ML20217H595
| ML20217H595 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 08/07/1997 |
| From: | Graesser K COMMONWEALTH EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20217H597 | List: |
| References | |
| BYRON-97-0180, BYRON-97-180, NUDOCS 9708130101 | |
| Download: ML20217H595 (18) | |
Text
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'f rl Hl 4 !.4 i % e ll August 7,1997 LTR: BYRON 97 0180 FILE: 2.01.0301 U.S. Nuclear Regulatory Commission Washington, DC 20555 0001 Attention: Document Control Desk SUBJECT Supplement to Application for Amendment to Appendix A, Technical Specifications, for Facility Operating Licenses l Byron Nuclear Power Station Units 1 and 2 Facility Operating Licenses NPF-37 and NPF-66 NRC Docket Nos. 50-454 and 50-455
" Electrical Power Systems, D, C. Sources"
REFERENCES:
- 1. Letter from K. L. Graesser (Comed) to NRC Document Control Desk transmitting Technical Specification Amendment Request for 125 volt de batteries, dated April 7,1997 (BYRON 97 0079)
- 2. Letter from G. F. Dick, Jr. (NRC) to 1. M. Johnson (Comed) transmitting a Request for Additional Information regarding the proposed replacement of Gould batteries with C&D Charter Power Systems batteries, dated June 20,1997 lh In Reference 1, Commonwealth Edison Company (Comed) submitted an application for amendment to Appendix A, Technical Specifications, for the 125 volt de batteries at Byron Nuclear Power Station. The NRC issued a Request for Additional Information (RAI) in Reference 2, Attachment 1 provides the requested information.
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As a result of Comed's response to the RAI, some of the marked-up Technical Specifications pages are afTected. The bases for proposed Improved Technical
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Specification (ITS) Surveillance Requirements 3.8.6 '. and 3.8.6.3 have been revised to indicate that the correction for level is not required when battery charging current is less than 2 amps for Gould and less than 3 amps for C&D when on float charge. Surveillance Requirement 4.8.2.1.2.f and proposed ITS Surveillance Requirement 3.8.4.4 are revised from the original submittal to correspond to the IEEE-450-1995. Surveillance Requirement 4.8.2.1.2.g has been added in order to retain the current surveillance i requirement for the installed Gould battery 111 until it is replaced in the refueling outage scheduled for November 1997. Since the battery capacity has essentially not changed in ;
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$ years and the results of both performance tests are near the manufacturer's rated
- capacity, Comed believes the battery should be capable of performing its intended function through its 20 year qualified life. Therefore, the 12 month performance test l
criterion aner 85% of service life should not be required.
Revised pages are included in Attachment 2 for current Technical Specifications and Attachment 3 for the proposed improved Technical Specifications. These pages replace the corresponding pages in the original submittal.
There is no impact on the original Attachment C," Evaluation of Significant llazards Considerations"and Attachment D," Environmental Assessment."
If you have any questions concerning this correspondence, please cortact Marcia Lesniak at (630) 663 7283.
Sincerely,
&abh.ld y K. L. Graesser Site Vice President Byron Nuclear Power Station Attachments cc: A.B. Beach, Regional Administrator - Region'lli G.F. Dick, Jr., Byron Project Manager -- NRR ~
S.D. Burgess, Senior Resident inspector - Byron Oflice of Nuclear Safety - IDNS
A'ITACilM ENT 1 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING Tile PROPOSED REPLACEMENT OF GOULD HA'ITERIES WITil C& D CilARTER POWER SYSTEMS HATTERIES NRC Ouestion 11 The proposed changes to Technical Specification (TS) 11ases for surveillance requirements 3.8.6.1 and 3.8.6.3 add that specific gravity is corrected for electrolyte temperature only for C&D batteries. What is the basis for the change and should it apply only to the C&D batteries?
Hvron Response:
A copy of a January 16,1997 letter from C&D Charter Power Systems (CAD) i addressing level correction is attached. C&D does not recommend correcting electrolyte specinc gravity for level. Gould (GNB), per their instruction manual, still recommends temperature and level correction. Since the Gould batteries are to be replaced at the next refueling outage on each unit, Byron is not requesting any Technical Specification changes with respect to the Gould batteries.
