Axpo says tests confirm safety of Beznau 1 vessel

Swiss utility Axpo said yesterday it has submitted "verifiable proof" to the country's nuclear safety regulator that aluminium oxide inclusions in the reactor vessel of unit 1 at its Beznau nuclear power plant do not affect the unit's safety.

Swiss utility Axpo said yesterday it has submitted "verifiable proof" to the country's nuclear safety regulator that aluminium oxide inclusions in the reactor vessel of unit 1 at its Beznau nuclear power plant do not affect the unit's safety.

Beznau unit 1 (Image: ENSI)

The unit has remained idle since May 2015 when it was taken offline for a scheduled outage. Ultrasonic inspections were made of the unit's vessel which "registered findings at some points in the base material of unit 1's RPV indicating minimal irregularities in the fabrication process". Axpo confirmed earlier this year the presence of aluminium oxide inclusions in the vessel.

Axpo submitted the safety case to the Federal Nuclear Safety Inspectorate (ENSI) on 14 November. The company said the safety case provides the results of all the tests and analyses it has carried out over the past six months on the vessel in order to produce the proof of physical integrity and safety case.

Axpo said the production of a replica part of the reactor pressure vessel used in Beznau 1 had shown that aluminium oxide inclusions in the vessel formed during its manufacture and not during the reactor's operation. "We were able to point out the source of the detected inclusions, and thanks to the replica, clarify the impact of these inclusions on the material properties, providing verification of fracture toughness and answer the question of available safety buffers," the company said.

"With the safety case, Beznau provides the verifiable proof that the reliability and safety of Beznau 1 is ensured in keeping with state-of-the-art science and technology, as well as national and international standards," Axpo said. The legal provisions for the safe operation of Beznau 1 have been fulfilled, it claimed. "From Axpo's viewpoint, there are no safety-technical concerns regarding the continued operation of the plant up until 2030," the company said.

ENSI will now review the submitted documentation, together with an international review panel.

Georg Schwarz, ENSI deputy director and director of its nuclear power plant division, said: "Ultimately however, it is ENSI's responsibility to decide on the possible continued operation of Beznau 1." He added, "Only if Beznau 1 fulfils the requirements of the legislator, then it will be able to start up again."

In May, Axpo said it expects to be given regulatory approval to restart the unit by the end of this year.

The two 365 MWe Westinghouse units at the Beznau plant are the oldest power reactors in Switzerland. Unit 1 began operating in 1969, while unit 2 entered operation in 1972. In addition to providing power, both units also produce district heating.

Researched and written
by World Nuclear News