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NRC ISSUES BULLETIN ON POTENTIAL DESIGN VULNERABILITY IN ELE

Daily newsbrief journal for July 2012, also see http://www.usdemocrats.com/brief for a global 100-page perpetual brief and follow twitter @usdemocrats


NRC ISSUES BULLETIN ON POTENTIAL DESIGN VULNERABILITY IN ELE

Postby admin » Fri Jul 27, 2012 11:10 am

NRC ISSUES BULLETIN ON POTENTIAL DESIGN VULNERABILITY IN ELECTRIC POWER SYSTEMS AT NUCLEAR POWER PLANTSThe Nuclear Regulatory Commission has issued a Bulletin to all nuclear power plant licensees requesting information about their electric power system designs and alerting them to apotential design vulnerability that could affect the operation of key safety equipment.On Jan. 30, Byron Station, Unit 2, shut down automatically due to unbalanced voltageentering the onsite power distribution system from the transmission network. The plant’s electricpower system’s protection scheme was not designed to sense the loss of one of three powerphases and automatically trip circuits to isolate the degraded outside power source and switch to emergency backup power. Plant operators diagnosed the problem eight minutes later and manually tripped the necessary circuits.The degraded offsite power source potentially could have damaged the plant’s emergencycore cooling system. NRC regulations and plant technical specifications require reliable off-siteand onsite power systems with sufficient capacity and capability to operate safety-relatedsystems. Therefore, the NRC staff is seeking information to verify compliance with existingregulations and plant-specific licensing bases. The staff will use the information it receives toinform the Commission and determine if further regulatory action is needed.The NRC issued Information Notice 2012-03 on March 1 to inform licensees of recentexperience involving loss of one of three phases of the offsite power circuit, including the Byron event. The current Bulletin requests licensees to provide information on their electric systemdesigns within 90 days. It applies to the 104 currently operating commercial power reactors and the four combined licenses for new reactors issued earlier this year. It does not apply to licenseeswho have permanently ceased operation and certified that the fuel has been removed from thereactor vessel.Bulletin 2012-01, “Design Vulnerability in Electric Power System,” is available on theNRC website. ###
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