ML20198E704
| ML20198E704 | |
| Person / Time | |
|---|---|
| Site: | Oconee, 05000000 |
| Issue date: | 01/23/1985 |
| From: | Nicolaras H Office of Nuclear Reactor Regulation |
| To: | Case E, Harold Denton, Edison G NRC |
| Shared Package | |
| ML20151L176 | List: |
| References | |
| FOIA-86-266 NUDOCS 8605280202 | |
| Download: ML20198E704 (2) | |
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UNITED STATES 8"
NUCLEAR REGULATORY COMMISSIOM g
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Docket No. 50-269 pgc_d h.
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MEMORANDUM FOR:
H. Denton R. Vollmer E. Case R. Bernero
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G. Edison H. Thcmpson g y&
Jh, h W D. Eisenhut B. Snyder f
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F. Miraglia T. Speis G. Lainas G. Holahan hp p
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D. Crutchfield D. Vassallo
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J. Zwolinski J. Miller
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John F. Stolz, Chief, Operating Reactors Branch #4, Division of Licensing
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~ Helen Nicolaras,' Pro,iect Manager Operating Reactors Branch #4, Division of Licensino
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SUBJECT:
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' DAILY HIGHOGHT'- MAIN STEAM SAFETY VALVES REPEATEDLY h
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Oconee Nuclear Station, Unit 1
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' The staff has been notified of preliminary results where the same 2 main
- steam safety valves repeatedly delayed to reseat after 2 reactor trips. The f first reactor trip occurred when the Generato". Field Rreaker opened and a
.g subsequent turbine trip occurred. The trippino of the turbine caused an anticipatory reactor trip, (Main steam safety valves 2 and 10 delayed to reseat and steam generator SG) pressure decreased to 900 psia. The SG pressure was later lowered to 850 osig to ensure reseating. The impact on the primary system was to reduce pressure to 1875 osig and temperature to 538'F (from 2155 psig and 580'F).
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i,The second r.eactor trip occurred one day later upon loss of main feedwater pumps. Again, main steam safety valves 2 and 10 delayed to reseat. A manual l
, reduction in main steam pressure was necessary to reseat the valves.
In
- addition, main steam safety valve #4 relifted on increasing steam pressure, following the reseating of valve #2 and 10.
The licensee states that the main steam safety valve behavior observed in these events has also been.
. observed in several previous trios. Also durino this transient, the
' emergency feedwater level control system did not properly maintain the Once Through Steam Generator level at the desired 25 inch level, instead allowing level to increase to a maximum of 50 inches.
The licensee does not know the cause of the delayed reseating of the valves at this time but will continue the investigation. Oconee Unit I was returned to power.
p en Nicolaras, Project Manager Operating Reactors Branch !4 Division of. Licensing 8605280202 860508 PDR FOIA
.l MURPHY 86-266 PDR
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