The U.S. Nuclear Regulatory Commission has issued a letter outlining three additional actions the Omaha Public Power District (OPPD) will take prior to restarting the 482 MW Fort Calhoun nuclear plant in Nebraska.
The plant, located 19 miles north of Omaha, is owned and operated by OPPD and has been shut down since April 2011 for a refueling outage and impacts from the Missouri River floodwaters.
The new action items include a requirement to address safety system functional failures, containment internal structure issues, and the use of Teflon as a sealant on electrical cables inside containment.
NRC is requiring OPPD to identify the causes and resolve issues that led to numerous safety system functional failures (SSFF) that were identified over the course of a year. A number of systems are paramount in safely shutting down the plant and cooling the reactor during an accident. If a key system has the potential for failure, the NRC defines it as a SSFF. An example is the June 2011 electrical switchgear fire that disrupted power to vital systems and components needed for the safe shutdown of the plant.
Additionally, OPPD must identify the causes and resolve two existing conditions inside containment. Plant workers discovered that structures supporting equipment do not meet all design requirements. Secondly, over 600 pipes housing electrical cables that run through the containment building are insulated using a material that is known to degrade under some accident scenarios involving high radiation exposure.
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