Mathematical Aspects Of Nuclear Data Covariance Matrix Preparation - An Example Of Delayed Neutron Data

The Bayesian approach was used to derive the variance-covariance of the delayed fission yields of actinides based on theoretical model. The GEF code was used for theoretical calculations. The code calculates the distribution of delayed fission yield data as a function of input model parameters which are randomly varied according to the assigned standard deviation levels. The correlations between different isotopes and energy ranges were deduced from GEF runs using the same input parameters. Example of results in the form of standard deviations and correlation coefficients for U-235, U-238 and Pu-239 at few different energies is presented.