Unit 3 of France's Gravelines Nuclear Power Plant Reconnected to Grid, Unit 4 Remains Shut Down

According to EDF on August 18, Unit 3 of the Gravelines Nuclear Power Plant in northern France was reconnected to the national grid at 3:55 a.m. local time on August 18. The unit had been automatically shut down at 7:43 p.m. on August 10 in accordance with established safety protection procedures due to a large influx of jellyfish into the seawater pump station filtration system.

The Gravelines Nuclear Power Plant has a total of six units. On August 10, a large number of jellyfish entered the pump station used to draw seawater for cooling nuclear facilities, affecting equipment such as pre-filters and filter drums. In accordance with operating procedures, Units 3 and 4 were automatically shut down; the operating team also shut down Unit 2 and reduced Unit 1's power to 50% to adapt to changing site conditions. Unit 5 was in a planned ten-year inspection outage at the time, while Unit 6 continued to operate.

Subsequently, Unit 2 was reconnected to the grid at 2:43 a.m. on August 13. Unit 1, however, was automatically shut down at 11:37 p.m. on August 13 due to a closed valve in the water supply circuit, which caused the water level in one of the three steam generators to drop too low. After inspection and handling by the operations and maintenance teams, Unit 1 was reconnected to the national grid at 7:25 p.m. on August 15. The water supply circuit is located in the non-nuclear section of the unit.

As of August 18, Units 1, 2, 3, and 6 of the Gravelines Nuclear Power Plant were in operation; Unit 4 remained shut down due to the large-scale jellyfish influx event; and Unit 5 continued its ten-year inspection.

EDF stated that the above shutdown and restart processes had no impact on facility safety, personnel safety, or the environment. The site had previously strengthened monitoring of the water intake system, including inspections and video surveillance of filter drums, as well as enhanced patrols around the intake channels. The seasonal appearance of jellyfish along the northern coast of France is not uncommon, and the occurrence of large-scale jellyfish swarms in the region has drawn increased attention in recent years.