Hydro & Nuclear Power (KHNP) says it is developing digital twin technology to monitor and control South Korea’s 26 nuclear power units more effectively. A digital model of a physical system will allow its central R&D centre in Daejeon to remotely check the units at all five NPPs – Kori, Wolsong, Hanbit, Hanul and Saeul – and react immediately to unexpected situations.

KHNP's digital twin development is currently based on detailed system blueprints of Saeul NPP’s units 1&2 in Ulsan. Its development is expected to be finished in 2026, the technology will be first deployed at Shin Kori NPP’s units 3&4 in Ulsan.

"The digital twin will allow us to simultaneously check reactor cores, turbines and generators in different power plants in a three-dimensional virtual world," a KHNP official told Korean Times. "The metaverse tool is a perfect counter-accident supporting measure. It is now in demand in the Czech Republic and Poland, which are seeking to import our nuclear power technologies."

As part of its digital twin drive, the Daejeon base has begun monitoring Hanul NPP’s unit 5 in Uljin, some 290 kilometres away, using a large computer screen showing the unit's digital replica in real-time. The screen shows the unit's reactor coolant pump (RCP), with hundreds of moving coloured dots representing the flow of the water inside the pump. The RCP monitoring system is now being tested.

The digital twin technology is part of ongoing development projects by KHNP's Artificial Intelligence Monitoring & Diagnosis (AIMD) Centre in Daejeon. Having set up a complete remote command centre for the power plants, the centre oversees the facilities and checks for any malfunctions by detecting signs of vibrations emanating from a power plant in trouble. The magnitude of the vibrations the centre can detect is so small that they are even undetectable to the plant experiencing the technical difficulty.

"By the time a power plant can detect a vibration, it is too late," an AIMD researcher said. He said vibration is a sign that signifies problems for not just a NPP but many other things, from automobiles and other machines to humans. "So we must detect it before they do and discern what's wrong and how to prevent it from developing into a bigger problem."

The AIMD centre’s AI uses cumulative big data on vibrations from KHNP's 12,387 mechanical parts that comprise pumps, generators and turbines in the five power plants as well as image registration deep learning.

A turbine at the Shin Kori 1 has 10 sensors that share the machine's movements every second with Daejeon. Since August 2022, the AI has run diagnostic testing on over 26,900 parts, issued 285 alarms and prompted the company to take necessary actions 58 times. KHNP, in 2021, registered the monitoring system under the trademark Prometheus and acquired a patent.

"The biggest strength of AI which distinguishes itself from human work is that it can monitor a large volume of facilities simultaneously," the AIMD researcher said. "It can also detect abnormal signs before any human can notice."

At another site inside the Daejeon base, the company is testing how its power plants can withstand earthquakes in a dedicated lab. The facility's need was made a priority was after the 2011 Fukushima Daiichi disaster in Japan and a 5.8 magnitude earthquake that rattled Gyeongju, North Gyeongsang Province, in 2016.

Inside the lab, two motor control centre (MCC) structures stand, one bolted tightly to the ground and the other one only having its base panel screwed to the ground while the rest is connected to the base with spring-like movable parts. As the lab initiates an artificial tremor, replicating the conditions of a quake with 0.2 gravitational force (close to a 7.4 magnitude earthquake), the bolted MCC shakes left and right quite violently while the other one only trembles slightly as the impact is mostly transferred to its base panel.

"We're like KHNP's home doctor," a researcher at the lab said. "We can test for extreme cases mimicking up to 4 g in force. It'll be applied to existing power plants later."

Image (top): Researchers at the AIMD Center inside KHNP's central R&D centre in Daejeon check the company's nuclear power plants operating across the country (courtesy of KHNP)

Image (bottom): Two motor control centres stand on top of one of KHNP's two quake generators inside the company's quake-proof test centre in Daejeon (courtesy of KHNP)