ML20045E046
| ML20045E046 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 06/25/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20045E042 | List: |
| References | |
| NUDOCS 9307010028 | |
| Download: ML20045E046 (9) | |
Text
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ff UNITED STATES NUCLEAR REGULATORY COMMISSION e
n WASHINGTON, D. C. 20555 t
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO THE INSERVICE TESTING PROGRAM RE00ESTS FOR RELIEF COMMONWEALTH EDIS0N COMPANY ZION STATION UNITS 1 AND 2 DOCKET NOS. 50-295 AND 50-304
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 granted or proposed alternatives have been authorized by the Commission pursuant to 10 CFR 50.55a(f)(6)(i), (a)(3)(i), or (a)(3)(ii). 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 with the specified requirements would result in a hardship or unusual difficulty without a compensating increase in the level of quality and safety.
NRC guidance contained in Generic Letter (GL) 89-04,
" Guidance on Developing Acceptable Inservice Testing Programs", provided alternatives to the Code requirements determined to be acceptable to the staff and authorized the use of thn alternatives in Positions 1, 2, 6, 7, 9, and 10 provided the licensees follow 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, implementation of the alternative is subject to NRC inspection.
10 CFR 50.55a authorizes the Commission to grant relief from ASME Code requirements or to approve proposed alternatives upon making the necessary findings. The 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).
This SE concerns a relief request and supporting information that was submitted in Commonwealth Edison Company's (CECO's) letter dated June 2,1993, for the Zion Station Units 1 and 2, IST Program. This new relief request deals with post-maintenance testing of its service water pumps following maintenance that could affect pump performance reference values and is evaluated below.
The Zion Station Unit 1 and 2 IST Program was developed to the requirements of ASME Section XI, Subsections IWP and IWV, 1980 Edition up to and including the Winter 1981 Addenda.
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The IST Plan for Class 1,2, and 3 Pumps and Valves is applicable for a j
120-month interval beginning December 31, 1983, for Unit I and September 19, i
1984, for Unit 2 (ending 12/31/93 for Unit I and 9/19/94 for Unit 2). The commercial service date for Zion Unit 1 is December 31, 1973, and September 19, 1974, for Zion Unit 2.
2.0 PUMP RELIEF RE0 VEST
- 1 CECO's letter dated June 2,1993, forwarded Revision 04/93 to the Second Interval Pump and Valve Inservice Testing Plan for Zion Station Units 1 and 2.
This revision consists of one new pump relief request, PR-12, related to. post-maintenance testing of service water pumps; a revision to pump relief request PR-04 to include the Residual Heat Removal Pumps; a revision to pump relief-request PR-ll (erroneously submitted as PR-10 in Revision 11/92); withdrawal of Technical Approach and Position, PP-02; and various clarifications as delineated in the Plan's revision summary.
2.1 Relief Reauest PR-12. Service Water Pumo Post-Maintenance Test Pump relief request PR-12 was submitted for the Service Water (SW) System Pump Inservice Testing (IST) following replacement, repair, or routine servicing (required by ASME Section XI, IWP-3111, "Effect of-Pump Replacement, Repair, and Routine Servicing on Reference Values").- The licensee determined that it cannot perform the required post-maintenance testing in accordance with Section XI during power operation for the SW pumps because the plant design-did not provide a length of straight pipe that is sufficient for accurate flow measurements. This is explained further in the staff's safety evaluation for Pump Relief Request PR-02, issued on March 24, 1993.
The SW pumps are vertical pumps.and are supplied with an emergency power source.
The function of the SW pumps is to provide lake water for cooling for both safety-related and non-essential heat exchangers and equipment.
The pumps also provide a redundant supply of water to the suction of the auxiliary feedwater pumps.
2.1.1 Licensee's Basis for Relief in its letter dated June 2, 1993, the licensee stated:
As stated in Zion's Pump Relief Request, PR-02, " Permanent flow instrumentation is installed on the common discharge headers for the Service Water (SW) pumps on both units.
