ML20086M309
| ML20086M309 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 12/12/1991 |
| From: | Tuckman M DUKE POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9112170330 | |
| Download: ML20086M309 (3) | |
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- _%))()lJgl{$4g DUKE POWER December 12, 1991 U.S. Nuclear Regulatory Commission Attn
- Document Control Desk 2
Washington, D.C.
20555 i
Subject:
Catawba Nuclear Station Docket Nos. 50-413 and 50-414 Supplement to General Relief Request for Pump Vibration In a letter dated october 11, 1991, the NRC requesced that additional information be provided for items related to the Catawba relief request dated March 16, 1990 and supplemented August 22, 1990.
The questions concern the use of vibration instrumentation, calibrated from 10 }{z t'
1000 liz, on pumps having a one third pump running speed less than 10 11 2.
These pumps include the Nuclear Service hater Pumps and the Control Area Chilled Water Pumps.
One-third pump speed for these two pumps corresponds to 3.95 and 9.8311z respectively.
The questions and responees are an.follows:
1.
What is - the basis or -rationale for - not calibrating instruments in the lower range and why is there not an apparent concern with subharmonic resonance?
The equipment available for calibtation by Duke Power Star.dard's Lab will not support calibration of the equipment to a
frequency less than 10 liz.
Duke's Standard's Lab can now calibrate the accelerometer down to 5 liz; however Duke still has a hardware limitation on the electronics portion of the calibration.
The AC voltage calibration source is not capable of producing a signal at a frequency less than 10 liz.
The predictive maintenance program does address sub-harmonic vibration signals taken on safety and non-safety
^
equipment.
In fact, full vibration spectra, from 3 liz to Each spects is-1000 11 2, are recorded and trended.
(subharmonic ;um divided' into various bands and superharmonic), thus providing good characterization of
.various vibration related malfunctions such as the oil whip or whirl concern in the subharmonic band.
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U.S. Nuclear Regulatory Commission December 12, 1991 Page 2 2.
Discusu the assumed instrunent accuracy and repeatability, and the banos for thoso assumptions, in the lower frequency rango.
one problem associated with using vibration f
instrumentation at low frequenclos in the field, is that the signal-to-noiso ratio often timos excoods acceptable levola and results in poor readings, The CSI Model 2110 instrument has boon equipped with analog integration circuitry that is loss susceptible to noiso at low frequencies.
The manufacturer-states that in field uso the Model 2110 will road within toleranco down to 10 !!z and that with analog integration the frequency rango can be loworod to - 3 liz.
Therefero, even though the instrumonto performanca is verified within tolerance to 10 11 2 by Duke's our Standard's Lab, the CSI Modol 2110 is still capable of obtaining repeatable measuromonts at frequencios loss than 10 lit.
L 3.
Phaso discuss the meaning of the following statement in your August 22, 1990 lotter; "Also the inntrument manufacturers specify that their accuracy stetomonts are valid.over this range under certain conditions (this can not be verified due to instrumont limitation)."
The analog integration circuitry combined with other firmware upgrados provides the instrument with tho capability to obtain repeatable results at frequencies as low as 3 liz.
The " instrument limitations" refer to the inability of Duke's calibration equipment to confirm the
_ performance of the CitI Model 2110 at frequencies loss than 10 112.
If you have 'any questions regarding this submittal - please contact Mary llateltino at (303)831-3414.
Very truly yours, N3 M.
S. Tuckman l
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._._m.___________.__.
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4 U.S. Nuclear Regulatory Commission Pago 3 December-12, 1991 xct S. D. Ebnotor Regional Administrator, Region II
)
R. E. Martin, OllRR i
I W. T. Orders Senior Resident Inspector
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