The Role of Experiments in the Development and Qualification of Thermalhydraulic Codes, as Experienced in the Development of the Cathare Code

Summary

On one hand, analytical tests are used to develop and to qualify physical laws; on the other hand integral tests are used for global verification. This integral tests should never be used for adjustment of correlations, rather, only in order to point out eventual needs for improvement.

A stepwise approach is recommended for the development work. The mechanical laws should be derived first. Using them as a basis for further interpretation of experimental results, the mass transfer laws should then be established. The wall heat transfer correlations are the last ones to be fixed. Of course the correlations required for the description of component behaviour are developed (or adjusted) only after the physical laws of pipe flow are fixed. A standard series of analytical tests which covers a very wide range of parameters is designed to be used as the basis of the systematic qualification process. This methodology leads to a complete consistent set of physical laws (named a Revision in the CATHARE code).

The qualification work together with the first verification calculations reveal needs for improvements, particularly in the areas of condensation and of reflood (grid effect, multidimensional effects), which we hope could be achieved through on-going or planned experiments.