The decision follows a request from Vattenfall, which owns the Forsmark nuclear plant on Sweden’s east coast.
Forsmark managing director Lars Fagerberg resigned last week in light of the recent safety concerns.
In the most serious incident, an electricity failure at the facility on Jul 25 last year led to the immediate shutdown of the Forsmark 1 reactor after two of four back-up generators, which supply power to the reactor’s cooling system, malfunctioned for about 20 minutes.
Some experts have suggested a catastrophic reactor meltdown was narrowly avoided.
The incident prompted authorities to shut down temporarily five of Sweden’s ten reactors for security checks and maintenance. Some of the reactors remained offline for several months.
At the request of the Swedish Nuclear Power Inspectorate, prosecutors are now investigating whether Forsmark’s operators broke the law in their response to the malfunction.
A damning internal report into safety standards at Forsmark was made public last month.
The report said a culture of lax security had developed, leading to a series of “potentially fatal accidents”.
And two of Forsmark’s three reactors were again shut down two weeks ago after a fault was found in rubber panels in one of the reactor’s housing. Both remain offline.
Nuclear power accounts for nearly half of Sweden’s electricity production.
Separately, a nuclear reactor at the Ringhals nuclear plant south of Gothenburg has been closed today while officials investigate a small leak.
The decision to shut down the Ringhals number 2 reactor was taken on Thursday evening after the leak was noted in the so-called primary system – the power station’s cooling system. Twelve litres of water per hour is currently leaking out, compared to a normal six litres per hour.
It is not yet known how long the reactor will be out of service.
“This is nothing serious,” said Lars Eliasson, head of production at Ringhals.