ML20010E184
| ML20010E184 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 08/20/1981 |
| From: | Papay L SOUTHERN CALIFORNIA EDISON CO. |
| To: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, NUDOCS 8109030179 | |
| Download: ML20010E184 (3) | |
Text
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50.55(e) Report y.
Docket Nos. 50-361/362 Southern Cslifornia Edison Company
&E P O box 800 2244 WAL NUT GROVE AVENUE RO S E M E AD, C ALWOR N I A 91770
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August 20, 1981
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~ ~' M Mr. R. H. Engelken, Director i)$
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Dear Mr. Engelken:
Subj ect:
Docket Nos. 50-361 and 50-362 San Onofre Nuclear Generating Station, Units 2 and 3 In a letter to your office dated June 22, 1981 we identified a condition involving loss of diesel generator output due to the unit tripping out on spurious high crankcase pressure signals.
We considered this condition to be potenti-ally reportable in accordance with 10CFR50.55(e).
On July 20, 1981 we notified you by letter that investigation of the condi-tion was not complete and requested an extension of reporting time to August 21, 1981.
The contributing factors of this con-dition are still under review.
Enclosed in accordance with 10CFR50.55(e) are twenty-five (25) copies of an interim report entitled, " Interim Report on Diesel Generator High Crankcase Pressure Signals, San Onofre Nuclear Generating Station, Units 2 and 3."
A final, summary report will be submitted on or before September 21, 1981.
If you have any questions regarding 2his report, we l
would be pleased to discuss this matter with you at your con-venience.
Very truly yours,
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Enclosures Victor Stello (NRC, Director I&E) cc:
l R. J. Pate (NRC, San Onofre, Units 2&3) 6,I
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INTERIM REPORT ON DIESEL GENERATOR HIGli CRANKCASE PRESSURE SIGNALS 1
San Onofre Nuclear Generating Station, Units 2 and 3 INTRODUCTION This interim report is submitted pursuant to 10CFR50.55(e)(3).
It de.:cribes a condition discovered during preoperational testing wheroin spurious diesel generator trips occurred with "high i
crank < tse pressure" on several of the engines.
This report includes a description of the situation, an analysis of the j
safety implications, and a summary of corrective actions taken to date.
By letter dated June 22, 1981, Edison confirmed notification to the NRC of this potentially reportable condition.
In a letter dated July 20, 1981, Edison reported that the investi-gation was incomplete and requested an extension on reporting time to August 21, 1981.
BACKGROUND i
During the diesel-generator (D/G) preoperational test program, frequent high engine crankcase pressure alarms and trips were encountered on engines of both D/G sets.
Diagnostic tests were conducted which determined the trips were spurious and did not reflect a true high pressure condition.
A subsequent investiga-tion revealed several causes and contributing factors.
Some potential contributing factors are still under review by the D/G vendor.
DISCUSSION The following discussion is responsive to 10CFR50.55(e)(3).
j Description of the Deficiency These spurious trips were found to occur under a number of condi-tions:
(a) trips occurred randomly during engine operation, I
(b) trips occurred when the switches or mounting panel received any shocks or substantial vibration, and (c) trips occurred after engine shutdown and would not clear to allow a restart.
l The investigation of the problem revealed several causes and contributing factors:
(a)
The installed switches were found to be of an incorrect i
model and pressure range.
l
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INTERIM REPORT ON Page Two DIESEL GENERATOR HIGH CRANKCASE PRESSURE SIGNALS San Onofre Nuclear Generating Station, Units 2 and 3
)
(b)
The sensing line was found to have low points which j
became filled with engine oil and caused erroneous I
input signals to the switches.
1
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(c)
The repeatability of the switches was not within spec-ification.
l
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The D/G vendor, Stewart & Stevenson Services, Incorporated of i
Houston, Texas, is still investigating the switch mounting and panel for proper support.
Analysis of Safety Implications t
l The diesel generator.s start automatically on either a Loss of Voltage Signal (LOVS) or Safety Injection Actuation Signal (SIAS).
The "high crankcase pressure" trip is bypassed when a SIAS is present.
However, spurious "high crankcase pressure" trips during a LOVS condition without SIAS could trip one or l
both of the redundant diesel generators and preclude manual restart until the trip clears.
Thus, the diesel generators could be disabled during a loss of offsite power for events which do not result in a SIAS.
1 Corrective Action i
i The corrective action in progress to date includes the following:
1 1.
The correct pressure switches have been inrtalled and calibrated.
2.
The sensing line size has been increased from 1/4 inch to 1/2 inch to preclude blockage and any capillary action.
i l
The line was rerouted to avoid pockets and sloped to the J
engine to prevent oll entering the line.
3.
The panel and switch support is presently being reviewed for adequacy by Stewart & Stevenson.
1 A final summary report will be provided on or before September 21, 1981.
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