Big crack on a reactor: new uncertainties for nuclear production
The EDF power plant in Penly, April 6, 2012. © CHARLY TRIBALLEAU - AFP
Text by: Pauline Gleize Follow
3 mins
EDF is facing a new difficulty in its French nuclear fleet after the discovery of a large crack in a reactor at the Penly power station in Normandy.
The crack phenomenon linked to "stress corrosion" - which forced the electrician to shut down more reactors than planned and to see its nuclear production drop drastically in 2022 - is not completely new, but this times, the problem is a bit different.
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First difference of this new crack: its size.
It is no longer a "
micro
" crack.
Its size has even reached a scale never before envisaged.
It extends over 155 millimeters, or about a quarter of the circumference of the pipe.
As for the depth, the cracks detected so far at the Penly power plant were of the order of 5 or 6 millimeters maximum.
This time, the maximum depth reaches 23 millimeters for a pipe with a thickness of 27 millimeters.
"
We are beyond what is acceptable from a safety point of view
," said Karine Herviou, deputy director general of the Institute for Radiation Protection and Nuclear Safety (IRSN) in an interview with AFP.
The risk, "
it's a leak on the main cooling circuit of the reactor, that was the issue
, ”she adds before tempering.
In the event of a leak, “
the cooling water will fall into the reactor building ” and would be “
weakly radioactive
”
anyway .
There would therefore be “
no issue in terms of releases to the outside”.
This remains “
obviously things to avoid
”.
Non-compliant repairs
Another difference: the reason and location of the problem.
This still concerns safety injection circuits - circuits which are used to send water to cool the reactor in the event of an accident
.
However, this crack was detected on another portion of this circuit, on an area which until then had not been considered sensitive to stress corrosion.
In the first case of "microcracks", long pipes, with more welds, were incriminated.
The most recent and most powerful reactors were therefore essentially concerned.
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This new crack does not seem to be related to the geometry of the system, but to non-compliant repairs at the time of the construction of the plant.
“
There was an approach which is not acceptable, which consisted a little in forcing the pipes to align them, to weld them, and there were defects on this weld which led to a second repair”
, explained Wednesday, March 8 to the Senate, Bernard Doroszczuk, the president of the Nuclear Safety Authority (ASN).
"Revise your strategy"
As part of the microcracks discovered in 2021, EDF had focused its checks on 16 of the 56 reactors, those which were considered sensitive to the phenomenon of corrosion.
Given that this new crack was detected in another area, and even if we do not yet know whether Penly's problem is singular or not
,
ASN has ordered EDF to "
revise its strategy
".
This will lead to the extension of stops at other sites to extend the controls.
According to the ASN, there should be no massive shutdowns.
It is still a bit early to know what the consequences will be for nuclear production.
The microcracks crisis has contributed to dropping nuclear electricity production to its all-time low last year and therefore to increasing EDF's abysmal losses.
The electrician suffered a net loss of 17.9 billion euros in 2022.
(
With
AFP)
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