U1.01/01 A Rovno NPP - Reconstruction of primary circuit overpressure protection system for Units 1 & 2 of Rovno Nuclear Power Plant, Kuznetsovsk, Ukraine

The primary overpressure protection system is designed to protect the reactor equipment and pipelines against primary circuit overpressure phenomena during different transients.

The primary overpressure protection system of Rovno NPP units 1 and 2 consists of two independent PORVs (pilot operated relief valves) connected to the pressurizer, each of which consists of one main valve (MV) and two pilot valves (PVs).

The original pressurizer PORVs were designed according to the regulations in force at the time of their manufacture (late 1970s) and installed in accordance with the existing design specifications. They were not compliant with modern requirements, safety standards and regulations in force, and, in particular, suffered from the following shortcomings/problems:

• the PORVs were not qualified for operation with steam-water mixture and water
• valve position indications were not available in control rooms
• cold overpressure protection of the primary circuit was not ensured
• the PORVs did not allow application of the 'feed & bleed' procedure
• piping resistance to loads resulting from certain transient and accident situations was not guaranteed.

It was therefore decided to reconstruct the primary circuit overpressure protection system at Units 1 and 2 of Rovno NPP in the frame of the TACIS 2001 programme for Ukraine.

The subject of the contract was the reconstruction of the primary circuit overpressure protection system at units 1 & 2 of Rovno NPP (VVER 440/V213) in order to solve the shortcomings/problems of the existing system.

It included project management, design, manufacture, testing and delivery of material and equipment for the overpressure protection system modernisation. The scope also included supervision of installation and commissioning, acceptance testing, support to licensing, certification, documentation and training of End User personnel by the Contractor.

The modernisation of the primary circuit overpressure protection system also provided the opportunity to modernise the related I&C and the scope of supply therefore also included the delivery of sensors and secondary devices for I&C modernisation.

The scope of the work covered by the contract included:

• Design of the new primary circuit overpressure protection system
• Supply of Pressurizer Pilot-operated Relief Valves (4 sets)
• Supply of the required I&C, I&C cabinets and software for each PORV
• Supply of diagnostic and monitoring systems for each PORV
• Supply of pressure measurement devices
• Supply of hermetic cable penetrations
• Supply of required spare parts, tools, testing devices and accessories

The tender procedure was originally launched in December 2003, but the procedure failed because the tender price significantly exceeded the available budget. It was necessary to re-evaluate the distribution of activities between the Contractor and the End User/Beneficiary and to give more responsibility to the latter for parts of the scope of the work. The Technical Specifications were modified accordingly and the tender procedure was re-launched with a successful conclusion.

The equipment and services were provided in accordance with the contract requirements. The general timetable of the activities was as follows:

• 2003 – 2004: Tender Launch and Signature of the supply contract
• 2004 – 2005: Detailed Design, preparation of the design documentation including the Technical Specification for Supply (TSFS)
• 2005 – 2006: Manufacturing & Factory Acceptance Testing
• December 2006: Delivery of safety valves and control system to RNPP
• 2007: Installation & Commissioning at Units 1&2
• 2008: Monitoring of 1 year warranty period
• Final Acceptance Certificates were signed for the installations in both Units in December 2008.

The achievement of this project increased significantly the safety and reliability of the plant.