ML19347C780
| ML19347C780 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 06/30/1975 |
| From: | CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | |
| References | |
| RO-750630, UE-3-75, NUDOCS 8102170092 | |
| Download: ML19347C780 (2) | |
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UNUSUAL EVENT REFORT Big Rock Point 1.
Report No: UE 3-75; Docket 50-155 2a.
Report Date: June 30, 1975 2b.
Occurrence Date: June 6, 1975 3.
Facility: Big Rock Point Plant, Charlevoix, Michigan k.
Identification of Occurrence:
Deficiency in automatic core spray flow estab-lishment for small and intermediate break LOCA.
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Conditions Prior to Occurrence: Plant shut down for modification work asso-ciated with A01-75 6.
Description of Occurrence: Review of existing and proposed changes to B8 Operations Procedure on the post-incident system revealed a conflict in es-tablishnent of core spray flow at adequate pressure as described in the FHSR 13.5.2.1 and in Technical Specifications Change No 26 design basis statements by General Electric on the redundant core spray sparger design and installa-tion.
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An analysis of the fire system in 1972 indicates that the main electric fire pump start will not occur until reactor pressure has dropped to 62 psia due to the static head correction (23 psi) that had been neglected in previous design and analyses. FHSR 13.5.2.1 related to the DBA and the original sparger indicates adequate flow at 215 psia following automatic initiation.
Technical Specifications Change No 26 design basis statements indicate ade-quate redundant core spray flow at a reactor pressure of 85 psia (85 psia being the automatic starting point for the main electric fire pump based on the pressure at the fire pump elevation). The core spray valves have always been designed to actuate at a decreasing reactor pressure of 215 psia and low reactor water level and the fire pumps designed to start on decreasing fire header pressure.
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Designation of Apparent Cause of Occurrence: Design deficiency.
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Analysis of Occurrence: The postulated start of core spray flow was examined relative to the 215 psia and 62 psia start for the DBA in December 1972 and found to delay establishment of flow by 1.9 seconds which was deemed insignifi-cant. The delay in establishment of flow from the then current analysis which assumed an 85 psia fire pump start was even less. For the small and intermedi-ate break LOCA, Technical Specifications Change No 32 of July 18,197h recog-nized the dependence on the off-site power requirement for the manual action of the fire system prior to the installation of the RDS system. This change pro-vided for remote manual use of the fire system to supply water to the feed-water
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system for flooding and assist depressurization prior to the need for core s
spray. As a result, procedures were developed to manually start the main fire pump.
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9 Corrective Action: Additional means of starting the fire pump during the small and internediate break LOCA were never established, assuming a loss of off-site power. On June 6,1975 procedural means were established for start-ing the fire pump remote manually in Section B8 of the Operating Procedures and local manually in D2.26 Emergency Procedure in the event of loss of all off-site power during the small and intennediate break LOCA.
A portion of the modifications associated with the RDS system includes auto-matic fire pump start on steam drum low water level. The RDS system modifi-cations will commence in about September 1975 li 5