ML20096G837

Forwards Addl Info to Further Facilitate Review of 840503 Proposed Tech Spec Change Re Dc Distribution Sys Requirements.Info Substantiates Variances from STS Based on Specific Design Parameters

ML20096G837
Person / Time
Site:	Farley
Issue date:	09/06/1984
From:	Mcdonald R ALABAMA POWER CO.
To:	Varga S Office of Nuclear Reactor Regulation
References
NUDOCS 8409110169
Download: ML20096G837 (19)

Text

{{#Wiki_filter:r Mamng Address Alibarrc Power Compzny 600 North 18th Strzet Post Office Box 2641 Birmingham, Alabama 35291 Telephone 205 783-6090 R. P. Mcdonald S'%' *002 AlabamaPower i zwaw w a s o September 6, 1984 Docket Nos. 50-348 364 Director, Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D.C. 20555 Attention: Mr. S. A. Yarga Joseph M. Farley Nuclear Plant - Units 1 and 2 Proposed Technical Specification Change to D.C. Distribution System Requirements Gentlemen: Alabama Power Company submitted a proposed technical specification change related to the Auxiliary and Service Water Buildings Battery systems on May 3, 1983. The proposed Technical Specifications ensured compliance with FSAR battery load assumptions with margin, provided -increased confidence of the batteries' operability and allowed time to correct certain battery conditions without undue plant shutMown.- This change would update the Farley Technical Specifications to conform with the format of the most recent Westinghouse Standard Technical Specifications (NUREG-0452, Revision 4), current industry practice, and Farley specific design-parameters. Since May of 1983 Alabama Power Company has made five (5) docketed submittals and held numerous telephone calls with the NRC Staff in an effort to support the review of - thi; proposed technical specification change. .In May of this year, Alabama Power Company received a copy of an NRC Staff position for the surveillance of the Auxiliary and Service - Water Building Batteries. This position was identical to the Westinghouse Standard Technical Specifications, which includes surveillance acceptance criteria which do not consider Farley specific design parameters. Alabama Power Company then provided, inforinally, the enclosed response which identifies each of the technical differences between the Standard Technical Specification and the Farley specific proposal and provides the technical justifications for Alabama Power I e4o,11oi69 84ovo6 ~' goo PDR ADOCK 05000348 l P PDR l

r Mr.'S. A. Varga September 6, 1984 U. S. Nuclear Regulatory Commission Page 2 ~ Company's position. The technical justifications have been provided to and concurred with by the Auxiliary Building Batteries' manufacturer. -The enclosed material and this letter are being provided in order to further facilitate the NRC review of the proposed technical specification change. This additional information, as well as the previous submittals which have been provided subsequent to the May 3, 1983 letter, were submitted to substantiate the variances from the Standard Technical Specifications based on Farley specific design parameters. Such submittals, however, have only provided additional justification and have not materially changed the originally submitted proposed change.- If there are any'further questions, Alabama Power Company is prepared to discuss the technical issues of this proposed change, at the NRC Staff's convenience, in a meeting in Bethesda, Maryland. Yours very trul, ,I i R. P. Mcdonald RPM /CJS:ddb-D6 Enclosu re cc: Mr. L. B. Long Mr. J. P. O'Reilly Mr. E. A. Reeves Mr.' W. H. Bradford E f W <q w-ww m y-- p-w m e-w

Specific Coments - Battery Technical Specification Change The proposed battery surveillance requirements are included in : 1. NRC Proposed Change Float Voltage for Category A Limf ts and Category B Limits should be 2.13 volts vice 2.02 volts 'and so indicated in T.S. Table 4.8.2. APCo Response The existing Technical Specifications requires a minimum float voltage of 2.02 volts. APCo proposed a float voltage of 2.07 volts in a submittal to the NRC dated May 3,1983 based upon the guidance of IEEE Standard 450-1980. In accordance with discussions with the NRC Staff, APCo resubmitted, in letter dated January 27,1984, Table 4.8-2 designating 2.02 volts as the float voltage limit based on the original Technical Specification criteria. - The-purpose of the battery technical specifications is to ensure that the batteries can perform their design function (i.e., provide a specified current discharge for two hours). Failure to comply with the battery technical specification results in shutdown of one or both Farley units within two hours. Technical Specifications should therefore define the minimum acceptable functional requirements rather than long-term optimization practices. APCo is committed to utilizing internal procedures to optimize battery performance. APCo's purpose in pursuing this technical specification change was to obtain a reasorable indicator of battery and battery cell degradation. The IEEE Stanoard 450-1980 float voltage criteria of 2.13 volts was not originally proposed because this crtteria is based on optimizing long term life expectancy rather than dettrmining battery degradation. - APCo's current prectice designates the " worst cell" as the pilot cell for Category A testing. Based on the worst case pilot cell, a Category A and B limit value' of greater than or equal to 2.08 volts with an additional' requirement that tne average float voltage of the battery cells be greater than or equal to 2.13 volts is therefore recommended. Utilizing a Category A and B liinit of less than 2.13 volts is justified because (1) cell voltage is not, by itself, a comprehensive indication of the state of charge of the battery, (2) a single cell (pilot cell) can have a degraded voltage (less than 2.08) and the battery as a whole can still perform its design function as discussed in the bases of the i Standard Technical Specifications, and (3) IEEE Standard 450-1980 does not consider a battery to be potentially degraded unless its voltage i drops below 2.07. volts. (1)

