ML20149K945
| ML20149K945 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 02/16/1996 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20149K942 | List: |
| References | |
| NUDOCS 9602220395 | |
| Download: ML20149K945 (21) | |
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UNITED STATES s
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NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 30eeH001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION an ATED TO INSERVICE TESTING PRMpA RELIEF RE00ESTS FOR ENTERGY OPERATIONS. INC.
ARKANSAS NUCLEAR ONE. UNIT 2 DOCKET NO. 50-368
1.0 INTRODUCTION
The Code of Federal Regulations,10 CFR 50.55a,. requires that inservice testing (IST) of certain American Society of Mechanical Engineers Boiler and Pressure Vessel _ (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 and grantod or proposed alternatives have been authorized by the Commission pursuant to 10 l
CFR 50.55a(f)(6)(1), (a)(3)(1), or (a)(3)(ii).
In order to obtain authorization or relief, the licensee must demonstrate that:
(1) conformance is impractical for its facility; (2) the proposed alternative provides an acceptable level of quality and safety; or (3) compliance would result in a i
hardship or unusual difficulty without a compensating increase in the level of i
quality and safety. Section 50.5Ea(f)(4)(iv) provides that inservice tests of l
pumps and valves may meet the requirements set forth in subsequent editions and addenda that are incorporated by reference in 10 CFR 50.55a(b), subject to the limitations and modifications listed, and subject to Commission approval.
NRC guidance contained in Generic Letter (GL) 89-04, ' Guidance on Developing Acceptable Inservice Testing Programs," provided alternatives tc the Code requirements determined to be acceptable to the staff and authorized the use of the alternatives in Positions 1, 2, 6, 7, 9, and 10 provided the licensee follows the guidance delineated in the applicable position. When an alternative is proposed which is in accordance with GL 89-04 guidance and is documented in the IST program, no further evaluation is required; however, implementatian of the alternative is subject to NRC inspection.
Section 50.55a authorizes the Comuission to grant relief from ASME Code requirements or to approve proposed alternatives upon making the necessary findings. The NRC staff's findings with respect to granting or not granting the relief requested or authorizing the proposed alternative as part of the licensee's IST program are contained in this safety evaluation (SE).
ENCLOSURE 9602220395 960216 PDR ADOCK 05000368 G
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In a letter dated January 21, 1994, Entergy Operations (the licensee) i submitted the Revision 2 of the Arkansas Nuclear One, Unit 2 (ANO-2) second i
10-year interval program for inservice testing of pumps and valves. The submittal includes responses to eight anomalies identified in the staff SE j
dated January 22, 1993. The Revision 2 contains five new relief requests, i
PR-7, PR-8, PR-9, GR-3, and GR-5, and nine revised relief requests, PR-4, PR-5, PR-6, EFW-1, SGS-1, RC-1 (part 2), SI-2, CS-1, CS-2, and GR-1.
Relief requests SW-1 and GR-3 were withdrswn; however, a new unrelated relief request was added to the program as GR-3.
Relief requests PR-1, PR-2, PR-3, GR-2, j
GR-4, SW-1, RC-1 (part 2), and SI-l were evaluated by the staff in the SE dated January 22, 1993, and remain unchanged.
l The licensee also provided information concerning relief requests in two subsequent letters. The February 10, 1995, submittal states that the relief 5
request SI-1 has been deleted and contains a new relief request PR-10 and two revised relief requests, PR-9 and RC-1.
Included in the May 31, 1995,.
i submittal is an additional revision to PR-5 that addresses the licensee's j
commitments made during a conference call with the staff on Iky 5,1995.
t An evaluation of the responses to the anomalies and the new and revised relief requests is provided below. The licensee's IST program covers the second i
10-year IST interval from March 26, 1990, to March 26, 2000. The ANO-2 IST 1
program is based on the requirements of the 1986 Edition,Section XI, of the ASME Boiler and Pressure Vessel Code.
2.0 SUMARY OF ANOMALY RESPONSES TO JANUARY 22. 1993. SAFETY EVAL.UAl10H l
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1 PR-4 The licensee requested relief PR-4 has been revised Provisional i
from the full-scale range to address the approval.
requirements of Section XI for adequacy of existing See the flow-rate instrumentation instrumentation and Section 3, used to test the charging pumps.
the burden of using below.
j Interim relief was granted in portable flow meters.
(a)(3)(ii) order for the licensee to address the adequacy of existing instrumentation and the' burden of using portable instruments that meet the Code requirements.
1
3 Ahomalyl iReliefi
[ Description).sfilsive?
l Licensee'Risponse; LNRC Action?
e
_ Request 0
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' Comments' 2
PR-5 The licensee proposed to measure PR-5 has been revised Provisional pump vibration velocity in to state that OH-6 approval.
accordance with OH-6 instead of requirements for See pump vibration displacement in vibration are Section 4, accordance with the 1986 Edition implemented with the below.
1 of Section XI.
Licensee should exception of the (a)(3)(ii) i comply with all vibration system frequency measurement requirements of response range OMa-1988, Part 6.
requirement of one-third minimum pump shaft rotational speed for the charging and sodium hydroxide pumps.
3 GR-1 The licensee should verify the GR-1 has been modified Licensee's accuracy of the remote position to state that both the response is indication with the valve in open and closed appropriate.
both the open and closed positions of the No further positions regardless of the valves will be NRC action valve's safety function.
verified.
is required.
4 GR-3 Regarding plant startup with The licensee deleted Licensee's inoperable valves, the TS must this relief request.
response is specifically permit plant A new unrelated relief appropriate.
startup with the valve request has been added No further inoperable. Additionally, if to the program as NRC action corrective action for a valve is GR-3.
is required.
deferred under this relief (See Section request, the valve should be 12 bclow, repaired or replaced and regarding successfully tested prior to new relief entering an operating mode where request the valve is required to be GR-3) operable.
