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September 8–11, 2025
Atlanta, GA|Atlanta Marriott Marquis
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Remembering ANS member Gil Brown
Brown
The nuclear community is mourning the loss of Gilbert Brown, who passed away on July 11 at the age of 77 following a battle with cancer.
Brown, an American Nuclear Society Fellow and an ANS member for nearly 50 years, joined the faculty at Lowell Technological Institute—now the University of Massachusetts–Lowell—in 1973 and remained there for the rest of his career. He eventually became director of the UMass Lowell nuclear engineering program. After his retirement, he remained an emeritus professor at the university.
Sukesh Aghara, chair of the Nuclear Engineering Department Heads Organization, noted in an email to NEDHO members and others that “Gil was a relentless advocate for nuclear energy and a deeply respected member of our professional community. He was also a kind and generous friend—and one of the reasons I ended up at UMass Lowell. He served the university with great dedication. . . . Within NEDHO, Gil was a steady presence and served for many years as our treasurer. His contributions to nuclear engineering education and to this community will be dearly missed.”
R. E. Alcouffe
Nuclear Science and Engineering | Volume 64 | Number 2 | October 1977 | Pages 344-355
Technical Paper | doi.org/10.13182/NSE77-1
Articles are hosted by Taylor and Francis Online.
We investigate a class of acceleration schemes that resemble the conventional synthetic method in that they utilize the diffusion operator in the transport iteration schemes. These schemes are not dependent on diffusion theory as being a good approximation to transport theory; they only make use of the diffusion equation form. The accelerated iteration involves alternate diffusion and transport solutions where coupling between the equations is achieved using a correction term applied to either (a) the diffusion coefficient, (b) the removal cross section, or (c) the source of the diffusion equation. The methods involving the modification of the diffusion coefficient and of the removal term yield nonlinear acceleration schemes and are used in keff calculations, while the source term modification approach is linear at least before discretization and is used for inhomogeneous source problems. A careful analysis shows that there is a preferred differencing method that eliminates the previously observed instability of the conventional synthetic method. Using this preferred difference scheme results in an acceleration method that is at the same time stable and efficient. This preferred difference approach renders the source correction scheme, which is linear in its continuous form and nonlinear in its differenced form. An additional feature of these approaches is that they can be used as schemes for obtaining improved diffusion solutions for approximately twice the cost of a diffusion calculation. Numerical experimentation on a wide range of problems in one and two dimensions indicates that improvement from a factor of from 2 to 10 over rebalance or Chebyshev acceleration is obtained. The improvement is most pronounced in problems with large regions of scattering material where the unaccelerated transport solutions converge very slowly.
