At 1418 EDT on 03/17/2014, it was determined the atmospheric stability classification data display on the plant process computer (
PPC) could have been potentially inaccurate.
In September 2012, implementation of a hardware and software modification to separate the meteorological tower computer from the PPC introduced a calculation error to the PPC software design that resulted in the PPC potentially displaying inaccurate stability class data. The ability to accurately perform dose assessment calculations could potentially be affected when using the stability class indication obtained from the PPC.
The availability and accuracy of backup stability class data via the meteorological tower computer or from Weather Services International were not affected.
Within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of discovery, the procedurally described alternatives for obtaining stability class data were implemented.
Subsequently, the PPC stability class software calculation was corrected and the PPC stability class display restored for use.
There was no impact to any emergency declaration because there were no actual emergencies from the time the modification was implemented until the error was corrected.
The licensee has notified the NRC Resident Inspector.
