On the Nuclear Shutdowns in Sweden

The AP has flashed the following story concerning an incident at the Oskarshamn nuclear power plant in Sweden:

Swedish nuclear authorities held an emergency meeting Thursday after two reactors were shut down at a plant in the southeast of the country.

The plant in Oskarshamn, about 250 kilometers (150 miles) south of the capital, Stockholm, shut down two of its three reactors late Wednesday after the company running the plant reported that "safety there could not be guaranteed."

The decision followed an incident last week at another nuclear plant in Sweden, in Forsmark, where backup generators malfunctioned during a power outage, forcing a shutdown of one of its reactors, said Anders Bredfell, a spokesman for the Swedish nuclear authority, SKI.

Since then, the former plant manager at Forsmark has been claiming that the incident at the plant is the most dangerous in the nuclear industry since Chernobyl, and that there was a risk of a meltdown. Greenpeace, rather predictably, has called for the country to shut down all of its nuclear power plants.

Per Jander over at the World Nuclear Association Blog disagrees:

This is absolute nonsense. The unit is in perfectly fine condition, plant management has sent in a report to the Swedish regulator (SKI) and is now awaiting permission to restart. No equipment is damaged, and reactor safety was never compromised.

A short circuit in an external switchyard resulted in a powerful transient and the power plant was automatically disconnected from the grid. Initially the power plant switched to in-house power generation, but through a complicated chain of events the turbines were stopped and power supply of the safety system was switched to two of the four back-up diesel generators. Normally all four diesel generators should provide the systems with power, but this time only two went online.

Safety systems are divided into four identical subsystems, each with their own diesel generator and capacity to manage 50% of the plant needs. If all subsystems and all diesels are working properly, there are twice the required capacity available. In this particular case, when two diesel generators started automatically and worked well during the entire chain of events, there were always sufficient power to cool the reactor and keep other safety functions online.

The serious aspect of this event is that the automatic power supply of safety systems were partly compromised because of a fault in the external grid. Because of possibilities of similar design, further three reactors in Sweden have been taken offline, and will not be restarted until the risk of a similar event is removed. The remaining six reactors in Sweden have a different design that prevents these kinds of issues.

When looking at this story, I hope our readers keep the Swedish domestic political situation in mind. As we've written in recent months, Sweden is on the verge of reversing its policy of phasing out the nation's nuclear power plants -- a notion that's shared by both center-left and center-right forces in the nation's parliament.

Further, public support for the industry has never been higher in the nation. A majority of Swedish voters are against early shutdown of the plants. For more on these polls, click here and here.

For many European Green parties, their efforts to shut down nuclear power plants all over the continent were a major high water mark in their history. The possibility that this decision in Sweden (and elsewhere) could be reversed would be a serious setback -- hence the tenor of Greenpeace's latest statement.

One last point: Even though the Swedish authorities didn't request the shutdown of any units, the owners of the plants did so voluntarily in order to address the problem.

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