R1.02/03A - Balakovo NPP - Acoustic Leakage Monitoring System for one Unit (ref AP 7.1.1.3-1)

Balakovo Nuclear Power Plant has four units completed and in operation; all units are of the VVER 1000-V320 type.

In the framework of the Tacis 97 Nuclear Safety Programme, the Contracting Authority (concern ROSENERGOATOM) and the End-User (Balakovo Nuclear Power Plant) requested a project to improve the operational safety of Unit 1 at the Balakovo NPP by installing a Leakage Monitoring System (LMS) for detecting potential leaks of coolant from the components and the piping systems of the primary circuit.

The main purpose of the Leakage Monitoring System (LMS) to be installed on the primary circuit is to:

• Detect, locate and assess the rate of coolant leaks that may appear in selected equipment and piping of the primary circuit and to produce related alarms to the operating personnel;
• Serve as a means of fulfilling the regulatory requirement for the continuous monitoring of the structural integrity of the primary pressure barrier within the containment, under normal and upset operating conditions.

The LMS will allow, in an early stage of the leak development, to take appropriate measures to prevent further incident/accident.

While ensuring the above functions, the LMS also supports the prevention of releases of radioactivity into the environment and therefore represents an effective measure for improving the nuclear safety of the unit.

No preference was pre-set concerning the basic functioning principle of the LMS. At the time, 2 LMS principles, acoustic and humidity, were known for implementation in NPPs. The choice of either humidity or acoustic principle, or any other principle of operation, provided that it was industrially proven and that it fulfilled the functions and requirements set out in the Technical Specification, was left to the Tenderer to propose.

The objective of the contract was the design, manufacture, conformity certification, factory acceptance testing, delivery, assistance to the End-User during licensing, supervision of installation, supervision of site acceptance testing and commissioning of a Leakage Monitoring System (LMS) for components and piping systems of the primary circuit of one unit at Balakovo NPP. The scope of work also included the provision of documentation, training and instruction in the use of the equipment, supervision of the first scheduled maintenance and the provision of spare parts.

The system to be supplied had to ensure the detection of leaks from the reactor upper unit and the pressurizer piping systems:

Reactor Upper Unit

The LMS to be supplied had to ensure the monitoring of the reactor upper unit (reactor vessel head equipment) which includes the following:

• Nozzle flanges of the RCPS (Reactor Control Protection System) actuators, neutron flux monitoring channels, temperature monitoring (total 91 flanges);
• Neutron flux monitoring jackets (total 16 jackets, 4 flange connections for each jacket);
• Conic sealing for the RCPS actuator jackets (total 61 seals);
• Flange of the air extraction pipeline from under the reactor head (2 flanges).

Pressurizer

• Nozzles, welds, bends of DN350 pipelines of the pressurizer surge line, along the whole length of the pipeline
• Nozzles, welds, bends of DN200 and DN100 pipelines of the coolant injection into the pressurizer.

The system comprised:

• Leakage monitoring and data processing equipment;
• Devices and parts for mounting, fastening and connecting the sensors;
• Cables and connection devices;
• All devices and components necessary for interfacing the new equipment with the visualisation and alarm equipment in the main control room and shutdown control room;
• All parts and devices, as well as special tools, necessary for installing, connecting, testing, calibration, commissioning, operating and maintaining the systems;
• Spare parts and consumables in quantities sufficient for 5 years of operation after the expiration of the warranty;
• All equipment and software associated to the acquisition of the necessary measurement signals, to their processing, to the performance of associated diagnostics and to associated Man-Machine-Interface ;
• All necessary simulation means for the system testing on-site;
• All necessary documentation in English and Russian;

The equipment to be supplied should be qualified according to Russian requirements and confirmed with the corresponding certificates. The Leakage Monitoring System had to meet the standards and safety qualifications according to Russian NPP requirements.

The Call for Tender was launched in February 2006 and tenders were evaluated in April 2006. The contract was signed with BALTIJOS INFORMACINES SISTEMOS UAB on 1 September 2006. The equipment was manufactured and the Factory Acceptance Testing (FAT) took place on 26-27 June 2008. Following correction of some deviations noted during the FAT, the equipment was delivered to Balakovo NPP in August 2008 and installed during the following outage in September/October 2008. Site Acceptance Testing (SAT) took place on 5-6 November 2008. Following correction of some deviations noted during the SAT, the system was accepted for putting into trial operation on 1 December 2008. The Provisional Acceptance Certificate was signed on 26 February 2009. The one year warranty period passed without incident and the project was closed.