Resonance parameter covariance representation: file-32 versus file-33

Sensitivity and uncertainty analysis in error propagation studies are carried out based on nuclear data uncertainty information available in the basic nuclear data libraries such as ENDF, JEFF, JENDL and others. The uncertainty files (covariance matrices) are generally obtained from analysis of experimental data. In the resonance region, the computer code SAMMY is used for analyses of experimental data and generation of resonance parameters. In addition to resonance parameters evaluation, SAMMY also generates resonance parameter covariance matrices (RPCM). The intent of this paper is to discuss the use of the RPCM in contrast to the use of a cross section covariance matrix (CSCM) representation. For so, the resonance evaluation for ⁴⁸Ti in the resonance range from 10^-5 eV to 400 keV is used. The RPCM is translated into two distinct CSCM by using a coarser (44 groups) and a finer group structures (380 groups). The results are presented and discussions of the feasibility of using these covariance representations are depicted. The results suggested that the use of the RPCM is preferred over the CSCM representation. However there are situations in which a fine-group group structure may be advised as for instance in the case where the RPCM lends itself to a huge covariance matrix representation