Background
Nuclear Power Plant Krško (NEK) in Slovenia has been a reliable provider of electrical energy since 1983. Utilizing a light pressurized water reactor, NEK supplies power to Slovenia and Croatia, covering a significant portion of their electricity demand. Customers have depended on NEK's services for decades.
Challenge
NEK's existing seismic monitoring system required a complete upgrade due to obsolescence, operational issues, and the need for system expansion. The new system had to comply with the latest Nuclear Power Plant (NPP) regulatory guides, including standards for lightning strikes, electromagnetic radiation, worst-case radiation scenarios, high-temperature effects, and safe shutdown procedures during earthquakes. The nuclear industry's stringent requirements for seismic monitoring necessitated adherence to mandates like US NRC Regulatory Guide 1.12 and ANSI/ANS-2.2-2016, covering Design Basis Earthquake (DBE), Safe Shutdown Earthquake (SSE), and Operating Basis Earthquake (OBE).
Solution
A custom GeoSIG seismic monitoring system was selected and tailored to NEK's specific needs. The implementation occurred in three stages. Key enhancements included:
- Optical connections between outdoor recorders and the main control cabinet to mitigate lightning impacts.
- Electrical lines designed and installed according to up-to-date electromagnetic compatibility (EMC) qualification code requirements to prevent interference.
- Relocation of in-housed recorders from accelerometer locations to the main control cabinet to shield them from radiation and environmental effects.
The entire system successfully underwent seismic and EMC qualification. The implemented Seismic Monitoring System (SMS) comprises a central cabinet, eight AC-7x-NPP accelerometers within the nuclear island, six field stations with scai recorders, an additional eight AC-7x-NPP accelerometers, a downhole AC-73-DH accelerometer, alarms to the main control room, and an AC power supply.
This project demonstrates how GeoSIG instruments provide quality and reliability cost-effectively.
