INDC(IND)-35G - IAEA Nuclear Data Services

- 54 -
Generation of Broad Group Errors and their Correlation Matrix
for Total Reaction Cross Section of U-238
(S.Ganeaan and V.Gopalakrishnan)
A recent Argonne National Laboratory evaluation has
provided the fine group values of errors and their correlation
matrices for U-238 from hk keV to 20.0 MeV energy region. This
fine group error matrix has a dimension of 55 x 55*
A practical problem in sensitivity analysis is
concerned with proper collapsing of the large correlation matrix
into a small sized matrix for determination of error associated
with calculations of neutronic parameters arising from cross
section uncertainties and their correlations.
A derivation made by us, invoking certain assumptions,
as detailed in Ref.2 gives the following expression.
A A A
c
where 2.j and £j" are the broad group values of the
errors and their correlation matrix. Q is the number of fine
groups in the broad group I and p the number of fine groups in
broad group J. It is assumed that the broad group boundary and
a fine group boundary coincide. Cp^