ML19210D641

LER 79-105/01T-0:on 791109,steam Generator Low Level Trip Setpoints to Steam & Feedwater Rupture Control Sys Channels 1 & 2 Found Less Conservative than Tech Specs.Caused by Error in Analysis to Determine Low Level Bistable Setpoints

ML19210D641
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
ML19210D631	List: ML19210D630 ML19210D641
References
LER-79-105-01T, LER-79-105-1T, NUDOCS 7911270418
Download: ML19210D641 (2)

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LICENSEE EVENT REPORT

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DATE 7 60 61 DOCKET NUMBER EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h o 2 l On 11/9/79 at 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-o 3 covered that our steam generator low level trip setpoints to Steam and Feedwater Rup- l o [ ure Control System Channels 1 and 2 were less conservative than the limits of T.S.

o s 3.3.2.2. This finding is being reported in accordance with T.S. 6.9.1.8.h. A Mode 3 l o e l restraint was placed on the unit until new values were determined and adjustments l 0 7 l made. A safety analysis is being made and will be forwarded as a revision. l o a l(NP-32-79-12) l 80 7 8 9 DE CODE SB E COMPONENT CODE SUSCOdE SU DE o 9 l C l H l@ y@ l A l@ lI N S Tl R Ul@ g@ g @

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CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h lil0llThe cause of the occurrence was an error in the analysis used in determining the i i steam. generator low level bistable setpoints. The analysis failed to take into 3 7 l account the actual pressures and temperatures as seet by the steam generator during l 3 3 l operation. On 11/17/79, the adjustments were made and ST 5031.14 was successfully l li i4 l l performed. The restraint was lifted.

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80 LOSS OF OR DAMAGE TO FACILITY TYPE DE SCRIPTION 1 9 (Zjgl NA j zOp ') J 7 7 8 9 _ 10 80 ISSUE DESCRIPTION 2 O [N_jhl NA el 911 '2 7 0 y ll lllil;i llj 7 8 9 10 68 69 80 5 Dan Trautman - 419-259-5000, Ext. 235 o VR 79-163 NAME OF PREPARER PHONE:

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TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEMENTAL 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

- [he less conservative than assumed.

Conditions Prior to Occurrence: The unit was in Mode 5, with Power (MWT) = 0, and Load (Gross MWE) = 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 I&E Bulletin 79-21 response, it was discovered that our steam generator low level trip setpoints to Stcam 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 C u Jower tube sheet as required by Technical Specifications.

As a result, a Made 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 analysis used in determining the steam generator low level bistable setpoints. The analysis failed to take into account the actual pressures and temperatures as seen by the steam generator during 7eration 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 proven 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 1398 278