05000346/LER-1980-028-01, /01T-0:on 800417,during Review of Station Procedures,Discrepancy Identified Between Plant Operating Practices & Safety Analysis.Caused by Safety Analysis Assumptions Being More Restrictive than Actual Conditions

/01T-0:on 800417,during Review of Station Procedures,Discrepancy Identified Between Plant Operating Practices & Safety Analysis.Caused by Safety Analysis Assumptions Being More Restrictive than Actual Conditions

ML19312D882
Person / Time
Site:	Davis Besse
Issue date:	04/28/1980
From:	Lingenfelter J TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19312D880	List: 05000346/LER-1980-028, Forwards LER 80-028/1T-0 05000346/LER-1980-028-01, /01T-0:on 800417,during Review of Station Procedures,Discrepancy Identified Between Plant Operating Practices & Safety Analysis.Caused by Safety Analysis Assumptions Being More Restrictive than Actual Conditions
References
LER-80-028-01T, LER-80-28-1T, NUDOCS 8005050310
Download: ML19312D882 (3)

LER-1980-028, /01T-0:on 800417,during Review of Station Procedures,Discrepancy Identified Between Plant Operating Practices & Safety Analysis.Caused by Safety Analysis Assumptions Being More Restrictive than Actual Conditions

Event date:
Report date:
3461980028R01 - NRC Website

text

U.S. NUCLEAR REGUL AToRY COMMISSloN NRC FORM 366 LICENSEE EVENT REPORT 80050 (1-771 50 3g CONTROL BLOCK: l l

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8 60 61 DOCKET NUMB ER 68 b3 EVENT DATE 74 75 REPORT DATE 80 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h 10121 l (NP-32-80-04) During a review of station procedures, a discrepancy between existing l

plant operating practices and the safety analysis was identified. Of primary =.eerng go g3; l is the assumption that pressurizer spray would be available following a steam genera-g ITTTl I This was determined g

tor tube rupture to reduce reactor coolant systera pressure.

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TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-32-80-04 DATE OF EVENT: April 17, 1980 FACILITY: Davis-Besse Unit 1 i

i IDENTIFICATION OF OCCURRENCE: Determination of Existing Conditions Outside Safety Analysis Conditions Prior to Occurrence: The unit was in Mode 5, with Power (MWT) = 0, and Load (Gross MWE) = 0.

Description of Cecurrence:

D'uring a review of station procedures, a discrepancy between existing plant conditions and the Davis-Besse Unit 1 safety analysis was identified. Chapter 15 of the FSAR discusses the steam generator tube rupture acci-dent and makes certain basic assumptions.

Of primary concern is the assumption that pressurizer spray will be available following the tube rupture to reduce Reactor Coolant System (RCS) pressure below the main steam safety valve setpoint pressure.

The accident analysis also identified the escape paths by which primary activity could be released to the atmosphere.

This analysis shows that during the steam generator tube rupture accident, the RCS pressure will drop and the Safety Features Actuation System (SFAS) Incident Level 2 1650 psig trip will be actuated.

As a result of emergency procedural changes which require the tripping of all Reactor Coolant Pumps (RCPs) on receipt of an SFAS 1650 psig Incident Level 2 alarm, the driving force for pressurizer spray will be lost un-til the RCPs are restarted.

Standard operator action time assumption for accident analysis at Davis-Besse is ten minutes.

When all four RCPs are tripped, the Steam and Feedwater Rupture Control System (SFRCS) will initiate auxiliary feedwater to both steam generators with each auxiliary feed pump turbine being supplied steam by its associated steam generator. The exhaust for the auxiliary feed pump turbine being supplied by the leaking steam generator constitutes a new path for primary system activity to the atmosphere. The loss of pressurizer spray and the new leakage path are not in agreement with the existing accident analysis.

These issues appear to be generic in nature and have been reviewed by the NRC in NUREG 0651.

Designation of Apparent Cause of Occurrence: NRC IE Bulletin 79-05C, in response to the Three Mile Island Unit II event, required the procedural changes by which RCPs are tripped on receipt of Incident Level 2 SEAS 1650 psig trip.

LER #80-028 A-n

TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-32-80-04 PAGE 2 Analysis of Occurrence: There was no danger to the health and safety of the public or to station personnel.

The assumptions used in the safety analysis are substantial-ly more restrictive than actual conditions.

Most significantly, actual primary coolant activity levels indicate that the quantity of failed fuel in the reactor core is approximately 100 times less than the 1% of failed core fuel assumed in the

Corrective Action

The steam generator tube rupture accident is being reanalyzed by the Babcock and Wilcox Company and Bechtel Power Corporation to determine how the loss of pressurizer spray and the new activity escape path will affect the offsite doses.

This analysis is currently scheduled to be completed by May 15, 1980.

Procedural guidelines which cope with this accident are being developed as part of the " Abnormal Transient Operator Guidelines" (ATOG) program being conducted by Babcock and Wilcox Company and the utilities owning Babcock and Wilcox plants.

Failure Data: There have been no previous similar reportable occurrences.

LER #80-028 9

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