NRC Ouestion 2:
The licensee states that the battery charging current is less than 3 amperes for C&D battery when it is on charge in accordance with the manufacturer's recommendation.
Please provide supporting data for the statement or provide a copy of the manufacturer's recommendation. Also, does the statement apply when the battery is on float?
Hvron Resnonse:
A copy of a December 20,1996 letter from C&D Charter Power Systems to Comed is attached. The manufacturer recommends 3 arnperes as the value of charging current to be used with the LCUN 33 cells. Also attached is a copy of an August 16,1994 letter from C&D Charter Power Systems to Public Service Electric and Gas Co. This letter provides a basis for the 3-ampere value for lead calcium cells of a similar size (LC/LCR 33).
The value of 3 amperes applies for both float and equalize voltages, based on discussions with C&D and the August 16,1994 C&D letter.
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NHC Ouestion 3:
Does the performance test for the Gould batteries envelope the service test? Please provide a copy of the service test profile. What is the value of the discharge current when conducting the performance test?
l Hvron Hesponse:
The performance test discharge rate does not envelope the service test profile.
The first 30 minutes is above the 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> discharge rate of 254 amperes. The following table lists the service test discharge rate in amperes for each of the existing safety related GNB 125 volt de batteries at Byron.
Hattery Hattery Hattery Hattery 111 112 211 112 0-1 563 522 545 514 minutes 1 30 373 352 362 351 minutes 30 120 186 173 175 172 minutes 120 240 92 87 86 83 minutes Senice 9/15/94 10/4/94 2/13/95 3/7/95 Test Date The performance test for each of the existing GNB 125-volt de batteries is 254 amperes for 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> to a 1.75-volts per cell average corrected to 77'F.
NRC Ouestion 4:
In sizing the C&D batteries, what aging factor is used? The licensee's submittal refers to a design margin of 1015%. Please provide the specific value used for the design margin.
Byron Response:
t The aging factor used in the sizing calculations is 1.25, which corresponds to sizing the battery to meet the design function when the battery has 80% of the manufacturer's rating.
The design margin used to size the C&D batteries is 10%. This is based on calculation BYR97-204/BRW97-0384 E, Revision 0, which uses a 1.10 design margin value in the sizing sheets for each of the batteries which corresponds to a 10% margin.
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NRC Ouestion 5:
With regard to battery degradation, what are the values of the last performance test?
There is a staf1' concern that if a battery degrades or reaches 85% ofits expected life, an 18 month period before the next test is conducted may be too long. Please provide a justification for the 18 month interval or propose a revised interval.
Byron Response:
The results of the last performance test for the Byron 125 volt de batteries are listed below:
Performance Capacity from Test Test Date Results
_Hattery 111 4/8/96 99.95 %
Hattery 112 4/29/96 10l%
Hattery 211 9/4/96 104.3 %
Hattery 212 8/19/96 106.82 %
The following table lists the received date for each of the batteries, the date equivalent to 85% of expected service life, and the period when the batteries are scheduled to be replaced. These batteries have an expected service life of 20 years.
Received 85% of Scheduled Date Espected Replacement Service Life Period to C&D Date Hattery Hattcry i11 12/6/79 12/6/96 11/7/97 to 2/28/98 Hattety 112 12/6/79 12/6/96 11/7/97 to 2/28/98 Hattery 211 9/25/79 9/25/96 4/11/98 to 5/26/98 Hattcry 212 9/25/79 9/25/96 4/11/98 to 5/26/98 Un.Ll i
Comed has no concerns with the installed Battery 111. Battery t il had a capacity of 99.95% in the performance test on April 8,1996. The previous performance test on Battery 111, on October 10,1991, demonstrated 99.97% of the manufacturer's rated capacity. The results of the two performance tests indicate that the battery has not reached the
" knee" of the curve of the typical capacity versus time characteristic of a lead acid cell. The battery only needs 80% ofits rated capacity to meet its intended function. Battery 111 is scheduled to be replaced during the upcoming refueling outage (about 18 years aller receipt and about 12 months afler reaching 85% of expected service life). Since the battery 3
capacity has essentially not changed in 5 years and the results of both performance tests are near the manufacturer's rated capacity, Comed believes the battery should be capable of performing its intended function through its 20 year qualified life Comed has no concerns with the installed Battery 112.11attery 112 demonstrated over 100% of the manufacturer's rated capacity in the April 1996 performance test, and the batter,i will be replaced about 12 months afler reaching 85% of expected service life. Furthermore, Battery 112 meets the proposed Technical Specincation revision that follows IEEE 450-1995, allowing performance testing at two year intervals.
