DescriptionUnder an IAEA regional project, a severe accident simulation trainer known as MELSIM is being developed for operators of Russian-designed WWER-440/213 nuclear plants. The trainer is a personal computer-based system that also serves to evaluate accident management strategies and to assess complex interfaces between emergency operating procedures and accident management guidelines. The trainer utilizes several computers working simultaneously on different areas of the simulation. Detailed plant operation displays, portions of which are shown here, are provided on colour monitor screens which show changing plant conditions.