05000251/LER-1979-010-01, /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

ML17338A852
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
ML17338A851	List: 05000251/LER-1979-010, Forwards LER 79-010/01T-0 05000251/LER-1979-010-01, /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-79-010-01T, LER-79-10-1T, NUDOCS 7907170164
Download: ML17338A852 (4)

LER-1979-010, /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:
2511979010R01 - NRC Website

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REPORTABLE OCCURRENCE 2~,79-10 LICENSEE EVENT REPORT PAGE ThO.

Additional Event Descri tion and Probable Consecuences:

Notification was.received, from oux NSSS vendor regarding a potential level b'as 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 refexence leg temperature

and, consequently fluid, density.

In the event of a high energy line"break inside containment, the increase in reference leg te=perature could theoretically

cause

a bias such that the indicated steam gene ator level could be 10%

greater than the actual level.

In the case o

a feedline break, this condition could slightly delay reactor trip and auxiliary feedwater initiation based'n low-low steam generator level.

This phenomenon could also exist in the post-accident containment environment and cause a similax discxepancy between indicated and actual steam generator level.

Additional Cause Descri tion and Corrective Action:

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

15% versus 0% used for accident analysis oasis.

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

There=o=e, a license amendment will be pxoposed to increase the limiting safety syste setpoint.

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

At present, we believe the effect o" the postulated difference between indicated and actual ste~m generator levels'would be. inconsequential.

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

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