Flow instrumentation could not 4
be installed on the individual discharge lines because the plant. design did not provide a sufficient length of straight pipe needed for accurate.
flow measurements.
In order to test the pumps individually, two of the SW pumps on the Unit being tested must be secured and the cross-tie valves between units must be closed."
Additionally, pressure switches located on the common unit supply headers will auto start an idle pump if the header pressure drops below
- 4 the setpoint. The low pressure needed to cause an autostart occurs when both units are at power, crosstie valves are closed, and only one pump supplying a unit. Auto start of the idle-pump will then result in -the'-
flow from both pumps being monitored by the common flow instrument. The auto start function is designed to maintain header pressure above the minimum design for service water during a Design Basis Event.
Individually flow testing the SW pumps during normal ' plant operation would jeopardize safety.
Per UFSAR Section'9.2.1, two SW pumps per Unit are required during normal plant operations to provide adequate cooling.
During normal plant operations, operating the system as required for inservice testing would violate the SW system design requirements described in the UFSAR and place the plant in an unsafe operating condition.
Relief request PR-02 was part of Revision 09/91, requested in a CECO letter dated September 16, 1991. The staff granted the requested relief in a letter dated March 24, 1993.
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2.1.2 Alternative Testing The licensee stated that:
Zion proposes an alternative to the requirements in IWP-3111, IWP-3300, and IWP-3110. During normal plant operation the alternative test would' be performed without measurement of the flow rate following maintenance where reference values may have been affected. This alternative provides an acceptable method to test the SW pump / motor combination because for each unique flow and head point on the pump performance curve there is a corresponding brake horsepower.
The proposed alternative would only be necessary during power operation af ter a SW pump has been replaced, repaired, or serviced where' reference value(s) may have been affected.
Zion considers this maintenance to be infrequent during power operation.
Therefore, this test methodology may only be performed only on those special occasions.
When a pump has been serviced offsite, the OEM or equivalent test facility will test the pump.
Pump head, flow, and brake horsepower will be measured to establish a new combination pump and motor characteristic' curve. As part of this test, data will be taken' at the previous lST flow reference value. The corresponding head and brake horsepower will be considered the " previous" (IWP-3111) reference test quantities to be used with the first inservice test at Zion Station.
Following installation of the replaced, repaired, or serviced pump where reference values may have been affected, Zion will perform an inservice test at power.. Zion will use brake horsepower as a required test quantity.
Flow will be manipulated until the brake horsepower corresponding to the reference flow is achieved.
When stable, the pump
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head and vibration will be measured. These values will be the new reference values for subsequent IST.
As required by IWP-3111, deviations between the previous and new set'of reference values shall be identified. Zion will compare the previous head and vibration reference values with the new values. The previous flow rate will be reconfirmed by varying the system resistance to the
'l corresponding brake horsepower value.
Verification that the new values-represent acceptable pump operation shall be placed in the record of tests.
In addition, during the next inservice test,-performed during a scheduled cold shutdown, Zion will perform this alternative testing described above. This test will be analyzed for satisfactory operation.
If satisfactory, Zion may establish an additional set of reference values from a second test, as allowed by IWP-3112, where flow rate will be measured. This will enable Zion to conduct subsequent IST in accordance with Subsection IWP at the frequency discussed in PR-02.
2.1.3 EVALUATION IWP-3110, " Reference Values" states that "[r]eference values are defined as one or more fixed sets of values of the quantities shown in Table IWP-3100-1 as measured or observed when the equipment is known to_be operating acceptably. All subsequent test results shall be compared to. these reference values or with new reference values established in accordance with IWP-3111 and IWP-3112.
Reference values shall be determined from the results of an inservice test which may be run during preoperational testing, or from the results of the first inservice test run during power operation.
Reference values shall be at points of operation readily duplicated during subsequent inservice testing."
