BNL-81629-2008-CP Few group collapsing of covariance matrix data based on a conservation principle H. Hiruta 1 , G. Palmiotti 1 , M.Salvatores 1,2 , R.Arcilla Jr 3 , P. Oblozinsky 3 , R. D. McKnight 4 1 Idaho National Laboratory, 2 CEA-Cadarache (France), 3 NNDC, Brookhaven National Laboratory , 4 Argonne National Laboratory Presented at the Covariance Workshop Port Jefferson, New York, June 24-27, 2008 National Nuclear Data Center Energy Sciences & Technology Department Brookhaven National Laboratory P.O. Box 5000 Upton, NY 11973-5000 www.bnl.gov Notice: This manuscript has been co-authored by employees of Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The publisher by accepting the manuscript for publication acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes.