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.
J. Barclay Andrews, II, K. F. Hansen
Nuclear Science and Engineering | Volume 31 | Number 2 | February 1968 | Pages 304-313
Technical Paper | doi.org/10.13182/NSE68-A18242
Articles are hosted by Taylor and Francis Online.
A numerical method for the solution of the time-dependent multigroup diffusion equations is presented. The method has the property that it is numerically unconditionally stable for all changes in reactor properties and all integration time-step sizes. The method assumes that the neutron flux and precursor concentration can be expressed as an exponential function over each time step. As a result of this assumption, and the factoring of the matrix form of the multigroup equations, it is shown that for the case of a constant step change in the properties of the system the asymptotic numerical eigensolution is proportional to the asymptotic eigensolution of the differential equations. An analysis of the truncation error associated with the method is also presented. Finally, a number of numerical experiments are presented which illustrate the accuracy, speed, and general utility of the method.