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4 fAnomal$.iRslid MDsicfipNonif5Essbel Eihensee: Rhs^ oNM NRC/ Action::
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5 EFW-1, The licensee proposes to verify The valves in EFW-1 Provisional SGS-1, the full-stroke capability of will be full-flow approval for SW-1, the valves in question by tested during EFW-1.
See SI-2, sample disassembly, inspection, refueling outages and Section 11.
CS-1, and manual exercise of the valve confirmed closed (f)(4)(iv) and CS-2 disk during refueling outages, quarterly.
Non-The licensee should (1) pursue intrusive testing as No further l
the use of non-intrusive testing an option has been NRC action and (2) part-stroke exercise the added to SGS-1, SI-2, is required valve following reassembly or and CS-1.
Valves for SGS-1, develop an alternative post-covered by SI-2 and SW-1, inspection test.
CS-1 will be part-SI-2, and stroked tested CS-1.
following reassembly and those covered by The licensee SGS-1 will be full-should stroke tested develop an following reassembly.
alternative The containment spray post-discharge header check inspection valves addressed in test, such CS-2 will not be full-as enhanced or part-stroked tested quality following reassembly assurance because such testing
- measures, will damage plant for CS-2.
equipment.
6 EFW-1, The licensee should have SW-1 has been No further SGS-1, adequate technical bases deleted. Valves NRC action SW-1, documented when additional group addressed in EFW-1 is required.
CS-1, valves are not disassembled when will now be full-flow and CS-2 an isolated problem is found in tested. Technical a scheduled valve.
justification will be documented for not disassembling additional group valves when problem is found with a scheduled valve.
5
- Animalyl J R$11efi IDeschihtio'niof1ssue Licensee Response?
(NRC/ction.-
3
' Request?
^and/or w4
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CommentsL 7
RC-1 Interim relief was granted for The licensee deleted Provisional one year or the following the portion of the approval.
refueling outage, whichever was request pertaining to See longer, provided the licensee the exercise testing.
Section 10.
considers leak testing other Regarding leak (a)(3)(i) upstream valves on the high testing, (2SI-27A and pressure side and considers the B) and (2SI-28A and B) use of non-intrusive methods to will be treated as two verify closure.
valve pairs; also 2SI-26A and B on the high pressure side will be individually leak tested to provide the required redundancy for pressure isolation valves.
8 The licensee was requested to The requested No further include information on how IST information is NRC action components were selected and how provided in is required.
testing requirements were of the j
identified for each component.
licensee's submittal
)
dated January 21, i
1994.
l 3.0 REVISED PUMP RELIEF RE0 VEST PR-4 PR-4 requests relief from Section XI, Paragraph IWP-4120, which states that the full-scale range of instruments for pump testing shall be three times the reference value or less. The pumps addressed in this requests are 2P-36A, B, and C in the chemical and volume control system that functions to deliver normal makeup to the reactor coolant system (RCS) and emergency boration upon safety injection actuation.
PR-4 was updated to address the concerns identified in the SE dated January 22, 1993, which granted an interim relief for one year or until the following refueling outage, whichever was longer, in order for the licensee to address the adequacy of existing instrumentation and the burden of using portable instruments that meet the Code requirements.
3.1 Licensee's Basis For The Relief Reauest The reference flow for each of the three positive displacement charging pumps is approximately 44 gpm. The flow instrumentation for the pumps is in the I
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6 comon injection header downstream of the tie-in for the three charging pumps.
The range of this instrumentation is'0 to 150 gpm, which exceeds three times the reference value (i.e., approximately 132 gpm).
The installed instrumentation meets the Code required accuracy of i 2 percent over this entire range.
Since the piping configuration imediately downstream of the charging pumps does not have sufficient length of straight piping runs, the only place flow instrumentation could be installed is in the comon injection header.
If. flow instrumentation that would meet the IWP-4120 range requirement were installed in this comon header, it would be over-ranged in i
the event that all three charging pumps were running. Since all three charging pumps are running during some accident conditions (i.e., er.argency boration on a safety injection actuation), it is undesirable to use an j
instrument with full-scale range meeting the Code requirement. A temporary instrument meeting the Code requirement is undesirable because of the location of the comon header (8 feet above the floor) and for as low as reasonably achievable (ALARA) considerations. The typical failure modes for these types of pumps involve large step changes in flow rather than gradual degradation.
The existing instrumentation is adequate to detect these failure modes. Also, repeatable test data has been obtained over the plant's 13 years of comercial operation.
l Based on the above, it is Entergy Operations' position that the installed l
instrumentation is adequate to monitor normal, emergency, and test conditions.
3.2 Proposed Alternate Testina Entergy Operations will continue to monitor charging pump performance with the installed flow instrumentation.
3.3 Evaluation The instrument accuracy and range requirements ensure that test measurements are sensitive enough to allow detection of degradation in pumps.
Section XI, Paragraph IWP-4110 states that accuracy for instrument used in the measurement of flow-rate shall be i 2 percent; and Paragraph IWP-4120 states that the full-scale range of each instrument shall be three times the reference value or less. A range of greater than three times the reference value can be acceptat,le if the instrument is proportionately more accurate than required.
As indicated in Section 5.5.1 of NUREG-1482, " Guidelines for Inservice Testing i
at Nuclear Power Plants," an alternative can be approved if the combination of l
range and accuracy yields a reading that meets i 6 percent of reference value.
