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Nuclear safety: Five recent 'near miss' incidents at US nuclear power plants

Fourteen safety-related events at nuclear power plants required follow-up inspections from the Nuclear Regulatory Commission, the NRC reported in 2010. These "near-miss" events "raised the risk of damage to the reactor core – and thus to the safety of workers and the public," concluded a new report, "The NRC and Nuclear Power Plant Safety in 2010," by the Union of Concerned Scientists. Here are five of these 14 "near miss" examples:

- Staff

The Diablo Canyon nuclear power plant, seen in this 2008 file photo, operated for 18 months with emergency systems – key to allowing the flow of water to cool the reactor core and containment vessel in the event of an emergency – disabled. (Michael A. Mariant / AP / File)

1. Diablo Canyon, California – Emergency systems disabled

At the Diablo Canyon nuclear plant, operators found themselves unable to open the valves that provide emergency cooling water to the reactor core and containment vessel, during a test on October 22, 2009.

A misguided fix of an earlier problem had prevented the emergency valves from opening, the NRC team sent to investigate found.

Tests after the valve repairs had failed to detect the problem, meaning that the reactor had operated for nearly 18 months with vital emergency systems disabled. Although the earlier modification impaired the emergency core cooling systems, workers could have opened the valves manually, which reduced the severity of the violation, the report said.


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