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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.
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Orlando, FL|Renaissance Orlando at SeaWorld
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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!
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Oak Ridge community roundtable explores workforce challenges
Federal and contractor officials, community leaders, and educators gathered in Knoxville, Tenn., on October 29 for a roundtable event focused on ensuring the Oak Ridge Office of Environmental Management (OREM) and its partners have the resources and infrastructure needed to support a robust, talented workforce in the years ahead.
Massimiliano Rosa, James S. Warsa, Michael Perks
Nuclear Science and Engineering | Volume 174 | Number 3 | July 2013 | Pages 209-226
Technical Paper | doi.org/10.13182/NSE12-57
Articles are hosted by Taylor and Francis Online.
A Fourier analysis is conducted in two-dimensional (2-D) geometry for the discrete ordinates (SN) approximation of the neutron transport problem solved with Richardson iteration (source iteration) using the cellwise block-Jacobi (bJ) and block-Gauss-Seidel (bGS) algorithms. The results of the Fourier analysis show that convergence of bJ can degrade, leading to a spectral radius equal to 1, in problems containing optically thin cells. For problems containing cells that are optically thick, instead, tends to 0. Hence, in the optically-thick-cell regime, bJ is rapidly convergent even for scattering-dominated problems. Similar conclusions hold for bGS, except bGS approaches the asymptotic, thick-cell regime at convergence rates higher than bJ. Hence, we have implemented the bGS algorithm on the Roadrunner hybrid, parallel computer architecture. A compute node of this massively parallel machine comprises AMD Opteron cores that are linked to a Cell Broadband Engine (Cell/B.E.). LAPACK routines have been ported to the Cell/B.E. in order to make use of its parallel synergistic processing elements (SPEs). The bGS algorithm is based on the LU factorization and solution of a linear system that couples the fluxes for all SN angles and energy groups on a mesh cell. For every cell of a mesh that has been parallel decomposed on the higher-level Opteron processors, a linear system is transferred to the Cell/B.E. and the parallel LAPACK routines are used to compute a solution, which is then transferred back to the Opteron, where the rest of the SN transport computations take place. Compared to standard parallel machines, a one-hundred-fold speedup of the bGS was observed on Roadrunner. Numerical experiments with strong and weak parallel scaling demonstrate that the bGS method is viable and compares favorably to full parallel transport sweeps (FPS) on 2-D unstructured meshes when it is applied to optically thick, multimaterial problems. Specifically, the strong parallel efficiency of accelerated bGS on Roadrunner can achieve 73% at 512 processors, compared with 32 processors, while efficiency is 34% for the (Opteron-only) implementation of FPS. The weak parallel efficiency of bGS is 58% while it reaches 10% for FPS. As expected, however, bGS is not as efficient as FPS in optically thin problems.
