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Organized to promote the advancement of knowledge in the use of nuclear science and technologies in the aerospace application. Specialized nuclear-based technologies and applications are needed to advance the state-of-the-art in aerospace design, engineering and operations to explore planetary bodies in our solar system and beyond, plus enhance the safety of air travel, especially high speed air travel. Areas of interest will include but are not limited to the creation of nuclear-based power and propulsion systems, multifunctional materials to protect humans and electronic components from atmospheric, space, and nuclear power system radiation, human factor strategies for the safety and reliable operation of nuclear power and propulsion plants by non-specialized personnel and more.
2020 ANS Virtual Winter Meeting
November 15–19, 2020
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UWC 2020: A call for transformational change
Bowing to current COVID-19 realities but buoyed by the success of June’s virtual Annual Meeting, ANS event planners returned to the virtual realm for this year’s Utility Working Conference. Originally scheduled for August 9–12 at Marco Island, Fla., the condensed event was held Wednesday, August 11, wherever registrants’ computer devices happened to be located.
In addition to 26 educational sessions and workshops, UWC 2020 featured an opening plenary session titled “Achieving Transformational Change: A leadership discussion,” moderated by Bob Coward, MPR Associates principal officer and ANS past president (2017–2018). Plenary panelists included representatives from three utilities—Arizona Public Service (APS), Exelon, and Xcel Energy—plus the Institute of Nuclear Power Operations (INPO) and the Nuclear Regulatory Commission.
Tracy E. Stover, James S. Baker, Michael D. Ratliff, Gretchen C. Mitschelen
Nuclear Science and Engineering | Volume 190 | Number 2 | May 2018 | Pages 176-194
Technical Paper | dx.doi.org/10.1080/00295639.2017.1417344
Articles are hosted by Taylor and Francis Online.
The classic Limiting Surface Density (LSD) method is an empirical calculation technique for analyzing and setting mass limits for fissile items in storage arrays. LSD is a desirable method because it can reduce or eliminate the need for lengthy detailed Monte Carlo models of storage arrays. The original (or classic) method was developed based on idealized arrays of bare spherical metal items in air-spaced cubic units in a water-reflected cubic array. In this case, the geometric and material-based surface densities were acceptably correlated by linear functions. Later updates to the method were made to allow for concrete reflection rather than water, cylindrical masses rather than spheres, different material forms, and noncubic arrays. However, in the intervening four decades since those updates, little work has been done to update the method, especially for use with contemporary highly heterogeneous shipping packages that are noncubic and stored in noncubic arrays.
In this work, the LSD method is reevaluated for application to highly heterogeneous shipping packages for fissile material. The package modeled is the 9975 shipping package, currently the primary package used to store fissile material at Savannah River Site’s K-Area Complex. The package is neither cubic nor rectangular but resembles nested cylinders of stainless steel, lead, aluminum, and Celotex. The fissile content is assumed to be a cylinder of plutonium metal. The packages may be arranged in arrays with both an equal number of packages per side (package cubic) and an unequal number of packages per side (noncubic).
The cubic arrangements are used to derive the 9975-specific material and geometry constants for the classic linear form LSD method. The linear form of the LSD, with noncubic array adjustment, is applied and evaluated against computational models for these packages to determine the critical unit fissile mass. Sensitivity equations are derived from the classic method, and these are also used to make projections of the critical unit fissile mass. It was discovered that the heterogeneous packages have a nonlinear surface density versus critical mass relationship compared to the acceptably linear response of bare spherical fissile masses. Methodology is developed to address the nonlinear response. In so doing, the solution to the nonlinear LSD method becomes decoupled from the critical mass of a single unit, adding to its flexibility. The ability of the method to predict changes in neutron multiplication due to perturbations in a parameter is examined to provide a basis for analyzing upset conditions.
A full rederivation of the classic LSD method from diffusion theory is also included as this was found to be lacking in the available literature.