ML16341F945
| ML16341F945 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 01/18/1991 |
| From: | Richards S NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Shiffer J PACIFIC GAS & ELECTRIC CO. |
| References | |
| NUDOCS 9101300115 | |
| Download: ML16341F945 (6) | |
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Docket 50-275 UNITED STATES NUCLEAR REGULATORY CONIMISSION REGION V 1450 MARIALANE,SUITE 210 WALNUTCREEK, CALIFORNIA94596 JAN 18 1991.
Pacific Gas and Electric Company 77 Beale Street, Room 1451 San Francisco, California 94106 v
Attention:
Mr. J.
D. Shiffer, Senior Vice President and General Manager Nuclear Power Generation Gentlemen:
SUBJECT:
REVIEW OF LICENSEE EVENT REPORT 1-90-015-00 Thank you for your Licensee Event Report (LER) 1-90-015-00, transmitted by PG&E letter DCL-91-003, dated January 7, 1991, and titled "ESF Actuation, P-14 (High-High Steam Generator Water Level), Due to Feedwater Regulating and Bypass Valves Leakage."
Our review of the report indicates some clarification may be required.
The report states that the root cause of the event on December 8, 1990, was valve leakage experienced during a startup from an inadvertent reactor trip.
The report further states that, as an action to prevent recurrence, the leaking valves were subsequently repaired in late December after a second inadvertent reactor trip.
Our understanding of the event indicates that the valves discussed in the LER (main feedwater check valve FW 531, main feedwater regulating valve FW 530, and the main feedwater regulating bypass valve FW 1530) were observed to be leaking and causing level control difficulties during unit restart attempts or reactor trips in December 1989, February 20, 1990, February 22, 1990, and also on June 14 and June 19, 1990.
Therefore it would appear the operators should not have been surprised by the leaking valves and either should have been pre-warned and provided with. a strategy for dealing with the leaking valves, or the valves should have been fixed at one of the earlier opportunities.
Operator statements after the December 8, 1990, event indicate that they were not aware of the valve conditions. It appears that the lack of operator knowledge should be considered as a root cause and appropriate corrective action considered.
Additionally, the fact that the valves leaked should not have caused a rapid level drop in steam generator 1-3 unless the water had a location to which to flow.
Your LER does not describe the flow path. It is our understanding that another valve, FCV420, the feedwater recirculation valve to the main condenser, was found to have substantial seat leakage on December 21, 1990, during an operations walkdown done in response to inquiries as to where the feedwater was flowing.
Therefore it appears that lack of timely investigative and corrective action after the previously observed level control events outlined above, may have been a contributing root cause and may indicate other appropriate corrective actions are required.
9101300115 910118
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Further we understand the safety analysis results, which the LER states were not adversely affected, are being reevaluated by your personnel given the possibility that significant portions of auxiliary feedwater flow could have been diverted to the condenser by these leaking feedwater valves.
Please give this event and event report further consideration and revise the report if appropriate.
In accordance with 10 CFR 2.790 (a),
a copy of this letter will be placed in the NRC Public Document Room Sincerely, S. A. Richards, Chief Reactor'Projects Branch cc:
J. A. Sexton, PGRE R.
F. Locke, PGSE J.
D. Townsend, PGKE (Diablo Canyon)
D. A. Taggert, PGSE (Diablo Canyon)
T. L. Grebel, PG&E (Diablo Canyon)
News Services, PGSE State of California
Further we understand the safety analysis results, which the LER states were not adversely affected, are being reevaluated by your personnel given the possibility that significant portions of auxiliary feedwater flow could have been diverted to the condenser by these leaking feedwater valves.
Please give this event and event report further consideration and revise the report if appropriate.
In accordance with 10 CFR 2.790 (a),
a copy of this letter will be placed in the NRC Public Document Room Sincerely, S. A. Richards, Chief Reactor Projects Branch cc:
J. A. Sexton, PGEE R.
F. Locke, PGSE J.
D. Townsend, PG8E (Diablo Canyon)
D. A. Taggert, PGKE (Diablo Canyon)
T. L. Grebel, PG5E (Diablo Canyon)
News Services, PGSE State of California yacc; T. 5ar%w RL,2ieesr+AA RY 3f PNarbut:jb 01/(4 /91 ST C
PY ES /
NO PMorrill 01/y( /91 EST COPY YE
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NO SRichards 01/iS/91 U
TCPY YES
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NO PD YES /
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