ML20045B797
| ML20045B797 | |
| Person / Time | |
|---|---|
| Site: | FitzPatrick  |
| Issue date: | 06/15/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20045B791 | List: |
| References | |
| GL-89-04, GL-89-4, NUDOCS 9306210095 | |
| Download: ML20045B797 (8) | |
Text
[p818tIOgg UNITED STATES ENCLOSURE
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k....,o SAFETY EVALUATION'BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO THE INSERVICE TESTING PROGRAM RELIEF RE0 VESTS POWER AUTHORITY OF THE STATE OF NEW YORK JAMES A. FITZPATRICK NUCLEAR POWER PLANT DOCKET NO. 50-333
1.0 INTRODUCTION
The Code of Federal Regulations,10 CFR 50.55a, requires that inservice testing (IST) of certain ASME Code Class 1, 2, and 3 pumps and valves be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel Code and applicable addenda, except where relief has been requested by the licensee and alternatives authorized or relief granted by the Commission pursuant to Sections (a)(3)(1), (a)(3)(ii), or (f)(6)(i) of 10 CFR 50.55a.
In proposing alternatives or requesting relief, the licensee must demonstrate that:
(1) the proposed alternatives provide an acceptable level of quality and safety; (2) compliance would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety; or (3) conformance is impractical for its facility.
NRC guidance contained in Generic Letter (GL) 89-04, " Guidance on Developing Acceptable Inservice Testing Programs," provided alternatives to the Code requirements determined acceptable to the staff.
The Code of Federal Regulations, 10 CFR 50.55a, authorizes the Commission to grant relief from ASME Code requirements upon making the necessary findings.
The NRC staff's findings with respect to granting or not granting the relief requested as part of the licensee's IST program are contained in this Safety Evaluation (SE).
In rulemaking to 10 CFR 50.55a effective September 8,1992, (See 57 Federal Reaister 34666), the 1989 edition of ASME Code,Section XI, was incorporated in paragraph (b) of Section 50.55a.
The 1989 edition provides that the rules for IST of pumps and valves shall meet the requirements set forth in ASME Operations and Maintenance Standards Part 6 (OM-6), " Inservice Testing of Pumps in Light-Water Reactor Power Plants," and Part 10 (OM-10), " Inservice Testing of Valves in Light-Water Reactor Power Plants."
Pursuant to (f)(4)(iv), portions of editions or addenda may be used provided that all related requirements of the respective editions or addenda are met, and therefore, relief is not required for those inservice tests that are conducted in accordance with OM-6 and OM-10, or portions thereof. Whether all related requirements are met is subject to NRC inspection.
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2.0 BACKGROUND
I In NRC letter dated January 8, 1992, the NRC issued a Safety Evaluation for the second 10-year interval inservice testing program for the James A.
FitzPatrick Nuclear Power Plant. The Power Authority of the State of New York (PASNY or Authority) responded to the program anomalies identified in the SE in their letter dated June 1,1992.
The staff reviewed PASNY's response to the anomalies and evaluated new or revised relief requests and issued a letter dated July 28, 1992, which included an SE.
In PASNY's letter dated Ja'nuary 21, 1993, additional information was provided related to the outstanding action discussed in the July 1992 NRC SE.
Specifically, Anomalies 4, 5, 6, 21, 22, and 25 required additional action by the licensee.
For Anomaly 4, the vibration requirements of OM-6 have been incorporated into Relief Request P9.
For Anomalies 6 and 22, Relief Requests P15 and V53 were deleted and the testing for the affected components will be performed in accordance with the Code.
For Anomaly 25, valve leakage limits have been incorporated into the test procedures for seat leakage testing in groups and this is now reflected in Relief Request V19.
For Anomalies 5 and 21, Relief Request P13 and V55 were revised to include additional justification for long-term relief.
P13 and V55 are evaluated below.
Additionally, PASNY provided a brief description of the IST Program development as requested in the July 1992 NRC SE. Whether the IST Program meets all Code and regulatory requirements is subject to NRC insnection.
3.0 EVALUATION OF REllEF RE0 VESTS j
With the evaluation of the following two relief requests, the FitzPatrick Inservice Testing Program relief requests review will be complete for Revision 6 of the program.
3.1 Relief Recuest V55 The licensee has requested relief from the test frequency requirements of ASME Code,Section XI, Subsection IWV-3521, for core spray check valves 14 CSP-62A/B. These Code Class 2 valves open to provide minimum flow required for the core spray holding pump and close to prevent reverse flow from the Torus. The relief request discusses the closure verification only.
