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The loose bolt incident at Koeberg

On the 11th November 2005 the reactor went into safe mode (a mechanical failure of the switchgear tripped the transmission lines) cutting supply to most of the Western Cape for about two hours.

On the 16th November 2005 there was a fire under a 400kV transmission line at Muldersvlei which caused the line to trip, causing severe voltage dips which resulted in Koeberg again shutting down. Various parts of the Western Cape were without electricity for hours at a time.

On the evening of the 23rd November 2005, a routine inspection of the backup safety system revealed a below-specification concentration of an important chemical, which resulted in a controlled shutdown of the reactor. Cape Town's backup electricity supplies proved to be sufficient until 25th November, when the backup capacity started running out and. From the 25th rotational load shedding was employed, with customers being switched off in stages for most of the day. Eventually, Koeberg was re-synchronised to the national grid on the 18th November 2005.

The Christmas day bolt

On Christmas Day, 2005, an 8cm (about the size of a finger) loose bolt found its way into the rotor of Unit 1, causing damage to some of the 105 bars that line the device, and putting the generator out of action for three to nine months, depending on the availability of spares. Investigations are still underway as to how this occurred.

This broken-down generator is as big as a train carriage. The generator where the "accident" happened is far removed from the nuclear activity. There is strict security for the generator where it is housed. It is probably impossible to throw a bolt in the generator while it is generating electricity, because of the unbearable heat in its immediate vicinity.

Plausible explanations include:

2006 ... the saga continues

On Saturday the 18th February 2006, the second generator unit was forced to shut down when it tripped at the same time as a generator at the Kendall Power Station. With Unit 2 shut down, the Western Cape province had to rely heavily on power transmitted from the north of the country. This plunged the Western Cape into a series of rolling blackouts for the next week.

On the 28 February 2006, a problem on the national grid between Beaufort West and Worcester caused overvoltage on other lines, Koeberg once again shut down, causing the plant to isolate itself from the national grid.

On 28 February 2006, just before the local government elections on 1 March 2006, the minister of Trade and Industry (Alec Erwin) announced that suspects who are suspected of having sabotaged Koeberg Nuclear power station have been identified. Subsequently a group, Imam Haroon Brigade, claimed responsibility for the alleged sabotage at the Koeberg Nuclear power station. According to the group, the mission was a direct attack on the South African government and its imperialist economy. The statement says: “This government which is an enemy of the people is the direct reason behind the suffering of the poor with their deliberate implementation of neo-liberal capitalist policies such as GEAR. South Africa has the biggest gap between the rich and poor in the world and movements such as the Landless movement and the anti-capitalist movement are essentially ignored.” The faction accused the SA Government of endorsing immorality and the spreading of fornication, adultery and sodomy.

The announcement of sabotage at Koeberg came alongside news that a number of senior nuclear engineers have left Koeberg, including the senior engineers responsible for accident analysis and integrated safety evaluation. In reply to a parliamentary question, Minerals and Energy Minister Lindiwe Hendricks said that during the last two years, as many as eight out of 60 senior professional engineers, seven out of 46 technical managers and five of 30 non-technical managers had left the power station. Hendricks said eight out of the 60 professional engineering posts were being filled "through the development of junior professional engineers". They included the posts of senior engineer (accident analyst): nuclear engineering; senior engineer (adviser): integrated safety evaluation group; senior engineer (steam generator): nuclear engineering and senior engineer (mechanical specifications): nuclear engineering.

On the 17th August 2006 Erwin finally admitted that there was actually no evidence of sabotage at Koeberg, "There is no evidence of any organised group of any sort being the agent of an act of sabotage at Koeberg...Accordingly, we share the view of the Eskom CEO that we have to ascribe this to human error."

Repair process
It wasn't a bolt!!

It was not, after all, a bolt in the generator of Koeberg's unit one that caused damage to the rotor; "Loose magnetic material, not the bolt, damaged the generator's insulation which in turn damaged the rotor and stator rods," a report completed by Eskom's corporate technical audit department, the generation division and staff of the generation safety and insurance department states (as reported in September 2006).


14 September 2006

Koeberg: It wasn't the bolt