The licensee states that the reference value for each of the charging pumps is approximately 44 gpm. The flow instrumentation range of 0 to 150 gpm exceeds three times the reference value by 14 percent. The instrumentation meets the Code required i 2 percent accuracy; however, combined with a range of i
0 to 150 gpm, an accuracy of i 1.7 percent would be needed to meet the 1
guidelines in Section 5.5.1 of NUREG-1482. Meeting the Code requirements would involve purchasing and installing more accurate flow rate instruments.
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7 Making these modifications could require an extended plant outage, which would constitute a hardship for the licensee. With regard to using portable flow instrumentation that meet the Code range requirements, there are problems involving access and ALARA considerations.
The licensee should determine the in-situ instrument accuracy and the repeatability of the conditions under which the measurements are made for each l
system application.
If the instrumentation is not sufficiently accurate and repeatable such that the combination of range and accuracy yields a reading that meets i 6 percent of reference value, the license should develop a method to compensate for the additional uncertainty when evaluating these pumps. One 1
possible method of accounting for the additional uncertainty would be to add the additional uncertainty onto measurements above the reference value and subtract the additional uncertainty from measurements below the reference value when comparing to the allowable ranges of flow.
3.4 Conclusion Based on the determination that the proposal provides a reasonable assurance of operational readiness and that compliance with the Code would result in hardship without a compensating increase in the level of quality and sdety, the proposed alternative is authorized pursuant to Section 50.55a(a)(3)(ii) i with the following provision. The licensee should either (1) demonstrate that the instruments provide indication that is sufficiently accurate and repeatable such that the combination of range and accuracy yields a reading r
'that meets i 6 percent of reference value or (2) develop a method to compensate for the additional uncertainty when evaluating these pumps.
4.0 REVISED RELIEF RE0 VEST PR-5 PR-5 requests relief from Section XI, Paragraph IWP-4500 regarding the measurement of displacement vibration amplitude for all pumps in the IST program.
In the January 22, 1993, SE, a relief was granted with a provision that licensee complies with all the vibration measurement requirements of OM-6.
PR-5 was updated to address this provision and respond to a commitment made during a conference call with the staff on May 5,1995. The update provides additional bases for the use of a vibration transducer readout system that does not meet the OM-6 accuracy requirement.
4.1 Licensee's Basis For The Relief Reauest Because of improvements in vibration measurement and analysis since Section XI was developed, ANO has utilized measurement of vibration velocity to more fully define the pump mechanical condition.
In keeping with the approval gained in the previous revision to the test program, as well as the ASME approved OM-6 inservice testing standard for pumps, ANO will utilize measurement of vibration velocity for all bearings presently requiring vibration measurement per Section XI.
8 4.2 Proposed Alternate Testina ANO-2 complies with all of the vibration requirements of OM-6 with the exception of the vibration transducer / readout system frequency response range requirement of one-third minimum pump shaft rotational speed for the charging and sodium hydroxide pumps. The ANO-2 charging pumps and sodium hydroxide pumps are positive displacement pumps that rotate at 197 rpm and 300 rpm, respectively. One third of 197 rpm is approximately 66 rpm while one third of 300 rpm is 100 rpm.
Entergy Operations has a vibration transducer / readout system with a lower response range of 300 rpm with i 5 percent accuracy.
Accuracy decreases if frequencies lower than 300 rpm are measured.
It would cost approximately $25,000 to obtain a transducer / readout system that would meet the OM-6 low frequency range requirement while maintaining i 5 percent accuracy for the charging and sodium hydroxide pumps. Entergy Operations does not believe that there is sufficient benefit to be gained by obtaining this low frequency transducer / readout system for this limited number of pumps. We propose, instead, to continue to monitor the charging and sodium hydroxide pumps with our existing vibration instrumentation.
Rubs and looseness are the types of vibration problems that are typically associated with reciprocating equipment. These types of degradation usually cause vibration at multiples of running speed or multiples of piston slap frequency (number of pistons times running speed). All of these harmonics are within the calibrated range of the existing vibration monitoring equipment.
Running speed vibration problems are below the calibrated range of the existing vibration equipment; however, these problems would still be detected with the existing vibration equipment. Additionally, running speed vibration problems are not typical for these pumps' designs.
4.3 Evaluation 1
The instrument accuracy requirements of OM-06, Paragraph 4.6 are to ensure that test measurements are sensitive enough to allow detection of degradation in pumps.
OM-6, Paragraph 4.6 states that accuracy for instrument used in the measurement of vibration shall be i 5 percent and allows either displacement or velocity as the measured parameter.
The Code requires the frequency response range of vibration measurements instruments to extend as low as one-third minimum pump shaft rotational speed.
The positive displacement pumps in question rotate at 197 rpm and 300 rpm, respectively. One third of 197 rpm is approximately 66 rpm; and one third of 300 rpm is 100 rpm. The licensee states that i 5 percent accuracy requirement cannot be met with the existing instrumentation for the charging and sodium hydroxide pumps at frequency lower than 300 rps.
The licensee did not adequately support the statement in the bases that vibration problems would still be detected with the existing equipment. The licensee should document the results of a study that demonstrates that these
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l pumps' are not susceptible to degradation mechanisms that result in increased vibration levels seen at frequencies near and below the pump rotational speed frequency, such as looseness of the bearings, misalignment, rubbing, and oil whip.
OM-6 allows either displacement or velocity in measuring vibration.
NUREG/CP-Olll, " Proceedings of the Symposium on Inservice Testing of Pumps and Valves," contains ~a paper presented by J. Howard Maxwell. " Measurements of Vibrational Parameters for Pump Testing," which states that displacement is the better parameter in determining vibration severitf or machines which operate below 600 rpm. The licensee should determine whether measuring displacement instead of velocity is appropriate for the pumps in this relief request.
i Meeting the Code requirements would involve purchasing accurate vibration i
instruments.
