ML20198Q885
| ML20198Q885 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 11/06/1997 |
| From: | Fields E NRC (Affiliation Not Assigned) |
| To: | James Chang SOUTHERN CALIFORNIA EDISON CO. |
| Shared Package | |
| ML20198Q864 | List: |
| References | |
| NUDOCS 9711130074 | |
| Download: ML20198Q885 (1) | |
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64 Nov:mber 6,1997 Mr. Chang, Thank you for your e-mailinquiry. One of the ideas that the information notice was attempting to communicate was that failure of a common reference leg impacts both trains of level instrumentation. Depending on the mode of failure, accuracy of indicated level could be marginaly impacted or, as was the case with the Oconee facility, grossly impacted. It is not the NRC's l
l intention to evaluate the adequacy of the design of your level sensing system, that is your responsibility. However, a common referenceleg, whether wet or dry, can potentially compromise train independence and may lead to common mode failures that could result in unnecessary challenges to safety systems and/or plant personnel.
Nick Fields
>>> " JOHN CHANG" <changjc@ songs.sce.com> 10/30/97 05:28pm >>>
Tom / Nick, I am evaluating IN 97-38, " Level sensing system initiates common modo failure of high pressure injection pumps", for applicability to SONGS Units 2 & 3.
It appears that this failure is applicable ONLY to LDST tank level transmitters with a common WET reference leg, that is, a reference leg filled with liquid.
At SONGS, our VCT (equivalent to LDST) tank level transmitters have a common DRY reference leg design.
A leak in the dry reference leg would create the oppcsite effect.
That is, the indicated level would be lower, not higher than the actual level.
Therefore, it appears that the Oconee event is applicable ONLY to level transmitters with WET common reference legs. It does not apply to transmitters with dry common reference legs.
Please call or respond by e-mail. Thanks.
John Chang.
714-368-6706 FAX 714-368-5360 9711130074 971106
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