Joint project

The RASPLAV* Project was regarded as a successor to the Three Mile Island Vessel Investigation Project (TMI-VIP)  completed in 1993. The TMI-VIP Project was set up to examine and assess the condition of the actual TMI lower head and thus offered a unique opportunity to study a severe accident in a commercial nuclear power plant. However, in order to better understand and model the complex phenomena taking place during interaction of molten fuel with the reactor vessel lower head, it was necessary to reproduce this interaction in a controlled environment where the governing parameters can be varied over a range of interest. This was the main objective of the RASPLAV Project.

The RASPLAV Project proposed to refine accident management strategies during a reactor core meltdown. Little was known about the complex interactions that took place during a core meltdown, so one of the project's primary goals was to develop an understanding of the process. The information gathered during the tests conducted at the Kurchatov Institute allowed scientists to develop models of a core meltdown. These models could then be used in the design of new reactors and to streamline accident management procedures already in place.

Two aspects of accident management were considered in the project. One was for existing reactors, where external cooling may not have been practical – the process and time sequence before melt-through were studied. This was to help develop management strategies for severe accidents. The other was for future and some existing reactor design to determine the heat transfer conditions under which cavity flooding could be a viable accident management option.

The project was done in two successive phases. The first phase was primarily dedicated to building the experimental and analytical infrastructure  The second phase investigated the progression of a severe accident, specifically the thermal loading imposed by a corium pool on the lower head of a light water reactor (LWR) vessel.

The project objectives were to:

  • obtain relevant data on the physical and thermal behaviour of the corium in large-scale tests
  • derive thermal-physical property data for various molten core materials
  • investigate the effects of stratification of molten materials.

The programme of work involved the use of the large facilities available at the Kurtchatov Institute in Russia. Four large-scale tests were carried out and were complemented by a series of smaller-scale experiments, all involving the use of materials representative of power reactor cores. Experiments with the test materials in molten conditions required temperatures of approximately 3000°C - a very challenging task, especially for large-scale tests. The analytical work was done at the Nuclear Safety Institute of the Russian Academy of Sciences (IBRAE).

After successful conclusion of the project in June 2000, the results were released in a final report (available below) presented and reviewed in November 2000 at the concluding Rasplav seminar, sponsored by the NEA and hosted by the German Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) in Munich, Germany. The project data remained proprietary until 2003.

Project data

The data abstract is public.

*Note: Rasplav (Cyrillic: расплав) is the Russian word for melt.


Belgium, Canada, Czech Republic, Finland, France, Germany, Hungary, Italy, Japan, Netherlands, Korea, Russia, Spain, Sweden, Switzerland, United Kingdom and United States

Project period

July 1994-June 2000


USD 6.9 million