05000250/LER-1979-021-01, /01T-0 on 790626:NSSS Vendor Notified Util of Potential Level Bias Which Could Delay Reactor Trip & Feedwater Initiation or Cause False Level Indications. License Amend Will Be Proposed to Increase Sys Setpoint

/01T-0 on 790626:NSSS Vendor Notified Util of Potential Level Bias Which Could Delay Reactor Trip & Feedwater Initiation or Cause False Level Indications. License Amend Will Be Proposed to Increase Sys Setpoint

ML19225A030
Person / Time
Site:	Turkey Point
Issue date:	07/10/1979
From:	Schoppman M FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19225A025	List: 05000250/LER-1979-021, Forwards LER 79-021/01T-0 05000250/LER-1979-021-01, /01T-0 on 790626:NSSS Vendor Notified Util of Potential Level Bias Which Could Delay Reactor Trip & Feedwater Initiation or Cause False Level Indications. License Amend Will Be Proposed to Increase Sys Setpoint
References
LER-79-021-01T, LER-79-21-1T, NUDOCS 7907170195
Download: ML19225A030 (2)

LER-1979-021, /01T-0 on 790626:NSSS Vendor Notified Util of Potential Level Bias Which Could Delay Reactor Trip & Feedwater Initiation or Cause False Level Indications. License Amend Will Be Proposed to Increase Sys Setpoint

Event date:
Report date:
2501979021R01 - NRC Website

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REPORTABLE OCCURRENCE 250-79-21 LICENSEE EVENT REPORT PAGE TWO Additional Event Description and Probable Consecuences:

Notification was received from our NSSS vendor regarding a potential level bias which could be imposed on the steam generator water level instrumentation signal.

This bias could occur as a result of high containment temperature influencing steam generator level transmitter reference leg temperature and consequently fluid density.

In the event of a high energy line break inside conti.inment, the increase in reference leg temperature could theoretically cause a bias such that the indicated steam generator level could be 10%

greater than the actual level.

In the case of a feedline break, this condition could slightly delay reactor trip and auxiliary feedwater initiation based on low-low steam generator level.

This phenomenon could also exis t in the post-accident containment environment and cause a similar discrepancy between indicated and actual steam generator level.

Additional Cause Description and Corrective Action:

Review of this information indicates there is no adverse safety significance because of the conservatism of our low-low steam 6enerator level trip setpoint, i.e.,

15% versus 0% used for accident analysis basis.

However, our Technical Specification limiting safety system setting requirement allows a setpoint of 5% for low-low steam generator level.

Therefore, a license amendment will be proposed to increase the limiting saf 2ty system setpoint.

Our review of the significance of post-accident steam generator level bias is continuing.

At present, we believe the effect of the postulated difference between indicated and actual steam generator levels would be inconsequential.

We are considering the use of correction factors for indicated steam generator level.versus containment temperature should this be necessary.

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