Temperature sensitivity of the equilibrium neutronics and accident analysis of the HTR-10

Journal Article · Fri Feb 07 00:00:00 EST 2025 · Progress in Nuclear Energy

DOI:https://doi.org/10.1016/j.pnucene.2025.105643· OSTI ID:2573281

Berens, Annie ^[1]; Bostelmann, Friederike ^[2]; Brown, Nicholas R. ^[1]

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1. Univ. of Tennessee, Knoxville, TN (United States)
2. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Pebble-Bed High-Temperature Gas-cooled Reactors (PB-HTGR) are moderated by the graphite in the fuel pebbles and the graphite reflector surrounding the pebble-bed. Because graphite is by far the most abundant material in PB-HTGRs and the primary moderator, accurate modeling of the graphite material, including density, impurities, and temperatures, is crucial for accurate computational modeling and simulation of these reactors. While main characteristics of the graphite components are often known, the local temperature is less well known and often averaged over all components. Here, this work studies the impact of considering accurate temperature profiles in the graphite material on the generation of a small PB-HTGR model at the state of equilibrium operation and on short-term accident progression. The fuel compositions for the PB-HTGR were determined using a jump-in equilibrium modeling method, the Axial Radial Zone Equilibrium Modeling (AR-ZEM) method. In contrast to previous work, the AR-ZEM method was used considering thermal-hydraulic feedback from the MELCOR code to determine temperatures of the fuel pebbles and the surrounding graphite reflector. The consideration of an axial and radial temperature profile in the core and reflector, as opposed to uniform material temperatures, had an impact of almost 1,300 pcm on the equilibrium core eigenvalue and caused significant differences in the discharged plutonium fuel inventory with up to 4.9% and 11.0% for Pu-239 and Pu-242, respectively. To assess the impact on short-term accident progression, two Anticipated Transient Without SCRAM (ATWS) events, a Pressurized Loss of Forced Coolant (PLOFC) and a Control Rod Withdrawal (CRW) with loss of flow, were simulated with MELCOR. The use of temperature profiles in the equilibrium core models did not reveal a significant impact on the temperature, power, or reactivity responses during the transients. In conclusion, a need for consideration of accurate temperature profiles, in particular for the graphite reflector, was found for the generation of equilibrium PB-HTGRs core models using jump-in methods, but detailed temperature profiles may not be necessary when performing conservative transient analysis.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Advanced Research Projects Agency - Energy (ARPA-E); USDOE Office of Nuclear Energy (NE)
• Grant/Contract Number: AC05-00OR22725
• OSTI ID: 2573281
• Alternate ID(s): OSTI ID: 2512435
• Journal Information: Progress in Nuclear Energy, Journal Name: Progress in Nuclear Energy Vol. 181; ISSN 0149-1970
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

HTGR
MELCOR
Pebble Bed Reactor
SCALE