05000346/LER-1979-105, Revised LER 79-105/01T-1:on 791109,during Review of IE Bulletin 79-21 Response,Noted Steam Generator Low Level Trip Setpoints to Steam & Feedwater Rupture Control Sys Channels 1 & 2 Were Below Tech Specs.Caused by Error in Poin

Revised LER 79-105/01T-1:on 791109,during Review of IE Bulletin 79-21 Response,Noted Steam Generator Low Level Trip Setpoints to Steam & Feedwater Rupture Control Sys Channels 1 & 2 Were Below Tech Specs.Caused by Error in Points

ML19260C354
Person / Time
Site:	Davis Besse
Issue date:	11/21/1979
From:	Trautman D TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19260C355	List: 05000346/LER-1979-105, Revised LER 79-105/01T-1:on 791109,during Review of IE Bulletin 79-21 Response,Noted Steam Generator Low Level Trip Setpoints to Steam & Feedwater Rupture Control Sys Channels 1 & 2 Were Below Tech Specs.Caused by Error in Poin
References
LER-79-105-01T, LER-79-105-1T, NUDOCS 7912260237
Download: ML19260C354 (2)

LER-1979-105, Revised LER 79-105/01T-1:on 791109,during Review of IE Bulletin 79-21 Response,Noted Steam Generator Low Level Trip Setpoints to Steam & Feedwater Rupture Control Sys Channels 1 & 2 Were Below Tech Specs.Caused by Error in Points

Event date:
Report date:
3461979105R00 - NRC Website

text

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TOLEDO EDISON COMP.%T DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLE'4 ENTAL INFORMATION FOR LER NP-32-79-12 DATE OF EVENT: November 9, 1979 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE:

Steam Generator low level trip setpoints found to be less conservative than assumed.

Conditions Prior to Occurrence: The unit was in Mode 5, with Power (MUT) = 0, and Load (Gross MNE) = 0.

Description of Occurrence:

On November 9, 1979 at 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br />, during the review of NRC IEE Bulletin 79-21 response, it was discovered that our steam generator low level trip setpoints to Steam and Feedwater Rupture Control System (SFRCS)

Channels 1 and 2 were less conservative than the limits of Technical Specification

3. 3. 2. 2.

The steam generator low level bistable trip setpoint was 23 inches + 2 inches. However, the re-evaluation of the method used to determine the setpoints based on actual versus indicated level found that the actual level would be less conservative than the minimum 20 inches of water above the lower tube sheet as required by Technical Specifications.

As a result, a Mode 3 restraint was placed on the unit until new values could be determined and adjustments to the bistable trip setpoint made. This occurrence is being reported in accordance with Technical Specification 6.9.1.8.h which re-quires prompt notification with a followup report within two weeks for an error in analysis, which would have permitted reactor operation in a manner less conser-vative than assumed.

Designation of Apparent Cause of Occurrence: The apparent cause of the occurrence was found to be an error in the method used in determining the steam generator low level bistable setpoints. The approach failed to take into account the actual pres-sures and temperatures as seen by the steam generator level transmitter during operation and in transients.

Analysis of Occurrence: A safety analysis is being performed and will be forwarded as a revision.

Corrective Action

On November 17, 1979, new steam generator low level bistable trip setpoints were established and adjustments were made. All four channels were pruven operable by performance of ST 5031.14, "SFRCS Monthly Surveillance Test".

The mode restraint relating this event was removed as of 1755 hours0.0203 days <br />0.488 hours <br />0.0029 weeks <br />6.677775e-4 months <br /> on November 19, 1979.

Failure Data: There have been no previous similar occurrences.

LER #79-105

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