UniLE Comed has no concern with the existing Unit 2 batteries. The Unit 2 batteries were tested in August and September of1996. The demonstrated capacities exceeded the manufacturer's rating. These batteries were tested near the 85% of service life date. The batteries are scheduled to be replaced during the spring 1998 outage. This replacement schedule meets the requirements of the existing Byron Technical Specification Surveillance Requirement 4.8.2.1.2.f and the proposed Technical Speci0 cation requirements, which meet IEEE 4501995, since the tested capacity demonstrated above 100% of the manufacturer's rating. Since the battery has demonstrated superior performance, meets the requirements ofIEEE 450-1995, and the replacement schedule meets the Technical Speci0 cation requirements, Comed believes the batteries should be capable of performing their intended function through the 20-year qualined life.
In order for the Byron Technical Speci0 cations to meet the requirements of IEEE 450 /95, as they apply to the new batteries, Surveillance Requirement 4.8.2.1.2.f and proposed ITS Surveillance Requirement 3.8.4.4 are revised from the original submittal to correspond to the IEEE-450-1995 as follows:
(Each 125 volt battery bank and its associated charger shall be demonstrated OPERABLE) At least once per 12 months during shutdown, by giving performance discharge tests or modined performance discharge tests of battery capacity to any battery that shows signs of degradation or has reached 85% of service life expected for the application. Degradation is indicated when the battery capacity drops more than 10% of rated capacity from its capacity on the previous performance test or modified performance test, or is below 90% of the manufacturer's rating. This requirement would be applicable to Batteries 112, 211, and 212, and would be applicable to Battery 111 upon entering Mode 4 for Unit 1, Cycle 9. A note is added that states if the battery has reached 85% of service life, delivers a capacity of 100% or greater of the manufacturer's rated capacity, and has shown no signs of degradation, performance testing at two-year intervals is acceptable until the battery shows signs of degradation.
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The current surveillance requirement for the installed llattery 111 (Gould) in retained until entering Mode 4 for Unit 1, Cycle 9 by adding Technical Specification Surveillance Requirement 4.8.2.1.2 g. The surveillance requirement duplicates existing Surveillance Requiren.ent 4.8.2.1.2.f for llattery ill only until entering Mode 4 for Unit 1, Cycle 9, Starting with Cycle 9, revised Surveillance Requirement 4.8.2.1.2.f would apply.
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Letter from C&D Charter l'ower Systems to Comed dated January 16,1997 a
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Dyron Nuclear P! ant Dyron,IL 61010 .
Attn; M. P. Petel Subject P.O. No. 360737 125 Volt Safety Related Batteries Operabit ty Criteda Gentlemen:
Correctino Electrolyte Specific Gravity for Level Correcting specific gravity for eiectrolyto level can' provide usefulInformation, but is essentially meaningless as a means for determining ba: tory operability. For one thing, correcting specific gravity for level presumes that once installed and on charge, all cellt, shipped will have cloctrolyte levels exactly at the high 'evelindicator. This is not a reasonsble expectation.
From a performance standpoint, the capabihty of a fully charged cell, or bettery, with a measured specific gravity of 1.215 @ 77'F, will be the samo regardless of electrolyte level (as long as it is between the high and low indicator marks). The key term here is
" fully charged", since this determination is not based on electrolyte level. For examplo, let's assume a cell or cells, for one reason or another (spillage during shipment) have electrolyte lavel(s) at the inw Intilcator after installation and float charging. Applying a typical level correction value of 0.030/ inch, one might assume that tho actual specmc gravity ic 1.186 when it fact it is still 1.215. It would, however, become approximateb>
1.185 If topped up with water and allowed to diffuse.
This then is the essence of the level correction factor, it allows the battery user to estimate wtiat the specific gravity will be after the cel!(s) have been topped up wrtn water. Thus, if cells have been deterintned to be in a fully charged state, but electrol)1e levels are below the high levelindicator, the user can determine if the cells require water or electmlyta (of the same specific gravity as originally provided). for the topping-up process, by applying the level correction to his "as found' specific gravity readings.
