ML20210R207
| ML20210R207 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 08/27/1997 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20210R186 | List: |
| References | |
| NUDOCS 9709020343 | |
| Download: ML20210R207 (6) | |
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Y UNITED STATES g
NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. ReseH001
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,1 SAFETY EVALUATION BY THE OFFICE OF NUCI PAR REACTOR REGULATION ret ATED TO RELIEF REQUESTS FOR THE INSERVICE TESTING PROGRAM SOUTHERN NUCI FAR OPERATING COMPANY. INC.
9 VOGTLE ELECTRIC GENERATING PLANT. UNITS 1 AND 2 DOCKET NOS. 50-424 AND 50-425
1.0 INTRODUCTION
- Title 10 of the Code of Federal Re=Wions (10 CFR) Section 50.55a, requires that inservice testing (IST) of certain American Society of Mechanical Engineers (ASME) Boiler and Pressure
- Vessel Code (ASME Code) Class 1,2, and 3 pumps and valves be performed in accordance with ASME OM Code 1990, except where relief has ben requested and granted or proposed attematives have been authorized by the Commission pursuant to 10 CFR 50.55a(f)(6)(l),a
- (a)(3)(i), or (a)(3)(ll). -In order to obtain authorization or relief, the licensee must demonstrate t
I that: (1) conformance is impractical for its facility; (2) the proposed attemative 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 -
into 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," provides attematives to the Code L
requirements determined to be acceptable to the staff and authorizes the use of the s_ltematives in Positions 1, 2,6, 7, 9, and 10, provided the licensee follows the guidance delineated in the applicable position. When an altamative 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 attemative is subject to NRC inspection.
in a letter dated May, 29,1997, Southem Nuclear Operating Company, Inc. (SNC or licensee),
submitted the second 10-year interval IST Program for Pumps and Valves for the Vogtle _
- Electric Generating Plant (VEGP), Units 1 and 2. - Included in this submittal were four relief requests, RR-G-1, RR-G-2, RR P-1, and RR-P 2. The NRC staffs findings with respect to
. authorizing attematives and granting or not granting the requested relief as part of SNC's IST program are contained in this safety evaluation (SE).
2.0 SCOPE The licensee's IST program was developed according to the requirements of the ASME OM Code 1990 Edition for pump and valve testing, with the exception of safety reiief valves. The Enclosure 9709020343 970827 PDR ADUCK 05000424 P
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2 safety relief valve testing program is based on the requirements of the ASME OM Code 1995 I
4 Edition. In a letter dated November 27,1996, the NRC approved the proposal to: (1) use ASME OM Code 1995 Edition for testing safety relief valves; (2) use ASME OM Code 1990 Edition for testing pumps and valves other than relief valves; and (3) schedule the Unit 2 IST program interval concurrent with the Unit 1 interval for the remainder of plant life. The second 10-year interval for both units began on May 31,1997.
The IST program was developed to comply with the requirements of 10 CFR 50.55a. SNC used GL 89-04 and its Supplement 1 (NUREG 1482) for guidance. SNC's determination as to whether a pump or a valve should be included in the program was based on its review of the Final Safety Evaluation Report and other design and licensing documents to identify the ASME Code Class 1,2, and 3 components within the scope of IST requirements as defined by the ASME Code. When full or partial stroke exercising of valves is not practicable, bases have been provided in the IST program as refueling outage justifications or cold shutdown justifications.
Based on a review of the IST program and ancillary information, no deviations from regulatory requirements or commitments were identified in the VEGP, Units 1 and 2, second 10-year intervalIST program for pumps and valves. The scope of the IST program, cold shutdown justifications, and refueling outage justifications, are subject to NRC inspection.
3.0 RELIEF REQUESTS RR-G-1 and RR-G-2 Relief Requests RR-G-1 and RR-G-2 were previously approved in an NRC letter dated November 27,1996. For RR-G-1, the NRC approved the proposal to use the ASME OM Code 1995 Edition for testing safety relief valves, and to use ASME OM Code 1990 Edition for testing pumps and valves other than relief valves. RR-G-1 Indicates that the requirements of Appendix 1 augment the rules of Subsection ISTC of the OM Code, as called for in the November 27,1996, letter. RR-G-2 was approved with regard to scheduling the Unit 2 IST program Interval concurrent with the Unit 1 interval for the remainder of plant life. The second 10-year interval for both units began on May 31,1997.
