A supplier has identified that steam temperature/pressure gauges, which where shipped to MULTIPLE nuclear power plants, were faulty; "it was concluded that a substantial safety hazard may exist"
The exact nature of the hazard is difficult to determine without detail data on how and where these pressure gauges are being utilized, hence the "may" in the quote from the NRC report. However they do identify the hazard as "substantial".
Our quick analysis of the situation indicates that as a result of 'zeroing out" the gauges at the factory a non linearity was introduced into the response curve of the instrument. The simple explanation is that large changes in pressures may result in small or no changes in the pressure readings.
Likely the greatest risk is during emergency conditions when having correct data may be exceedingly critical to any decision making process. Additional risks include: premature failure of steam turbines from improper steam phase change conditions, or sudden catastrophic failure of components unknowingly being operated at 'redline' conditions.
The event reports indicate that the manufacturer has been able to create serial number specific calibration charts to address the issue. However based on our own armchair analysis, we find it dubious that a substantial nuclear plant safety hazard arising from a non-linearly responding pressure gauge would be addressed without physically testing the response curve of each pressure gauge against the new "repair" calibration data.
The event report indicates that the Nuclear Sites affected by this substantial safety hazard are:
"Farley, D.C. Cook, Palo Verde, ANO-1, Calvert Cliffs, Point Beach, Oconee, Catawba, Waterford 3, Braidwood, La Salle, Davis Besse, Crystal River 3, Vogtle, Millstone, Diablo Canyon, Salem, Hope Creek, San Onofre, South Texas, Watts Bar, Comanche Peak, Wolf Creek, St. Lucie, Dominion Energy - Unspecified, and Northeast Nuclear Energy - Unspecified."
The NRC event reports associated with these findings are
#47693 on 2/24/12
#47693 on 3/06/12
#47716 on 3/06/12
Please note that the NRC apparently has changed the way it implements links to its event reports, as a result the above links may not point to the correct locations after 3/6/12. In that event, you will need to look up the event reports on the NRC website by date and event number.
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