. Specific Comments Farl'ey would have experienced problems complying with the NRC proposed voltage criteria.of 2.13 volts over the past four years. Evidence of-this-is provided by battery cell data taken for this period of time for the six battery. sets.. This data, taken monthly, indicated that in twenty' cases the presence of at.least one cell with a voltage below 2.13, with 2.10 volts-tof 2.11 volts being the predominant values. The L low cells were scattered randomly throughout the battery sets. . Cell voltages of'less than 2.13 volts under normal float. charge are, ~ therefore, not an unusual occurrence, and based on Farley experience, have certainly not indicated inoperability of-an entire battery. In the i 20 cases where at least one cell was below 2.13 volts, the minimum average. specific gravity was 1.197_ on a 1.210 battery. A specific - gravity of 1.197 equates to a capacity of approximately: 90% of the batteries capability which is well above that required by the FSAR load profile. Also, in every case equalization restored the battery cell 4 voltages to within normal balance criteria. Equalization at Farley ' takes from 72 to.200 hours, being restricted by d-c coil. voltage limitations'of 138 volts. ~ The susceptability of lead calcium battery _ cells' to variations in float . voltage as compared to lead antimony and the reasons for this - . characteristic are provided in Attachments 1 and 1A _which depicts Gould . lead calcium cell voltage characteristics and typical. lead calcium and lead antimony characteristics. For a Gould lead calcium cell of 1.215 i specific-gravity, a cell float voltage of 2.2. volts is obtained at a

float charge of 5.5 milliamps/100AH. For lead antimony (new battery) this value is typically 63 mi111 amps /100AH while for an older battery it

.is over 400 milliamps/100AH. A small change in float charging current of only 3.2 milliamps/100AH on <1ead. calcium. cells (e.g., caused by-- slight battery case leakage due to dust,Lmiscallaneous contamination, or -an acidic condition), can cause a ce11' voltage to. drop.1 volts from 2.2 to 2.1 cell voltage.. This,is below the NRC Proposed Talue of 2.13 volts and would require,;if..the NRC value is, adopted, APCo to initiate immediate corrective action to equalize voltage. Based on' experience at ~ Farley, this is r.ot an indication of a discharge condition, but rather i simply a variation in. floa.t voltage. Further, the steep slope of the a' TAFEL Lines of Lead Calcium, shown in Attachment 1 and 1A and comparison of lead calcium.and lead antimony ficat current requirements suggest that lead calcium cells'will have a wider float voltage variation per 3 cell _than older type batteries (particularly in actual-plant environments). 'Further discussion of lead calciun float voltage variations is provided ~in ~ Attachment 2, a paper by Robert N.' Alexander, President of South Western Battery Company. This paper supports lead calcium float voltage imbalance _ as a common characteristic of lead. calcium batteries. (2) 4 ~ W -twW-7 -es-T-e- -m.ay-T3 - tv*- f9---uw,-- 1 p-T h w ,*4 qq-v,W-ag ew, ige-g-g v e vee

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Specific Conmients.

