INFO THE DEPECHE. Corrosion on the nuclear fleet: the ten-year shutdown of the Golfech power plant extended by six months

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Started on February 26, the third ten-year shutdown of reactor No. 1 of the Golfech nuclear power plant, which was due to end this summer (in August), will finally be extended for another six months. The reason, a corrosion problem on the auxiliary circuit piping resulting in small cracks. The studies to be carried out and the work to be instructed have led the plant to postpone the reconnection of the reactor to February 2023.

Fifteen days after publication the annual report of the nuclear safety authority (ASN) which gave a “very passable” assessment of the safety performance of the Golfech nuclear power plant, which has nevertheless been the subject of a “rigorous safety plan” since 2019 (our box), the problems have arisen. accumulate for the CNPE (nuclear electricity production center) in Golfech.

On the occasion of the third ten-year inspection of reactor no. 1 – the oldest of the two 1300 MWe PWRs (pressurized water reactors) in operation on the Tarn-et-Garonne site – which began on February 26, and programmed to last until the beginning of August, anomalies were noted in the safety injection circuit (LAUGH).

“We were brought to checks during this ten-year shutdown having revealed “indications” (abnormalities) on this RIS circuit”, indicates Romain Philippeau, EDF manager of communication at the Golfech plant. Irregularities which led to in-depth checks and additional expertise by ultrasound or radiography” specifies the information note opened since January 14 by EDF, and updated over the progress since the discovery of these corrosion problems on portions These inspections are taken very seriously, these “circuits being important for the safety of the installations”, assures the note from EDF, the last update of which dates from May 19.

Remember, in fact, that the “RIS” auxiliary circuit makes it possible to inject borated water into the reactor core in order to stop the nuclear reaction. It also maintains the volume of water in the primary circuit in the event of a loss of primary coolant accident. However, this problem does not only affect the Golfech plant.

Since last year when these corrosion problems were first detected on the piping at the Civaux power plant, 12 EDF power plants out of 56 in the French nuclear fleet have been affected by this corrosion problem. “In-depth metallurgical expertise will be carried out in the weeks to come”, certifies Romain Philippeau who is not yet able at this stage to say whether these anomalies are due to “stress corrosion” (SCC) or “thermal fatigue” (1).

On the side of the Golfech Local Information Commission (CLI) which, together with the director of the power plant, Cyril Hisbacq, visited this unit outage last month, we are leaning towards the trail of an anomaly due to the ” geometry of pipe lines”. A phenomenon that would be linked to the very design of the latest French nuclear power plants. A point on which the ASN remains very cautious.

In April, the director of the plant organized a visit during the outage to the members of the CLI of Golfech
Photo Golfech nuclear power plant

The consequences of these corrosion problems on the auxiliary circuit piping resulting in small cracks are not neutral for the Golfech power plant, they will cause the duration of this ten-year shutdown to be extended. “The studies to be carried out and the work to be instructed lead us to postpone the reconnection of reactor no. 1 to February 2023”, informs us Romain Philippot, i.e. six months behind the planned restart of the reactor.

The nuclear policeman still pinpoints the operation of the plant

With only three significant incidents reported in 2021, the Golfech nuclear power plant did much better than in previous years with 33 incidents in 2019, a record. A rigorous safety plan has since been instituted by ASN. The nuclear policeman in his annual report published on May 17 notes after 14 days of labor inspection spent at the Golfech nuclear power plant that “the efforts undertaken in this context have not yet translated into visible results. […] the shutdown of reactor 2 in 2021 highlighted shortcomings […] lack of skills, serenity and insufficient organization in the control room.” A stoppage which was “extended by 4 and a half months in the initial program”. Joined by us, the management of the plant takes note of the recommendations of the ASN to progress.”In 2022, the priority is safety, with in particular the improvement of the skills of our employees”, indicates Romain Philippeau, specifying that the training plan for this new generation is continuing with training and repetitions of procedures “There has been progress noted in terms of the environment and radiation protection”, adds the communication manager of the plant.

(1) These defects appear in the form of microcracks (initiated on the surface of the material) spreading through the thickness of the part. The mechanism that causes cracking is called stress corrosion cracking (SCC).

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