Swiss utility Axpo said last week that the restart of unit 1 of its Beznau nuclear power plant has been deferred to late February 2018.

In June, Axpo announced 31 October as the planning and target date for the reactor to resume operation, but the Federal Nuclear Safety Inspectorate (Ensi) has requested further material inspections following the discovery of aluminium oxide inclusions in its reactor vessel.

Beznau 1, a 365MWe pressurised water reactor has been offline since a routine outage in March 2015 after which 925 material flaws were discovered on the reactor pressure vessel. Axpo said the defects did not occur during operation of the reactor but during the forging of the pressure vessel in France in 1965. In spite of the renewed delay, Axpo is convinced that there are no safety-related issues regarding the continued operation of the unit.

Meanwhile, Beznau 2 was reconnected to the grid on 28 September following its annual maintenance and refuelling outage during which Ensi carried out various tests on the reactor pressure vessel as well as repeated tests on components, fittings and systems. Ultrasonic tests did not produce any results which would prevent a further safe operation of the plant, Ensi said.