Table 4.8-2-(En01osure 1) contains voltage individually as a criteria for action. The: values ~ selected then must credibly delineate where

-battery capacity or operatility.is in. question. From Farley's experience it is' apparent that 2.13 volts does not meet this r ~ requirement. Neither does 2.10 volts since at this value batteries have been completely operative with,.in the 20 cases, a minimum of 90% capacity. Therefore, a value lower'than 2.10 volts is indicated as being; appropriate. Using Attachment 1, which is applicable to the Farley batteries, negative plate polarization ceases at approximately 2.16 volts and positive plate polarization ceases where no current enters the battery at the open circuit voltage of 2.055 volts. As discussed in Attachment 3, at-a positive plate polarization.of not greater than 25 millivolts, accelerated positive plate corrosion takes place. Such corrosion seriously. degrades battery life if allowed to continue. This value is . 2.055 volts, open circuit voltage, plus ~.025 volts polarization for a . total of 2.08~ volts. Since this is a value which is critical to overall battery operation, APCo maintains that 2.08 volts is the voltage below which corective action.is required. A value greater than or equal to 2.08'is therefore selected by APCo for limits in Category A and B. It should be further noted, however,.that even though a cell may be in jeopardy for the long term at 2.08 volts, the capacity of the battery is ~ still not known until specific gravity is measured. Cell voltage and specific ~ gravity in combination are, in APCo's opinion, accurate indicators of battery condition whereas cell voltage alone is not. .In conclusion, a Category A and B limit of greater than or equal to 2.08 voltc with an additional requirement that the average float voltage be greater than or equalito 2.13 volts are considered not only more ~ appropriate float voltage limits, but are enhancements from the existing 2.02 float voltage limit. These limits, considered in conjunction with ' specific gravity criteria discussed below, are more than adequate to ensure battery operabilty and capacity. (3) . o

Specific Comments 2. NRC Proposed Change Float Voltage for Category B Allowable Value should be 2.02 volts. APCo Response The NRC Staff and APCo agree on the Category B allowable loat voltage value. 3. NRC Proposed Change Specific Gravity for Category A and B Limits should be 1.200 and 1.195, respectively, with the additional requirement that the specific gravity for the average of all connected cells be greater than or equal to 1.205. APCo Response NRC Proposed Category A and B Specific Gravity Limit Values-of 1.200 and 1.195 vs APCo Proposed Values of 1.195 and 1.190 The existing Technical Specifications require a limit, as approved by the NRC, of 1.190 because the Technical Specification limit serves two (2) different batteries ( Auxiliary Building and Service Water). These batteries were supplied by different manufacturers and have different recommended specific gravities. For human factors concerns, APCo prefers to maintain a single Technical Specification limit for both batteries. The scope of Standard IEEE 450-1980 states that it is limited to -providing recommended practices, including acceptance criteria, to optimize the life and performance.of large lead storage batteries. Specific ' gravity and-the frequency of inspections of the batteries are. important ingredients in the optimization of battery performance. As a result, the IEEE Standard proposed frequencies of inspections and associated acceptance criteria are such that the specific gravity will not degrade between inspections. In the judgement of APCo, if the frequency of inspections had been increased, then the established limit values' could have been lower. APCo currently performs the IEEE-450 quarterly inspection for each battery cell every 31 days. This is three (3) times as frequent as either technical specifications or the IEEE Standard require; therefore, the proposed specific gravity values are considered conservative for the Farley Nuclear Plant. (4)

-Specific Comments = The APCo proposed limits can be further justified based upon the margin within the batteries. Supporting.information for the margins described below are included.in Attachment 4. There is greater margin for the -Service Water Building battery than the Auxiliary Building battery; therefore, only tne Auxiliary Building battery is discussed below. A fully charged Auxiliary Building battery has a specific gravity of 1.215. With this specific gravity, there is approximately a 40% margin - between the Auxiliary Building battery capacity and the FSAR assumed loads. The APCo proposed values of 1.195 and 1.190 for the Category A and B lin;its are conservative for Farley since the 1.190 specific gravity value represents a margin of greater than 10 percent and 1.195 represents a 16 percent margin to the battery capacity when discharged at the FSAR required loads. Recognizing that it is the " worst" ' cell that is considered the pilot cell, and that the APCo proposed Category A value has been increased from the existing 1.190 value to 1.195, in all likelihood each cell would be above the APCo proposed Category B limit of 1.190. This, in conjunction with the average limit of 1.195 discussed below, guarantees that the battery would have an actual margin of greater than or equal to 16% which represents a 6% increase over existing T.S. requirerrents. The margins for-1.190 and 1.195 specific gravity values are conservative since they assume that the battery is discharged at the FSAR rate to arrive at the beginning specific gravity of 1.190 and 1.195. These margins include a penalty for " depletion", the seriousness of which is proportional to the discharge rate. More specifically, should discharge occur during operation,.it is expected that the rate of discharge would be much less than the FSAR discharge rate. 'Therefore, the specific gravity values of 1.190 and 1.195 represent more battery capacity under actual operating conditions than the above 16% and 10% margin estimates. NRC Proposed Category B Average Specific Gravity Limit Value of 1.205 vs APCo Proposed Value of 1.195 The NRC proposes that the specific gravity.for the average of all connected cells be greater than or equal to 1.205. APCo proposes that the specific gravity be 1.195 which is based on the FSAR required loads plus an adequate margin of 16%. The minimum average specific gravity to meet the FSAR loads is approximately 1.181 as shown in Figure 2 of. (5)

