ML20057B064
| ML20057B064 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 09/13/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20057B062 | List: |
| References | |
| NUDOCS 9309170118 | |
| Download: ML20057B064 (7) | |
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- I+, UNITED STATES E W E NUCLEAR REGULATORY COMMISSION f' W ASHINGTON, D.C. 20566-0001 1
\...../ l SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO THE INSERVICE TESTING PROGRAM RE0 VESTS FOR RELIEF DUOVESNE LIGHT COMPANY
- BEAVER VALLEY POWER STATION. UNIT NO. 1 DOCKET NO. 50-334
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 and <
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). In order to obtain authorization or relief, the licensee must demonstrate that: i (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 hardship or unusual difficulty without a compensating increase in the level of quality and safety. Section 50.55a(f)(4)(iv) provides that inservice tests of 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 Lctter (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 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, implementation of the alternative is subject to NRC ,
inspection. ;
The Code of Federal Regulations, 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 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).
In rulemaking to 10 CFR 50.55a effective September 8,1992, (see 57 federal Register-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 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-930917011e 930913 DR ADDCK0500g4 i
Water Reactor Power Plants," and Part 10 (0M-10), " Inservice Testing of Valves 4
in Light-Water Reactor Power Plants." Pursuant to 10 CFR 50.55a(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 subject to Commission approval. Because the alternatives meet later editions of the Code, relief is not required for those inservice tests that are conducted in accordance with OM-6 and OM-10, or portions thereof, provided all related requirements are met. Whether all related requirements are met is subject to NRC inspection.
2.0 BACKGROUND
On May 6, 1991, the NRC issued a SE for the Beaver Valley Power Station, Unit 1, second 10-year interval IST program relief requests. The SE included 29 anomalies for the licensee to address. In a January 24, 1992, SE, the results of an analysis of safety injection check valve testing was issued.
Duquesne Light Company (DLC) responded to the anomalies and the January 1992 SE in a letter dated August 18, 1992. The NRC reviewed the licensee's actions taken to address the anomalies and evaluated revised relief requests in a December 30, 1992, SE which identified seven open anomalies. DLC, in their letter dated June 21, 1993, submitted information related to the seven open anomalies and included Revision 9 of the Beaver Valley Power Station, Unit 1, IST program.
In response to NRC comments in the December 1992 SE, the licensee committed to incorporate guidance for using pump curves into the applicable relief requests for Unit I and Unit 2. The NRC approved the use of pump curves for the primary component cooling water pumps and service water pumps for Beaver Valley Power Station, Unit 2, in a SE dated July 12, 1993, provided the guidance in the evaluation be incorporated into the program for using the pump curves for inservice testing which the licensee committed to do in their June 21, 1993, letter. Relief Request 11 discusses using pumps curves for the inservice testing of the Unit I component cooling water pumps (see Section 3.1 below).
The Beaver Val %y Power Station, Unit 1, IST program covers the second 10-year interval which commenced on October 1,1986, and ends September 30, 1996. The program was based on the requirements of the ASME Code,1983 Edition with addenda through the Summer 1983 Addenda.
3.0 EVALUATION OF RELIEF RE0 VESTS The actions taken for the remaining seven anomalies (2, 6,13,14,15, 26, and-
- 27) were described in the June 21, 1993, submittal. The actions are adequate to address the concerns identified in the previous SEs. A brief summary of these seven anomalies and the actions taken follows:
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Anmaaly No. Deseription ActIana Takan Ststus 2 and 6 use of either permanent or Tenporary test gauges (which meet Complete.
temporary pressure gauges the Code requirements) will be used at existing test for the ptmp inservice testing until connections at the suction permanent instrunentation is of the charging and quench installed.
spray gmps.
13 and 14 Method used to verify Portable ultrasonic flow meters were Conplet e, full-stroke open used to measure flow through each of capability of the safety the branch lines during testing injection parallel branch performed in the test refueling line check valves should outage (1R9). As a second be revised to ensure flow verification, a flow calculation was is through att valves, performed. The portable ultrasonic flow meters will be used for future testing of these check valves.
15 Method used to verify The safety injection acctmulator Complete.
full-stroke open discharge check valves were tested Revised method capability of the safety during the last refueling outage should be injection accunulator (1R9) by measuring a flow continued for discharge check valves coefficient value during a blowdown future testing, should be revised. at reduced acctmulator pressure in conjunction with a nonintrusive test.
