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).

Short fuel rod experiments were carried out in the framework of the EU 5FWP COLOSS Project. The simultaneous dissolution of UO2 pellets and ZrO2 by molten Zr was investigated with PWR and VVER samples.

The PACTEL facility is designed to model the thermal-hydraulic behavior of VVER-440 type pressurized water reactors currently used in Finland. These reactors have several unique features that differ from other PWR designs

This facility comprises a water supply pipe, a quartz test section (110, 180 or 290 mm diameter) in which the debris bed is placed, together with its instrumentation, and a steam relief pipe. It is used to conduct refl ooding tests by means of injecting water onto a bed of metal particles heated by induction. The instrumentation measures the different temperatures and pressures in the debris bed, the fl ow of injected water and the fl ow of generated steam.

Facility consists of the hemispherical test vessel, a volumetric heating system in the test vessel to simulate the decay heat, a heating furnace to generate and pour the simulated corium melt, and a multitude of instrumentation to characterize the status of the melt. The test vessel is a 1:5 scaled RPV of a typical PWR with no penetrations of the lower head, and is equipped with different measurement techniques like heat flux sensors and thermocouples. The hemispherical bottom is closed by an upper lid and different openings in this upper lid allow the pour of melt to the central region or close to the perimeter of the lower head. Test vessel can be cooled by water or air at the outer surface, as it is surrounded by a second cooling vessel.

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 REKO-3 test facility allows the investigation of catalyst samples inside a vertical flow channel under well defined conditions comprising gas mixture, flow rate and inlet temperature.

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.

Condensation studies at LUT started with an open pool test facility (POOLEX) modeling the suppression pool of the BWR containment. During the years 2002-2006, the facility had several modifications and enhancements as well as improvements of instrumentation before it was replaced with a more versatile PPOOLEX facility in the end of 2006

The DISCO-C facility serves to investigate melt dispersal from the reactor pit when the reactor pressure vessel lower head fails at low system pressure of less than 2 MPa. The fluid dynamics of the dispersion process is studied using model fluids, water or bismuth alloy instead of corium, and nitrogen or helium instead of steam. The effects of different breach sizes and locations, and different failure pressures on the dispersion can be studied.

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).

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.