Type of Facility: Source Term


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.


In severe accidents with primary-to-secondary leakages, the retention of fission products in horizontal steam generators is poorly understood. The understanding of fission product deposition in realistic steam generator conditions is needed in realistic release estimates in PSA studies, and to design efficient accident management procedures. This is considered very important because steam generator tube rupture sequences are included in the risk dominant sequences.

Tube dimensions of the HORIZON model steam generator and Loviisa VVER-440 steam generators are approximately same. Thus it can be assumed that experiments give realistic results.

In addition to the steam generator section itself, the HORIZON facility includes a lot of equipment needed for steam and aerosol generation, and for measuring the thermal-hydraulic parameters as well as the aerosols concentrations.

The inlet and outlet chamber aerosol mass concentration is monitored with Tapered Element Oscillating Microbalance (TEOM) on-line mass monitor and the particle size distribution is measured on-line with the Electrical Low Pressure Impactor (ELPI). Aerosol sampling system includes heated sampling lines, two diluters (first diluter in system pressure is computer controlled and uses heated dilution air), pressure reducer and sampling valves. It is possible to change sampling point between inlet and outlet chambers.
Facility is dismanteled.

Type of Facility: 
Source Term
Number of experiments: