Covariance analyses of self-shielding factor and its temperature gradient for uranium-238 neutron capture reaction

Otsuka, Naohiko; Zukeran, Atsushi*; Takano, Hideki*; Chiba, Go; Ishikawa, Makoto

Covariances of the self-shielding factor and its temperature gradient for the uranium-238 neutron capture reaction have been evaluated from the resonance parameter covariance matrix and sensitivity of the self-shielding factor and its temperature gradient to microscopic nuclear data. The resonance parameters and their covariance matrix for uranium-238 were taken from JENDL-3.3, while the sensitivity coefficients were calculated by varying resonance parameters and temperature. A set of computer code modules has been developed for calculation of the sensitivity coefficients at numerous resonance levels. The present result shows that the correlation among resonance parameters yields a substantial contribution to the variances of the self-shielding factor and its temperature gradient. In addition to the variances of these quantities, their correlation matrices in the JFS-3 70 group structure are also obtained.