This communication presents a first set of experiments dedicated to the stu
dy of the interactions between caesium and UO2 particles emitted at 2300 de
grees C from a reconstituted nuclear fuel and deposited onto relatively ine
rt surfaces (Al foils). It demonstrates that any further behaviour of Cs st
rongly depends on the temperature and on the oxidizing potential of the atm
osphere acting on deposited radioactive particles.