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
May 2024
Jan 2024
Latest Journal Issues
Nuclear Science and Engineering
June 2024
Nuclear Technology
Fusion Science and Technology
Latest News
NRC approves transfer of Vallecitos to North Star for D&D
By an order dated April 25, the Nuclear Regulatory Commission has approved the transfer of ownership of GE Hitachi Nuclear Energy’s Vallecitos Nuclear Center to NorthStar Group Services for nuclear decontamination, decommissioning, and environmental site restoration.
Jeffery D. Densmore, Edward W. Larsen
Nuclear Science and Engineering | Volume 146 | Number 2 | February 2004 | Pages 121-140
Technical Paper | doi.org/10.13182/NSE04-A2398
Articles are hosted by Taylor and Francis Online.
A new variational variance reduction (VVR) technique is developed for improving the efficiency of Monte Carlo multigroup nuclear reactor eigenvalue and eigenfunction calculations. The VVR method employs a variational functional, which requires detailed estimates of both the forward and adjoint fluxes. The direct functional, employed in standard Monte Carlo calculations, requires only limited information concerning the forward flux. The variational functional requires global information about the forward and adjoint fluxes and hence is more expensive to evaluate but is more accurate than the direct functional. In calculations, this increased accuracy outweighs the extra expense, resulting in a more efficient Monte Carlo simulation. In our work, we evaluate the variational functional using Monte Carlo-calculated forward flux estimates and deterministically calculated adjoint flux estimates. Also, we represent the adjoint flux as a low-order polynomial in space and angle, which is accurate for diffusive systems. (In such systems, which are common in reactor analysis problems, the angular flux is locally nearly linear in space and angle.) Using this adjoint representation, we develop specific VVR methods for eigenvalue problems, in which an estimate of the eigenvalue k in a criticality calculation is desired, and eigenfunction problems, in which an estimate of a detector response due to a fission neutron source during a criticality calculation is desired. The resulting VVR method is very efficient for the problems of interest. With a set of example problems, we demonstrate the increased efficiency of the VVR method over standard Monte Carlo.