Specific Coments Additionally, bringing the a' erage of all cells up to 1.205 is not v required to meet FSAR loads:as described above. Therefore, the APCo . proposed specific-gravity of '1.195.for. the average of all connected p cells is adequate because-it exceeds the value required to meet the FSAR irequirements with sufficient margin. 4. NRC Proposed Change ~ Category B s'pecific gravity should have an allowable value of 1.205 for ~ ' individual cells and an average value for all connected cells of 1.195. The NRC also proposed chahging the cell allowable variance from.080 to .020.: APCo Response ~ NRC Proposed Category B Allowable Specific Gravity Value 1.205 vs APCo Proposed Value of 1.190 The NRC proposes to change'APCo's Category B allowable specific gravity of 1.190 to 1.205. The 1.190 value proposed by. Alabama Power Company is ~ the currently existing value:in the Farley Technical Specifications. The 1.190 value provides a margin of over 10% above the FSAR design loads as discussed in the above response to NRC Proposed Change #3. Also stated in this response and applicable to this concern is the argument that the' more frequent inspection intervals of APCo exceed the-4 requirements of IEEE Standard 450-1980, and therefore the more stringent limits.of the IEEE Standard need not apply.. Additifonally, IEEE Standard 450-1980 is predicated on the assumption 5that the~ values provided therein are indicators of when corrective

action.is recommended to be taken to optimize battery performance not (when a battery is to be-determined inoperable. - Technical specification

' values should be the minimum required. values for operability, not l recommended' optimization practices since the' technical specifications require plant shutdown in 2 hours when batteries are declared inoperable. The corrective action recommended by IEEE. Standard 450-1980 for reduced sp'ecific gravity of individual cells is to equalize the cell s. This process, developed by the battery manufacturer, requires . from 35'.to 180' hours; this period is significantly longer than the two .(2) hours. permitted by the' technical specifications before one or both ~ Tof the units must be shut down.. The technical specification Category B allowable value for specific gravity should therefore be 1.190 to allow ~

battery cells to be equalized rather than needlessly replaced due to an L overly restrictive technical.' specification limit of 1.205.

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Sp:cific Comm:nts NRC Proposed Category B Allowable Average Specific Gravity Value of All Connected Cells of 1.195 vs APCo Proposed Value of 1.190 The NRC proposes to change the Category B allowable average specific gravity for all connected cells from 1.190 to 1.195. APCo proposes that this value remain 1.190. An average specific gravity value of 1.190 for all connected cells ensures that the battery as a whole will perform its design function with margin (10%) when compared to the FSAR required loads. The minimum required specific gravity to meet the FSAR assumed loads is 1.181. NRC Proposed Category B Specific Gravity Allowable Variation Value of 0.020 vs APCo Proposed Value of 0.080 The NRC proposal for changing.080 to.020 has been interpreted by . Alabama Power Company to mean a change of the surveillance to read: ".020 below the average of all connected cells" The NRC proposal to change the 0.080 specific gravity value to 0.020 is acceptable to APCo if the wording of the criteria is modified to read: ".020 below the allowable average (1.190) of all connected cells" The allowable average of all connected cells has been shown in the previous response to NRC Proposed Change #3 to have sufficient margin above the FSAR required loads (greater than 10% margin for a specific gravity of 1.190). Use of the " average of all connected cells" instead of the " allowable average" would involve ;nnecessary replacement of cells when only an equalization charge is required. CJS:ddr-DS (7)

ELECTRICAL POWER SYSTEMS E4ctoSORE l D.C. DISTRIBUTION - OPERATING SURVEILLANCE REQUIREMENTS (Continued { MAy Sg B3 Lemcirbt TABLE 4.8-2 BATTERY SURVEILLANCE REQUIREMENTS CATEGORY A (1) CATEGORY B ' Paramater Limits for each Limits for each Allowable (3) designated pilot connected cell (2) value for each cell connected cell Electrolyte > Minimum level > Minimum level Above top of Level indication mark, indication mark,

plates, and < 1/4" above and < 1/4" above and not maximum level maximum level overflowing indication mark indication mark Float Voltage.

