A top-down reflooding model was developed for the French best-estimate
thermal hydraulic code CATHARE. The paper presents the current state
of development of this model. Based on a literature survey and on comp
atibility considerations with respect to the existing CATHARE bottom r
eflooding package, a falling film top-down reflooding model was develo
ped and implemented into CATHARE version 1.3U. Following a brief revie
w of previous work, the paper describes the most important features of
the model. The model was validated with the Winfrith single-tube top-
down reflooding experiment and with the REWET-II simultaneous bottom a
nd top-down reflooding experiment in a rod bundle geometry. The result
s demonstrate the ability of the new package to describe the falling f
ilm rewetting phenomena and the main parametric trends both in a simpl
e analytical experimental set-up and in a much more complex rod bundle
reflooding experiment.