The VERCORS programme, which involves tests with short fuel-rod samples, has proved to be a rich source of information regarding FP release and tranport.

FARO (Furnace And Release Oven) experimental facility began the experiments of the LWR-MFCI phenomena in 1990 in collaboration with several reactor safety research organizations from European Union member countries and with the participation of the United States Nuclear Regulatory Commission.

The ARISG-I was developed to estimate the aerosol deposition in the near-field of tube breach under dry conditions. It was based on ‘filter concept’, which means that aerosol flowing through a bundle of obstacles is submitted to forces that tend to clean up the gas by removing particles onto obstacle surfaces. Under SGTR conditions, the major deposition mechanisms in the break stage are turbulent deposition and inertial impaction.

Complex measurements were performed at the integral high temperature test facility CODEX (COre Degradation Experiment) between 1995-2002 with electrically heated UO2 fuel rod bundles. The main advantages of the CODEX facility are the use of real UO2 pellets, the sophisticated data acquisition technique including aerosol measurements and the large flexibility in the selection of test conditions. The most imporant limitations are the use of fresh – non-irradited - fuel pellets and the application of electrical heating burdened with positive temperature feed-back effect.

The TOSQAN experimental vessel is a large stainless steel cylindrical enclosure (volume 7m3, height 4m, internal diameter 1.5m) with double walls. A coolant circulates in between the walls to regulate the wall temperature from 60 °C to 160 °C. Non radioactive aerosols, steam and non explosive gases can be injected at different controlled flow rates via diverse injection pipes located at different locations of the enclosure. Different instrumentation is used, namely PIV (particle image velocimetry), LDV (laser doppler velocimetry), rainbow refractometry, out of focus imaging and SRD (spontaneous Raman diffusion) spectrometry.

The Institute for Nuclear Research Pitesti was founded in 1971 as a unit of strategic importance, having as field of activity the scientific research, design, technological development and scientific and technical responsibility for the development of nuclear energy in Romania.

This programme sets out to reduce uncertainties when evaluating the environmental release of radioactive products such as iodine or ruthenium following a core meltdown accident in a pressurised water reactor (PWR). The experimental data gained from this programme are used to develop and validate numerical simulation tools needed to assess the consequences of such an accident and to evaluate the efficiency of the prevention means.

The experimental programme named KAJET is being performed to investigate features of a pressurized melt jet and the interaction with substratum material. Compact melt jets, rather than a spray-type melt release, are simulated using iron and aluminium oxide instead of corium. The melt is generated by a thermite reaction. The experiments provide general information about erosion processes and data for the validation of computer codes (or, if possible, simplified correlations) which then are able to transfer the results to reactor conditions.

(LWR OFF-NORMAL BEHAVIOUR INVESTIGATION) A Reactor Thermal-Hydraulic Safety Research Programme carried out by the Commission of the European Communities at the Ispra Site of the Joint Research Centre.

VITI (‘‘VIscosity Temperature Installation’’) facility has been developed to measure viscosity, density and surface tension on corium up to 2600 C by aerodynamic levitation. But it is also used as small crucibles heating for material interactions tests. Samples of less than 100 g can be studied in VITI.

The PREMIX experiments have been performed to study the premixing of sizable amounts of very hot oxidic melts with water when being released as a jet in a reasonably characterized way and with full optical access. Alumina at 2600 K from a thermite reaction was used to simulate the corium melt. A technique has been developed to retain the molten iron in the source so that the contribution of iron to the melt is well below 10 %. PREMIX involves the full physics of the mixing process including jet break-up and melt drop fragmentation. But, of course, on the other hand, the initial and boundary conditions are more difficult to control and to vary compared to experiments with solid spheres such as QUEOS.

In case of a steam explosion, e.g. as a consequence of a severe reactor accident, part of the thermal energy of the melt is transferred into mechanical energy. At Forschungszentrum Karlsruhe, the ECO experiments are being directed to measure the conversion factor under well-defined conditions. The programme was launched in 2000. Alumina from a thermite reaction is used as a simulating material instead of corium. Dimensions of the test facility as well as major test conditions, e.g. temperature and release mode of the melt, water inventory and test procedure, are based on the former PREMIX experiments (from 1994 to 1999).