3.1.1 Licensee's Basis for Relief
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The licensee states:
"There are no position indicators or other means to verify closure of these valves; thus, the only practical method of verifying
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closure is by means of back-leakage tests.
Due to the lack of appropriate isolation and test connections, these valves cannot be verified to close by means of a reverse flow test. Any system modification performed to provide a means by which these valves can be backflow-tested will result in an arrangement that requires set-up and connection of a hydrostatic pump in a high radiation area.
System line-up changes and effort involved with testing would constitute an unreasonable burden on the plant staff."
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... 3.1.2 Alternative Testina The licensee proposes:
"During the next reactor refueling outage, the system will be modified to provide an appropriate means of reverse flow testing these valves to verify closure.
Following the modification, during each refuel outage, these valves will be verified to close via a hydrostatic leak rate test."
3.1.3 Evaluation For certain valves, it is impractical to perform testing during power operation or during cold shutdown conditions.
Factors to consider for extending testing to refueling outages are:
(1) test setup time; (2) test valve alignments that might create off-normal conditions that could compromise the safety of the plant, systems, or components; and (3) requirements for systems to remain operational during power operations and cold shutdown conditions, etc.
In the licensee's basis, the impracticality for performing reverse flow testing of these core spray check valves during cold shutdown conditions is identified as items (1) and (2). During power operations, the area is a high radiation area, limiting access due to personnel exposure controh and ALARA.
The latest approved edition in 10 CFR 50.55a(b), the 1989 Edition of the ASME Code,Section XI, refers to 0M-10 for inservice testing requirements. OM-10, paragraph 4.3.2.2, provides that tests may be deferred to refueling outages when testing is not practical more frequently. The licensee's proposal, therefore, is in accordance with the requirements of OM-10, paragraph 4.3.2.2.
The staff may approve the use of portions of later Codes, provided all related requirements are met, pursuant to 10 CFR 50.55a, paragraph (f)(4)(iv).
Related requirements include 4.3.2.4 and 4.3.2.6.
3.1.4 Conclusion The alternative frequency proposed is approved pursuant to 10 CFR 50.55a (f)(4)(iv) provided all related requirements are met and relief is not required for implementation. Whether all related requirements are met is subject to NRC inspection.
3.2 Relief Reauest P-13 The licensee has provided additional information related to the frequency response range of the vibration measurement instruments used to monitor.the standby liquid control (SLC) pumps, llP-2A/B, in the FitzPatrick IST Program.
Relief from IWP-4520(b), which requires that vibration measurement instruments shall have a frequency response range from one-half minimum to at least maximum pump shaf t rotational speed, is requested.
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3.2.1 Licensee's Basis for Relief The licensee states:
"The nominal speed of the SLC pumps is 520 RPM which correlates to a rotational frequency of 8.67 Hz.
IWP-4520(b) requires vibration instrumentation be accurate to i 5% full scale over a range of 4.33 - 8.67 Hz for these pumps.
The Authority has purchased new instruments for use during surveillance testing with certified accuracy of i 5% full scale over a range of 5 - 2000 Hz.
Calibration is verified accurate using a system test methodology over a range of 6 - 500 Hz in units of displacement and 6 - 1000 Hz in units of both velocity and acceleration. The system test verification is limited by the capability of the calibration shaker system to accurately sustain vibration at meaningful amplitudes outside the tested frequencies.
The certified calibration i 5% range is arrived at through addition of individual transducer and meter inaccuracies over the stated frequency range.
The instrument lower frequency response limits are a result of high-pass filters installed to eliminate low-frequency elements associated with the input signal from entering the process of single and double integration.
These filters prevent low frequency electronic noise in from distorting readings in the resultant units (inches per second and mils). As a side effect, any actual vibration occurring at low frequencies is filtered out.
This is a necessary trade-off, as I my of electronic noise at 4.33 Hz translates to approximately equal to 20.86 mils peak-to-peak with the accelerometer used with these instruments.
The Authority has extensively researched this issue concerning Code compliance and intent, and strongly feels that, for these pumps, procurement of equipment capable of meeting the Code required accuracy is impractical with little or no benefit.
Instrumentation capable of meeting the Code for these pumps is cumbersome, difficult to operate, prone to human error, costly to purchase, and expensive to calibrate.