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ATmc4 MENT 1 A BEHAVIOR OF CELLS ON FLOATING CHARGE SHOWING: A. TOTAL CELL VOLTAGE VS. FLOAT CURRENT B. POSITIVE AND NEGATIVE PLATE POLARIZATIONS VS. FLOAT CURRENT (TAFEL LINES) 1 -~ 2.35 o I 2.30 "w / / /. $? 2.25 g 7 p 00 l 2.20 / 2 15 e y e 2.10 4>- ~ y ,/ / H o. 2.05 Sci 2.00 I = LEAD CALCIUM II: LEAD ANTIMONY (NEW) i III = LEAD ANTIMONY (OLD) P Ne + 250 3 I om +200 --'y s wo g$ s# / III + 150 ,s y s / s 1 +100 OPTIMUM RANGE 2 F - ~~--~ OF POSITIVE PLATE ,, ~"~ p Pol.ARIZATION s i g' f + 50 g _.___g. g f}# ~~' a-0 I l OPEN CIRCulT VOLTAGE OF CELL - 2.06 VOLTS (1.213 SR GRAV. AT 25'C) 1 1 s x 5-0 N I ( s N - 50 N \\ . Ir ~ \\ N gII N o$ -150 \\ \\ o I \\ -200 w w ad N 1 N s 2 P 4 1 2 5 10 20 50 10 0 200 500 1000 2000 o g FLOAT CURRENT - MILLIAMPERES PER 100 AH Z 13

[ RTU ~ > h-k.probably cros2 from two sources: An th:r possibla s:urce cf this misunderst nding is th t le d-cIlcium resembles pure le-d end pure

1. Wh:n tha trad-c Icium battery is charged cnly 1:cd is used fcr the rostttes sometimes called a tiny float current will pass through it, even

" corroding buttons" which are pressed into the lead-at elevated float voltages. I4ad-antimony 'l takes much more current at the same float antimony grid of the Manchester positive plate. "Therefore", the reasoning goes, " pure lead (or lead-voltages. The reason is the electrochemical calcium) must corrode more rapidly than lead-anti-development of the countervoltages of the two mony". The fallacy is that most of the corrosion on batteries, and has nothing to do with ohmic resistance. The behavior on float of lead-cal-the " corroding buttons" does not come about during float service. It is put there at the factory by first cium resembles in some ways that of a chemically corroding the lead with nitrates or "sulphated" battery, whose high countervoltage chlorides, then by electrolytically converting this is developed from ohmic resistance. However, corrosion product to lead dioxide. a "sulphated" battery on charge gasses heav-ily, while a calcium battery does not. The te "sulphated" is used in the vernacular, mean,rm uCan't Be Cycled" ing a condition where a dis' charged battery has been allowed to stand until lead su!phate par-This is untrue. While the vast majority of lead-ticles have become hard and crystalh,ne. calcium batteries are built for floating service where they are not cycled frequently, there is no reason - The earliest lead-calcium batteries were made "U

• • "". t,be built for strictly cycling se for telephone se vice exclusively, and were ice.'" This again is entirely a matter of mecham,rv-cal mechanically designed for maximum ampere-design, a cycle senice battery being considerably hour capacity at low rates of discharge without different from a floatmg service battery.

