Both houses of the Swiss Parliament have refused to put a time limit on the life of its NPPs, indicating a possible shift in the nuclear phase-out policy adopted five years ago after the Fukushima disaster in Japan. Most parliamentarians agreed that it was pointless and premature to close the safe plants that were still working. This would also avoid the possibility of operators claiming financial compensation in the event of an early closure.

The Swiss have been debating the future of its five nuclear plants since 2011. Under the phase-out decision adopted that year, all plants were due to be closed on reaching their maximum operating period of 50 years. Switzerland also dropped plans to build three new power reactors. Currently, approximately 40% of Switzerland’s energy comes from nuclear power. Switzerland’s Energy Strategy 2050 plans to bridge the gap through increased use of hydropower and alternative energy sources and with energy efficiencies.

Some of the older plants have been the cause of some concern with opponents pressing for their closure. Switzerland has the world’s two oldest operating nuclear units – the single unit Mühleberg NPP in Bern canton, which began operating in 1972, and unit 1 at Beznau NPP in Aargau canton, built in 1969. On 2 March, BKW-FMB Energie, operator of Mühleberg, told Federal Nuclear Safety Inspectorate (ESNI) that it will permanently shut the 373MWeboiling water reactor on 20 December 2019, provided that legal conditions necessary to begin immediate dismantling are implemented. This is in line with its stated target of closing the plant by the end of 2019. It will then take 15 years to decommission the plant, The clean-up bill is expected to reach CHF800m ($801m).

In January 2015 ENSI approved upgrades proposed by BKW for the continued operation of Mühleberg until 2019. BKW received a limitless operating licence for Mühleberg, but then announced in late 2013 that the station would be permanently shut down in 2019 instead of the planned 2022 because of "uncertainty surrounding political and regulatory trends".

In December 2015, ENSI asked BKW to submit plans for "safe technical operation" once power production ends at the facility. ENSI said BKW must submit "plans and analysis" for "basic safety goals" for the period following the end of power production and before decommissioning work begins, including the cooling of fuel in the reactor vessel, unloading the fuel, and storage and cooling in the used-fuel pool before the fuel assemblies are transferred away from the site.