Swiss regulator approves Mühleberg upgrades

Thursday, 29 January 2015

Switzerland's Federal Nuclear Safety Inspectorate (ENSI) has approved upgrades proposed by utility BKW for the continued operation of the Mühleberg nuclear power plant until 2019.

Mühleberg (Image: ENSI)

Although having earlier received a limitless operating licence for Mühleberg, BKW announced in late 2013 that the plant will be permanently shut down in 2019 instead of the earlier planned 2022 because of "uncertainty surrounding political and regulatory trends." The single 372 MWe boiling water reactor began operating in 1972.

At the end of June 2014, BKW submitted to ENSI details of planned upgrades to ensure the plant's safe operation to 2019. More extensive upgrades would have been required for the plant to operate beyond this.

On 27 January, ENSI announced that it had approved BKW's retrofit concepts. ENSI will provide its report to the Federal Nuclear Safety Commission (NSC) for a second opinion. After that ENSI will publish its formal order.

BKW has proposed upgrading the emergency cooling pumps at the plant, as well as installing a new emergency reactor cooling water system and reinforcing the emergency cooling system for the used fuel pools. The company has earlier said that, by implementing these measures, it will exceed the safety margin stipulated by ENSI.

While approving these upgrades, ENSI has also requested that BKW perform non-destructive tests on the reactor core shroud during each annual safety review at Mühleberg.

ENSI has set two technical criteria for cracks found in Mühleberg's core shroud, which may not be exceeded. ENSI deputy director Georg Schwarz said, "With this is mind, we ensure that the stability of the core shroud is guaranteed with a safety margin." Based on current knowledge, ENSI does not expect the cracks in the core shroud at Mühleberg to reach these limits before its final decommissioning in 2019. However, if there is an unexpected change in the development of these cracks, "we have defined the limits for switch-off," Schwarz added.

BKW said that ENSI's report confirms that safety at Mühleberg "meets high standards." It added, "The measures approved by the ENSI will further increase the safety margin and robustness of systems for the remaining five years of operation."

BKW said it will "satisfy the requirements and start implementing the retrofit measures immediately. BKW is still anticipating the cost of the retrofits to be in line with the figure announced in summer 2014 of CHF 15 million ($16.3 million)."

Researched and written
by World Nuclear News