ML19317F396
| ML19317F396 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 11/13/1975 |
| From: | DUKE POWER CO. |
| To: | |
| Shared Package | |
| ML19317F388 | List: |
| References | |
| RO-287-75-10, NUDOCS 8001140645 | |
| Download: ML19317F396 (2) | |
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' DUKE POWER COMPANY' OCONEE NUCLEAR STATION i
1 Report No.: 'UE-287/75-10 Report Date: November 13, 1975 Event-Dato:. October.5, 1975 Facility: ~Oconee. Unit 3',. Seneca,~ South Carolina
'dentification'of Event: Weld failure on sample line from Low Pressure I
Injection System cooler
! Conditions Prior to Event:
Unit at cold shutdown Description of Event:
On October.5, 1975, while the'Oconee Unir 3 3A LPI train was in the decay heat removal mode,: a.1" sample line from the discharge of the 3A LPI j
cooler separated from the LPI cooler discharge line. The 3A cooler was isolated and decay heat removal was continued with the 3B decay heat 4
" cooler.
t Designation of' Apparent'Cause of Event:
'l This event.was.apparently caused by cavitation occurring at high flow
. rates in the butterfly control valve 3LP-12 located in the cooler discharge line.
This'. cavitation caused the line to vibrate excessively during operationiin the' decay heat removal mode and consequently _resulted in a i
weld: failure in the-sample line.
t e
Analysis of Event:-
This event involved the' failure of a 1" sample line while the unit was in a cold. shutdown condition. ' The redundant' LPI cooler, 3B, was not. af fected and.was operated-to provide : sufficient decay heat removal while the 3A LPI train ~was isolated and repairs completed.
It is concluded that-the health i
- and safety of the public;was_unaffecter by this event.
2
~ Corrective' Action:
UThe 3A 'LPI train was isolated,ithe weld repaired, and dye penetrant testing was performed to assure systemLintegrity.
In. addition, several representative welds, ' including corresponding welds in Units -I and' 2 wil1~ be dye penetrant
, tested.' This; testing'will.be completed byLJatuary 15,;1976.
The causative' cavitation problem:has existed in the LPI cooler discharge
. : lines for~allfof the.0conee units. The problem was initially experienced
' with. valves 1LP-12 and :-14 and 2LP.-12 ^and -14,- located in the LPI cooler
- discharge,linesjof(Units 11;and;2,-and occurred under conditions'of low 3
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-- a coolant flow through these lines. Af ter careful review, a decision was made to replace these valves with valves of a globe body design which would eliminate
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the cavitation problem.
These valves for Units 1 and 2 were ordered in June, 1975.
It was not considered that this cavitation problem would occur in Unit 2 LPI coolers since the piping arrangement differs from Units 1 and 2 and valves 3LP-12 and'-14 are of a different design, intended to alleviate the cavitation effects as experienced in Units 1 and 2.
A cavitation problem was experienced with Unit 3, however, but differed from that experienced with Units 1 and 2 since it occurred at high rather than at low flow rates.
Currently, after performing a comprehensive evaluation of this incident, it has been concluded that replacement valves identical to those being procured for Units 1 and 2 are necessary to alleviate the cavitation problem in Unit 3.
The procurement of these valves is being finalized.
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