ANS is committed to advancing, fostering, and promoting the development and application of nuclear sciences and technologies to benefit society.
Explore the many uses for nuclear science and its impact on energy, the environment, healthcare, food, and more.
Explore membership for yourself or for your organization.
Conference Spotlight
Nuclear Energy Conference & Expo (NECX)
September 8–11, 2025
Atlanta, GA|Atlanta Marriott Marquis
Standards Program
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!
Latest Magazine Issues
Sep 2025
Jan 2025
Latest Journal Issues
Nuclear Science and Engineering
September 2025
Nuclear Technology
Fusion Science and Technology
August 2025
Latest News
From operator to entrepreneur: David Garcia applies outage management lessons
David Garcia
If ComEd’s Zion plant in northern Illinois hadn’t closed in 1998, David Garcia might still be there, where he got his start in nuclear power as an operator at age 24.
But in his ninth year working there, Zion closed, and Garcia moved on to a series of new roles—including at Wisconsin’s Point Beach plant, the corporate offices of Minnesota’s Xcel Energy, and on the supplier side at PaR Nuclear—into an on-the-job education that he augmented with degrees in business and divinity that he sought later in life.
Garcia started his own company—Waymaker Resource Group—in 2014. Recently, Waymaker has been supporting Holtec’s restart project at the Palisades plant with staffing and analysis. Palisades sits almost exactly due east of the fully decommissioned Zion site on the other side of Lake Michigan and is poised to operate again after what amounts to an extended outage of more than three years. Holtec also plans to build more reactors at the same site.
For Garcia, the takeaway is clear: “This industry is not going away. Nuclear power and the adjacent industries that support nuclear power—and clean energy, period—are going to be needed for decades upon decades.”
In July, Garcia talked with Nuclear News staff writer Susan Gallier about his career and what he has learned about running successful outages and other projects.
William E. Kastenberg
Nuclear Science and Engineering | Volume 37 | Number 1 | July 1969 | Pages 19-29
Technical Paper | doi.org/10.13182/NSE69-A20895
Articles are hosted by Taylor and Francis Online.
A general formalism for the determination of stability criteria by the method of comparison functions is derived for nuclear reactors whose system dynamics are governed by a coupled set of space-dependent nonlinear differential equations. The results obtained are applicable to the nonlinear multigroup diffusion equations with temperature feedback. A stability criterion for the nontrivial equilibrium state is presented in a theorem. In addition, two corollaries are presented for the particular cases of negative feedback. The criteria so obtained represent a measure of the “dissipative” forces as estimated by the eigenvalues of the linearized problem vs a measure of the “disruptive” forces caused by the feedback. If the net effect is dissipative then the system is asymptotically stable in the sense of Lyapunov. Two examples are presented to illustrate the formalism and use of the criteria. In the second example, a stability criteria for two-group theory with linear temperature feedback is derived directly from the equations of motion by this method.
