(405.4010) WISE Amsterdam - The lawsuit is a result from the discovery mid-october of a stud bolt (weight 1.3 kg) in the channel of one of its three steam generators. Investigations into the bolt affair showed with "certainty" that the incident was due neither to a defect in the plant's maintenance quality assurance nor to human error. Just above the place where the bolt was located is a vertical elbow in the channel.
This indicates clearly that someone must have thrown the bolt on purpose into the channel head, according to Max Morel, director of Cruas. The investigation eliminated all explanations except willful degradation for the presence of the stud bolt in such an inaccessible spot. But neither EDF nor the local gendarmerie had any idea who could have perpetrated the sabotage act. It is not even known whether the perpetrator was from the EDF or from an outside contractor.
In the last week of September a maintenance crew was re-assembling a swing check valve upstream of a steam generator channel head. One of the special stud bolts, which they had removed earlier was found missing. They re-opened the valve and inspected (with mirrors) if the bolt was fallen inside. When they saw nothing they concluded that the bolt was incidently removed or mistakenly thrown away. In mid-October Cruas-2 was restarted after the scheduled maintenance and refuelling. A member of the cleaning crew (and also the acoustic detection system) heard an unusual loud noise from the vicinity of the channel head. The main coolant pumps were stopped. The missing bolt had caused damage to the inner lining of the channel head in several places. According to Morel the damage was slight; a maximum impact of 0.5 millimeters out of the lining thickness of 7 mm.
Source: Nucleonics Week, 4 November 1993
Contact: WISE-Paris, 5, Rue Buot, F- 75013 Pads. Tel: + 33 1 456 54793. Fax: +33 1 458 97357
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