ML20034H013
| ML20034H013 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 03/11/1993 |
| From: | Marsh W SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9303150071 | |
| Download: ML20034H013 (2) | |
Text
.
]~
i
~
^
k.
~.,
Southem Califomia Edison Company 23 PARKER STREET 1RVINE. CAL IFORNIA 92718 March 11, 1993 w.m WAG E R C. WHSH A$53T ANT MANAGE P4 (714)4!.4 4403 NUCt.LAft $4f GUL A TORY AF r AiHS U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D. C. 20555 Gentlemen:
Subject:
Docket No. 50-361 and 50-362 Special Report - Inoperable Meteorological Instrumentation San Onofre Nuclear Generating Station, Unit 2 and 3 This report is being submitted in accordance with Technical Specification (TS) 3.3.3.4 (a) for Meteorological Instrumentation, of Facility Operating Licenses NPF-10 and NPF-15 for San Onofre Units 2 and 3.
The TS requires Southern California Edison (SCE) to submit a special report when one or more channels of the meteorological monitoring instrumentation becomes inoperable for more than seven days.
Two channels of meteorological instrumentation (primary and secondary) provide delta temperature monitoring. Each channel is provided with two temperature sensors, one sensor at the 10 meter elevation and the other at the 40 meter elevation.
These sensors provide input to a computer for delta temperature readings.
On February 22, 1993, the meteorological monitoring delta temperature instrument was declared inoperable when it was noted that the difference between the primary and secondary channels was excessive. The secondary channel is providing erroneous data causing a discrepancy between the two channels. The cause of the erroneous data is intermittent thereby complicating and delaying corrective maintenance such that the delta temperature indication could not be returned to service within seven days of the initial inoperability. The problem manifests itself for a few hours and then disappears for an interval of several hours to several days before reappearing. Troubleshooting efforts have not yet been able to identify the cause of the problem during the brief periods when the delta temperature indication is erroneous. The intermittent nature of the problem will also require additional time to validate the effect of corrective maintenance.
A consultant from Dames & Moore, who previously maintained and operated the meteorological instrumentation, has confirmed that the present troubleshooting strategy is correct. Efforts to isolate, identify, and repair the problem will continue until the repairs are satisfactorily completed.
In the interim, the primary delta temperature channel continues to provide accurate stability class data.
120061 9303150071 930311 U
PDR ADOCK 05000361 S
PDR d
n f;iL,._,I
~
Document Control Desk March 11, 1993 l
The NRC will be notified by letter when the differential temperature instrumentation is returned to service.
If you require any additional information, please let me know.
Sincerely, lh 0lY,
u i
i cc:
J. B. Martin, Regional Administrator, NRC Region V 7
M. B. Fields, NRC Project Manager, San Onofre Units 2 and 3 C. W. Caldwell, NRC Senior Resident Inspector, San Onofre Units 1, 2 & 3 t
J
?
l
!