USE OF COVARIANCE MATRICES IN A CONSISTENT (MULTISCALE) DATA ASSIMILATION FOR IMPROVEMENT OF BASIC NUCLEAR PARAMETERS IN NUCLEAR REACTOR APPLICATIONS: FROM METERS TO FEMTOMETERS

A new approach is proposed, the consistent data assimilation, that allows to link the integral data experiment results to basic nuclear parameters employed by evaluators to generate ENDF/B point energy files in order to improve them. A practical example is provided where the sodium neutron propagation experiments, EURACOS and JANUS-8, are used to improve via modifications of {sup 23}Na nuclear parameters (like scattering radius, resonance parameters, Optical model parameters, Statistical Hauser-Feshbach model parameters, and Preequilibrium Exciton model parameters) the agreement of calculation versus experiments for a series of measured reaction rate detectors slopes. Future work involves comparison of results against a more traditional multigroup adjustments, and extension to other isotope of interest in the reactor community as {sup 56}Fe, actinides, and fission products.