R1.07/03B - Novovoronezh NPP - Replacement of feed water control valves on one unit (AP ref 7.1.1.3-4)

Novovoronezh NPP operates three VVER reactors; Novovoronezh Unit 3 and 4 are VVER 440/V-179 models with a net capacity of 385MWe, and Novovoronezh Unit 5 is a V-187 reactor with a net capacity of 950MWe. Units 1 and 2 are permanently shutdown and under decommissioning. Construction of the first reactor at Novovoronezh site started in 1957 and the reactor began commercial operation in December 1964, while construction of the fifth reactor started in March 1974, and the reactor began operation in February 1981. Novovoronezh 3 and 4 are scheduled to close in 2016 and 2017, respectively, and Novovoronezh 5, after implementation of a number of safety improvement measures, in 2035. A new nuclear power plant at Novovoronezh site is being constructed, consisting of two VVER-1200 reactors, with two more such reactors proposed for operation in 2017-2019.

The feedwater control valve replacement strategy included the necessary materials, tools, equipment, spare parts, documentation and services required for the design, sub-supplies, manufacture, inspection, testing, cleaning, preservation, packing, delivery to site, warranty and training of NNPP staff, as well as technical supervision during installation, testing and commissioning.

The European Commission programmed replacement of feedwater control valves at Novovoronezh Unit 5 already in the framework of the TACIS 1997 nuclear safety programme. However, the project preparation experienced difficulties which resulted in delays, and the implementation phase of the project was eventually programmed in the TACIS 2003 nuclear safety programme.

This project aimed at improving the reliability of Novovoronezh NPP Unit 5 (VVER-1000/187) through a replacement of the main Steam Generator (SG) Feedwater Control Valves. These valves are designed to maintain the flowrate of feedwater and the SG level in accordance with power level during normal operation as well as transient conditions.
The IAEA issue books for VVER 1000 reactors (model V-320 and its predecessors, the so-called 'small series', including model V-187; See Refs. 1 and 2) indentified a low reliability of the feedwater control at VVER plants as a safety issue. Consequently the European Commission launched a project to address this issue in the framework of TACIS 2003' nuclear safety programme.
The overall objective of this project was to procure and install the new feedwater control valves at Novovoronezh Unit 5.

The contract was awarded to Russian Atommasheksport (Volgodonsk city), a winner of the European Commission tender. The supply contract was signed in September 2006.

The scope of supply included:

• Feedwater control valves for four steam generators, assembled with electric drive and actuating instrumentation;
• Set of spare parts according to the list of spare parts, including the spare parts for first overhaul;
• Specialized equipment and tools required for assembly, operation, repairs and verification;
• A set of reference rings;
• Electrical and I&C cables.

The supplier manufactured the valves, and performed factory acceptance tests (FAT) in November 2007; consequently the equipment was delivered to NvNPP in December 2007.

Note that the same manufacturer supplied feedwater control valves to Zaporozhe NPP in Ukraine under TACIS project U1.03/02B3 and that during the course of that project several problems were encountered with the valve actuators (see Contract 85720). This eventually resulted in the supplier replacing the defective valve actuators by another type of actuator from a different manufacturer. These problems were communicated to Novovoronezh NPP and the EC and NvNPP ensured that the lessons learned from the Zaporozhe project were implemented at Novovoronezh. Consequently, the valves supplied to NvNPP were installed with the same replacement actuators that were finally accepted at Zaporozhe NPP.

The installation was performed during the 2008 outage (14 July to 20 August 2007). The Provisional Acceptance Certificate was issued on 28 October 2008 which followed by a two-year warranty period.

The Final Acceptance Certificate was issued on 20 October 2010.

References

1. Safety Issues and their Ranking for WWER 100 model 320 NPPs, IAEA-EBP-WWER-05 (March 1996).
2. Safety Issues and their Ranking for 'Small Series' WWER-100 Nuclear Power Plants, IAEA-EBP-WWER-14 (September 2000).