Making this purchase could be a hardship for the licensee. The licensee should determine the in-situ instrument accuracy and the repeatability of the conditions under which the measurements are made for each system application.
If the-licensee cannot demonstrate that the instrumentation used to determine pump vibration provide indication that is sufficiently accurate and repeatable to detect degradation and permit the use of the allowable ranges of OH-6, Paragraph 4.6, they should develop a method to compensate for the additional uncertainty when evaluating these pumps. One possible method of accounting.for the additional uncertainty would be to add the additional uncertainty onto measurements when comparing to the allowable ranges of vibration.
4.4 Conclusion i
Based on the determination.that the proposal provides a reasonable assurance of operational readiness and that compliance with the Code would result in hardship without a compensating increase in the level of quality and safety, the proposed alternative is authorized pursuant to Section 50.55a(a)(3)(ii) with the following provision. The licensee should either (1) demonstrate that the instruments provide indication that is sufficiently accurate and repeatable to detect degradation and permit the use of the allowable ranges of OM-6, Paragraph 4.6, or (2) develop a method to compensate for the additional uncertainty when evaluating these pumps. When new or replacement vibration instruments are obtained in the future, the instruments should meet all applicable Code requirements.
5.0 REVISED RELIEF RE0 VEST PR-6 PR-6 requests relief from the requirements of Section XI, Paragraph IWP-3100 for establishing fixed differential pressure and flow rate reference points when testing service water pumps 2P-4A, 4B, and 4C. The licensee proposes to use pump curves to compare differential pressure and flow rate during pump tests.
In the January 22, 1993, SE, a relief was granted with a provision j
that seven elements (identified in Section 5.3 below) and the correct definition of percent deviation are to be incorporated into the IST program.
PR-6 was updated to address this provision.
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10 i
5.1 Licensee's Basis For The Relief Recuest These pumps provide an assured source of cooling water to various safety related and safe shutdown components. They also provide cooling water to various balance-of-plant components during normal plant operation. During normal plant operation, either two or three service water pumps are required i
to be in operation. The pumps provide cooling water flow to the two safety grade service water loops and to the non-safety grade auxiliary cooling water loop.
Interrupting the cooling water flow to these loops would result in a plant transient or a plant trip. The system flow requirements are defined by the service loads of the supplied components. Throttling of the pump discharge valve would cause a loss of adequate flow to certain heat exchangers and aligning additional loads to achieve a repeatable flow condition is not
- feasible due to system loading variations.
5.2 Proposed Alternate Testina Entergy Operations proposes to. utilize multiple sets of reference values in the form of a curve as opposed to one or more fixed sets of values for t
monitoring pump hydraulic performance.
The reference flow versus differential l
pressure (oP) curve represents hydraulic performance over the entire flow range of the pump. The reference curve is generated by varying system loading i
to span the range of flows encountered in normal operation and encompass the flows required to meet system requirements for an accident condition.
Pump 6P 1s measured at each flow point and the flow vs. AP reference curve is j
generated. Alert and required action range curves are derived as multipliers i
of the reference value curve such that the appropriate acceptance criteria is specified at any point on the curve.
The reference value curve is reconfirmed or a new one defined by the collection of several data points (at least five points) at various flows following significant maintenance activities involving rotating assembly removal, repair or replacement. The reference curve is reconfirmed by performance of the normal inservice quarterly test following less significant maintenance activities.
The system load requirements define the flow at which a particular in service test is run. The pump differential is measured and compared to the reference curve and associated acceptance criteria at that flow.
The delta between the reference curve and the actual pump operating point is converted to a percent deviation value which is used for trending purposes. The percent deviation is calculated by subtracting the reference curve value from the test value and then dividing by the reference curve value.
The result is then multiplied by 100 to obtain percent deviation.
Entergy Operations proposes to continue to use a single reference value for 3
vibration monitoring purposes.
In-plant testing has shown that the use of a curve for monitoring this parameter due to varying flow conditions is unwarranted. The test results indicate that the vibration levels are not flow 1
dependent over the range of typical in service test flows associated with these pumps.
1
11 5.3 Evaluation The ASME Section XI, IWP requires that pump flow rate and differential pressure be evaluated against reference values to monitor pump condition and to allow detection of hydraulic degradation. When it is impractical to test a pump at a reference value of flow and differential pressure, testing in the "as-found" condition and comparing values to an established reference curve may be an acceptable alternative.
Pump curves represent a set of infinite reference points of flow rate and differential pressure.
Establishing a reference curve for a pump when it is known to be operating acceptably, and basing the acceptance criteria on this curve, can permit evaluation of pump condition and detection of degradation, though not in accordance with IWP.
There is, however, a higher degree of uncertainty associated with using a curve to assess operational readiness. Therefore, the development of the reference curve should be as accurate as possible. Additionally, when using reference curves, it may be more difficult to identify instrument drift or to trend changes in component condition.
The service water pumps, 2P-4A, 4B, and 4C, operate under a variety of flow rate and differential pressure conditions. Varying the flow rate of these pumps is impractical during normal plant operating conditions because of potential for loss of adequate flow to heat exchangers.
Interruption of cooling water flow could cause a reactor transient or a trip.
As discussed in Draft NUREG-1482, " Guidelines for Inservice Testing at Nuclear Power Plants," Section 5.2, the use of pump curves for reference values of flow rate and differential pressure are acceptable for specific pumps where it is impractical to establish a fixed set of reference values.
The SE dated January 22, 1993, granted relief provided that the following elements be incorporated into the inservice testing program and procedures for developing and implementing the curves:
(1)
Curves are developed, or manufacture's pump curves are validated, when the pumps are known to be operating acceptably.
(2)
The reference points used to develop or validate the curve are measured using instruments at least as accurate as required by the Code.
(3)
Curves are based on an adequate number of points, with a minimum of five.