The number of vendors that supply instrumentation accurate at these frequencies is limited, and there are even fewer qualified vendors capable of performing the required calibration services.
Most standard calibration laboratories provide calibration services only to a minimum of 10 Hz.
In addition to the impracticability of procuring the instruments, the Authority feels that the instruments presently used are adequate to assess the condition of these pumps. The manufacturer of these pumps, Union Pump Co.,
Battle Creek, Michigan, has stated that the puraps, beirg of a simplified reciprocating design, have no failure mechanism: that would be revealed at frequencies less than shaft speed.
Union Pump has stated that all failure modes of this pump resulting in increasing vibration will be manifested at shaft speed frequency or harmonics thereof.
In light of the information provided by Union Pump, monitoring subsynchronous vibration for these pumps is not needed, but supersynchronous readings will provide meaningful information in the detection of imminent machinery faults.
. A search of the nuclear plant reliability data system (NPRDS) database has revealed only one failure reported for pumps of this or similar design whose discovery mentioned increased vibration levels. The cited cause of the failure was improper end play set leading to bearing failure.
Failures of this type would normally be detected at running (shaft) speed frequency, harmonics thereof, or nonharmonic supersynchronous bearing defect frequencies.
It should also be noted that these are standby pumps which are normally operated only during pump and valve testing.
In the unlikely event this-system is required to fulfill its design function, only one of the two redundant pumps need operate for a period of 23 to 125 minutes.
In addition to vibration monitoring performed for'the IST Program, these pumps are included in the Authority's Rotating Equipment Monitoring Program.
Vibration spectral data is periodically collected and analyzed for the pump and gear motors in addition to those required by the Code. The equipment used by the Rotating Equipment Monitoring Program is certified accurate 5% over a frequency range 5 - 2000 Hz and is also limited by discrete frequency analysis and trending using FFTs [ Fourier Fast Transform].
Vendor specifications state that this equipment should provide fairly accurate data down to 2 Hz in units of acceleration using the raw transducer signal, negating the need for integration.
Study of low-frequency spectra taken in units of acceleration with these instruments has revealed no distinct subsynchronous peaks above the noise floor acceleration signal.
In light of the rigorous testing and limited design run time (for these pumps], it is not likely that a minor mechanical fault would prevent these pumps from fulfilling their design function and unlikely that development of a major fault would go unnoticed.
In conclusion, the Authority feels that the use of high quality, commercially available vibration monitoring equipment calibrated to be at least accurate 5% full scale over a range of 6 Hz to 500 Hz (nominal shaft speed - 8.67 Hz) is an appropriate method of monitoring the mechanical condition of the SLC pumps.
Such instruments will provide meaningful and useful measurements over the frequency range in which pump faults will develop and manifest. This meets the intent of the Code and certainly will neither adversely impact system reliability nor the health and safety of the general public.
In-addition,.it relieves the Authority of the burden and expense involved in the procurement, calibration, training, and certification associated with obtaining new equipment which is simply not needed to adequately assess the condition of the subject pumps."
3.2.2 Alternative Testina The licensee proposes:
"The vibration measurements will be taken using instrumentation accurate i 5% full scale over a frequency range of 6 Hz to 500 Hz. The data will be evaluated per IWP-3200."
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. 3.2.3 Evaluation Paragraph IWP-4520(b) of the ASME Code,Section XI, requires vibration instrumentation to have a frequency response range of the readout system from one-half minimum speed to at least maximum pump shaft rotational speed. The Code requirements are general in order to cover the various types of pumps installed in safety-related applications in nuclear power plants.
The Code vibration monitoring requirements apply most generally to pumps operating above 600 rpm and may be either too prescriptive or not prescriptive enough-for other specific pump applications. Moreover, the frequency spectrum of the complex signals generated by machines is characteristic of each machine or each pump, constituting a unique pattern, referred to as the " machine signature." Analysis of the signature allows identification of vibration sources, and monitoring of the change over time permits evaluation of the mechanical condition of the pump.
In order to identify sources of noise and vibration, the peaks of the measured frequency spectra are correlated with data pertaining to the possible vibration source components in the machine.
For reciprocating pumps, the sources of vibration from unbalanced forces and couples will generally give rise to vibrations at the running speed or higher order multiples of the running speed. Vibrations at one-half or lower of running speed may indicate
" oil whip" in journal bearings, or looseness in bearings. Though the relief request does not describe the type of bearings in the SLC pump, the licensee has contacted the pump manufacturer who indicates.that these pumps have no failure mechanisms that would be revealed at frequencies less than shaft speed. Therefore, for the SLC pumps, the Code requirements for the su'oharmonic vibrations would provide no useful information about the condition of the pumps.
