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2025 ANS Winter Conference & Expo
November 9–12, 2025
Washington, DC|Washington Hilton
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The Standards Committee is responsible for the development and maintenance of voluntary consensus standards that address the design, analysis, and operation of components, systems, and facilities related to the application of nuclear science and technology. Find out What’s New, check out the Standards Store, or Get Involved today!
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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.
Song Hyun Kim, Hong-Chul Kim, Jong Kyung Kim, Jea Man Noh
Nuclear Technology | Volume 177 | Number 2 | February 2012 | Pages 147-156
Technical Paper | Fission Reactors | doi.org/10.13182/NT12-A13362
Articles are hosted by Taylor and Francis Online.
The Dancoff factor is used in deterministic codes for the calculation of resonance absorption. In using the Monte Carlo simulation, some techniques, such as repeated structure, are commonly used for geometry modeling of pebbles and kernels. However, these methods, with some assumptions, can cause an error in the calculation of the Dancoff factor. In this study, a Monte Carlo simulation method for the evaluation of the Dancoff factor was developed to solve these problems. Random sampling and rejection techniques are used for geometry modeling of pebbles and kernels. Also, the random selection method of the pebble type is used for modeling of the fuel and moderator pebbles that are randomly mixed in the core. By using this method, the Dancoff factor was calculated, and the results were compared with the results calculated by the INTRAPEB code and the MCNP5 code. The results of the average intrapebble Dancoff factor agree well within 1% difference compared with the result of the other study that was calculated by the INTRAPEB code. The result of the average interpebble Dancoff factor was underestimated by [approximately]8%, compared with the result by using the MCNP5 code. Analysis shows that the difference is caused by modeling assumptions in using the MCNP5 code. In addition, the Dancoff factor of the HTR-PRTEUS reactor and its spatial dependency were evaluated. The results show that the method can be used in the calculation of the Dancoff factor with the consideration of the spatial dependency with good accuracy. It is expected that the method can simply calculate the average Dancoff factor calculation without the direct modeling of the complex pebble bed reactor geometries. Also, the Monte Carlo simulations with various fuel-to-moderator ratios can be evaluated. Therefore, it will be a powerful method to evaluate the Dancoff factor with consideration of a real geometrical distribution for the pebble bed reactors.
