A1.01/06A Leak Detection System Medzamor NPP

Prior to this project the European Commission awarded a service contract to the Nuclear Research Institute (NRI), Czech Republic, to carry out detailed design studies to define an optimal solution for the introduction of the LBB (Leak-Before-Break) concept at Unit 2 of Metsamor NPP, Armenia. The subject of the LBB study was the primary circuit, including pressurizer's surge lines. This service contract included the development of detailed technical specifications for a new Leakage Detection System (LDS) that would satisfy LBB monitoring requirements and replace the old Acoustic Leak Monitoring System (ALMS).

Starting from the specifications developed within the NRI service contract, the main objective of the A1.01/06A project was to establish an LDS at Metsamor NPP, Unit 2. The work included designing, manufacturing and testing the required equipment, issuing the standard equipment certificates, then delivering equipment to the site, supervision of the installation, performing site testing, commissioning and acceptance testing, preparing design documentation, operating and maintenance instructions, providing specific training to personnel, supplying required spare parts, performing warranty repairs.

The installation of the LDS for LBB was successfully completed in 2008 by Skoda JS, Czech Republic, as main contractor. The new system is applicable for a timely detection of coolant leakages from the six main circulating loops and the connected surge lines, according to the international standard ISA-67.03-1982 (Standard for Light Water Reactor Coolant Pressure Boundary Leak Detection). The integrated detection system is based on three different detection sub-systems, each using a diverse measurement principle. The sensitivity of the system is at least 1.9 liter/min; a value required as minimum for a reliable and timely detection of surge line breaks. The LDS incorporates 3 monitoring subsystems, utilizing three different leakage detection methods, as follows:

• LEMOP (leakage detection based on acoustic measurements);
• HUMOS (leakage detection based on humidity measurements);
• RAMOS (leakage detection based on radiation level measurements).

The integrated LDS generates warnings and alarm signals in the Main Control Room (MCR) when a leak exceeding the allowed leakage limit is detected. The system monitors the 6 primary circuit loops and the associated surge line piping in the reactor confinement. The new LD system was subjected to a detailed in-situ validation procedure before entering regular operation and utilization in the MCR.