Many of the failures that occur in nuclear fuel rods in light water reactors around the world are caused by the phenomenon of mechanical interaction between pellets and cladding (PCMI). The process is extremely complex to simulate, therefore the models involved must be continuously improved and subjected to validation with experiments and comparison to other similar codes.

This benchmark study of PCMI aims to improve the understanding and modelling of PCMI. The study engaged investigators representing the main fuel performance simulation groups in the world. After a detailed analysis of the results of all the participants, a series of conclusions have been drawn. The results are captured in two volumes: Volume 1: Hypothetical Beginning-of-Life Power Ramps (this publication) and Volume 2: Validation of Beginning-of-Life Power Ramping (NEA, 2024).