From fission yield measurements to evaluation: Propositions of ²³⁵U(n_th,f) Fission Yields for JEFF-4

The study of fission yields has a major impact on the characterization and understanding process its applications. products have direct influence amount neutron poisons that limit fuel burnup evaluation decay heat reactor after shutdown. Fission yield represents synthesis experimental theoretical knowledge in order to perform best estimation mass independent product yields. Today, lack correlations between different observables induces some inconsistencies evaluations. For instance, uncertainties are drastically overestimated while this observable is known. In last decade, covariance matrices been proposed but part those neglected. A consistent matrix depends global from data up models used. collaboration develops new methodology field for future version JEFF-library coupling analyses CEA NNL institutes.