Reactor Physics - Modeling and Evaluation of Fission Observables

This article is dedicated to fission observables, which constitute important nuclear data for numerous applications, which explains the substantial efforts made by the international community to evaluate them. These data concern :

• fission yields ;

• the characteristics (energy spectra and multiplicities) of "prompt" neutrons and gammas.

In order to understand how these nuclear data are evaluated, we feel it's essential first to recall the main stages in the fission process. Nuclei (called "fission fragments" or "fission products", depending on the stage) may be formed, and particles (mainly neutrons and gamma rays) may be emitted with a probability that depends on both the time and energy required for their emission.