Chronology: from the findings in Belgium to the proof of safety from Beznau 1
In the summer of 2012, findings are detected in the basic material of the reactor pressure vessel of the Belgian nuclear power plant Doel-3. As a result, nuclear power plants in Switzerland also have to carry out inspections. Since findings are also detected in the reactor pressure vessel of Beznau 1, Axpo needs to prove it was safe. The Swiss Federal Nuclear Safety Inspectorate ENSI accepts this proof in 2018.
| August 2012 | The Belgian safety authority FANC, the federal agency for nuclear control, informs foreign safety authorities that numerous findings have been detected in the basic material in the Belgian nuclear power plant Doel-3. Later, similar findings are also discovered in the reactor pressure vessel at Tihange-2. |
| August 2012 | Since the reactor pressure vessel of Mühleberg nuclear power plant (Switzerland) was produced by the same manufacturer as the Belgian vessel, ENSI requests additional information from BKW. |
| August 2012 | Mühleberg nuclear power plant (Switzerland) continues to perform an ultrasonic inspection of the reactor pressure vessel during the annual inspection. It is performed according to ENSI’s standards. The ultrasonic inspection does not yield any indication of findings like those at the Belgian nuclear power plant Doel. |
| January 2013 | ENSI demands that Beznau nuclear power plants 1 and 2 and Gösgen compile information about production, basic material and inspections of the forged parts in the reactor pressure vessel. |
| August 2013 | Action upon recommendation from the Western European Nuclear Regulators Association WENRA, ENSI demands that the Gösgen and Beznau nuclear power plants use ultrasound to inspect the basic material of their reactor pressure vessels for possible errors during the next regular inspection. |
| July 2015 | The inspection of the reactor pressure vessel at Gösgen nuclear power plant confirms that it is in good condition. |
| July 2015 | During ultrasound measurements in the reactor pressure vessel at Beznau 1, indications requiring evaluation are detected. ENSI requires that these findings be evaluated. |
| November 2015 | Axpo submits a project plan for assessing the findings to ENSI. ENSI appoints an international expert committee. |
| December 2015 | ENSI grants Beznau nuclear power plant 2 approval to restart. The findings detected have no impact on safety. |
| March 2016 | ENSI states its position regarding the project plan. |
| November 2016 | Axpo submits the documents for characterising and evaluating the findings in the basic material of the reactor pressure vessel in Beznau 1. ENSI and the International Review Team begin the inspection. |
| December 2016 | ENSI requests additional samples. |
| December 2017 | Axpo submits the revised proof of safety to ENSI. |
| March 2018 | ENSI concludes that the non-metallic confinements have no negative impact on the safety of the reactor pressure vessel. |
For the reactor pressure vessel at Leibstadt nuclear power plant (Switzerland), the inspections and findings from Doel-3 and Tihange-2 are not as significant. The KKL does appear on the list of facilities that may have been impacted that was published by the Belgian safety authority, but both its manufacturer and production process are different from those of the Belgian reactors. Milled – not forged – material was used for the cylindrical seal rings, the curved floor and the cover of the reactor pressure vessel.