Stockholm, Dec 3 (IANS): A Swedish nuclear reactor that was taken off-grid in August will not restart until next year, utility company Vattenfall said.

Ringhals 4 was due for the restart on January 31, 2023, following five months of repair works. However, the relaunch has now been postponed to February 23, Vattenfall said.

The reactor was shut down in mid-August for annual maintenance, and was about to be restarted when a pressure vessel was damaged during testing, reports Xinhua news agency.

Initially, Vattenfall said the repair work would take three months, but this is the second time the restart date has been pushed back.

"The work is going well, but parts of the work are taking longer than expected," Ringhals CEO Bjorn Linde said.

Among other things, a full-scale model of the nearly 13-meter-high pressure vessel has been constructed so that tools can be tested, and staff can rehearse procedures.

"The repair is complex and all available resources are working hard towards restarting production at Ringhals 4, as nuclear power is in demand in the Swedish electricity system," Linde said.

According to Vattenfall, the reactor has an output of 1,130 megawatts (MW) and an energy expert told Dagens Nyheter (DN) newspaper that the delays may result in further price rises.

"We are having an extreme situation with horrible prices. All lost (electricity) production is bad news," Lina Bertling Tjernberg, a professor in Power Grid Technology at Sweden's Royal Institute of Technology, told DN.

According to the Swedish Radiation Safety Authority, the country has six remaining nuclear reactors, after four were decommissioned in 2017-2020.

Together, they account for around 30 per cent of Sweden's electricity production.