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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.
J. Vujic, E. Greenspan
Nuclear Science and Engineering | Volume 129 | Number 1 | May 1998 | Pages 1-14
Technical Paper | doi.org/10.13182/NSE98-A1960
Articles are hosted by Taylor and Francis Online.
Neutronic characteristics are investigated of critical configurations consisting of U and moist rock, which may be formed if large enough quantities of highly enriched U (HEU) are released, transported, and deposited in the rock below the repository. A companion study investigated neutronic characteristics of similar critical configurations consisting of weapons-grade Pu (wPu) and moist rock.Two modes of U deposition are considered: uniform homogeneous and heterogeneous. The latter is assumed to be of the form of thin planar deposition layers separated by relatively thick slabs of rock, making a constant pitch lattice. Three neutronic characteristics are examined: the critical U loading, and the variation, with the change of operating conditions, of the multiplication factor k; the time-eigenvalue ; and the effective neutron generation time . They are compared against the characteristics of the corresponding wPu-rock systems. The study is done parametrically by solving time-independent transport equations. The effect of various mechanisms (including water removal, U and rock temperature increase, homogenization of fissile and rock materials, and the system expansion) on the neutronic characteristics is studied independently.A surprising finding is that heterogeneous depositions of HEU in moist rock can have a positive reactivity feedback due to spectrum hardening. Moreover, the magnitude and temperature dependence of heterogeneous U-rock systems can be comparable to those of Pu-rock systems despite the fact that they are due to entirely different mechanisms: reduction in the spatial self-shielding in the HEU systems compared with an increase in the effective fission-to-absorption cross-section ratio in the wPu systems.It is concluded that heterogeneous HEU deposits in moist rock can be just about as autocatalytic as critical wPu deposits but require approximately twice the critical mass. Three mechanisms were found to have a potential for a large positive reactivity insertion: water removal, rock temperature increase, and homogenization. The magnitude of each of the three positive reactivity feedbacks in the HEU systems is similar to the magnitude in the corresponding wPu systems.