The licensee indicates that the instrumentation used for inservice testing vibration monitoring has an accuracy of i 5% full scale over a range of 5 to 2000 Hertz.
Evidently, for the remaining pumps other than SLC pumps, the instrumentation meets the Code requirements based on the running speed of the pumps. The relief request indicates that accelerometers are used.
The most widely used vibration sensing instruments are accelerometers. Accelerometers have a frequency response range of ideal operation, with amplitude distortions at low frequencies. While other types of transducers may provide more accurate signals in a lower frequency response range, the advantages of accelerometers (light-weight, rugged, wide frequency response, good temperature resistance, moderate pricing, availability) in monitoring the remaining pumps would outweigh the advantage of having instrumentation that would meet the Code requirements for the SLC pumps _ (" cumbersome, difficult to operate, prone to human error, costly to_ purchase, and expensive to cal ibrate"). Additionally, the licensee indicates that the SLC pumps will be monitored as part of the Rotating Equipment Monitoring Program by periodically collecting and analyzing vibration spectral data / frequency analysis using Fourier Fast Transform (FFT) analyzers. A spectral analysis provides the entire spectrum of vibration frequencies as compared to the vibration data required by the Code (mils peak-to-peak for displacement) and will allow for w
r monitoring potential failure modes at different frequencies. Therefore, the proposed alternative provides an adequate level of assurance of the operational readiness of the SLC pumps.
Because the pumps have no known subsynchronous failure modes, imposition of the Code requirements for the vibration instrumentation would be of little to no benefit for assuring the quality and safety of the operation of the SLC pumps.
Imposition would create a hardship on the licensee by requiring that a different type of vibration monitoring instrumentation be procured, maintained, and operated, solely for the standby liquid control pumps which have no know failure modes at the vibration frequencies that would be imposed.
3.2.4 Conclusion Relief is granted for utilizing the existing vibration monitoring instrumentation for the standby liquid control pumps pursuant to 10 CFR 50.55a (a)(3)(ii) based on the hardship that would be created with no apparent benefit to quality and safety of the operation of the pumps if the Code requirements were imposed.
4.0 CONCLUSION
Based on the review of the FitzPatrick IST Program relief requests, the NRC staff concludes that the relief requests as evaluated and modified by the SE will provide reasonable assurance of the operational readiness of the pumps and valves to perform their safety-related functions. The NRC staff has determined that approval of the proposed alternatives pursuant to 10 CFR 50.55a(f)(4)(iv) and (a)(3)(ii) is authorized by law and will not endanger life or property, or the common defense and security, and is otherwise in the public interest, giving due consideration to the burden upon PASNY that could f
result if the ASME Code requirements were imposed on the facility.
Principal Contributor:
P. L. Campbell Date: June 15, 1993 I
e
o Mr. Ralph E. Beedle June 15, 1993 i
pursuant to 10 CFR 50.55a(a)(3)(ii), based on the hardship that would be created with no apparent benefit to quality and safety if the applicable ASME Code requirements were imposed.
This action closes TAC No. M85702.
Sincerely, Original signed by Daniel G. Mcdonald For Robert A. Capra, Director Project Directorate I-1 Division of Reactor Projects - I/II Office of Nuclear Reactor Regulation
Enclosure:
Safety Evaluation cc w/ enclosure:
See next page I
Distribution:
Docket File C. Vogan PCampbell, 7/E/23 NRC & Local PDRs B. McCabe JNorberg, 7/E/23 PDI-1 Reading 0GC T. Murley/F. Miraglia,12/G/18 E. Jordan, MNBB 3701 J. Partlow,12/G/18 G. Hill (2)
E. Rossi, 9/A/2 ACRS (10)
J. Lieberman, 7/H/5 OPA S. Varga OC/LFDCB J. Calvo V. McCree, EDO, 17/G/21 R. A. Capra C. Cowgill, RGN-I
- See previous concurrence LA:PDI-l PM:PDI-l OGC*
D:PDI-1 CVogan a/ u BMcCabNih[m JHull RACapra i
b/d/93 L/h /93 06/d9/93 66/if/93
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OFFICIAL RECORD COPY FILENAME: FIT 85702.LTR 4