A research program on reflood of an overheated core and corresponding topics is running at KIT, including large scale bundle tests at IAM-WPT , various kinds of separate-effects tests at IAM-AWP , model development and code application.

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.

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 objective of the EMAIC (Emission AIC) facility is to characterise the physico-chemical nature of the aerosol source term resulting from the vaporisation of control rod material made of the metals Silver (Ag), indium (In), Cadmium (Cd) after their cladding rupture during a PWR severe accident.

(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.

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.

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.

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.

Boron carbide rod degradation test and associated releases.

The experimental programme becarre (2001-2010) belongs to the international “source term” programme. The becarre programme Objectives involve better understanding the degradation phenomena occurring in boron carbide (B4c) control rods during a core meltdown accident and determining the laws governing steam oxidation of B4c pellets and relocated mixtures. These laws will be used to both quantify the gases produced during oxidation, and estimate their potential effect upon iodine releases into the environment. The programme results will help improve the icare 2 code which is being developed by irsn.

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 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.

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.