Heatwave: explanation of exemptions and overheating limits at power plant exits

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Published on 19/07/2022

The exemptions granted to 4 nuclear power plants (out of 18) for their thermal discharges, in the current context of heat wave, generate a lot of comments.

Let us recall, once again, that these discharge temperature and upstream-downstream temperature constraints (which concern all thermal power plants) aim to protect ecosystems, and essentially impact the electricity production of power plants located on rivers. water not being equipped with air-cooling systems allowing the discharged water to be sufficiently cooled, over a few hours to a few days a year.

What the Nuclear Safety Authority (ASN) says:

“EDF’s proposals are acceptable in view of the feedback from environmental monitoring specifically carried out during previous heat waves” (indeed the subject is not new, it has been monitored since the 70s, and decision-making is based on the history of collected data)

“The operator of the electricity transmission network (RTE) considers that maintaining a minimum power of the nuclear power plants of Blayais, Golfech and Saint-Alban is essential for the security of the electricity network.

“The limit values ​​set by ASN could then no longer be complied with. Consequently, EDF has asked ASN for a temporary modification of the requirements governing thermal discharges from these power plants, together with ‘an enhanced monitoring program.’

Consult the source on the official ASN website

To find out what this is in concrete terms, here is a summary of the existing authorizations and the exemptions granted. The temperature rise limits are maintained or even reinforced.

The use of these derogations is limited to situations where RTE requires the operation of the installation to ensure the security of the electrical network or the consumption-production balance.

Another perspective: currently France produces part of its electricity with gas, imports a large part of the electricity it consumes, and wind power produces very little throughout Europe from the West.

Even by accentuating the efforts of sobriety, the alternative to these derogations is therefore:
– Endangering the continuity of the electricity supply
– Increased use of fossil fuels (electricity imported is mainly produced with gas and coal)

Global warming will increase the probability of these unavailabilities, but:
– These future effects are modeled on the basis of IPCC scenarios.
– By 2050, lost production remains very low ( around 3% in the most unfavorable scenarios).
– There are technical solutions, and the location of future reactors can be thought out according to this constraint.