SHORT DESCRIPTION OF THE PMK-2

The PMK-2 is a scaled-down model of the Paks Nuclear Power Plant equipped with VVER-440/213-type reactors of Soviet design. It is a full pressure model of the plant with a volume and power scaling of 1:2070. Due to the importance of gravitational forces in both single- and two-phase flow the elevation ratio is 1:1 except for the lower plenum and pressuriser . The six loops of the plant are modelled by a single active loop. The coolant is water under the same operating conditions as in the plant, so transients can be started from nominal operating conditions.

The core model consists of 19 electrically heated rods with uniform power distribution. In the core the heated length, spacer type and elevations, as well as the channel flow area are the same as in the Paks NPP. The main circulating pump of the PMK-2 serves to produce the nominal operating conditions and to simulate the flow coast-down following pump trip. The pump cannot be applied to two-phase conditions; therefore it is accommodated in a by-pass line. The flow coast-down is modelled by closing a control valve. For natural circulation the by-passed cold leg part is opened. The horizontal design of the VVER-440 steam generator is modelled by horizontal heat transfer tubes between hot and cold vertical collectors in the primary side. In the secondary side of the steam generator the steam/water volume ratio is maintained. From the emergency core cooling systems the four hydroaccumulators of the Paks NPP are modelled by two vessels. They are connected to the downcomer and upper plenum similar to those of the reference system. The high and low-pressure injection systems are modelled by the use of piston pumps.

In the first design of the PMK-NVH facility only the primary circuit of plant was modelled. This version was used until 1990. The PMK-2 facility is an upgraded version - first of all by addition of a controlled secondary heat removal system - extending the capability of the test loop to transient processes initiated by events in the secondary circuit.

PMK-2

Feedwater pump