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The following event description is based o … The following event description is based on information currently available. If through subsequent reviews of this event, additional information is identified that is pertinent to this event or alters the information being provided at this time, a follow-up notification will be made via the ENS or under the reporting requirements of 10CFR50.73.</br>On August 22, 2005, at approximately 1605 hours Mountain Standard Time (MST), Palo Verde Nuclear Generating Station (PVNGS) Unit 2 commenced a reactor shutdown required by Technical Specification 3.0.3. </br>Westinghouse notified Palo Verde that the current version of the Common Q based Core Protection Calculator System (CPCS) software is not consistent with the system design requirements and Technical Specification Bases regarding the system response to analog input module errors. In that a failed sensor input or failure of the two analog input modules in a given CPCS channel (four total channels) would not result in a CPCS channel trip. At Palo Verde, the CPCS provides the reactor trip functions for Low Departure from Nucleate Boiling Ratio (DNBR) and High Local Power Density (LPD). A failed input sensor would be the most likely cause for both of the redundant input modules to indicate errors simultaneously because the two redundant input modules within a safety channel are connected to a single sensor. A similar scenario would occur if both analog input modules simultaneously failed. In both cases the result would be a failure of the channel without initiating a trip signal. </br>Operations evaluated the non-conforming condition and declared all four channels of the CPCS inoperable. Limiting Condition for Operability (LCO) 3.3.1 only addresses up to two automatic RPS trip channels inoperable, therefore Operations entered LCO 3.0.3 at approximately 13:26 MST.</br>The event did not result in the release of radioactivity to the environment and did not adversely affect the safe operation of the plant or health and safety of the public. The required offsite power sources are operable and the electrical grid is stable.</br>The Common Q based CPCS is installed at the following nuclear power plant site in the United States: Palo Verde Unit 2. At this time, this condition is not transportable to Palo Verde Units 1 and 3.</br>All Emergency Core Cooling systems and their Emergency Diesel Generators are fully operable if needed. </br>The NRC Resident Inspector was notified of this event by the licensee.as notified of this event by the licensee.
23:05:00, 22 August 2005 +
41,939 +
20:10:00, 22 August 2005 +
23:05:00, 22 August 2005 +
The following event description is based o … The following event description is based on information currently available. If through subsequent reviews of this event, additional information is identified that is pertinent to this event or alters the information being provided at this time, a follow-up notification will be made via the ENS or under the reporting requirements of 10CFR50.73.</br>On August 22, 2005, at approximately 1605 hours Mountain Standard Time (MST), Palo Verde Nuclear Generating Station (PVNGS) Unit 2 commenced a reactor shutdown required by Technical Specification 3.0.3. </br>Westinghouse notified Palo Verde that the current version of the Common Q based Core Protection Calculator System (CPCS) software is not consistent with the system design requirements and Technical Specification Bases regarding the system response to analog input module errors. In that a failed sensor input or failure of the two analog input modules in a given CPCS channel (four total channels) would not result in a CPCS channel trip. At Palo Verde, the CPCS provides the reactor trip functions for Low Departure from Nucleate Boiling Ratio (DNBR) and High Local Power Density (LPD). A failed input sensor would be the most likely cause for both of the redundant input modules to indicate errors simultaneously because the two redundant input modules within a safety channel are connected to a single sensor. A similar scenario would occur if both analog input modules simultaneously failed. In both cases the result would be a failure of the channel without initiating a trip signal. </br>Operations evaluated the non-conforming condition and declared all four channels of the CPCS inoperable. Limiting Condition for Operability (LCO) 3.3.1 only addresses up to two automatic RPS trip channels inoperable, therefore Operations entered LCO 3.0.3 at approximately 13:26 MST.</br>The event did not result in the release of radioactivity to the environment and did not adversely affect the safe operation of the plant or health and safety of the public. The required offsite power sources are operable and the electrical grid is stable.</br>The Common Q based CPCS is installed at the following nuclear power plant site in the United States: Palo Verde Unit 2. At this time, this condition is not transportable to Palo Verde Units 1 and 3.</br>All Emergency Core Cooling systems and their Emergency Diesel Generators are fully operable if needed. </br>The NRC Resident Inspector was notified of this event by the licensee.as notified of this event by the licensee.
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00:00:00, 22 August 2005 +
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02:20:23, 2 March 2018 +
20:10:00, 22 August 2005 +
true +
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-0.122 d (-2.92 hours, -0.0174 weeks, -0.004 months) +
23:05:00, 22 August 2005 +
Technical Specification Shutdown Due to Core Protection Calculator System (Cpcs) Software Not Consistent with System Design Requirements. +
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