Swiss nuclear plant is off the grid for an indefinite period

Gösgen SO nuclear power plant is off the grid for an indefinite period Keystone-SDA

The Gösgen nuclear power plant in Däniken in canton Solothurn is not producing any electricity until further notice. The operator must provide evidence of fallback in case of a possible overload in the feedwater pipework system. The supervisory authority ENSI has not given any time frame for this.

The safety scenarios are very comprehensive and require more time to prepare than originally planned, the media office of the Gösgen-Däniken nuclear power plant said on Tuesday in response to an enquiry from the Keystone-SDA news agency.

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Submission of readiness evidence to the Swiss Federal Nuclear Safety Inspectorate (ENSI) will depend on the progress of the preparation. In response to an enquiry, the ENSI media office did not provide any information on how long it will take to review the documents. “We cannot estimate this at present,” it said.

Annual review has long been completed

Three weeks ago, the operator announced that the plant would remain offline longer than planned following the annual inspection. The plant was shut down on May 24 for the overhaul. According to the operators, it is currently in a safe, shutdown state.

The replacement of non-return valves in the feed water system is planned as part of the technical modernisation. New calculation methods were used in the process. These had shown that in the event of a pipe rupture, overloads or pressure peaks could occur in individual areas of the feedwater pipework system in the non-nuclear part of the plant. The nuclear power plant operator informed the supervisory authority ENSI.

Supervisory authority decides on authorisation

The nuclear power plant can only be restarted once ENSI has given the go-ahead after checking the evidence. If a nuclear power plant is not connected to the grid as planned, this costs the operator money. As most of the electricity is usually sold in advance, the missing electricity has to be purchased. The media office of the Gösgen nuclear power plant said that the costs cannot yet be quantified.

The plant generates around eight billion kilowatt hours of electricity per year, covering around 13% of Switzerland’s electricity consumption. It began commercial operation in 1979. The main shareholder is Alpiq (40%), followed by Axpo Power, CKW, the City of Zurich and Energie Wasser Bern.

Adapted from German by DeepL/ac

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