(4)
Points are beyond the " flat" portion (low flow rates) of the curve in a range which includes or is as close as practicable to design basis flow rates.
(5)
Acceptance criteria based on the curves do not conflict with Technical Specification or Facility Safety Analysis Report operability criteria, for flow rate and differential pressure, for the affected pumps.
c e
12
)
(6)
If vibration levels vary significantly over the range of pump 1
conditions, a method for assigning appropriate vibration acceptance criteria should be developed for regions of the pump curve.
(7)
When the reference curve may have been affected by repair,
)
replacement, or routine service, a new reference curve shall be determined or the previous curve revalidated by an inservice test.
The licensee's response addresses elements 1, 3, 4, 6, and 7, above.
l Elements 2 and 5 should also be incorporated into the IST program. With regard to converting test data for trending purposes, the proposed calculation i
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for " percent" deviation has been corrected in accordance with the SE dated January 22, 1993.
5.4 Conclusion Based on the determination that compliance with the Code requirements is impractical, and considering the burden on the licensee of causing potential reactor transients or trips if the Code requirements are imposed, relief is granted from the Code requirements pursuant to Section 50.55a(f)(6)(1) provided the elements 2 and 5, indicated above, are incorporated into the IST program.
l 6.0 NEW RELIEF RE0 VESTS PR-7 1
PR-7 requests relief from the requirements of Section XI, Paragraph IWP-3100 for establishing fixed differential pressure reference point when testing charging pumps 2P-36A, B, and C.
The licensee proposes to use varying differential pressures during pump tests.
6.1 Licensee's Basis For The Relief Reauest The charging pumps provide normal make-up to the RCS and provide emergency boration upon safety injection actuation.
The flow from these positive displacement pumps does not vary appreciably with variations in differential pressure. The discharge pressure of a positive displacement pump is determined by system conditions, not flow, as is the case with centrifugal pumps. The charging pumps discharge pressure is dependent upon RCS pressure.
Technical Specification Amendment No.138 (2CNA109205, dated October 5, 1992) allows RCS pressure to vary between 2025 psia and 2275 psia during power operation. Given the operating principles of positive displacement pumps and the operating condition of the charging pumps, it is impractical to set a pressure and measure flow.
6.2 Proposed Alternate Testina Entergy Operations proposes to measure flow and differential pressure for the charging pumps. A reference value will be determined and Code limits set for 1
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13 flow. Differential pressure will not be set but will be allowed to vary between 2000 psid and 2300 psid since RCS pressure will be varying between 2025 psia and 2275 psia as allowed by Technical Specifications.
The range allowed for differential pressure is greater than the Technical Specification allowed range to account for variations in suction pressure.
Since flow will be essentially the same over this pressure range, the ability to detect pump degradation will not be compromised by letting differential pressure vary between 2000 psid and 2300 psid. Historical data demonstrates that the charging pump vibration characteristics are not appreciably affected by allowing pressure to fluctuate over the proposed range.
If a pump test becomes due during cold shutdowns (i.e., when RCS pressure is low), or if maintenance is performed on a pump during cold shutdown, then a s
functional test will be performed to meet Technical Specification requirements for emergency boration. When RCS pressure allows, then the Code required post maintenance test or regular test that was deferred will be performed.
6.3 Evaluation j
The ASME Section XI, IWP requires that pump flow rate and differential pressure be evaluated against reference values to monitor pump condition and to allow detection of hydraulic degradation. The charging pumps 2P-36A, B, i
and C operate under varying differential pressure conditions.
The discharge pressure for these positive displacement pumps depends on the RCS pressure, which is allowed by Technical Specifications to vary between 2025 psi and 2275 psi. A positive displacement pump flow does not vary appreciably with variations in differential pressure.
It would not be practical under these circumstances to establish a fixed differential pressure reference point for testing the positive displacement charging pumps.
When it is impractical to test a pump at a reference value of flow and differential pressure, testing in the "as-found" condition and comparing values to an established reference curve may be an acceptable alternative.
Pump curves represent a set of infinite reference points of flow rate and differential pressure.
Establishing a reference curve for the positive displacement pump when it is known to be operating acceptably, and basing the acceptance criteria on this curve, can permit evaluation of pump condition and detection of degradation, though not in accordance with IWP.
However, because of a greater potential for error associated with the use of pump curves, the following elements should be incorporated into the inservice testing program and procedures for developing and implementing the curves:
(1)
Curves are developed, or manufacture's pump curves are validated, when the pumps are known to be operating acceptably.
1 (2)
The reference points used to develop or validate the curve are measured using instruments at least as accurate as required by the Code.
7
-j 14 (3)
Curves are based on an adequate number of points, with a minimum of five.
i
.(4)
Points are in a range which includes or is as close as practicable to design basis flow rates.
l (5)
Acceptance criteria based on the curves do not conflict with Technical Specification or Facility Safety Analysis Report o)erability criteria, for flow rate and differential pressure, for tie affected pumps,
)
i (6)
If vibration levels vary significantly over the range of pump i
conditions, a method for assigning appropriate vibration acceptance criteria should be developed for regions of the pump curve.
(7);
When the reference curve may have been affected by repair, replacement, or routine service, a new reference curve shall be determined or the previous curve revalidated by an inservice test.
The acceptable alternative to establishing a fixed set of. reference values is delineated in NUREG-1482, " Guidelines for Inservice Testing at Nuclear Power Plants," Section 5.2, "Use of Variable Reference Value for Flow Rate and Differential Pressure During Pump Testing."
6.4 Conclusion Based on the determination that compliance with the Code requirements is.
impractical, and considering the burden on the licensee to establish code required test conditions, relief is granted from the Code requirements pursuant to Section 50.55a(f)(6)(i) provided the guidelines in NUREG-1482, Section 5.2 are incorporated into the IST program.
