1. Origin of nuclear data. Evaluations

Nuclear data for nuclear reactor studies in particular are derived from measurements and physical models. They are made available :

• or in the form of a computerized compilation of experimental data;

• or in the form of an assessment. In the latter case, they are produced by nuclear physicists, known as evaluators, following a delicate and lengthy (≈ 1 man · year/isotope) process of analyzing measurement results, implementing adjustment methods and theoretical formalisms