DUKOVANY AND WATER

Water is a key raw material important for the operation of the Dukovany Nuclear Power Plant.  The source of utility water used at the power plant for transferring heat in the reactor, moderating the fission reaction, steam production for the generation of electricity in steam turbines, but also for cooling various technological systems and for conducting residual heat via a cooling tower, is the nearby Dalešice Waterworks on the River Jihlava.  Raw water is pumped to the power plant from the bottom reservoir of the Dalešice reservoir system and is placed in the gravity water cistern, and from there it flows to the power plant by gravity.  Aside from evaporation from the cooling towers which reaches a maximum of 1 cubic meter per second at full operation of all four Dukovany blocks in summer, the entire raw-water system is closed.  Excess wastewater and stormwater are conducted to a retention tank via a continuous detection system, and from there it is returned to the bottom reservoir of the Dalešice reservoir system via a natural channel.  In the entire history of the power plant, its operation never had to be interrupted due to the water level in the Dalešice reservoir system or due to summer temperatures.  Long-term measurements and studies conducted in the EIA process during the preparation of the NNS at this site have demonstrated a sufficient amount of water for operating a power plant with an aggregate capacity of up to 3,250 MWe.

The supply of drinking water for the entire power plant facility is provided by a drinking water line from the Znojmo area.

THE DALEŠICE RESERVOIR

The Dalešice waterworks was built as a source of raw process water for the Dukovany nuclear power plant.  It has been used for that purpose since 1978.  The waterworks consist of two reservoirs: the top reservoir in Dalešice, with a capacity of 127 mil. cubic metres, and the bottom balancing reservoir at Mohelno, which is 7 km long and whose dam is comprised of the concrete body of the flow-through Mohelno hydro power plant.  The divider between the two reservoirs is formed by the Dalešice pumped storage hydro power plant, with the highest functional gravity dam, 100 metres high.

Following the general repair and upgrade, the total capacity of the Dalešice PWHPP is 4x 120 MWe.  There are 4 units installed with reverse Francis turbines, for a gradient of 90 m, which operate both in the turbine mode for power generation and in a pumping mode.  Thanks to the gradient, it is a pumped storage hydro power plant with the fastest run-up speed, of 60 seconds, and therefore it plays an irreplaceable role in regulating the national energy system.

An integral part of the Dalešice reservoir is the Mohelno flow-through hydro power plant, with two units with a capacity of 1.2 MWe and 0.6 MWe.  The reservoir forms a lake that is 7 km long and holds 17.1 mil. cubic metres of water, as a source of cooling water for the Dukovany nuclear power plant.

Today, the water reservoir is also used for recreational purposes, for raising fish, for flood-reduction, and to improve the flow of water in the river during dry periods.