Izvestia Vysshikh Uchebnykh Zawedeniy. Yadernaya Energetika

The peer-reviewed scientific and technology journal. ISSN: 0204-3327

Experimental estimation of the effect of contact condensation of steam-gas mixture on the VVER passive safety systems operation

3/22/2017 2017 - #01 Global safety, reliability and diagnostics of nuclear power installations

Morozov A.V.

DOI: https://doi.org/10.26583/npe.2017.1.02

UDC: 621.039.58:536.423.4

The paper presents the results of experimental study of the effect of contact condensation of steam-gas mixture on the operation of VVER passive safety systems and the steam generator in emergency condensing mode. The contact condensation takes place when subcooled fluid is supplied in the accumulator tank of VVER reactor facility passive core flooding system (the HA-2 system) in the presence of non-condensable gases. Water supplied to the second stage of hydro accumulators can be used for increasing the operating time of the VVER steam generator in the emergency condensing mode and ensuring longer core cooling. Low liquid outlet velocity (less than 1 m/sec), necessitated to ensure safety systems operation in passive mode constitutes the distinguishing feature of the investigated processes.

The experiments were performed on the test facility with the parameters specific to the primary circuit of the reactor facility within 24 hours after the accident initiation for different concentrations of gas in the steam-gas mixture. Nitrogen and helium, which replaces hydrogen, were used as the non-condensable gases. It was established as the result of the experiments that the increase of concentration of non-condensable gas in the volume the HA-2 hydro accumulator model up to 45% leads to the reduction of intensity of contact condensation of steam from the steam-gas mixture by ~29% in the experiment with nitrogen and by ~57% in the experiment with helium. The obtained experimental data can be used for numerical simulation of emergency processes in the VVER reactor facility during operation of passive safety systems taking into account the removal of steam-gas mixture from steam generator by supplying the subcooled liquid jet into the volume of second stage HA-2 accumulator tanks.

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VVER steam generator condensation mode contact condensation non-condensable gases steam-gas mixture