter Conference & Expo
November 9–12, 2025
Washington, DC|Washington Hilton
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Senate EPW Committee to hold Nieh nomination hearing
Nieh
The Senate Environment and Public Works Committee will hold a nomination hearing Wednesday for Ho Nieh, President Donald Trump’s nominee to serve as commission at the Nuclear Regulatory Commission.
Trump nominated Nieh on July 30 to serve as NRC commissioner the remainder of a term that will expire June 30, 2029, as Nuclear NewsWire previously reported.
Nieh has been vice president of regulatory affairs at Southern Nuclear since 2021, though since June 2024 he has been at the Institute of Nuclear Power Operations as a loaned executive.
A return to the NRC: If confirmed by the Senate, Nieh would be returning to the NRC after three previous stints totaling nearly 20 years.
Tatiana Siaraferas, Yves Robert, Massimiliano Fratoni
Nuclear Technology | Volume 211 | Number 8 | August 2025 | Pages 1774-1808
Research Article | doi.org/10.1080/00295450.2024.2430120
Articles are hosted by Taylor and Francis Online.
Verification and validation of the Monte Carlo particle transport code Serpent 2 depletion calculation capabilities in the context of tristructural isotropic (TRISO) particles was performed against available data from the second Advanced Gas Reactor irradiation campaign (AGR-2), which was irradiated in the Advanced Test Reactor (ATR) at Idaho National Laboratory. The AGR-2 test train contained both uranium oxycarbide (UCO) and uranium dioxide (UO2) TRISO particles, which were irradiated for 12 ATR power cycles over a period of 3.5 years.
For this study, the AGR-2 test train was reconstructed in full detail using Serpent 2, and depletion calculations replicating the experimental irradiation conditions were performed. The fast neutron fluence and AGR-2 fuel burnup resulting from the depletion calculations for the 12 irradiation cycles are compared with the corresponding reported MCNP-computed data. The total AGR-2 fuel burnup accumulated by the end of the AGR-2 test train irradiation is also compared with available experimental data. The fission product inventory at the end of the AGR-2 irradiation obtained from the Serpent 2 depletion calculations is compared with the reported computational data.
The Serpent 2 results for the fast neutron fluence (En > 0.18 MeV) differ on average by 5.10% from the MCNP-computed results. Similarly, the Serpent 2 model underpredicts the AGR-2 fuel burnup at the end of the irradiation by 5.13%, on average for all capsules, when compared with the MCNP-computed results and by 2.01% when compared with the experimental results. Last, the fission product inventory calculated by Serpent 2 is underpredicted by 5.27%, on average for all capsules, in comparison with the reference MCNP data. Serpent 2 is generally in satisfactory agreement with the AGR-2 reported values. These results provide confidence in the performance of Serpent 2 depletion calculations for TRISO fuel particles.
