Dossier Nuclear Energy

Video: Safety case

An explanatory film about the reactor pressure vessel of Beznau Unit 1. 

Two interviews

"KKB is in good condition"

Mike Dost, Beznau power plant Director on the ENSI decision

"Safety ensured"

ENSI gives green light for Beznau 1 nuclear power plant

ENSI confirms safety case

The Federal Nuclear Safety Inspectorate (ENSI) has confirmed the supplementary safety case submitted by Axpo at the beginning of December 2017 for Unit 1 of the Beznau nuclear power plant (KKB). This marks the successful completion of the roadmap defined by the supervisory authority and collaborating international experts in an extensive analysis process. The plant can now return to service.

With ENSI's safety case approval, KKB verifiably authenticates the safety of the Unit 1 reactor pressure vessel (RPV) in compliance with the state of the art as well as national and international regulations. The safety case also corroborates earlier assessments and tests, and validates an adequate margin for the safe operation of the plant for over 60 years.

As one of the most extensive investigations on the topic of RPVs, KKB has set international standards with the safety case. The analyses were extensive and complex. Work was carried out in collaboration with internationally renowned experts and leading companies and organisations.

During the shutdown, maintenance and periodic function tests were performed at the plant.

The most important answers

The safety case

The safety case presents the methods and results of all tests that Axpo performed in the course of nearly three years in order to provide proof of safety. The additional analyses that were carried out last year corroborate the proven safety of the plant, as already demonstrated in mid-November 2016. Axpo's extensive analyses unequivocally confirm the cause of the inclusions (aluminium oxide) detected in 2015. It was confirmed that these occurred during the manufacture of the RPV and not during plant operation. With the help of a replica of an RPV ring, Axpo was also able to clarify the impact of non-metallic inclusions on material properties, provide the integrity verification, and respond to the question of the available safety margin for continued operation of the plant.
The safety case proves that the reactor pressure vessel fulfils all national and international provisions and requirements for the continued safe operation of KKB Unit 1. 

Material tests

In the course of the root cause analysis, material tests verified and validated the source of the inclusions. Thanks to a RPV replica ring, it was possible to carry out extensive material tests demonstrating that the aluminium-oxide inclusions have no negative impacts on the RPV material properties and that its integrity is fulfilled for long-term operation of 60 years.  

Lengthy testing process

The supervisory authority ENSI repeatedly stated that it would take the necessary time to perform an extensive, technical review of the documentation submitted by Axpo. The timeframe is understandable given the complexity of the safety case. The endorsement of our extensive safety case attests to the high safety standards of the plant. 

Preventing deterioration during shutdown

Axpo took measures to prevent deterioration during shutdown. These were communicated to the authorities and presented on plant tours. Periodic inspections and maintenance were carried out in the same manner as if the plant had been in operation. Function tests were performed regularly and moving components were repeatedly rotated. In order to fulfil all the safety-technical requirements, the plant will undergo a detailed inspection before the restart. Axpo specialists will ensure the safe operation of the plant. 

Is the Beznau nuclear power plant safe?

The Beznau nuclear power plant fulfils all safety requirements. With continuous retrofitting and renewal investments in the range of CHF 2.5 billion, Axpo has ensured that KKB complies with the required safety standards at all times. The Swiss supervisory authority ENSI has confirmed previous assessments with the endorsement of the latest safety case. Axpo plans to operate the plant as long as it is safe and economical. Decommissioning is not a topic at this time. With the continued operation of the plant, Axpo ultimately makes a valuable contribution to the implementation of the Swiss Federal Council’s energy strategy. 

Media conference of 6 March 2018 (German only)

On March 6, Axpo held a media conference on the topic of the "Safety case Beznau 1 nuclear power plant" in Brugg. The presentation material is available for download: