Federal regulators have cited Xcel Energy Inc. for unsafely postponing repairs to a broken detector designed to warn of high-level radiation being released from its Prairie Island nuclear power plant in Red Wing, Minn.

No release occurred during the nearly 10 months the detector wasn't working, but the Nuclear Regulatory Commission said Wednesday that Xcel violated safety regulations by not fixing the problem on the Unit 1 reactor right away.

Workers replaced the failed detector last May after NRC inspectors questioned the Minneapolis-based utility's delay. In a statement Wednesday, Jim Lynch, an Xcel vice president at the plant, said the plant has changed procedures so radiation monitors will get timely repairs.

One effect of the regulatory action, classified as a second-tier or "white" finding of low to moderate safety concern, is that the Prairie Island plant, 45 miles southeast of the Twin Cities, will be subject to enhanced federal inspections for the next year. The violation carries no fine.

The "Hi-Range Vent Gas Radiation Detector" is important in the event of an emergency release of radiation, a rare event. The detector gives a readout in the plant's control room that would help plant officials and emergency responders decide how to react to a radiation release.

Plant operators weren't left in the dark when the detector failed in July 2011. The venting pipe has a second sensor that detects low-level radiation. If that sensor showed a release, plant workers could take a sample manually from the vent pipe and test for high-level radiation.

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Terry Pickens, director of nuclear regulatory policy for Xcel Energy walked by one of two steam powered generators at Prairie Island nuclear plant north of Red Wing.

But the NRC concluded that Xcel's alternative method wasn't good enough.

"Even though the issue did not have an impact on the public, the NRC requires measures be in place and maintained to ensure the health and safety of the public is protected during certain emergency events," NRC Regional Administrator Charles Casto said in a statement.

Xcel said it won't appeal the violation. The company lost an initial challenge. At an NRC hearing in February, Xcel conceded the repair didn't get high priority because plant officials wrongly accepted the alternative measures as adequate.

"I assure you that won't happen again," a plant official told the NRC.

David Shaffer • 612-673-7090 Twitter: @ShafferStrib