NRC sends inspectors to Progress NC Harris reactor

May 7 (Reuters) - The U.S. Nuclear Regulatory Commission will send a
four-member special inspection team to Progress Energy's Harris nuclear
plant in North Carolina to review the April failure of two main steam isolation
valves, the agency said in a release on Monday.  
    Progress shut the 900-megawatt Harris nuclear power plant April 21 for a
planned refueling. 
    As the unit was cooling down, two main steam isolation values failed to
close, the NRC said. Operators were able to partially close one valve in a half
hour while the other valve took three hours to close, the agency said.  
    Main steam isolation valves are used to shut off steam and restrict the
release of that steam during certain accident scenarios.  
    The NRC said a potential safety risk existed at the Harris plant had an
accident occurred while the valves were in a degraded state.  
    "There was no immediate threat to public safety, but this event does raise
important questions that need to be addressed," said Victor McCree, the NRC's
region II administrator.      
    The Harris inspection is the fourth initiated this year by the NRC. 
    At least 16 special inspections related to safety and five related to
security were begun in 2011, the most since the agency began the current program
in 1999, officials said.   
    While the issues that prompted special action by the NRC vary from plant to
plant, NRC Chairman Gregory Jaczko said late last year staff was looking for a
common thread that may contribute to the increase in inspections.  
    So far, the staff has not identified a common cause, an NRC spokesman said
Monday. 

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