R1.07/04D - Steam Generator Emergency Feed-Water System at Novovoronezh NPP - Lot 2 : Stop, Check and Control valves

The emergency feedwater system (EFWS) at Novovoronezh NPP Unit 5 (VVER-1000/V187) is used to supply feedwater to its four steam generators (SG) in emergency situations and also in start-up and shutdown conditions.

Before the project implementation, all three EFWS pumps were located in one common compartment close to each other, which posed a considerable risk of their simultaneous failure due to a common cause (a fire, flooding, etc. of the compartment). Moreover, the emergency feedwater was distributed to the four SGs through an emergency feedwater header and emergency feedwater lines that were not fully physically separated from the normal operating feedwater system.

Such a configuration imposed elevated risk of the entire feedwater system failure due to a common cause resulting in deterioration of residual heat removal from the reactor in case of a serious accident. This possible loss of a basic safety function (reactor residual heat removal) has been identified by the IAEA as a safety issue of category III.

In the frame of the Novovoronezh NPP Unit 5 Safety Enhancement Programme, an additional EFWS that would meet current safety requirements was to be installed. The EFWS installation project included construction of a separate building for the system housing, installation of the new system equipment, its connection to the existing systems, necessary checks and tests, preparation of the operational and maintenance documentation and system commissioning.

The EFWS had to consist of three redundant trains with each train including:

• demineralised water tank of 1000 m3 volume
• pump set supplying up to 150 m3/h of water into SG at related pressure
• low-pressure and high-pressure pipelines
• associated valves
• sensors and other instrumentation
• independent essential power supply.

This main EFWS equipment had to be supplied through the R1.07/04D project established within the TACIS Nuclear Safety Programme and financed by the European Commission. The equipment supply was divided into 4 lots and implemented under three separate contracts:

1. supply contract number 99580 on the Lot 1
2. supply contract number 129848 on the Lot 2
3. supply contract number 129486 on the Lot 3 and Lot 4.

The objective of the 129848 contract on the Lot 2 was delivery, installation and testing of the following valves designed and manufactured for use at NPP and compatible with the existing interfaces at the NvNPP Unit 5:

1. isolation (stop) valves including
   • 9x high-pressure motor-operated isolation valve DI 150 mm (DI = Diameter Internal)
   • 3x low-pressure motor-operated isolation valve DI 200 mm
   • 3x low-pressure motor-operated isolation valve DI 50 mm
   • 9x low-pressure manually operated isolation valve DI 80 mm
2. 13x high-pressure check valve with remote position indicator, DI 150 mm
3. 6x high-pressure motor-operated control valve, DI 150 mm
4. 1x low-pressure manually operated isolation valve for common industrial application, DI 50 mm
5. 1x low-pressure check valve for common industrial application, DI 50 mm
6. Set of welding rings
7. Special assembling, testing and maintenance tools

A part of the contract were factory and site acceptance tests, contractor’s assistance in on-site installation, pre-commissioning functional tests and EFWS integration tests, delivery of design, operating and maintenance documentation, necessary certificates, delivery of spare parts of the individual valves, training of maintenance and operations personnel and after-sales services (maintenance support).

This contract was concluded with the Corporation Splav. The contract value was € 697,855.09.

The contract was signed on 9.2.2007 and the implementation started on 10.2.2007; the place of equipment acceptance was Novovoronezh NPP. The Kick-off Meeting of the contract took place on 16.5.2007. According to the original contract, the equipment had to be delivered within 16 months, but by the Contract Addendum 3, the time limits for delivery was extended to 30 months for the isolation and check valves and to 34 months for the control valves.

The equipment was fully delivered on 2.8.2010 and the installation was finished on 30.8. 2010. The End User personnel training was performed within 5 days in March 2010. The provisional acceptance tests were performed and Provisional Acceptance Certificate was issued on 18.9.2011. The Final Acceptance Certificate was issued after expiry of the 1-year warranty period on 18.9.2012.