The essential technological distinctions of the AES-2006 project with VVER-1200 reactor, equipped with passive safety systems, determine some specifics in the character of accidents with the coolant leaks from the reactor primary circuit and the refusal of active part of the emergency core cooling system.

In the case of an accident with depressurization of the reactor primary circuit, the system of passive heat removal (PHRS) ensures the transition of steam generators (SG) into the mode of steam condensation. As a result, a condensate comes to the core, providing its additional cooling. But in the case of beyond design basis accident the rupture of second circuit pipelines or PHRS steam-condensation path is possible. At such type of accidents the feed water level in SG vessel will be decrease, what can results in the deterioration of its condensation power.

For experimental investigation of the condensation mode of VVER steam generator, a large scale HA2M-SG test facility was constructed in IPPE. The test facility incorporates VVER reactor SG model with volumetric-power scale of piping is 1:46, PHRS heat exchanger imitator, cooling by process water and buffer tank, equipped by steam supply system from the IPPE heat power plant. The facility main equipment connected by pipelines and equipped by valves. The elevations of the main equipment correspond to those of reactor project.

Experiments at the HA2M-SG test facility have been performed at the pressure 0.36 MPa, correspond to VVER reactor pressure at the last stage of the beyond design basis accident. On the base of the results of these experiments the correlation of condensation power from feed water level in SG model was obtained. The results of carried out tests make it possible to draw a conclusion about sufficiently large stability of VVER steam generator working in condensation mode to feed water level decreasing.

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