TABLE IWP-3100-1 INSERVICE TEST QUANTITIES Quantity Measure Observe Speed N (if variable speed)
/
Inlet pressure P
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i Differential pressure oP
/
Flow rate Q
/
Vibration amplitude-V
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Proper lubricant level or pressure
/
Bearing temperature T
/
b NOTE:
(1) Measure before pump startup and during test.
n IWP-3111, "Effect of Pump Replacement, Repair, and Routine Servicing on Reference Values" states (in part) "When a reference value or set of values may have been affected by repair or-routine servicing of the pump, a new reference value or set of values shall be determined or the previous value reconfirmed by an inservice test run prior to, or within 96 hr after, return of the pump to normal service. Deviations between the previous'and new set of reference values shall be identified, and verification that the new values represent acceptable pump operation shall be placed-in the record of tests (IWP-6000)."
IWP-3300, " Scope of Tests" states that "[e]ach inservice test shall include I
the measurement and observation of all test quantities in Table IWP-3100-1 except bearing temperatures, which shall be measured during at least one inservice test each year."
The licensee proposes to measure and observe the SW pump / motor brake horsepower, in lieu of flow, during retests conducted at power, to confirm pump operability following replacement or repair where the reference values may have been affected.
To test the SW pumps individually as would be required to comply with the-Code, given the Zion plant design, two of the three SW pumps on the Unit being tested would have to be secured and the cross-tie valves between units would~
have to be closed. This'would be an unsafe condition while operating because it would result in inadequate cooling for the operational loads of the service water system.
To do this safely, the licensee would have to either shut the plant down or significantly reduce power. This would be unnecessarily burdensome if an acceptable alternative is available for the period between restoration from maintenance and the next scheduled cold shutdown.
If the Code requirements were imposed, the licensee would have to install flow measuring instrumentation on the discharge of each SW pump.
This would require major plant modifications because the current plant design does not provide a sufficient length of straight pipe on the pump discharge to install accurate flow measurement instrumentation.
The proposed alternative, to use brake horsepower (i.e., a calculated pump horsepower based on a measured pump motor power) instead of a flow rate as the
" set" reference parameter when conducting the post-maintenance testing to verify pump operability is a reasonable approximation of the pump test methodology described in the Code (which sets either flow or differential pressure).
The pump and motor characteristic curve will be developed at an offsite test facility following pump servicing to establish the " design" l
characteristics of the pump.
Based on a telephone conference call with the licensee on June 14, 1993, calculated head will be compared to design head'at four separate points on the pump and motor characteristic curve (which specifies pump head, flow rate, and brake. horsepower).
The licensee's proposed alternative includes an additional parameter that can be monitored i
e., brake horsepower.
This alternative, when coupled with the licensee's commitment to complete an inservice test where flow rate is measured during the next scheduled cold shutdown, provides an adequate means to trend
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degradation of these pumps. 'In addition, since these_ pumps are normally running and are routinely monitored during plant operation, any significant-degradation in pump performance should be readily apparent. ?Therefore, the:
test methodology provides reasonableLassurance of the operational readiness of; the-SW pump and is an acceptable interim test until an inservice test as described in the Code can be safely conducted at cold: shutdown conditions in-n accordance with Relief Request PR-02.
1 This test methodology is only approved for post-maintenance. testing after offJ 3
site servicing where new pump and motor ~ characteristic curves have been:
developed. The post-maintenance test methodology is not approved.for..
1 maintenance conducted on site'that might affect the service water pump performance reference values.
Based on a telephone conference callion June 14, 1993,-the licensee indicated that the requested relief was intended to apply in situations in which extensive maintenance'was' performed-off site and was not intended to address maintenance performed onsite in'which new-curves for verification of acceptable performance are not devel'oped...If!it is determined that PR-12 should also apply to onsite maintenance, a revision to
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the relief request should be-submitted addressing the actions-that-will be.
taken in that situation.
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1.4 CONCLUSION
1
~ Due to the limitations in the design configuration for the service; water
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. pumps, compliance with the Code requirements is impractical.because-thel i
licensee would' have to' install flow measuring instrumentaion_ on ~ the. discharge of each SW pump, which would require major plant-modifications' because' the current plant design. does not provide a sufficient length of. straight pipe on.
the pump discharge to install accurate flow measurement instumentation.
