As a consequence of the outage, Ringhals 4 is operating at half capacity. The production outage is expected to last into the beginning of next week, Vattenfall says in a press release.
Half of Sweden's nuclear reactors are already closed for maintenance. The fact that Ringhals 4 is also running at half speed is keeping already-high electricity prices up, especially in southern Sweden, says Patrik Södersten, an electricity-price expert at Fortum.
When we don't have these large nuclear power plants running, we are very dependent on the weather, he says.
The greatest impact on electricity prices will be in southernmost Sweden, where they are already unusually high, partly due to low water levels.
There, the price will jump to 74 öre tomorrow, compared to 19 öre today, which is partly due to the problems in Ringhals 4, he says.
He is not worried about the outage in Ringhals 4 - right now.
But if the problems drag on, it can become a perfect storm.
The reason for the production interruption in Ringhals 4 is a water leak in one of the generators.
Ringhals 3 has been shut down for annual maintenance work since the beginning of May.
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