P go 2 16 January 107 M.P. Patel Another drawback in using level corrected spo rfic gravrty to determine battery operability is that the corrections sometimes given in the manufacturers Operating Manucle are approx.imato values based on worst case vanables inherent in various cell designs. In other words, the amount of specific gmvity increase due to water lots be eveporation and electrolyWs, depends on the init:al volume of electrolyte betwoon the ,
bl Db and low levelindicators, and the ratio of electrolyte volume to plate volume. For tne Dyron LCUN 33 cells, the actual correctJon value is 0.019 sp.gr. per inch. l In summary, to employ electrolyte level correction factors that have any meaning, you must (a) substantiate tMt the cells are in a fully chars;ed state, (b) substantiate that I there is no specific Dravity gradlent (stratification)in the cells, and (c) have records indicating the exact specific gravity lovels for all cells as rocoived and initially charged, and records of all subsequent fluid additions. .
IEEE 4501995 and C&D's Opc ating Instructions do not recommend correcting electrolyte specific gruv:ty for level.
Ficat Voltaoo vs. Lifq For optimum battery life, the float voltage should be at a value that results in poshive plato polarizations between 50 ond 100 millivolts abovo open circuit. In C&D lead calcium alloy batterios of the LCUN 33 design, this occurs when float charged at 2.20 to 2.26 volta per cell at 77F.
At voltages be:vw 2.20 volts, the positive platus may not seculve unuugh cununt tu remain in a fully charged state by offsetting intemallosses. This generally results in a greater than normal voltage spread botiveen cells, and an increased rate of plato aging.
At voltages above 2.25 volts, the positive plates are receiving more current than is normally required, increasing the rato of grid oxidation (corrosion), and shortening nominallife. For example, tests have shown the continuous float charging at 100 millivolts posit}ve plate potentf al results in cell life of 20 to 22 years at 77F; et 130 millivolts, life is 16 to 18 years at 77F; and at 150 millivolts, life is 13 to 15 years at 77F.
When C&D inormally ages cells for qualificaUon, postuvo plate pelanzauons are matntained between 50 and 100 millivolts.
I trust the above is clear and con:ise, if you have any questions, don't hesitate to call me Sincerely.
$% kW k.w Graham Wa'ker Manager, Applications Engineenng niu
Letter from C&D Charter Power Systems to Comed dated December 20,1996
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CHARTER POWER SYSTEMS 1400 union Meenng Road P.O. Box 3053 Dive Dell. PA 19422 085B Telephone (21$) 619 2700 Fax (215)619 7840 20 December 1996 Comed Company Attn: M. Patel Site Engineenng Byron Nuclear Station 4450 N. German Church Rd.
Byron,IL 61010 Subjeet: P.O. No. 360737 125 Volt Safety Related Batteries Technical Specification Requirements Gentlemen:
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t Your existing Technical Specification and Battery Surveillance Requirements allows you to disregard pilot cell specific gravity if the battery charging current is less than 2 amperes, and/or allows you to neglect correcting specific gravity forp electrolyte levelif the battery charging current is less than 2 amperes.
For the higher capacity LCUN 33 replacement cells C&D recommends this value of charging current be changed to 3 amperes, if you have any questions, please call me at (215) 619 7846.
Very truly yours, V% %
Graham Walker, Manager, Applications Engineering 4
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Letter from C&D Chaner Power Systems to Public Service Electric and Gas Company dated August 16,1994 i
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e CHARTER POWER SYSTEMS 3043 Walton F4ond Plymouth Meeting, PA 19402 Telephone (215) 828 9000 FAX (215) 834 7306 10 August 1994 i
Public Service Electric & Gas Co.
