ML20070N944
| ML20070N944 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 05/02/1994 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20070N943 | List: |
| References | |
| NUDOCS 9405100239 | |
| Download: ML20070N944 (5) | |
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8 UNITED STATES
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NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT N0. 71 TO FACILITY OPERATING LICENSE NPF-68 AND AMENDMENT N0. 50 TO FACILITY OPERATING LICENSE NPF-81 GEORGIA POWER COMPANY. ET AL.
V0GTLE ELECTRIC GENERATING PLANT. UNITS 1 AND 2 DOCKET NOS. 50-424 AND 50-425 1.0 INTRODVCTION By letter dated November 19, 1993, as revised March 31, 1994, Georgia Power Company, et al. (the licensee) proposed license amendments to make two changes to the Technical Specifications (TS) for Vogtle Electric Generating Plant (Vogtle), Units 1 and 2.
These changes would, as recommended by the Nuclear Regulatory Commission (NRC), incorporate surveillance procedures in compliance with draft Institute of Electrical and Electronic Engineers (IEEE) Standard 450-1992, " Recommended Practice for Maintenance, Testing, and Replacement of Large Lead Batteries for Generating Stations and Substations."
The first proposed change would revise the plant battery maintenance and testing practices in the TSs, particularly the performance discharge test (PDT) schedule.
The second proposed change would reduce the minimum cell float voltage specified in TS Table 4.8-2, " Battery Surveillance Requirements," and in associated TS Bases 3/4.8.1, 3/4.8.2, and 3/4.8.3, "A.C. Sources, D.C Sources, and Onsite Power Distribution," from 2.10 volts to 2.07 volts.
The licensee's revised submittal of March 31, 1994, changed the initial request to provide increased conformance to an associated draft IEEE Standard 450 maintenance and testing practice. The revision imposes restrictions on cell replacements for degraded batteries that are in late stages of service life. These restrictions were requested by the NRC staff and do not affect the NRC staff's conclusions of no significant hazards considerations published in the Federal Reaister (58 FR 67847) on December 22, 1993.
2.0 EVALVATION 2.1 Battery Maintenance and Testina The first proposed change would, in part, delete TS 4.8.2.1.f, which currently requires that each 125-volt battery bank and one associated charger be demonstrated OPERABLE:
f.
At least once per 18 months, during shutdown, by giving performance discharge tests (PDT) of battery capacity to any 9405100239 940502 PDR ADOCK 05000424 P
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. battery that shows signs of degradation or has reached 85%
of the service life expected for the application.
Degradation is indicated when the battery capacity drops more than 10% of rated capacity from its average on previous l
performance tests, or is below 90% of the manufacturer's rating.
The present TS 4.8.2.1.f would be replaced by a new Table 4.8-3, " Performance Discharge Test Surveillance Requirements." The new Table 4.8-3 would establish a schedule for PDTs. The intervals between tests would depend upon the remaining life of the battery and upon the degradation detected. As used here and in the TS, degradation is defined as.a drop of more than 10% in battery capacity from the previous test, or a battery capacity less than 90%
of the battery's specified capacity.
A consequence of comparing the latest test result with the preceding test result, rather than with some kind of-average of earlier tests, is that the measure of the degradation experienced is reduced.
However, because of the 90% lower limit to battery capacity also specified in the TS new Table 4.8-3, no significant change in the schedule of PDTs would result.
A further part of this first proposed change would alter TS 4.8.2.1.e, which currently requires that each 125-volt battery bank and one associated charger be demonstrated OPERABLE:
e.
At least once per 60 months, during shutdown, by verifying that the battery capacity is at least 80% of the manufacturer's rating when subjected to a performance dischar'ge test.
Once per 60-month interval this performance j
discharge test may be performed in lieu of the battery l
service test required by Specification 4.8.2.1.d.
The battery service test (BST) is currently required to be made every j
18 months.
The proposed TS replacement would read:
e.
By verifying during shutdown, that the battery capacity is at least 80% of the manufacturer's rating when subjected to a performance discharge test, in accordance with Table 4.8-3.
l The change from 60 months to "during shutdown" is a reduction in the interval between PDTs and, therefore, does not increase the risk of battery failure.
The normal interval between shutdown of each Vogtle unit is 18 months.
The change with respect to the deletion of the BST is not in the direction of reduced risk.
Rather, the basis for accepting it is that (1) there is no significant increase in risk of battery failure, and (2) the deletion of a BST is consistent with other recent TS battery surveillance changes.
However, the NRC staff currently recommends that when a licensee proposes to eliminate a BST, it should be replaced with a modified PDT; that is, a PDT
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! that starts with a maximum discharge rate period, that is followed by the PDT i
constant current test. A generic modified PDT consists of a 1-minute
. discharge at the maximum rate specified for the battery, followed by the PDT.