26 Control room emergency air These valves will be stroke timed by Cotoplete.
bottle outlet trip local observation of valve position isolation valves should be change. Because the Code monitored for degradation requirements will be met, Relief during quarterly testing. Request VRR-37 has been deleted in Revision 9 of the IST program.
27 Nonintrusive methods for A review has been initiated. Current actions verifying full or partial Portable flow meters are being used are acceptable, stroking of check vstves 66ere practical and nonintrusive Actions to be should be investigated, methods are being applied for coupleted by including the installation selected valves. The review the next 10-of flow instrunentation continues for other test methods and year interval where feasible. application to other check valves update for all not currently monitored with flow or check valves nonintrusive technicpes. The review not currently wit! be completed and the results tested with incorporated into the next 10-year flow or intervat program, nonintrusive techniques.
3.1 Relief Reouest 11 Per IWP-3100 and Table IWP-3100-1, for performing inservice testing of pumps, the resistance of the system is to be varied until either the measured differential pressure or the measured flow rate equals the corresponding reference value. The other test quantities shall then be measured or observed. For the component cooling water pumps, the use of pumps curves has been requested.
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i 3.1.1 Licensee's Basis for Relief i
The licensee states: )
The amount of Reactor Plant Component Cooling Water System flow is dependent on the plant's seasonal heat load requirements and on River Water System and seasonal Ohio River water temperatures. The overall amount of flow may vary by several hundred gallons per minute between cold winter months and hot summer months.
Varying Component Cooling header flows by adding or removing heat loads from service in order to increase or decrease flowrate to a specific reference value is not practical. An exact flowrate cannot be duplicated because flow to some heat exchangers cannot be throttled and those that can be throttled are not always capable of being throttled due to system heat load requirements. The test is typically performed by either isolating or placing into service non-essential heat exchangers which results in a gross flow change. For this reason, a wider range of flow values, as on a pump curve, is needed as a reference.
In addition, to throttle flow 'to a reference value during hot summer months when flow demand is greatest requires the use of a manual butterfly valve at the discharge of the pumps. A butterfly valve is not designed to be used as a throttle valve so throttling may result in excessive wear and premature failure of the valve. No other valves are available to throttle header flow. Also, operating experience has shown that any throttling of the pump discharge butterfly valves results in a large reduction in cooling water flow to the reactor coolant pump thermal barrier heat exchangers, bearing lube oil coolers and motor stator air coolers. Reduced header flows result in low flow alarms and heatup of the Reactor Coolant Pumps to near required manual pump trip setpoints which could ultimately result in a plant trip. Finally, the added thermal cycling of these coolers for pump testing could cause premature degradation of these heat exchangers.
IWP-3112 provides for multiple sets of reference values. A pump curve is merely a graphical representation of the fixed response of the pump to an infinite number of flow conditions which are based on some finite number of reference values verified by measurement. Relief is, therefore, requested to use a pump curve, which should provide an equivalent level of quality and safety in trending pump performance and
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degradation. Flow will be permitted to vary as system conditions require. Delta-P [ differential pressure] will be calculated and converted to a developed head for which ASME ranges will be applied.
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3.1.2 Alternative Testina The licensee proposes:
A pump curve (developed per the guidelines in [the IST program] Section I, " Pump Testing Requirements") will be used to compare flowrate with developed pump head at the flow conditions dictated by plant seasonal heat load requirements per Reactor Plant Component Cooling Water Pump l Tests, 10ST-15.1, 10ST-15.2, and 10ST-15.3, each quarter. Since normal l flow varies, the most limiting vibration acceptance criteria will be i used over this range of flows based on baseline vibration data obtained !
at various flow points on the pump curve. !
3.1.3 Evaluation Some designs, such as the component cooling water system described above, do ;
not facilitate testing at a single reference point or a set of multiple '
reference points. In these cases, it may be necessary to develop pumps curves to use as the basis for variable reference points. It is impractical to perform testing in accordance with the Code requirements for the component ,
cooling water pumps based on the lack of throttling capability without l creating transients in the reactor coolant pumps which could cause a plant !
trip and without creating a potential personnel hazard. To impose the Code- ;
required test method would be an undue burden on the licensee in that damage i to the plant equipment could occur, a plant transient / trip could occur, and personnel could be subjected to unsafe conditions. The alternative testing i can provide an adequate level of assurance of operational readiness of the i subject pumps without creating these adverse conditions.