In addition, given the Z1on plant design, compliance:with the Code would require.
securing two of the three SW pumps on the Unit being tested and the cross-tie valves would have to be closed. This would be an unsafe ccndition because' it would result in inadequate cooling for the operational. loads of the. service water system.
Based on the iupracticality and the burden on the~ licensee if the Code requi,ements were imposed, and considering the licensee's proposed.
i alternative t< sting, relief is granted pursuant to 10 CFR 50.55a(f)(6)(1).
aq 3.0 Relief Reouest PR-ll-i n
The_ revision to PR-ll was limited to a change.in the number.
It was previously submitted as PR-10, but there was.already'a relief request I
designated as PR-10.
The review of'PR-11 for the containment spray pumps was
- y performed and the results were included in the NRC Safety Evaluation dated:
June'14, 1993.
Therefore, no further review is' required and the relief'which was' approved remains effective.
4.0 Relief Reauest PR-04 The revision added the residual heat removal pumps to the scope of PR-04 which requested deletion of the requirements to measure bearing temperature annually.
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L and proposed to monitor for degradation of the bearings using the data from the vibration measurements taken in accordance with the inservice' testing program.
There are no additional requirements related to deletion of the -
bear.ing temperature measurement.
Because.the. latest edition of the ASME Code,Section XI (1989 Edition), which has been incorporated in 10 CFR 50.55a(b), no longer' requires measurement of the bearing temperature, the change to the.
scope of this relief request of adding the residual heat removal pumps to the scope of PR-04 is acceptable and is approved for implementation pursuant to 10 CFR 50.55a(f)(4)(iv).
Principal Contributor: David Fischer Dated: June 25,1993 m
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... Mr. D. L. farrar-June 25,1993 Ceco's Relief Request PR-ll was-limited to a change'in the relief: request -
number. Relief Request PR-ll was~ approved as Relief Request.PR-10 in the-staff's SE issued on June 14, 1993.
In the enclosed SE,,the staff is granting the change in relief request number because.it does not involve any: technical change to the original Relief Request.
t The staff also reviewed the revision to Relief Request PR-04-that.added the residual heat removal pumps.to the scope of PR-04, which was approved in an SE-issued on June 4, 199'.
The change to the scope of this relief-.' request is acceptable since the latest edition of the ASME Code,Section XI' (1989 Edition) which has been incorporated in 10 CFR.50.55a(b), no. longer requires measurement of the bearing temperature. The staff is, therefore, granting the-1 requested relief in the enclosed SE.
The staff has determined that the relief granted 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.that could result if the applicable ASME Code-requirements were imposed on the facility.
Sincerely, original signed by D. V. Pickett for James E. Dyer, Director Project Directorate'Ill-2 Division of Reactor Projects -'Ill/IV/V-Office of Nuclear Reactor Regulation
Enclosure:
Safety Evaluation cc w/ enclosure:
See next page DISTRIBUTION:
Docket File NRC & Local PDRs PDIII-2 r/f T. Murley/F. Miraglia J. Partlow E. Rossi J. Lieberman J. Roe J. Zwolinski J. Dyer C. Moore C. Shiraki OGC E. Jordan G. Hill (4)
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The staff will continue its review of. Revision 04/93-to the Second Interval l
~ Pump and Valve Inservice Testing Plan for Zion Station Units I 'and 2.
Sincerely, James E. Dyer, Director Project Directorate III-2 Division of Reactor. Projects - III/IV/V Office of Nuclear-Reactor Regulation R
Enclosure:
Safety Evaluation cc w/ enclosure:
See next page DISTRIBUTION:
Docket File NRC & Local PDRs PDIII-2 r/f
.T. Murley/F. Miraglia
.J. Partlow E. Rossi J. Liebern,an J. Roe J. 7wolinski J. Dyer C. Moore C. Shiraki OGC E. Jordan G. Hill (4)
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