ML19329B572
| ML19329B572 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 07/25/1977 |
| From: | Batch S, Lingenfelter J TOLEDO EDISON CO. |
| To: | |
| Shared Package | |
| ML19329B494 | List: |
| References | |
| NUDOCS 8002050708 | |
| Download: ML19329B572 (3) | |
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TOLEDO EDISON COMPANY
\\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 (the architect / engineer for Davis-Besse Unit I) asked for comparison of the set 4
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 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
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limits in the affected areas as indicated in Table 3-6aa (pages 3-47b and 3-47c)
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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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