The Material Scaling (MASCA) Project was a follow-up of the RASPLAV Project  and investigated in-vessel phenomena during a severe accident. Specifically, it addressed the influence of the chemical composition of molten corium on heat transfer to the pressure vessel environment. The project addressed this by investigating stratification phenomena of the molten pool and the partitioning of fission products (FP) within the different layers of the melt. The project was scheduled to be completed in July 2003, but continued until 2006 under the project's second phase (MASCA-2), given the experimental needs that still existed and the quality of the experimental work done up to that point.

MASCA phases

First phase (2000-2003)

The first phase of tests aimed to resolve remaining uncertainties about the heat load on the reactor vessel and thus the possibility of retaining the melt in the vessel. These uncertainties are mainly associated with scaling effects and coupling between the thermal-hydraulic and chemical behaviour of the melt. Supporting experiments and analyses, in addition to helping understand key in-vessel phenomena, facilitated a consistent interpretation of the results. The experiments were carried out with corium compositions prototypical of power reactors which use iron and steel materials. The MASCA experimental goal was achieved through corium tests of different scale and was complemented by pre- and post-test analyses and development of computational models. Additional measurements of thermo-physical properties of the melts such as density, thermal conductivity and liquidus-solidus temperatures considerably expanded the material properties data obtained during the RASPLAV Project.

The major goals of the MASCA Project were to:

• investigate the influence of chemical behavior on heat transfer in stratified molten pools of prototypical compositions
• investigate FP behaviour in a molten pool and in particular:
  • partitioning of FP between layers in case of stratification
  • partitioning of FP between phases during melting and solidification
  • distribution of FP simulants in the melts
• expand the material properties database
• develop computer models describing the relevant phenomena.

Separate effects were studied in series of small- and mid-scale experiments. Corium tests were performed in the RASPLAV, TULPAN, TF, STF, KORPUS, and TIGEL facilities. Salt tests were performed in the RASPLAV-A-Salt-3 facility.

Second phase (2003-2007)

The second phase (MASCA-2) was an extension of the first one. It was based on experiments that were mainly carried out at the Kurchatov Institute and that made use of a variety of facilities in which the corium compositions prototypical of power reactors could be tested. The tests aimed to provide experimental information on the phase equilibrium for different corium mixture compositions that can occur in water reactors. In order to enhance the application of MASCA results for reactor cases, the influence of an oxidising atmosphere and the impact of non-uniform temperatures (presence of crusts or solid debris) was addressed. The programme was also intended to generate data on the relevant physical properties of mixtures and alloys that were important for the development of qualified mechanistic models.

The first meeting of the MASCA-2 project was held in October 2003 in Madrid, Spain. The refurbishment of several facilities began in order to accommodate the specific requirements of the new test conditions. A MASCA seminar was held in June 2004 to review the project results to date. A project integration report was provided to participants and a MASCA-2 conluding seminar was held on 11-12 October 2007 in Cadarache, France.

Project data

The data abstract is public.