4.0 RELIEF REQUEST RR-P-1 RR-P-1 requests relief from the requirements of ISTB 4.6.1(b)(1), which requires the full scale range of analog instruments to be not greater than three times the reference value. This relief request pertains to boric acid transfer pumps, 1(2)-1208 P6-006 and -007.
- 4.1 Licensee's Basis for Reouestino Relief The licensee states:
Suction pressure gages P1-10115 and PI-10116 have a full scale range of 30 inches of mercury to 15 psig, or -15 psig to 15 psip with an accuracy ofi 0.15 psig. Since pressure readings when the pump is running will always be positive, the range of interest for IST is 0 - 15 psig. The actual suction pressure experienced during surveillance testing is approximately 2 psig which results in a
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maximum allowable range of 016 psig to satisfy the Code requirements; The -
Code allowable tolerance would be 10.12 psig (0.02 x 6). Since the only purpose for measuring suction pressure is to use in determining differential pressure, for
. comparison to the test re%rence value, a total difference of 0.03 (0.15 - 0.12) psig -
in the measurement of d tJerential pressure will have no impact on the repeatability or the accuracy of the pump test. Therefore, the existing suction pressure gages.
. provide adequate means for measuring the pump suction pressure and do not jeopardize the adequacy of the testing being performed.-
4.2 Altam=*= Testina -
The licensee proposes that the existing suction pressure gauges be utilized for IST of the referenced pumps.
4.3 Evaluation 4
The instrument accuracy and range requirements of ISTB 4.6.1 are to ensure that test measurement is sufficiently sensitive to changes in pump condition to allow detection of degradation. - l STB 4.6.1 states that: (1) accuracy for instruments used in the measurement of differential pressure and pressure shall be t 2%; and (2) full-scale range of pump instruments.
shall be three_ times the reference value or less. The range of greater than three times the reference value can be acceptable if the instrument is proportionately more accurate than required. As indicated in Section 5.5.1 of NUREG-1482," Guidelines for Inservice Testing at Nuclear Power Plants,* an altemative can be approved if the combination of range and accuracy yields a reading that meets
- 6% of reference value.
In the case of RR-P-1, suction pressure gauges are used to measure differential pressures -
across the boric acid transfer pumps. A reference value for the suction pressure of 2 psig and an accuracy of
- 0.15 psig yield an accuracy of
- 7.5%, a value which does not meet the.
guideline of t 6% in Section 5.5.1 of NUREG-1482. However, the effect of this
- 7.5%
uncertainty on the differential pressure has not been adequately addressed. The basis should
- be expanded to address applicable error components, including the discharge pressure instrumentation accuracy, and how the error components are' combined to determine the differential pressure measurement accuracy.
Meeting the Code requirements would involve purchasing and installing pressure instruments that meet the Code requirements.: Making these modifications would be a hardship for SNC.
Using the existing suction pressure gauge for an interim period of 6 months would be
' appropriate in order provide a reasonable opportunity for SNC to submit additional information to justify the proposed attemative. Compliance during the interim period would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.-
The staff finds that_SNC's proposed altemative provides reasonable assurance of operational -
- readiness during the interim period.
The licensee should determine the in situ instrument accuracy and the repeatability of the
' ' conditions under which the measurements are made for each application. If the instrumentation -
used to determine pump differential pressure is not sufficiently accurate and repeatable to
4 detect degradation and permit the use of the allowable ranges of ISTB 4.6.1, a method should be developed to compensate for the additional uncertainty when evaluating these pumps.- One possible method is to add the addtional 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 pressure differential.
_4.4 Staff Conclusion Based on the determination that the proposal provides 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 altamative is authorized pursuant to 10 CFR 50.55a(a)(3)(ll) for an interim period of 6 months. During this interim period, the basis should be expanded to address applicable error components, including the discharge pressure
' instrumentation accuracy, and how the error components are combined to determine the
. differential pressure measurement accuracy. The licensee should either demonstrate that the instruments provide Indication that is sufficiently accurate and repeatable to detect degradation
, and permit the use of the allowable ranges of ISTB 4.6.1, or develop a method to compensate
- for the additional uncertainty in the differential pressure measurement when evaluating these pumps.
