ML17304B274
| ML17304B274 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 06/21/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17304B272 | List: |
| References | |
| NUDOCS 8906290131 | |
| Download: ML17304B274 (8) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 ENCLOSURE SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION INSERVICE TESTING PROGRAM FOR PUMPS AND VALVES PALO VERDE NUCLEAR GENERATING STATION UNITS 1'
AND 3 3.9.6 Inservice Testing of Pumps and Valves INTRODUCTION The Code of Federal Regulation, 10 CFR 50.55a(g),
requires that inservice testing (IST) of 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 specific written relief has been requested by the licensee and granted by the Commission pursuant to 10 CFR 50.55a(a)(3)(i), (a)(3)(ii), or (g)(6)(i).
In 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 difficulties without a compensating increase in the level of quality and safety or (3) conformance with certain requirements of the applicable Code edition and addenda is impractical, for its facility.
The Regulations, 10 CFR 50.55a(a) (3)(i), (a) (3)(ii), and (g) (6)(i),
authorize the Commission to grant relief from these requirements upon making the necessary findings.
The NRC staff's findings with respect to granting or not granti'ng the relief requested as part of the licensee's IST Program are contained in the Safety Evaluation (SE) dated November 15, 1988 and in this, supplement to the SE.
EVALUATION The pump relief requests numbers 7 and 8 addressed in this supplement to the SE were part of the licensee's IST program submittal dated August 11, 1986, but were not included in the resubmittal dated Septebmer 10, 1987.
The staff, with assistance from its contractor EG&G, Idaho, evaluated these relief requests in accordance with the requirements of 10 CFR 50.55a and using the acceptance criteria of the Standard Review Plan, NUREG-0800 Section 3.9.6, and the Draft Regulatory Guide and Value/Impact Statement titled, "Identification of Valves for Inclusion in Inservice Testing Program."
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1.
Pum Relief Re uest Number 7
The licensee has requested relief from the pump bearing temperature measurement as required by Section XI, Table IWP-3100-1 for all pumps in the IST program 1.1 Licensee's Basis for Re uestin Relief "Industry data has shown that bearing temperature changes,due to degrading bearings only occur s after major degradation has occurred at the pump.
Prior to this, the vibration measurement would provide the necessary information to warn the operator of an impending malfunction.
Therefore, this parameter will not be measured, since its information is after the fact."
1.2 Evaluation The annual bearing temperature measurement is an unreliable method of evaluating pump bearing degradation and deletion of this measurement will not adversely affect the licensee's pump monitoring program.
Many of the bearings of the centr ifugal pumps included in the Palo Verde, Units I, 2, and 3 IST Program are water cooled, thus, bearing temperature measurement may be significantly influenced by the temperature of the pumped fluid and changes may not necessarily be indicative of bearing degradation or failure.
Industry experience has shown that when serious degradation of pump bearings
- occurs, bearing temperatures remain relatively constant until just prior to the actual bearing failure.
With the bearing temperature measurement being taken on an annual basis, the detection of bearing fai lure during the test is unlikely.
Deletion of the requirement to measure bearing temperature annually would not impact the effectiveness of the Palo Verde pump monitoring program.
Further, the licensee is utilizing pump vibration measurements which should be able to detect degrading bearings.
Bearing temperatures taken at one year intervals provide little statistical basis for determining the incremental degradation of a bear ing or any meaningful trending information.
The burden on the licensee.if the Code requirements were imposed would not be justified by the limited information that would be provided about pump bearing condition.
Based on the determination that the measurement of bearing temperatures annually provides little meaningful data and does not contribute significantly to the effectiveness of the Palo Verde pump monitoring program re1ief can be granted as requested pursuant to 10 CFR 50.55(a (3)(ii).
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2.
Pum Relief Re vest Number 8 The licensee has requested relief from the Section XI, Table IWP-3100-2 limits for the Acceptance-range (high) value, Alert-range (high) value, and for the Required-action range (high) value for differential pressure measurements for all centrifugal pumps in the IST program and has proposed to raise the Acceptance-range (high) limit to 105%, Alert-range (high) limits to 105K to 107% and the Required-action range (high) limit to greater than 107% of reference value for differential pressure measurements.
2.1 Licensee's Basis for Re uestin Relief "Small increases in differential pressure (delta P) which activate Alert and Action range for centrifugal
- pumps, are meaningless.
Small positive increases in observed differential pressure caused by instrument uncertainty, water density, difficulty in obtaining accurate discharge pressures (due to pressure osci llations as noted in IWP-4150),
and instrument error result in spurious actuation of alert required action.
Increasing the alert and required action ranges to parallel the low level alert/required action range wi 11 prevent needless pump testing and equipment unavailability.
Acceptance Range to be 0.93 to 1.05 delta P
, High Alert Range to be 1.05 to 1.07 delta P
, and High Required Ac%ion Range to be greater than 1.07 delta P
r'.2 Evaluation Table IWP-3100-2 identifies the pump parameters to be monitored during pump tests and the a,llowable ranges of those parameters.
Paragraph IWP-3210 permits the use of "reduced range limits" if justification is provided.
The licensee's proposal to raise the Acceptance-range (high) limits from 102% to 105K, Alert-range (high) limits from 105% to 107% and the Required-action range (high) limit to be greater than 107% of, reference values for differential pressure measurements for all centrifugal pumps in the IST program,
- however, has not provided sufficient information to demonstrate that pump degradation wi 11 be detected prior to the pump being unable to perform its safety function.
The licensee has not provided the staff with information that identifies the specific pumps with which difficulties occur while being tested in accordane with the requirements of Section XI.
The licensee has not provided information that discusses the cause(s) of the data scatter encountered during pump tests or provided a basis to show that significant degradation will not affect required pump operability if the proposed methodology is utilized.
Based on the determination that the Code requirements are not impractical and that the licensee has not demonstrated that the proposed alternate
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E limits will provide adequate detection of pump degradation at least equivalent to the requirements of the Code, relief cannot be granted as requested.
CONCLUSION The staff's review indicates that the justification for the pump relief request number 7 in the licensee's IST program submittal of August ll, 1986 is acceptable and the rel'ief can be granted as requested.
The staff has determined that granting relief pursuant to 10 CFR 50.55a(a)(3)(ii) is authorized by.law and will not endanger life or property, or the common defense and: security.
In making this determination the staff has considered the alternate testing being
. implemented and whether, compliance. would result in hardship without a compensating increase in the level of safety or quality.
The pump relief request number 8 is denied.
The review by the staff and its contractor,
- EGSG, showed that the licensee did not provide adequate information to justify granting relief per 10 CFR 50.55a requirements.
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