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Event Report Forms (ERFs) are filed to the IAEA. Sometimes there are multiple event reports, updating the rating, the event description. Here you only see the latest event report

ERF send date: Thu, 16-08-1990
ERF description: Incident with infringement of technical operation specifications, resulting in a prolonged shutdown of the Superphenix reactor.
From 20 June to 3 July, following an inadvertent inflow of air into the primary circuit, the reactor operated with a sodium impurity level exceeding the limit stipulated in the technical specifications.
The Creys-Malville plant was connected to the grid on 8 June 1990. From 10 June, during the increase to rated power (1240 MW), the level of impurities (oxides, hydrides, etc.) in the primary sodium increased, although it remained within the permitted limits.
This increase is normal and to be expected: it reflects the slight contamination of the sodium caused by work carried out when the reactor was shut down.
After 20 June the impurity level measurements changed more rapidly and exceeded the permitted values, while the filter cartridges which purify the sodium became clogged. This abnormal increase was due to oxidation of the sodium caused by air entering through a faulty compressor.
As the analysis of physical and chemical samples to determine the impurity level was difficult, the operator decided to shut down the reactor only on 3 July (in fact, an automatic shutdown due to an electrical fault took place shortly before the scheduled shutdown).
The temperature of the reactor after the shutdown was maintained at 250 deg C to ensure that the impurities remained dissolved in the sodium and were not deposited on the metal surfaces. In July the operator changed the primary sodium purification cartridges and sodium purification began. At the end of August the operator will report on the quantity of impurities in the primary circuit and how long it will take to purify the sodium completely. The reactor cannot be started up again until the level of impurities returns to normal and until the lessons learned from the incident itself and from the infringement of the technical operation specifications have been taken into account.
The Central Service for Nuclear Installation Safety (SCSIN) has asked the operator to report on the potential consequences of this incident for plant safety and to suggest the necessary corrective measures. The physical characteristics of the contaminated sodium changed over several days without the tests made by the operator revealing that air was entering the argon circuit or that the sodium characteristics were deteriorating.
Taking into account the failures described above and the delay in returning the plant to service, this incident is classified at Level 2 of the severity scale.
BASIS FOR RATING:
DIFFICULTIES IN RATING:
ERF rating date: 14-08-1990
ERF contact person: Mr. J. Breuil
ERF address: 99 rue de Grenelle, F-75700 Paris, France
ERF affiliation: Ministere de l'industrie, Service central de surete des, installations nucleaires

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