Nuclear Department P.O. Box 230 Hancocks Bridge, NJ 08038 Attn: Tim Johnson t
Subject:
Salem Nuclear Generating Station, Units 1 and 2 125 Vott Safety Related Batteries Model LC and LCR 33 for Batteries A, B and C Gentlemen:
l The following discussion describes battery conditions with regard to its state of charge and operability status.
From an operability perspective, the battery state of charge is defined as the charged condition that will allow the battery to have sufficient capacity to supply design loads for the specified pened of time, to minimum terminal voltage, while experiencing specified environments.
The discussion will be limited to charging current and electrolyte strength as they relate in determining battery operability as described in the proposed Standard Technical j
Specification (STS) for the Salem Plant. The state of charge of a battery can be determined in either one of two methods provided in IEEE 450 and the STS. On9 method uses specific gravity, corrected for level and temperature; and the other uses a stabilized float charging current. Some characteristics and limitations of each method are given below.
Stabillied Float Charalna Current When fully charged at a stabik ed voltage and temperature, the LC/LCR-33 battery cell, depending on age, should require between 250 and 500 milliamperes of charging current to maintain recommended float voltage; and between 700 and 1600 milliamperes of charging current to maintain recommended equahze voltage.
Stabilization, however, is often difficult to achieve because charger output voltage fluctuations, occasional short duration power failures, or periodic transfers Detween redundant chargers, result in a brief discharge / charge cycle on the battery; and although the capacity removed from the battery is quickly replaced, the charging current for many days thereafter is often much greater than the
- stabilized float current" Since it requires approximately the same amount of time for a lead calcium battery to achieve charging current stabilization, regardless of the depth of discharge, AS8%
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CHARTER POWER SYSTEMS 3043 Walton Hoad Plymouth Meeting, PA 19462 Telephone (215) 620 9000 FAX (216) 834 7306 16 August 1994 Page 2 the battery would be considered fully charged long before the charging current reached a stabilized minimum value.
The charging charactonstics of lead calcium batteries are well known. Basically, after a discharge of any length, the initial charging current h high (up to the limits of the battery charger)for the duration is takes for the battery to reach its float voltage, then declirtes, rapidly at first, but very slowly once the current falls toward milliamp values. In battenes of the LC/LCR 33 capacity range, the charging current will be well above nominal float values when the battery has 100% of the amount of the discharged ampere hours replaced (Reference 1).
Lead calcium batteries have recharge efficiencies in the 98 to 99 percent range, therefore it is easy to conclude that once 100% of the ampere hours removed by a discharge have been replaced, the battery will have sufficient capacity to meet design 1
loads at that moment, even though the charging current is well above the nominal float value. For LC/LCR 33 battery cells, a charging current of 3 amps or less wou'd be indicative of a battery in an operable state of charge.
The limitations of this surveillance method is that a meter capable of reading small currents on the order of 5 amperes or less is necessary, and a specific charging (float) current limit be established for each particular battery size. This value will vary somewhat with age, voltage, and temperature, and these variations must be factored into the use of this method.
Specific Gravitv. Corrected for Level and Temocrature For constant potential, current limited charging methods which prevail in standby battery applications, there is practically no gassing in lead calcium cells to mix the electrolyte, so specific gravity readings are unreliable fer determining operability unless there has been a very long period of stabilized float. 01abould be noted that STS's originated at a time when both lead antimony and lead calcium batteries were employed in safety rotated systems in almost equal proportjens. For lead antimony cells, voltage and specific gravity are better indicators of state of charge than charging current. But today, the vast majority,if not all, of 1E batteries are of the lead calcium type.)
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CHARTER POWER SYSTEMS 3043 Walton Road Plymoum Meeting, PA 19462 Telephone (215) 826 0000 FAX (215) 834 7306 16 August 1'994 Page 3 This surveillance method presumes that all cells, once received and fully charged, will have an electrolyte level at the high levelindicator, and have been equalized to not less than tne nominal specific gravity strength of 1.215 at 77*F. It also assumes that no electrolyte stratification (specific gravity g"dient) exists, or that multiple readings have been taken to mitigate this condition. Fr . lead calcium cells, specific gravity of the electrolyte, without correlating the values with voltage and charging current and existing performance margins, should not be used as the sole enteria for determining batter'y operability. Since they are however, we recommend STS Category A, B, and C surveillance requirements for minirnum specific gravity be 0.005 sp.gr. less the values currently established by the NRC. This would make the limits 1.195 sp.gr. for Category A; 1.190 sp.gr. (cell) and 1.200 sp gr. (battery) for Category B; and 1.190 sp.gr. (battery) for Category C.
