The nuclear reactor fleet of French company EDF recorded a record level of so-called ‘environmental’ unavailability on the morning of August 12. This is due to intense heat and a mass influx of jellyfish into the pumping stations of the Gravelines power plant in northern France. According to AFP calculations, the volume of unavailable capacity reached 20.4% — this was determined based on data that EDF has published since 2015.
Shortly before 10:00, EDF’s nuclear fleet recorded a new peak in unavailability due to ‘environmental constraints’ or ‘external reasons related to the environment.’ In total, this affected 13 reactors, while the previous record was 12 reactors on the night of July 14 to 15. As a result, 20.4% of the nuclear fleet’s production capacity was unavailable. Eight reactors were completely shut down (Bugey 3, Cattenom 1, Chooz 1 and 2, Golfech 2, Gravelines 2, 3 and 4), and five were operating at reduced capacity (Saint-Alban 2, Tricastin 1 and 4, Gravelines 1 and 6).
Jellyfish shut down part of the Gravelines reactors
This loss of capacity is largely due to unscheduled complete or partial shutdowns of five out of six reactors at Gravelines — the largest nuclear power plant in Western Europe, located on the North Sea coast. Reactors 1, 2, 3, 4 and 6 were shut down or switched to reduced mode on Monday and Tuesday for several days because several tons of jellyfish entered the pumping stations used to draw seawater to cool the nuclear facilities.
Units No. 1 and No. 6 resumed operation at full capacity around 10:00. Reactor No. 5 is undergoing scheduled maintenance. The shut-down Gravelines 2 reactor is planned to be reconnected to the grid on Wednesday evening at 23:00.
How heat and drought affect reactor operation
In addition to Gravelines, the shutdowns or reductions in production of other reactors are related to intense heat and drought, which affect the temperature or water levels of rivers. France has 57 nuclear reactors, which provide about 70% of the country’s electricity production. All of them are located near rivers or the sea to ensure the cooling of the facilities.
In the event of drought or heat, the reduction in river flow and the increase in water temperature can force EDF to reduce or even stop production to protect the environment and biodiversity. Under these conditions, the operator cannot discharge chemical or radioactive effluents or additionally heat the rivers by returning heated cooling water to them.
Source: Libération
