Three Mile Island nuclear plant shuts down unexpectedly

Three Mile Island plant, scene of the worst nuclear power accident in the US, shut down automatically after failure of a coolant pump. Officials say the Three Mile Island shutdown poses no threat.

The Three Mile Island nuclear power generating station in Middletown, Pa., shown here in a 2011 file photo, shut down automatically Thursday when a coolant pump failed. It's the second shutdown at the plant in two months.

Bradley C Bower/AP/File

September 21, 2012

A malfunctioning pump at the site of the worst nuclear power plant accident in U.S. history has triggered an automatic shutdown.

Thursday's shutdown at Pennsylvania's Three Mile Island was the second in as many months. Government regulators and plant officials say it poses no threat to public health or safety. Operator Exelon Generation Co. says no detectable levels of radiation escaped.

The failure of a coolant pump tripped a computerized system that shuts downs the reactor. The Nuclear Regulatory Commission says once the reactor has cooled, plant workers can access the containment building and troubleshoot.

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The plant also automatically shut down Aug. 22 while operators were manually shutting it down for repairs.

The plant is named after the island where it's located in the Susquehanna River. It had a partial meltdown of a reactor in 1979.