ML19329B572

RO NP-32-77-07:on 770715,investigation Revealed High Energy Pipe Break Blowout Panels in Negative Pressure Boundary Designed to Blow Out at Less Pressure than Calculated for Loca.Caused by Design Deficiency.Design Changed

ML19329B572
Person / Time
Site:	Davis Besse
Issue date:	07/25/1977
From:	Batch S, Lingenfelter J TOLEDO EDISON CO.
To:
Shared Package
ML19329B494	List: ML19329B492 ML19329B572
References
NUDOCS 8002050708
Download: ML19329B572 (3)

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\s, DAVIS-BESSE UNIT ONE NUCLEAR POWER STATION

, SUPPLEMENTAL INFORMATION FOR LER NP-32-77-7 DATE OF EVENT: July 15, 1977 FACILITY: Davis-Besse Unit I .

IDENTIFICATION OF OCCURRENCE: Unrecognized Accident Analysis Condition - High Energy Pipe Break Blowout Panels Pressure Setpoint.

Conditions Prior to Occurrence: The plant was in Mode 4 with Power (MWT) = 0 and Load (MWE) = 0.

Description of Occurrence: A Field Quality Control Engineer employed by Bechtel 4 (the architect / engineer for Davis-Besse Unit I) asked for comparison of the set pressure of the blowout panels to the pressure calculated to occur on the' panels under a Loss of Coolant Accident (LOCA) condition. The subsequent Bechtel inves-tigation showed the blowout panels were designed to blowout at 0.5 psid which is less than the 0.8 psid that was calculated to occur af ter a LOCA. These blowout panels are part of the negative pressure boundary wall and were installed to pro-tect the penetration rooms from overpressurization if a steamline or feedwater <

I break would occur. These panels should have been designed not to blowout under

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LOCA pressure conditions.

Bechtel notified Toledo Edison's Power Engineering Department which then notified station persor'el of the occurrence at 1615 hours0.0187 days <br />0.449 hours <br />0.00267 weeks <br />6.145075e-4 months <br /> on July 15, 1977. This placed the station into the Action Statement of Technical Specification 3.6.5.2, which requires shield building integrity in Mode 4.

Designation of Apparent Cause of Occurrence: The cause of this occurrence has been determined to be a design deficiency in the failure by Bechtel to compare the blowout pressure with the pressure calculated to occur after a LOCA.

Analysis of Occurrence: Since the initial fuel core has never achieved critica-lity, excessive radioactivity would not be released if a LOCA did occur. There-fody, no threat occurred to the health and safety of the public or station per-sonnel.

Corrective Action: A design change which increased the relief point of the blow-out panels to 1.0 psid was completed by 1900 hours0.022 days <br />0.528 hours <br />0.00314 weeks <br />7.2295e-4 months <br /> on July 16, 1977. This re-moved the station from the Action Statement of Technical Specification 3.6.5.2.

High energy line breaks were re-analyzed in the areas of the auxiliary building affected by the change in the relief points. It was determined that peak pres-ge~'s sures resulting from any of these breaks were consistently below the design g ) limits in the affected areas as indicated in Table 3-6aa (pages 3-47b and 3-47c)

\~~/ of the Davis-Besse Unic I Final Safety Analysis Report (FSAR). ,

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TOLEDO EDISON COMPANY

DAVIS-BESSE UNIT ONE NUCLEAR POWER STATION SUPPLEMENTAL INFORMATION FOR LER NP-32-77-7 PACE 2 With the, design and relief point changes, the FSAR blowout pressures on pages 3-47r (Room 236), 3-47w (Room 303), and 3.47x (Room 314) are now 1.0 psid.

Failure Data: No previous similar events have occurred.

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