Balunov B.F., Lychakov V.D., Scheglov A.A., Matyash A.S., Starukhina K.S.
I.I. Polzunov Scientific and Development Association on Research and Design of Power Equipment, Saint-Petersburg, Russia
This paper discusses the water and air-cooled passive heat removal systems, used to ensure safety of the nuclear power plants. On the basis of experiments with the model of the heat exchanger for the NPP-2006 passive heat removal system designed for the LNPP-2, the uneven distribution of steam consumption among the individual tubes of this heat exchanger was revealed. However, in the design mode of operation, characterized by the velocity pressure of the steam flow in the inlet of the upper collector of less than 1 kPa, this unevenness is not noticed. Test results of the emergency cooling system of the KLT-40S reactor show an analogy of turbulent convection in upward heating and downward cooling turbulent water flows. At the same time, there was a slight decrease in the heat transfer intensity at close values of the forced and natural heat transfer coefficients.
Thermal-hydraulic tests of six full-scale recirculation cooling plants with a staggered bundle array of cross-ribbed tubes show the preference of using the thermal calculation method outlined in RD 24.035.05-89 and allow to expand its range of application on the area of lower values of Reyn-olds numbers. Also in this paper we consider the use of recirculation cooling plants for reduction of the emergency pressure of the steam-air mixture under the containment shell. Results of the tests show that during the condensation of steam from the vapor-air mixture, the nominal thermal power of the tested recirculation cooling plant increases in four times. Simulation of the emergency mode, i.e. condensation of saturated steam at atmospheric pressure on the outer surface of the finned tubes with stopped fan and preserved designed flow rate of the cooling water increased thermal power in 20 times.
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