regard to one minute ratings. They had slightly higher internal resistance than other " Cells Won't Float Right" batteries specifically designe service. This, however, is ent re y a matfor switchgea[ This derives from the fad that lead-calcium cells r in a battery exhibit wider variations in individual mechamcal design, and lead-calcium batte s designed for switchgear and even engine cran - voltages than do antimony. The concern would be ing service have been available for many years. valid if the variations observed among calcium cells gg g Fortunately, they do not. " Grids Corrode Faster than Antimony" No two cells of any battery are precisely identical. There are small differences m rates of self-discharge, False. A properly manufactured lead-calcium posi-and in traces oflead sulphate remaining in the plate tive grid corrodes at about 1/3 the rate of lead-pores. The lead-calcium battery on float is an exce!- antimony on test, and at 1/4 to 1/5 the rate of lent mdicator of these minor and insigmftcant varia-lend-antimony in service. However, if the lead-cal-tions, while the lead-antimony battery is not. cium grid is poorly made, it can corrode faster than Referring to Figure 5,it can be seen that within its lead-antimony opposite number. Too high a the float voltage range (2.17 to 2.25 volts / cells) a calcium content, poor quality castings, or castings variation of a few milliamperes per 100 A.H. In float by high pressure methods into a relatively cool mold (die casting) can cause a high corrosion rate for current will produce very large changes in cell polarization for the lead-calcium cell, while this 1:nd-calcium alloys."" The techniques employed by same change in cell voltage with respect to current th2 manufacturer are the determining factor, will be scarcely observable in the lead-antimony cell. The idea .at lead-calcium corrodes more rapidly The wide variations between cell voltages in a lead-may have come from observations of older batteries calcium battery will be most pronounced following cf this, type where some,tuation is normal, and agrowth, of the positive a recharge, when a few traces of lead sulphate pt;tes is apparent. This, si remain in some of the cells. This situation, however, well designed lead-calcium, battery has room to s completely harmless to the battery and will grad-accommodate moderate positive plate growth. About ually correct itself. 109 growth should be anticipated during the total A voltage variation problem is apt to occur if a life cf the battery. As a battery remains in service, lead-calcium battery is allowed to stand several 1:ad dioxide corrosion product builds up on the sur-mon;hs prior to installation. Lead sulphate particles faces of its positive grids, which occupies more remaining in the plates following manufacture, plus space than the base lead from which it was formed. those produced by self-discharge, tand to clump In consequence, the corrosion product exerts an together forming hard crystals which are not easily cxpansive force on the grid. The response to this broken down by the float current. The response, to f.re2 differs between lead-calcium and lead-antimony charging current will vary among cells, creating alloys. Both alloys have similar tensile strengths, but fairly wide voltage variations. The actual amount of the antimony alloy tends to be brittle, while the lead sulphate involved is very small, and generally calcium alloy 5 more ductile. The result is that under harmless to the battery capacity, but years may pass the pressure of the corrosion product, lead-antimony before cell voltages stabilize. This situation is not a clloy cracks and breaks, while lead-calcium stretches. major problem, but it is annoying, and should be 15

avlided. The extremtly 1:w self-discharge rzte of through the battery ct this v:ltage I;vil is suffi-Icid calcium etils effers a temptation to 1: ave thtm ciently high to esver tha n:rmal range of self-dis-off charge if lengthy construction delays occur; but charge variations among the cells. Users whose in this instance. it is well to treat them with the equipment can tolerate this slightly increased volt-4 r* same respect accorded lead-antimony batteries. age may enjoy freedom from the chore of equalizing, and generally take advantage of this bonus. "Must Be. Floated At A Much Higher Voltage Than Antimony,, A real problem existed with some of the earlier lead-calcium batteries floated at 2.17 volts per ceti, Lead-calcium can be floated at higher voltages when meter calibration error or charger voltage drift than lead-antimony without the damage that would allowed the actual float voltage to fall to 2.15 volts / be caused to lead-antimony at these voltage levels; cell or lower. At this voltage level, there was not enough current passing through,tive plates a h: wever, lead-calcium doesn't have to be. floated at maintain the polarization of the posi e voltage significantly higher. The float range of the required 40 mi,llivolts, and th2 lead-antimony cell is 2.15 to 2.17 volts per cell, keeping these positives.charg. there was difficulty while the same range for lead-calcium is 2.17 to 2.25 ed. Because of this, y,j s per cejj. modifications were made to the batteries causing a The source of the misunderstanding may be that 81 ght increase in current at lower float voltage levels, such increase being sufficient to maintain th2 lead-calcium battery, when floated at 2.20 volts adequate polarization on the positive plates, and to per cell cr above will not require equalizing charges. make floating at 2.17 volts / cell safe and much less it has been found that the float current passing critical. V. A FIFTY YEAR BATTERY? In the autumn of 1967, Willihnganz of C & D well the extrapolation agrees with, performance over Batteries presented a paper before the Electrochemi-the last 20 years. It is moreover, based on the ett Society describing a method whereby batteries produ'et of only one manufacturer, who is not claim-c:uld be tested for life characteristics at an accele-ing such life. Not all batteries would last 50 years, rated rate."n The method made use of the Arrhenius even if they possessed the potential. Adverse operat-equation which in practical effect states that the ing conditions and simple manufacturing errors r:te of a chemical process doubles for each 10' C. risa in temperature. Willihnganz's method provides would preclude this. Nonetheless, the distinct possi-bility, perhaps even the probability, exists that the an extremely useful tool for the battery engineer 50 year battery is now in common use without being who formerly had a wait of 15 to 20 years before so acknowledged. Certainly a 30-year life for a well-the success or failure of his design could he told; made lead-calcium battery can be confidently and moreover, the tests provided some highly interesting conservatively predicted. data concerning lead-calcium batteries, past and present. Assuming that Willihnganz's extrapolations are In an effort to determine how well life as predicted valid, the lead-calcium battery should reake possible hv the accelerttad test method correlated with actual some developments in the battery industry which field experiene, laboratory personnel examined a will be of great benefit to the user. Among these are: significant proportion oflead-calcium batteries which had been in actual service for 15 years, and pre-

