Direct condensation of steam in a water tank at sub-atmospheric pressures

Abstract

In the nuclear fusion reactor, ITER, the Loss of Coolant Accident (LOCA) in the Vacuum Vessel has to be managed with pressure suppression systems working at sub-atmospheric pressure. The operating conditions differ considerably from those experienced in the fission nuclear power plants such as BWR. The direct condensation at sub-atmospheric conditions is not sufficiently known, therefore, the effectiveness of systems operating at these particular conditions have to be investigated experimentally. A research program is being carried out at the University of Pisa, funded by ITER, in order to study the steam direct condensation for nuclear fusion reactor conditions. For this purpose, an experimental test facility was designed and built and an extended experimental program was performed. Video cameras were used to visualize the steam condensation at different mass flow rates. This paper deals with the elaboration of images of the steam jet flowing from a hole in the water. The steam condensation regimes depend on three governing parameters: downstream exit pressure, water temperature and steam mass flow rate per hole. Moreover, the condensation regimes are characterized by different shapes of steam jet. The image analysis permitted to determine the heat transfer coefficient in the stable condensation regime at sub-atmospheric conditions. The results obtained are compared with those correspondent at steam condensation at atmospheric pressure, emphasizing the great importance of the downstream exit pressure and the subcooling on the steam condensation.

Experimental Analysis of Steam Condensation Heat Transfer Coefficient in Water Pool at Sub-Atmospheric Pressure

“…The measured values of videos 7606 and 7616 are plotted with already published HTC and L/D data [14], related to single steam plume in stable condensation regime (8 blue points in Figure 7 and Figure 8, respectively). Each point in the below figures represents a steam plume, an overall number of 44 plumes is therefore analysed in this work.…”

“…Guerrini of the University of Pisa. The available data set [14] was expanded adding 30 datapoint (7606) at B about equal to 0.5 (orange in the above figures) and 6 datapoint (7616) at lower B (i.e., about 0.15, green in the same figures). In particular, the HTC correlations of Hwan [4] and Yeon [3] and the L/D correlations of Chul [2] and Yeon [3] were taken as reference, having the closer range of validity (even if not precisely suitable) to the performed experimental tests.…”

“…In this scenario, the DCC effectiveness was investigated in an extended IOP Publishing doi:10.1088/1742-6596/2177/1/012041 2 experimental activity carried out at Department of Civil and Industrial Engineering (DICI) of the University of Pisa, aimed to contribute to fill the literature gap and supporting a knowledge advancement and dissemination. An experimental Small Scale Test Facility (SSTF) was arranged to experimentally simulate, in a Reduced Condensation Tank (RCT) of 4.5 m 3 , steam condensation in a water pool at subatmospheric pressure (up to 5 kPa abs) [12]- [14]. In particular, the postulated transient scenario occurring in one (Small LOCA Tank, SLT) of the four tanks of the VVPSS, as consequence of the ICE cat.…”

Experimental qualification of the ITER pressure suppression system by means of a large scale facility: assessment of similitude analysis

“…The reduced experimental rig SSTF [2][3][4][5] was designed, assembled, instrumented, commissioned and operated at lab. Guerrini UNIPI-DICI for investigating steam condensation in water pool at pressure lower than atmospheric values and evaluating the contribution of the affecting parameters: water pool temperature, water head over the injection hole/s, cover gas pressure and steam mass flow rate discharged.…”

“…Under financial support of ITER Organization (IO) an extensive experimental programme was performed at the laboratory B. Guerrini of the University of Pisa, Department of Civil and Industrial Engineering (DICI), adopting a smallscale test facility (SSTF) [2][3][4][5]. The main component is the reduced condensation tank (RCT) of 4.5 m 3 (about 1/22 scale factor), partially filled with water having a cover gas in vacuum conditions up to 10 kPa abs.…”