The NRC approves the use of variable reference values of flow rate and j differential pressure in those cases where the licensee clearly demonstrates -
in the relief request the impracticality of establishing a fixed set of reference values. The licensee must ensure that the method of evaluating these pump parameters to detect hydraulic degradation and determine pump i operability is essentially equivalent to the Code requirements for allowable ranges in Table IWP-3100-2.
The licensee must establish a valid pump characteristic curve to employ this test methodology. This curve must be devaloped from empirical data or supplied by the pump manufacturer and verified by measurements taken when the pump was known to be in good operating condition. The following is an example.
of a test plan that would be acceptable:
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Pump flow rate is measured with the pump operating as found. This flow rate is used to set a point on the pump characteristic curve. The pump differential pressure is then measured with the pump operating as found.
This differential pressure is compared to the differential pressure obtained from the pump curve for the measured flow rate. The pump is in ;
the acceptable range if the measured differential pressure is 0.93 to 1.02 !
times the value from the pump curve, and is in the alert range if the 1
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o measured differential pressure is 0.90 to 0.93 or 1.02 to 1.03 times the value from the pump curve. The pump is in the required action range if the measured differential pressure is < 0.90 or > 1.03 times the value from the pump curve.
Since pump vibration readings may vary widely with changes in pump flow rate and differential pressure, the licensee must employ a method of evaluating pump vibration measurements taken with the pump operating in possible as-found conditions to ensure that a degraded pump would be declared inoperable and repaired.
The following elements are to be incorporated into the IST of pumps using pumps curves:
- 1) Curves are developed, or manufacturer'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 curves in a range which includes or is as close as practicable to design basis flow rates.
- 5) Acceptance criteria based on the curves does not conflict with Technical Specifications or Facility Safety Analysis Report operability criteria, for flow rate and differential pressure, for the affected pumps.
- 6) If vibration levels vary significantly over the range of pump 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. ' #
A method for evaluating pump operability is necessary for variable flow systems where it is not practical to return to the same flow configuration for each subsequent inservice pump test. This may be the case for systems where temperature or flow is controlled at a variety of locations, such as component cooling water systems. It may not be practical for the licensee to take manual control of each of these local stations and duplicate the overall system reference conditions, as required by the Code, during quarterly pump testing.
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o Utilizing the manufacturer pump-specific curves for flow and differential pressure may enable the licensee to evaluate the pump in as-found system conditions. In this case, these values must be confirmed by in-situ testing.
Another method would be the development of pump curves by varying system conditions and plotting a graph of the results over the range of conditions expected during the system's normal operation. It is also important to develop a method of evaluating pump vibration measurements taken with the pump operating over the range of possible as-found conditions, since this is a variable pump parameter. This is to ensure that a severely degraded pump, either hydraulically or mechanically, is declared inoperable and repaired.
The licensee's proposed alternative does not specify details of the referenced test procedures (10ST-15.1/2/3); therefore, a review by the licensee must be performed to ensure that all of the guidance discussed above is incorporated into the testing using pump curves. In their cover letter submitting this relief request, the licensee committed to using the guidance (including the seven elements) for inservice testing using pump curves. The relief request, or the IST program with reference in the relief request, should be revised to include the guidance.
3.1.4 Conclusion Relief should be granted pursuant to 10 CFR 50.55a(f)(6)(1) based on the impracticality of testing the subject pumps in accordance with the Code requirements and in consideration of the burden if these requirements were imposed, provided the licensee incorporate the guidance discussed in the evaluation into the implementation of the inservice testing as committed.
4.0 CONCLUSION
Based on the review of the Beaver Valley Power Station, Unit 1, IST Program relief request, the NRC staff concludes that relief as evaluated and modified by the SE will provide reasonable assurance of the operational readiness of the pumps to perform their safety-related functions. The NRC staff has determined that granting relief pursuant to 10 CFR 50.55a(f)(6)(i) 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 Duquesne Light Company that could result if the ASME Code requirements were imposed on the facility.
Principal Contributor: P. Campbell Date: September 13, 1993
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