Nuclear data for /sup 235/U, /sup 238/U, and /sup 239/Pu in the unresolved resonance region

Transmission and fission self-indication were measured for the isotopes /sup 235/U, /sup 238/U, and /sup 239/Pu in the unresolved resonance region for a wide range of material thicknesses. The fission cross section of /sup 235/U serves as standard. The other isotopes are the basic fuel components in plutonium fast breeder reactors. The experimental results obtained were analyzed together with average cross-section data using the multilevel R-matrix formalism. The objective of the consistent analysis was to estimate sets of mean resonance parameters. For this purpose, a new multilevel ladder technique was developed (Monte Carlo method) that enabled calculation of all the functionals of interest including their sensitivity coefficients related to the mean resonance parameters. Hence, the perturbation approach and the correlated random sampling technique were employed.