7.0 NEW RELIEF RE0 VEST PR-8 PR-8 requests relief from the requirements of Section XI, Paragraph IWP-3100, which states that pump parameters shown in Table IWP-3100-1 be measured and
. evaluated to determine pump condition.
For the low pressure safety injection pumps 2P-60A and B in question, flow can only be established through a non-instrumented minimum-flow path during quarterly testing.
During cold shutdowns, these pumps will be full-flow tested through a fully instrumented flow path. PR-8 proposes to follow GL 89-04, Position 9, " Pump Testing'Using Minimum-flow Return Lines With or Without Flow Measuring Devices," which provided alternatives to the Code requirements determined to be acceptable to the staff and authorized the use of the alternatives provided the licensee follows the guidance delineated in the applicable position. The alternative proposed is in accordance with GL 89-04 guidance. No further evaluation is required; however, implementation of the alternative is subject to NRC inspection.
i
15 8.0 NEW RELIEF RE0 VEST PR-9 PR-9 requests relief from the requirements of Section XI, Paragraph IWP-3100, which states that pump parameters shown in Table IWP-3100-1 be measured and evaluated to determine pump condition.
For the high pressure safety injection 4
pumps 2P-89A, B, and C in question, flow can only be established through a non-instrumented minimum-flow path during quarterly testing. During cold shutdowns, these pumps will be full-flow tested through a fully instrumented flow path.
PR-9 proposes to follow GL 89-04, Position 9 " Pump Testing Using Minimum-flow Return Lines With or Without Flow Measuring Devices," which provided alternatives to the Code requirements determined to be acceptable to the staff and authorized the use of the alternatives provided the licensee l
follows the guidance delineated in the applicable position. The alternative 1
proposed is in accordance with GL 89-04 guidance. No further evaluation is required; however, implementation of the alternative is subject to NRC inspection.
l 9.0 NEW RELIEF RE0 VEST PR-10 For the high pressure safety injection pump 2P-898, PR-10 requests relief from Section XI, Paragraph IWP-3230(a), which requires that if deviations fall within the Alert Range of Table IWP-3100-2, testing frequency be doubled until the cause of the deviation is determined and the condition corrected.
PR-10 proposes to follow the OH-6, Paragraph 6.1 requirements relative to doubling the frequency of testing in the Alert Range for the quarterly mini-flow testing but not for the cold shutdown frequency full-flow testing.
9.1 Licensee's Basis For The Relief Reouest ANO-2 utilizes OH-6 for vibration testing (Relief Request PR-5, provisionally authorized January 22,1993,2CNA019304). This pump's outboard bearing vibration was within the OM-6 Alert Range (> 0.325 in/sec and < 0.70 in/sec) specified in Table 3.
This range was entered when the pump was full-flow tested following maintenance during refueling outage '2R10 in accordance with GL 89-04, Position 9.
The pump's flow rate met design requirements.
Both IWP and OM-6 require that the test frequency be doubled if the results of pump testing falls within the Alert Range. As in this case, where the pump can only be full-flow tested during cold shutdowns, doubling the test frequency is clearly impractical.
The predominant vibration frequency ) resent is at the vane pass. The pump vendor was contacted and indicated t1at this pump design normally has high vane pass vibration at mini-flow and at full flow (near run out conditions).
According to the vendor, when the vane pass vibration is predominant at the outboard bearing, it is indicative of a bad flow angle against the pump vanes.
This can occur during mini-flow and full-flow testing. As the pump " wears in," it is probable that the vano pass amplitude will decrease because
" feathering" of the vane tips will allow a better flow angle.
16 During 2R10 testing, both the horizontal and vertical vibration measurements on the outboard bearing were in the Alert Range.
During the next practical test, during 2P95-1, the vertical vibration level had decreased to below the Alert Range.
The horizontal level also had decreased, but was still within the Alert Range.
9.2 Proposed Alternate Testina This pump will continue to be tested quarterly on mini-flow.
If the pump falls within any Alert Range during the mini-flow test, the pump mini-flow testing frequency will be doubled. The cold shutdown frequency for full-flow testing this pump will be continued.
9.3 Evaluation The Code requires that if a measured test parameter falls within the..ert Range, testing frequency be doubled until the cause of the deviation is determined and the condition corrected. The licensee indicates that the outboard bearing vibration for the high pressure safety injection pump 2P-89B was within the Alert Range during refueling outage 2R10 and during a subsequent test 2P95-1. The licensee had contacted the vendor about the problem and determined that a pump of this design normally has high outboard bearing vibration at mini-flow and full-flow conditions as the pump " wears in."
Data from two test results indicate that the vibrations are decreasing; it appears that the deviation will probably correct itself when the pump
" wears in."
The high pressure safety injection pump 2P-89B is mini-flow tested quarterly and full-flow tested during cold shutdowns. The vibration and differential pressure measurements would be part of the quarterly mini-flow test, which can be doubled in frequency.
The flow measurement frequency, however, cannot be doubled during the mini-flow test because of a non-instrumented flow path.
Ilnder these conditions where a measured parameter is in the Alert Range and a testing frequency cannot be doubled, the Code requires determining the cause of the deviation and correcting the condition by the next scheduled test, which is now at doubled the quarterly frequency.
However, given the circumstances of what the licensee and the vendor have determined about the cause of the deviation, the acceptable corrective action would be to allow additional time for the pump to " wear in."
The increased test frequency should hasten the wearing in process.
With the exception of the flow measurements during the mini-flow testing, the licensee should be able to double the frequency of testing until the vibration is below the Alert Range.
For deviations other than those caused by the normal wearing in process, the licensee is expected to follow the Code requirements.