1. A battery of 50-year life, of great economic dicted probable life for a large majority of these benefit to users such as large telephone com-batteries in excess of 20 years. The accelerated test panies whose equipment loads will probably method had predicted a life of from 20 to 25 years conti tue increasing As load grows, paralleled far these batteries produced in 1951, thus correlating batteries could be added without the necessity cxcellently.

of replacing earlier stringc, What is most significant is that the same accele-rated test method, when applied to cells being

2. A battery of 20 to 30 year life, meeting the manufactured in 1967, predicted in most cases a life needs of most users whose equipment would span in creess of 50 years, suggesting that a great become obsolete or its location changed at amount of progress had been made in lead-calcium about this age. Such a battery could be pro-battery technology.

vided using thinner grids at lower cost, and providing the same electrical characteristics in The idea of a battery lasting 50 or 'nore years is a smaller space and with less weight. hard to digest: it would mean that during its use, both maker and user of the battery would spin out

3. Maintenance free automobile batteries lasting thar working hves. Further, the equipment the bat-5 or. 6 years, using thin grids with higher tsry operated would probably become obsolete long relative electrolyte capacity.

before hattery failure. It should be borne in mind that this 50 year life

4. Batteries tailored to meet almost any age and maintenance requirement, at a cost consistent prediction is a mathema'tical extrapolation, however with the application.

IG

m p. l 1328'l ' Tiin uri.i. systru TEclixicri. Jot'nxAiOEPTEuuEu tsio, ^ Ft. OAT on Envriox. 3329 sideration of ikiat operation. Tl ey refer, of course, only td a'" typical"I

• • f

• ""'.#".=0,{.... SoJut. ions for.utich this is not so :

-lead. calcium cell design, the characteristics of which'are representative-

$ 3

.e y ma uw in*ad, I, can be asuined to becom6 Jof one type.of cell suitable for this kind of service.. approxnnately equal to -, - I, or I.,. In the case of the former, from ' I " ' * " " " ' ""s inulymlent of I/. nr. crt.L ' uEn' Avion,' PAsAutTEus von tyricAL I. san-cat.ciru WEi.t.s - g jgowmg ruults nre by no means all.melusive but indicate, i instead, sons of the elTects to be expected. ' When a constant float voltage, V, is maintained across'a cell, it is f .the cell polarization which is controlled. This is given by n..n - l', i " "* OII' #"*I""I fl""' C**II'i" ' l l';;;; =,, - 3 and is related to the float current I which flows. f through both positives and negatives by equations (15) and (10). Thus, i1*i = 7.5 uA/Ah, I;_; = -7.5 uA/Ah,: II = -27.5 uA/Ah, V - 2.170 V/ cell at 25 C. In this case, ~ f specification of I'f and the plate parameters determines the condition. of the cell during float operation. While the discussion here deals only v..o/m\\.. = 2170 -- 20dl = 109, with the steady-state, it is clear that a cell inadequately maintained in these circumstances will be no better maintained in actual use. From = 70 log [(I - 4)/7.5) + 110 log [(I, - 27.5)/7.5), f the previous section, adeqiinte maintenance of positive plates is con-. and I = 50.5 A/Ah,,, = rg, mV,,_ = L-nl mV..This repre.<ents, sidered to require Q_W mV so that grid corrosion is not acceleruled; f .N Adequate maintenance of the' negatives requires only that v. <; 0, but. more or less, the average

