The aim of the DEFOR (Debris Bed Formation) program is clarification of the phenomena that govern formation of the debris bed in different scenarios of corium melt release into a deep water pool and quantification of the debris bed properties related to coolability.

The CHIP programme aims to reduce the level of uncertainty on radioactive iodine releases during a core meltdown accident in a nuclear reactor. The programme results will also be used to better define the means and measures to be implemented in order to limit such releases.

The KROTOS test facility is a relatively small scale experimental installation dedicated to the study of:

• (a) molten fuel-coolant pre-mixing either with prototypic reactor melts or simulants such as alumina up to 5 kg;
• (b) progression and energetics of spontaneous and triggered fuel-coolant interactions (vapor explosions).

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.

The KROTOS test facility is a relatively small scale experimental installation dedicated to the study of: (a) molten fuel-coolant pre-mixing either with prototypic reactor melts or simulants such as alumina up to 5 kg; (b) progression and energetics of spontaneous and triggered fuel-coolant interactions (vapor explosions).

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.

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.

Determination of the vaporization rate according to the composition and the thermodynamic conditions of the corium (with FP simulants) was the aim of the COLIMA (COrium LIquid and MAterials) experiments. The facility provided representative conditions of the aerosols suspended inside the containment of PWRs under a severe accident.

The VULCANO facility is mainly composed of a furnace and a test section, which is thoroughly instrumented. In the experiments with prototypic material the furnace has the following characteristics:

• Capability to melt oxidic mixtures of various compositions (UO2, ZrO2, SiO2, FeOx) with the possible addition of metals.
• Liquidus temperature of the load between 1700 and 2900 °C.
• Capacity to melt & pour 100 kg. •Continuous low pouring rates (0.1–1 l/s).

The test section of the facility consists of a scaled-down model of VVER-440 steam generator, which has a bundle of 38 tubes with inlet and outlet chambers (hot and cold chamber, respectively), and a secondary side with the steam outlet line but without droplet separators and steam dryers.

The aim of the RECI (RECombiner & Iodine) program was to quantify the iodide → iodine conversion in realistic conditions of recombiner operation, albeit under the following constraints: the experiments were to be performed with non-radioactive substances, and without hydrogen. The comprehensive tests grid allowed to investigate into the decomposition of cesium and cadmium iodides under thermal-hydraulics conditions that mimics the recombiner operation, despite the technical limitations of the RECI test bench.

SIMECO program at KTH was performed to investigate the heat transfer of natural convection in an internal heated liquid pool, simulating a molten corium pool which may be formed in the reactor lower plenum during a severe accident.