9.4 Conclusiom Based on the determination that the proposal provides an acceptable level of quality and safety, the proposed alternative is authorized pursuant to Section 50.55a(a)(3)(i) with the following provision. For deviations other than those determined to be normal and caused by the pump's wearing in
17 process, the licensee is expected to follow the Code requirements. With the exception of the flow measurements during the mini-flow testing, the licensee should double the frequency of testing until the deviation is below the Alert Range.
10.0 REVISED RELIEF RE0 VEST RC-1 RC-1 requests relief from the leak test frequency requirement of Section XI, IWV-3422 for the high pressure safety injection to RCS hot leg check valves 2SI-27A, 2SI-27B, 2SI-28A, and 2SI-28B.
In the SE dated January 22, 1993, interim relief was granted for 1 year or the following refueling outage, whichever was longer, to allow the licensee time to provide reasonable alternatives.
10.1 Licensee's Basis For The Relief Reauest These valves prevent reversal of reactor coolant flow into a lower pressure system and allow flow during long-term core cooling to prevent boron precipitation. The absence of isolation valves on the downstream side does not allow individual leak rate testing of these valves.
The low pressure side of these valves is monitored for back leakage.
10.2 Proposed Alternate Testina 2SI-27A and 2SI-28A will be treated as one valve. 2SI-27B and 2SI-28B will also be treated as one valve.
These valve pairs are demonstrated to be leak tight during power operation.
Per IWV-3421 these valves do not require a leak test. The low pressure side of these valve pairs is instrumented, 2PI-5105 and 2PI-5106, and will alarm in the control room in the event of high pressure; hence demonstrating that these valves, as a pair, are leak tight.
If one or both of these valve pairs were leaking and if other valves were leaking such that no pressure buildup is observed on 2PI-5105 and/or 2PI-5106, then leakage though these valve pairs would still be detected as an increase in unknown leakage when the daily reactor coolant system leakage test is performed.
In the event the RCS unknown leakage becomes significant (greater than 1 gpm), then additional steps will be performed to determine if the leakage is through 2SI-27A and 2SI-28A and/or 2SI-278 and 2SI-28B.
In addition, 2SI-26A and 2SI-26B will be individually leak rate tested to provide another pressure isolation valve between the high and low pressure piping. The leak rate testing performed on 2SI-26A and 2SI-26B will meet the requirements of IWV-3420.
10.3 Evaluation l
These valves have a safety function to both open and close. The licensee states in the letter dated February 10, 1995, that these valves are exercised during cold shutdowns in accordance with the Code requirements.
18 The Code also requires leak testing, since these valves form a pressure boundary for the RCS.
It is not practical to individually leak test these valves in accordance with Section XI, Paragraph IWV-3420 because necessary taps are not installed. The licensee proposes to treat (2SI-27A and B) and (2SI-28A and B) as two valve pairs and to demonstrate the leak tightness of each valve pair during power operation.
In addition, the valves 2SI-26A and B on the high pressure side will be individually leak tested in accordance with IWV-3420 to provide the second leak tested barrier in the lines on the high pressure side.
It is not clear from the information provided, however, that the proposal to take credit for leak testing only one of the two valves in each identified pair would not create a conflict with regulatory or license requirements, such
~
'as the Technical Specifications and the plant safety analysis.
If there is no conflict, the licensee's proposal provides a reasonable assurance that these valves will perform their pressure isolation function.
10.4 Conclusion Based on the determination that the proposal provides an acceptable level of quality and safety, the alternative is authorized pursuant to Section 50.55a(a)(3)(i) with the following provision. The licensee should ensure that leak testing only one of the two valves in each identified pair, (2SI-27A and B) and (2SI-28A and B), would not create a conflict with regulatory or license requirements.
11.0 REVISED RELIEF RE0 VEST EFW-1 EFW-1 requests relief from the requirements of Section XI, Paragraph IWV-3520.
For the check valves 2EFW-2A and B in the emergency feedwater system, the licensee proposes to full flow test in accordance with the GL 89-04, Position 1, " Full Flow Testing of Check Valves." This test will be performed during refueling outages.
11.1 Licensee's Basis For The Relief Reauest These valves allow service water as emergency supply to steam generators.
There is no means available to verify that the disks in valves 2EFW-2A and 2EFW-2B move promptly away from the seat when the closing differential is removed and flow through the valve is initiated.
Furthermore, partial-or full-stroke exercising of these valves during power operation or cold shutdown would introduce water of unacceptable chemical quality into the secondary coolant.
11.2 ProDosed Alternate Testina These valves will be full flow tested during refueling outages when the service water piping is flushed. During refueling outages, pipe spools downstream of these valves (but upstream of the emergency feed water (EFW) pumps) are removed to flush the subject piping using the service water pumps.
This is done to prevent chemical contamination of the EFW system with service
19
)
i water and subsequent contamination of the steam generators during plant i
startup.- Flow through 2EFW-2A and 2EFW-2B is confirmed by using a strap-on ultrasonic flow meter (i 5 percent accuracy).
Flow through these valves will be confirmed to be greater than 550 gpm.
The EFW pumps are required to inject 485 gpm at accident conditions. Hence, full flow will be passed though 2EFW-2A and 2EFW-28. This alternative testing meets the requirements of GL
}
89-04, Position 1.-
These valves are confirmed closed each quarter.
11.3 Evaluation i-The check valves 2EFW-2A and 2EFW-2B are required by the Code to be exercised
-quarterly or, if impractical, during cold shutdowns. This testing is an assessment of valves' operational readiness and demonstrates that the 2
obturators are capable of moving to their safety function positions. The licensee states that during power operations and cold shutdowns full-or partial-stroke exercising these valves would not be practical because the j
testing would introduce water of unacceptable chemical quality into the secondary coolant.
