Abstract
The program PUFF-IV is used to process resonance parameter covariance information given in
ENDF/B File 32 and point-wise covariance matrices given in ENDF/B File 33 into group-averaged
covariances matrices on a user-supplied group structure. For large resonance covariance matrices,
found for example in 235U, the execution time of PUFF-IV can be quite long. Recently the code
was modified to take advandage of Basic Linear Algebra Subprograms (BLAS) routines for the most
time-consuming matrix multiplications. This led to a substantial decrease in execution time. This
faster processing capability allowed us to investigate the conversion of File 32 data into File 33
data using a larger number of user-defined groups. While conversion substantially reduces the
ENDF/B file size requirements for evaluations with a large number of resonances, a trade-off is
made between the number of groups used to represent the resonance parameter covariance as a
point-wise covariance matrix and the file size. We are also investigating a hybrid version of the
conversion, in which the low-energy part of the File 32 resonance parameter covariances matrix is
retained and the correlations with higher energies as well as the high energy part are given in File 33.
