Two International Standard Problems (ISP) have been successfully concluded in 2003. The ISP-41, performed in three steps, including comparison with experiments and parametric calculations, was purely dealing with iodine chemistry in the containment. The integral ISP-46 on the Phébus FPT-1 experiment included one part devoted to the same issue. The main outcomes from both exercises are first summarised. Then the lessons learnt on modelling and integral aspects as well as the implications for plant studies are given. Some weaknesses are still remaining in the iodine chemistry models and codes. They have been identified, and improvement is expected from the results of newly launched experimental programmes and from modelling effort.
(1) : IRSN
(2) : GRS