ZAT continues the modernization of RRCS systems for Kozloduy NPP

ZAT is successfully continuing the implementation of the Reactor Rod Control System (RRCS) modernization project for Units 5 and 6 of the Kozloduy Nuclear Power Plant in Bulgaria.
In July 2025, FAT tests of the RRCS equipment for Unit 5 of Kozloduy NPP in Bulgaria were carried out at our company’s premises, with the participation of representatives from the nuclear power plant and the main subcontractor, ES Group Europe.

“This is one of our key products, implemented on the ZAT SandRA Z100 platform. The system for Kozloduy NPP, equipped with VVER-1000 reactors, consists of 44 control cabinets, 21 transformers, equipment for the main and emergency control rooms, and service components. The design and manufacturing of such a volume of equipment for both plant units took two and a half years,” says Karel Stočes, ZAT Marketing and Sales Director.

As part of the FAT tests, the control algorithms and the diagnostic part of the system, including visualization and archiving in the SandRA Horus HMI software, were successfully verified. All tests were completed successfully, including a 72-hour comprehensive continuous operation test.

The first part of the delivery, i.e., the RRCS system for Unit 6 of Kozloduy NPP, was shipped in the first quarter of this year. Installation of the equipment will take place during the scheduled outages in 2025 and 2026. The aim of replacing the RRCS equipment was not only to obtain a modernized system but also to enable a future transition to non-Russian reactor rod control drives.

The RRCS from ZAT is the only system on the market capable of operating with all known types of reactor control rod drives for VVER-1000 units and newer generations, including VVER-1200, as well as with LKP-M/4 drives with a design service life of 40 years. “The ability to work with all available drives has been verified on the manufacturers’ test stands. At the same time, the system allows for increased maneuverability of the units,” adds Karel Stočes.

ZAT, together with Škoda JS, holds a patent related to the latest generation of LKP-M/4 drives developed by Škoda JS. Our company’s RRCS is the only system capable of operating with these drives.

To date, the RRCS system has been reliably operating on sixteen nuclear units with VVER-440 reactors in five countries and on eleven nuclear units with VVER-1000 reactors in three countries. At present, another four RRCS systems are ready to be commissioned.