These recommendations are based on several' actors: (1) A fully charged battery with all cells having a measured specific gravity of 1.190 (due to over watering, for example) will have approximmely 93% of the performance capability of the same cells with 1.215 i
specific gravity. This reduced performance would not impact operability unless margins for temperature and aging are exceeded. Note that a fully charged battery with 1.195 specific gravity in all ce:12 will have approximately 94% of the capacity of an identical battery with 1.215 spec Sc gravity. Sizing calculations would demonstrate how much margia actually exists. (2) A nominal 1.215 sp'.gr. battery with electrolyte of 1.190 in all cells, but with nominal float voltages and a charging current less than 3 amps would indicate the cattery is recharging from a discharge, and the electrolyte has yet to fully diffuse. In this situation, the voltage and charg!ag current would i,1dicate the battery has sufficient capacity (assuming temperature and aging margins have not been compromised) to meet design loads.
Thus, if a battery meets our rectsmmended Category C parameters, and historical data demonstrates that there is sufficient capacity margin, then adequate assurance exists that the battery will meet i'.s design loads during the time corrective action occurs.
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a CHARTER POWER SYSTEMS 3043 Walton Road Plymouth Meetmg, PA 19402 Te.ephone (215) 828 9000 FAX (715) 834 7306 a 16 August '.994 Page 4 i
By way of historical note, the IEEE Battery Working Group (BWG) recommendations to the NCR relative the STS surveillance category limits for specific gravity were as follows:
Cateoorv A
- minimum value to be determined by the user and the battery manufacturer e
level correction unnecessary if no specific gravity gradient exists and charging current is less than ( ) amps for parameters outside the limits, the battery is operable if within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, Category C values are measured and are within the limits; and all Category A and Category B parameters are within their limits within 30 days Catecory B minimum values for cell and battery limits to be desarmined by the user and the battery manufacturer no more than 10% of the cells can be at the minimum limit (i.e., one cell with a low specific gravrty does not render a battery inoperable, nor does it significantly rede .e the capability of the battery to perform its design function) l
- for parametsrs outside the limits, the battery is operable if Category C values and the charging current are within their limits within 7 days, and Category 8 parameters are restored within 30 days.
{ Cateoory C minimum vaiues to be determined by the user and the battery manufacturer in summary, for lead calcium batteries the specific gravity of the electrolyte is important when these readings are used as indicators of the state of charge and/or the need for an equalizing charge. But there are severallimitations to their accuracy, and there are other indicators that must also be app!ied ' hen determining battery operability. It is important that knowledgeable personnel sie involved in the surveillance, maintenance, inspection, and auditing of t!.e batteries. It is equally important that experienced battery personnet select the teest indicators for their installation to determine battery condition and/or corrective actions required, M 896 s , nn -
e CHARTER POWER SYSTEMS 3043 Watson Acao Plymouth Meeting, PA 19462 Telephone (215) 828 9000 FAX (215) 834 7306 10 August 1994 Page5 I trust the above is clear and concise. If you have any questions, please call me.
Very truly yours, k L ,
Graham Walker Manager, Applications Engineering I
References:
- 1. C&D Laboratory Report No.1430,6 July 1970, Chame Characten'stics of LCU 23 Cells on a 100 Ampera Current Umited. 2.22 Volts /Ced Rechame Following Dischames of 200, 300, 400 and 500 Ampete :r*nurs t
. Attachments:
. Reference 1 e
5 Aug 94 Kyle Floyd Memo to IEEE BWG - STS Topics
. Technical Paper for Publication, Assessment of Lead Acirt Battery State of Charge by Monitoring Float Chaming Current c
)
RS-t'96
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