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Conference Spotlight
2025 ANS Winter Conference & Expo
November 9–12, 2025
Washington, DC|Washington Hilton
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Empowering the next generation: ANS’s newest book focuses on careers in nuclear energy
A new career guide for the nuclear energy industry is now available: The Nuclear Empowered Workforce by Earnestine Johnson. Drawing on more than 30 years of experience across 16 nuclear facilities, Johnson offers a practical, insightful look into some of the many career paths available in commercial nuclear power. To mark the release, Johnson sat down with Nuclear News for a wide-ranging conversation about her career, her motivation for writing the book, and her advice for the next generation of nuclear professionals.
When Johnson began her career at engineering services company Stone & Webster, she entered a field still reeling from the effects of the Three Mile Island incident in 1979, nearly 15 years earlier. Her hiring cohort was the first group of new engineering graduates the company had brought on since TMI, a reflection of the industry-wide pause in nuclear construction. Her first long-term assignment—at the Millstone site in Waterford, Conn., helping resolve design issues stemming from TMI—marked the beginning of a long and varied career that spanned positions across the country.
Carlotta G. Ghezzi, Brian D. Wirth, Nicholas R. Brown
Nuclear Science and Engineering | Volume 198 | Number 5 | May 2024 | Pages 1036-1050
Research Article | doi.org/10.1080/00295639.2023.2230031
Articles are hosted by Taylor and Francis Online.
This work assesses the failure behavior of the silicon carbide (SiC) layer in TRIstructural ISOtropic (TRISO) fuel particles with BISON during both steady-state and transient conditions for the MHTGR-350 design by General Atomics. A one-dimensional BISON model for a uranium oxycarbide–bearing TRISO is developed to simulate a power level of 50 mW/particles up to 12.4% fissions per initial metal atom (FIMA). Stress predictions for the materials of interest are presented as a function of burnup, along with the SiC failure probability computed using Weibull statistics under the assumption of realistic SiC quality.
A design-basis accident (DBA) that involves control rod withdrawal is then simulated in BISON at various burnup levels. Boundary conditions during the DBA are obtained from RELAP5-3D. The predicted SiC failure probability is 3 × 10−14%. This value does not increase during the transient as a function of burnup since irradiation induces a compressive hoop stress state that reaches a maximum absolute value of around 300 MPa. This compressive stress compensates the tensile loading conditions introduced by the transient. The tensile components appear amplified at higher burnups since they increase from 100 to 140 MPa going from 6% FIMA to 12.4% FIMA. Nonetheless, burnup provides a negligible impact on the overall failure probability predictions for SiC, as transient conditions do not translate to a stress increase toward tensile values at any of the considered burnups.
Additionally, a two-dimensional (2-D) exploratory BISON model is developed to determine the effects of inner pyrolytic carbon (IPyC) crack formation on SiC. IPyC failure is predicted using Weibull statistics at 105 days from the beginning of irradiation, which is set as the time for crack initiation using XFEM in the 2-D BISON model. Stress concentrations induced by the crack cause the SiC failure probability to increase with respect to the intact particle case by approximately 10 orders of magnitude. Maximum stress concentrations are found at the time of crack formation, after which stress relaxation is observed during remaining steady-state irradiations and subsequent transient simulations. Considerations are made on the results of the 2-D model being contingent on both mechanical and anisotropy properties for pyrolytic carbon. Recommendations are provided for future work involving higher dimensionality models, further investigations on uncertainties, material properties, and additional designs, such as the fluoride salt-cooled high-temperature reactor, that operate at higher burnups.