}
In rulemaking to 10 CFR 50.55a effective September 8, 1992, (See 57 FR 34666),
the 1989 edition of ASME Section XI was incorporated in 10 CFR 50.55a(b). The 1989 edition provides that the rules for IST of valves may meet the requirements set forth in OM-l').
Pursuant to Section 50.55a(f)(4)(iv),
portions of the 1989 edition may be used provided that all related requirements of the edition are met. The licensee's proposal to full-flow test during refueling outages and to verify closure of the valve quarterly is consistent with OM-10, Paragraph 4.3.2, which allows full-stroke exercising that is not practicable during power operation or cold shutdown to be deferred to refueling outages. This relief request also documents the justification for deferral of stroke testing in accordance with OM-10, Paragraph 6.2(d).
.Regarding the full flow used to verify a check valve's full-stroke to the open position, EFW-1 proposes to follow GL 89-04, Position 1, which specified alternatives to the Code requirements determined to be acceptable to the staff and authorized the use of the alternatives provided the licensee follow the J
guidance delineated in the Position. The proposed alternative is in
)
accordance with GL 89-04 guidance.
11.4 Conclusion The alternative to defer full-stroke exercising to refueling outages as described in Section 11.2 is approved pursuant to Section 50.55a(f)(4)(iv) provided that all related requirements, including Paragraphs 4.3.2 and 6.2(d),
of OM-10 are met.
Implementation of related requirements is subject to NRC inspection.
~
Regarding the methodology used to verify a check valve's full-stroke to the open position, GL 89-04, Position I specified alternatives to the Code j
requirements determined to be acceptable to the staff and authorized the use
l
~
20 l
of the alternatives provided the licensee follow the guidance delineated in the Position. The proposed alternative is authorized for use in accordance with GL 89-04.
Implementation of the alternative is subject to NRC j
inspection.
'12.0 NEW RELIEF REQUEST GR-3 GR-3 requests relief from the requirements of Section XI, Paragraph IWV-3417(a), which states that corrective actions be initiated based on a comparison of each test result to the previous test result. The licensee proposes to establish reference values for each power operated valve when the valve is known to be in a good operating-condition and initiate corrective i
action based on a comparison of each test result to the reference values.
This proposal is consistent with GL 89-04, Position 5, " Limiting Value of i
Full-Stroke Times for Power Operate.i Valves," which provided alternatives to the Code requirements determined to be acceptable to the staff and authorized the use of the alternatives provided the licensee follow the guidance i
delineated in the applicable position. No further evaluation is required; l
however, implementation of the alternative is subject to NRC inspection.
i 13.0 NEW RELIEF RE0 VEST GR-5 GR-5 requests relief from the requirements of Section XI, Paragraph IWV-3522, which states that if the test is made by use of flow through the valve, the pressure differential for equivalent flow shall be no greater than that observed during the preoperational test. This' request pertains to swing or l
tilting disc check valves whose function is to open. The licensee proposes to follow the guidelines of GL 89-04, Position 1, " Full Flow Testing of Check i
Valves," and Position 2, " Alternative to Full-Flow Testing of Check Valve."
NRC guidance contained in GL 89-04 provided alternatives to the Code l
requirements determined to be acceptable to the staff and authorized the use of the alternatives in Positions 1 and 2 provided the licensee follows the guidance delineated in the applicable position. This relief request, however, does not-show that the guidance of GL 89-04, Positions 1 and 2, is met. The-licensee should identify the valves in question and provide details showing compliance with the GL 89-04 guidance. When an alternative is proposed which is in accordance with GL 89-04 guidance and is documented in the IST program, no further. evaluation is required; however, implementation of the alternative is subject to NRC inspection.
The staff is re-examining the adequacy of Position 1 of GL-89-04, which states that "a check valve's full-stroke to the open position may be verified by passing the maximum required accident condition flow through the valve," since merely passing design basis flow does not ensure obturator movement or indicate a missing, misaligned, or a stuck open obturator. Any change in Position 1 will be addressed in future correspondence.
For those cases where J
l l
?
21 only design basis flow is used to verify full-stroke of check valves, it would be appropriate for the licensee to consider including other positive means to verify full obturator movement.
14.0 CONCLUSION
S The staff concludes that the relief requests as evaluated and modified by this SE will not compromise the reasonable assurance of operational readiness of the pumps and valves in question to perform their safety-related functions.
The staff has determined that approval of relief requests pursuant to 10 CFR 50.55a(f)(4)(iv), (f)(6)(1), (a)(3)(i), or (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.
In making this determination pursuant to 10 CFR 50.55a(f)(6)(1), the staff has considered the impracticality of performing the required testing and the burden on the licensee if the requirements were imposed.
Principal Contributor:
K. Dempsey Date:
February 16, 1996 l
.=
[
-1.*. l-Mr. Jerry N. Yelverton interest.
In making this determination pursuant to 10 CFR 50.55a(f)(6)(i),
the staff has considered the impracticality of performing the required testing and the burden on the licensee if the requirements. were imposed.
Sincerely, ORIGINAL SIGNED BY:
William D. Beckner, Director Project Directorate IV-1 Division of Reactor Projects III/IV Office of Nuclear Reactor Regulation Docket No. 50-368
Enclosure:
Safety Evaluation cc w/ enc 1:
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RZimmerman WBeckner GKalman PNoonan JDyer, RIV OGC JMitchell, RIV GHill (2)
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EHoller Document Name: AR88762.LTR SEE PREVIOUS CONCURRENCE
- OFC LA/PDR PM/PD4,-1 OGC D/PD4-1 NAME PNoo[ewYk GKdan/vw EHoller*
WBeckN DATE h /'N 8 /$ /h 2/14/96
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