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.
Division Spotlight
Education, Training & Workforce Development
The Education, Training & Workforce Development Division provides communication among the academic, industrial, and governmental communities through the exchange of views and information on matters related to education, training and workforce development in nuclear and radiological science, engineering, and technology. Industry leaders, education and training professionals, and interested students work together through Society-sponsored meetings and publications, to enrich their professional development, to educate the general public, and to advance nuclear and radiological science and engineering.
Meeting Spotlight
2024 ANS Annual Conference
June 16–19, 2024
Las Vegas, NV|Mandalay Bay Resort and Casino
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
Apr 2024
Jan 2024
Latest Journal Issues
Nuclear Science and Engineering
May 2024
Nuclear Technology
Fusion Science and Technology
Latest News
Glass strategy: Hanford’s enhanced waste glass program
The mission of the Department of Energy’s Office of River Protection (ORP) is to complete the safe cleanup of waste resulting from decades of nuclear weapons development. One of the most technologically challenging responsibilities is the safe disposition of approximately 56 million gallons of radioactive waste historically stored in 177 tanks at the Hanford Site in Washington state.
ORP has a clear incentive to reduce the overall mission duration and cost. One pathway is to develop and deploy innovative technical solutions that can advance baseline flow sheets toward higher efficiency operations while reducing identified risks without compromising safety. Vitrification is the baseline process that will convert both high-level and low-level radioactive waste at Hanford into a stable glass waste form for long-term storage and disposal.
Although vitrification is a mature technology, there are key areas where technology can further reduce operational risks, advance baseline processes to maximize waste throughput, and provide the underpinning to enhance operational flexibility; all steps in reducing mission duration and cost.
Erin D. Fichtl, James S. Warsa, Jeffery D. Densmore
Nuclear Science and Engineering | Volume 165 | Number 3 | July 2010 | Pages 331-341
Technical Paper | doi.org/10.13182/NSE09-51
Articles are hosted by Taylor and Francis Online.
Under some circumstances, spatial discretizations of the SN transport equation will lead to negativity in the scalar flux; therefore, negative-flux fixup schemes are often employed to ensure that the flux is positive. The nonlinear nature of these schemes precludes the use of powerful linear iterative solvers such as Krylov methods; thus, solutions are generally computed using so-called source iteration (SI), which is a simple fixed-point iteration. In this paper, we use Newton's method to solve fixed-source SN transport problems with negative-flux fixup, for which the analytic form of the Jacobian is shown to be nonsingular. It is necessary to invert the Jacobian at each Newton iteration. Generally, an exact inversion is prohibitively expensive and furthermore is not necessary for convergence of Newton's method. In the inexact Newton-Krylov method, the Jacobian is inverted using a Krylov method, which completes at some prescribed tolerance. This tolerance may be quite large in the initial stages of the Newton iteration. In this paper, we compare the use of the exact Jacobian with two approximations of the Jacobian in the inexact Newton-Krylov method. The first approximation is a finite difference approximation. The second is that used in the Jacobian-free Newton-Krylov (JFNK) method, which performs a finite difference approximation without actually generating the Jacobian itself. Numerical results comparing standard SI with the three methods demonstrate that Newton-Krylov can outperform SI, particularly for diffusive materials. The results also show that the additional level of approximation introduced by the JFNK approach does not adversely affect convergence, indicating that JFNK will be robust and efficient in large-scale applications.