The Paks nuclear power plant is equipped with pressurized water reactors of the VVER-440/213 type. These plants have a number of special features, namely, six-loop primary circuit, horizontal steam generators, loop seal in both hot and cold legs, safety injection tank setpoint pressure higher than secondary pressure, etc. As a consequence of the special design solutions, the transient behavior of such a reactor system is different from the usual pressurized water reactor system behavior. To study the transient behavior of these plants, the PMK-2 integral-type facility, a thermal-hydraulic model of the Paks nuclear power plant, was designed and constructed.
A short description of the specific design solutions of the VVER-440/213-type plants is given with the modeling aspects and similarity criteria applied to the design of the PMK-2 facility. Since the startup of the facility in 1985, 48 experiments have been performed primarily in an international framework with the participation of several experts from European and overseas countries to study one- and two-phase natural circulation, loss-of-coolant accidents, special plant transients, and experiments in support of the accident management measures. The results of several experiments illustrate the system effects of special design solutions and the effectiveness of bleed-and-feed accident management measures. A brief commentary on the thermal-hydraulic system code validation is provided, and conclusions are offered.