5.0 RFt IEF REQUEST RR-P-2 Relief is requested from ISTB 6.1, which states that if deviations fall within the required action
- range of Table ISTB 5.2-1, the pump shall be declared inoperable until the cause of the deviation has been determined and the condition corrected.
- This relief request pertains to all pumps in the IST program.
5.1 Lleansea's A=In for Raanastina Relief The licensee states:
The ASME Section XI Code,1989 Edition, subsection IWP-3230(c) states that; Corrective action shall be either replacement or repair per IWP-3111, or shall be an analysis to demonstrate that the condition does not impair pump operability and that the pump will still fulfill its function. A new set of reference -
values shall be established after such analysis.
The OMc-1994 Addenda (ISTB 6.2.2) and the OM 1995 edition (ISTB 6.2.2) both state that;
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I If the measured test parameter values fall within the required action range of Table :
5.2.1 1 Table 5.2.12, Table 5.2.21, or Table 5.2.31, as applicable, the pump shall be declared inoperable until either the cause of the deviation has been determined and -
the condition corrected, or an analysis of the pump is performed and new reference values are established in accordance with ISTB 4.6.
l The Code applicable for the first intervs1 IST Program (1983 ASME XI), and the latest issued Code both provide for analysis of pump data in lieu of repair or replacement of the pump If the test parameters fall within the required range. The OM Code-1990 Edition did not include such ptovisions. Communications with members of the OM Code Committee indicated tnat this was an oversight and that it was never intended to delete the ability to analyze the test data and determine if the pump is still capable of performing its intended
- safety function.
5.2 Altammia Testino_
The licensee proposes:
L
. Should pump test parameters fall within the required action range of Table ISTB l
5.2 2 (OM Code 1990 Edition), then the OM Code 1995 Edition, subsection ISTB
.6.2.2 will be utilized. Since subsection ISTB 4.6 in the 1995 Code Edition references ISTB 6.2.2, subsection ISTB 4.6 from the OM Code 1995 Edition will also be applied.
5.3 - Evaluation The licensee proposes to implement the 1995 Edition of the ASME OM Code, Subsection ISTB 4.6, "New Reference Values," which is not currently endorsed by the NRC. This t subsection allows that:
In cases where the pump's test parameters are either within the alert or the required action ranges of ISTB 5.2.1.1, Table ISTB 5.2.1-2 Table ISTB 5.2.21, or Table ISTB 5.2.3-1, and the pump's continued use at the changed values is
. supported by an analysis, a new set of reference value[s] may be established.
lThis subsection also states that the analysis shall include both a pump level and a system level
- verification of pump operational readiness, the cause of the change in pump performance, and an evaluation of all trends indicated by available data.
The licensee's proposal provides an acceptable level of quality and safety since the corrective action, as required by OM Code-1990, Subsection ISTB 6.1, can be an analysis that demonstrates the operational readiness of the pumps. Establishing new reference values are also allowed by OM Code-1990, Subsection ISTB 4.5. The corrective action analysis must provide reasonable assurance that the degradation mechanism will not cause further degradation such that, before the next pump test or before repairs can be performed, the pump
'would fail. This analysis is subject to NRC inspection.
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5.4 Staff Conclusion The attemative is authorized pursuant to 10 CFR 50.55e(a)('t)(i) based on the acceptable level of quality and safety that will be provided by the alternativc.
6.0 CONCLUSION
Relief' Requests RR G 1 and RR-G-2 were previously approved in an NRC letter dated November 27,1996, Relief Request RR-P-2 is authorized pursuant to 10 CFR 50.55a(a)(3)(i).
1 Relief Request RR P-1 is authorized pursuant to 10 CFR 50.55a(s)(3)(ii) for an interim period of 6 months from the date of this SE to allow the licensee time to either demonstrate that the pressure instruments provide indication that is sufficiently accurate and repeatable to detect pump degradation and permit the use of the allowable ranges of ASME OM Code, Subsection ISTB 4.6.1, or develop a method to compensate for the additional uncertainty in the differential pressure measurement when evaluating these pumps.
Principal Contributor: K. Dempsey Date: August 27, 1997 I