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Currents during both segments of the modified PDT are greater than or equal to the design-basis duty cycle currents for the battery.
i A modified PDT is a test of the capability of the battery to provide a high 2
current, short duration load at greater than the minimum design voltage, followed by a test of the capability of the battery to provide sufficient current at above the minimum design voltage for the duration of the design j
cycle.
I The licensee proposes to add a note to TS 4.8.2.1.d that would allow a l
modified PDT in lieu of the BST. ' The note is similar to the present note, which allows the PDT to be substituted for the BST at 60-month intervals.
The j
added note would ensure that the battery would be capable of supplying the
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high current early loads, even when the battery has reached or exceeded 85% of j
its expected life.
As noted in Section 7 of IEEE Standard 450-1993, " Battery Replacement i
Criteria," replacement cells are not usually recommended as the battery nears I
its end of life. The NRC staff requested that the licensee revise Footnote 5 l
of new Table 4.8-3 as proposed November 19, 1993, consider appropriate limitations upon cell replacements late in battery life. On March 31, 1994, i
j the licensee revised the proposed footnote to state that:
4 5.
When battery life is greater than 85% of the expected j
life of the battery and degradation is indicated, cell replacement shall not be used to restore the capability of the battery for more than one year, and 4
the battery shall be replaced within one year of the date of the discovery of the cell degradation.
The NRC staff finds the revised Footnote 5 to adequately limit cell l-replacement for degraded batteries late is service life, and to adequately
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address the recommendation of IEEE Standard 450-1993, Section 7.
The revised l
Footnote 5 is, therefore, acceptable.
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The NRC staff finds that the proposed changes in battery maintenance and i
testing are consistent with draft IEEE Standard 450-1992; with the improved
" Standard Technical Specifications for Westinghouse Plants (NUREG-1431)," and with recent license amendments issued by the NRC.
The NRC accepts the research discussed in NUREG/CR-4096, " Test Series 3:
Seismic Fragility Tests of Naturally-Aged Class 1-E C&D LCU-13 Battery Cells" and NUREG/CR-5448, j
" Aging Evaluation of Class 1-E Batteries:
Seismic Testing").
The research concluded that batteries maintained and operated in accordance with 1
IEEE Standard 450-1980 should last their expected life time.
The research also concluded that the tests provided in the subject standard and the NUREGs could ensure the capacity and seismic capability of the plant batteries.
The i
proposed TS changes for battery maintenance and testing are, therefore, j
acceptable.
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2.2 Cell Float Voltaae The minimum Category B cell float voltage (CFV) of 2.10 volts in the present TS Table 4.8-2 would be replaced by a minimum Category B CFV of 2.07 volts.
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The basis for the change is that the battery manufacturer has said that the l
CFV of 2.10 volts is unnecessarily high and that 2.07 volts adequately ensures that the battery is free of internal cell problems that would necessitate cell replacement.
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The licensee also cites Appendix Cl of three IEEE Standards:
(1) 450-1980, j
(2) 450-1987, and (3) draft 450-1992.
The same appendix in all thre,.
standards, states:
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A cell voltage of 2.07 V.or below under float conditions and not caused by elevated temperature of the cell indicates internal cell j
problems and may require cell replacement.
A minimum CFV of 2.07 volts is also consistent with the new Standard Technical j
i Specifications, NUREG-1431, Table 3.8.6-1, Category C.
Category C voltages ensure that the battery has sufficient capacity, plus margin.
j Although the reduction from 2.10 volts to 2.07 volts for the minimum allowed i
CFV is a reduction in battery capacity margin, it is the combined opinions of i
the battery manufacturer, the IEEE, and the NRC staff, through the recommendations of NUREG-1431, that it is not a significant reduction. As i
long as the CFV is greater than 2.07 volts,'it is not by itself indication of i
internal cell degradation.
Moreover, the NRC staff finds the proposed change to be consistent with the cited IEEE standards and the " Standard Technical' Specifications for Westinghouse Plants" (hUREG-1431).
It is also consistent with changes the NRC staff has previously approved on other nuclear power plants such as Crystal River.
Therefore, the proposed change to the cell float voltage is acceptable.
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3.0 STATE CONSULTATION
j In accordance with the Commission's regulations, the Georgia State official j
was notified of the proposed issuance of the amendments.
The State official had no comments.
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4.0 ENVIRONMENTAL CONSIDERATION
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The amendments change requirements with respect to installation or use of a i
facility component located within the restricted area as defined in 10 CFR l
Part 20 and change surveillance requirements. The NRC staff has determined i
that the amendments involve no significant increase in the amounts, and no i
significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a i
proposed finding that the amendments involve no significant hazards l
consideration, and there has been no public comment on such finding 1
P (58 FR 67847, dated December 22,1993). Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.
5.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributors: C. Morris D. Hood l
Date: May 2,1994 l
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