2D effects in the core during the reflooding phase of a LOCA

In a PWR core the power is not identical from one assembly to another and this may result in 2D phenomena which have to be studied in order to know whether it is necessary to take them into account in safety codes or not and, if yes, to define the simplest models suitable for that. An experimental programme has been conducted during which numerous aspects were investigated. Boil up and reflood tests (constant and oscillating flow rate) have been performed which show the effect of various parameters and somewhat clarify the problem of fall back and cross flows as well as their consequences on quench front propagation and heat transfer in the dry region. (author)