Title:

Adjoint-Based Eigenvalue Sensitivity to Geometry Perturbations, and a Warning

Speaker:

Dr. Jeffrey Favorite

Affiliation:

Los Alamos National Laboratory

When:

Thursday, October 14, 2010 at 11:00:00 AM   Add to Calendar

Where:

Boggs Building, Room 3-47 (3rd Flr)

Host:

Mostafa Ghiaasiaan
mghiaasiaan@gatech.edu
4-3746

Abstract

The sensitivity of the ë eigenvalue (ë = 1/keff) to the location of a material interface is derived from the standard adjoint-based sensitivity formula. The sensitivity equation applies only to uniform expansions or contractions of a surface, not to surface translations or rotations. However, the equation is related to Rahnema’s earlier first-order perturbation estimate for the change in ë resulting from a more general change in the location of an interface. We compare the sensitivity equation with the perturbation equation. We apply the perturbation equation to the translation of a sphere. We apply the sensitivity equation to the radial dimensions of Zeus, a cylindrical critical assembly. For a flat surface (a plane), a translation in the direction of the normal (or in the opposite direction) is equivalent to an expansion or contraction, so we apply the sensitivity equation to the translation of the bottom half of Zeus. We find to our surprise that the perturbation and sensitivity equations do not work well for the translations of bodies, and we thus conclude with warnings and cautions.

Biography

Dr. Jeffrey A. Favorite has been a scientist in X-Division at Los Alamos National Laboratory since 1998. His interests include perturbation and sensitivity theory, neutron multiplication and criticality, and neutron and photon shielding. He is a practitioner and developer of deterministic and Monte Carlo transport methods. He received his Bachelor of Nuclear Engineering in 1993, his Master of Nuclear Engineering in 1994, and his Ph.D. in Nuclear Engineering in 1998, all from Georgia Tech.

Notes

Refreshments will be served.