ML19260C354

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: ML19260C354
References
LER-79-105-01T, LER-79-105-1T, NUDOCS 7912260237
Download: ML19260C354 (2)

Text

U. S. NUCi.E AR REGULATORY COMMISSION NRC FORQ136G

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' LICENSEE EVENT REPORT IFLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

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8 9 l 0 l H l D I B l S l 1 l@l 0 l 0 l - l 0 l 0 l N l P l F l - l 0 l 3 l@l 4 l1 l 1 l LICENSEE CODE 14 15 LsCENSE NUMBEH 23 26 LICENSE TYPE J0 $7 CAT $8 CON'T to i

[g"7 l L l@l 0 l 5 l 0 l - l 0 l 3 l 4l 6 @l 68 69 1 l1 l 0 ] 9 l 7 l 9 ]@l111 EVENT DATE 74 75 REPORT DATE 80 l 2 l 1 l 7 7 8 60 61 COCKET NUYSER EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br /> during the review of NRC I6E Bulletin 79-21 response, it was (lis-to 2 l On 11/9/79 at o 3 l covered that our steam generator low level trip setpoints to Steam and Feedwater Rup- l I

o 4 lture Control System Channels 1 and 2 were less conservative than the limits of T.S.

This finding is being reported in accordance with T.S. 6.9.1.8.h. A Mode 3 l o 3 l3.3.2.2.

l l o 16 l 1 restraint was placed on the unit until new vclues were determined and adjustments l

0 7 l made.

A safety analysis is being made and will be forwarded as a revision.

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12 18 19 20 REVISION 8 9 10 11 REPORT 7

SEQUENTtAL oCCURAENCE No.

CODE TYPE LE R/RO _ EVENT YE AR l7 l9 j j .__ l REPORT NO.

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]g 41 l2Nl@ [_1}h 4 43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS l 1[g l The cause of the occurrence was an error in the method used in determining th The approach failed to take into I If g ] steam generator low level bistable setpoints.

l j g l account the actual pressures and temperatures as seen by the steam generato 1 On 11/12/79, the adjustments were made, and ST 5031.14]

[ g l transmitter during operation.

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Dan Trautman PHONE:

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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 ) h }-7 078