Raising the Danube bed threshold at the Paks Nuclear Power Plant Raising the Danube bed threshold at the Paks Nuclear Power Plant

Raising the Danube bed threshold at the Paks Nuclear Power Plant Raising the Danube bed threshold at the Paks Nuclear Power Plant
The purpose of the planned intervention is to ensure that sufficient water is available for the safe operation of the cooling system of the Paks Nuclear Power Plant, even when the Danube water level is extremely low. One of the possible technical means for this is the bottom rib to be created in the river section between the cold and hot water channel, which will raise the water level in the vicinity of the NPPs water extraction structure in case of low water. At the same time, the sealing of the cold water channel and the determination of the required pump capacity are also being developed, so that the safety cooling water is available in an emergency. An updated hydraulic model created by combining a LIDAR survey made in 2013 and the most recent bed survey provides the basic data for the design. When compiling the construction technology, we strove to ensure that the water level required for the safe operation of the Paks Nuclear Power Plant is reached as soon as possible, before the end of the investment, with parallel work processes. The transverse structure of the planned facility consists of two split sections. One section is the sunken sill located below the current water level, while the other section is a rib 1.0 meters higher than the sill. In order to avoid underwater washout, a 1.0-meter-thick stone cover is required for a length of 250 meters. The water level can already be raised by the transversal work, so the safe operation of the nuclear power plant will occur within 45 days from the start of construction, even in case of a record low Danube water flow. A bottleneck in the implementation of the intervention is the production capacity of the surveyed quarries and the transport distance. The use of the 2.7-ton, 1x1-meter concrete blocks in Dunakiliti was examined for the quantitative replacement of the water construction stone, but the contractors transportation costs came out to be unrealistically high. It would be advisable to examine the utilization of the transport capacity of the Hungarian Armed Forces. In order to speed up the work, the construction can be divided into 2 well-separated work areas. The first is the work area on the right bank according to the direction of flow, which is located in the section between the cold and hot water channels of the Paks Danube nuclear power plant. Access to the work area can only take place through the area of the Nuclear Power Plant. The stone will be transported directly to the place of installation by trucks with the help of floating works assembled as a bridge, provided by an external contractor. The other work area is the left bank part of the Danube riverbed, which belongs to the economic area of Dunaszentbenedek. The planned facility will be built using dry technology, as a stone rib that gradually builds up from the shore towards the middle of the river. For the implementation, the construction machinery - with the exception of trucks - and manpower will be provided by the staff of the Hungarian Armed Forces. Traffic on the Danube waterway cannot be ensured during the construction period. After construction, as soon as the improved hydrological situation allows, the sunken threshold must be demolished by 1.0 meters, thereby making the waterway safe again. More details in the technical description and design documentation, which are part of the public procurement documents.