Enquiries keep three plants offline

30 October 2001

Three of Germany’s nuclear plants have recently had to extend their annual maintenance outages, as a result of safety concerns.

Corrosion damage was detected at the 1300MWe Biblis B reactor during its annual maintenance outage. The federal environment ministry has asked for a comprehensive assessment and corrective action to be put in place before the plant would be allowed to reopen.

The federal ministry said it had been told that the damage had been undetected for the last 23 years but new testing technology had revealed it.

Operator RWE said that the defects had been spotted in the corrosion protection system of the plant’s cooling water cycle.

In a separate incident, after a routine outage, the 1424MWe Philippsburg 2 was restarted and allowed to operate for several days without sufficient amounts of boric acid in three of four emergency water dump tanks. After the restart, a sample of borated water was taken from two of the tanks, in accordance with the operator handbook, and a boron concentration of 1950 parts per million (ppm) was measured. Regulations require a concentration of 2220ppm to assure that criticality would be halted. The shift leader, who was responsible for the decision to keep the unit operating after the boron deficiency was discovered, has been indefinitely suspended as a result.

At the time, reactor inspectorate Technischer Überwachungsverein (TÜV) felt that the plant’s safety was not disturbed at any time, and the incident warranted no further action. However, the Federal Ministry of Environment and Nuclear Safety (BMU) examined the incident in more detail and threatened EnBW with legal action, including suspension of its operating licence.

Following criticism of the handling of the incident, TÜV said it would have personnel implications within the organisation. TÜV stressed that EnBW only revealed some pieces of information after the appraisal report was issued, but admitted it should have given the incident a higher rating.

EnBW agreed to shut the reactor voluntarily in order to enable it to clarify unanswered questions about the incident. The environment and transport minister of Baden-Württemberg, Ulrich Müller, has called for a quick restart of the unit.

Also last month, the annual maintenance period of E.ON’s 907MWe Isar KKI 1 reactor was extended to review security procedures, a measure precipitated by heightened security concerns following the September 11 attacks in the USA. The threat of possible attacks has also led to calls to phase out the older nuclear stations even earlier than planned. Economics Minister Werner Müller said that, in return for phasing out older nuclear plants earlier, more modern plants could be allowed to stay on line for longer than planned.

Germany’s Red-Green coalition government recently guaranteed that the operation of the country’s nuclear plants would be free from political interference, in return for the main energy companies agreeing to limit the operating lifetimes of the existing plants.

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