• behavior of a " typical" or, perhaps more accu-rately, a desmib!c cell. Both plate polarizations are good and float

-t-in both cases, some margin is obviously desirable. operat_on should be most satisfactory under these conditions. i g The quantities of principal ir.terest, then, are I, v., and v.. In the f Q) light of the previous discussion, these are taken to be detennined by the 3.2 Normal Range Cells, Stamlard float Conditions" f ' parameters 1*., I'_,1*, T, and l',. In all of the calculations, h,*, b, I,V = 5-10 uA/Ah, Il_ = -(5-10)uA/Ah, Il'= -(20.-35)uA/Ah, and I, are assumed invariant and, together 'with the. temperature. dependent factors, are assigned the values given earlier.1*., Il., and. l', = 2.170 V/ cell at 25*C. The ranges in the following tables corre-I! depend on design and method of manufacture and can vary con-spomi to the range in I..,5-10 uA/Ah. h siderably. Cells with values lying within the limits given for the " typical" I /(uA/Ah). I; = -20 uA/Ah. I; = -35 uA/Ah f g cell of the previous section are desenbed m the fo!!owing as normal ja range" cells. As a point of reference, a cellwith mid-range vahies of these U ~ ~" #'gj"g' E3'II 2 47 4-02 S parameters is hereafter described as n'" median" cell. Temperature and f* " -l

1. A/Ah 45.5-54.8 56.S-65.7 float voltage depend, of course, on conditions of use and can also vary, v./mV I; = -20 uA/Ah 17 = -3, uA/Ah Standard conditions, as in the Bell System, are taken here to be 25*C -

I!_ = -5 uA/Ah 5G--10 ca-as and 2.170 V/ cell. I! = -10 uA/Ah 6 1.10 73,, For a given set of parameters, I and then v. and v. can be calculated f v./mV 13 = -20 uA/Ah Il = -a, uA/Ah from equations (15) and (16), taking into account two restrictions: (i) n. must be positive or zero and g. must be negative or zero. l II " -0 A/Ah -(53-69) ~ ~ -(43-61) Solutions giving negative v. or positive,_ are physically inadmissible, { Il - -10 uA/Ah -(45-60). -(37-54) for in reality the charge <lischarge reactions poiss the plate potentials In all cases the plate polarizations are adequate and float operation - at zero polan,zation and tlye plates then discharge. At y_. - 0, the net shouhl be satisfactory under the standard condi.tions-discharge rate of the postive is I - I.. - I, ; at g - = 0, that of the f negative is I + I.. + I,. 3.3 Median Cell, S:amlant Float l'oltage, l'arial Temperature f (ii) The rate of~ oxygen rethietion at the negative cannot exceed the I*.== 7.5 uAMh, 4 = 'A5 4/4 g = _>I, gg g = rate of oxygen evolution at the positive; that is, -I, can be no greater 2.170 V/ cell at 5,15,25,35, and 45*C.

__ ; Attachment 4 . Supporting Information For Battery Margin l1. The Auxil'iary Building. battery FSAR Discharge load (FSAR 8.3.2.1.1) ~ is equal to: ' s

(430 Amps x L117 mins /60 min /hr) + (920 amps x 3 mins /60 min /hr) =

'884.5 amp-hrs. Lwhich-is divided by the required discharge period of 2 hours to ~ 'obtain-required Amperes. (884.5/2) = 442.25 amperes required. t _2. Using the manufacturer's discharge curve for the NCX-1800 -(See Lattached Figure 1, Typical.. Discharge Characteristics of NCX-1800) and the average discharge rate of 442 amps, the total amp ' hours ... avail abl e is.1440. The availability of 1440 amp-hrs in the battery 4 is obtained.by selecting 442 on the "X" axis,. extending vertically until the 1.75 volt (FSAR 8.3.2.1.1) line is intersected, and' then extending left' horizontally to the "Y" axis where Amp-Hrs. ( AH) is read as 1440.y Note that the 442; amps is an_ average discharge rate. ~ We consider this to be a conservative (on the high side) rate since battery characteristics ' are such that the lowest " discharge rate, 430 amps ;in this case, should be used which would provide for a capacity total of over -1440 AH by using the same p process as before,- only starting at.430 amps on the "X" axis. ~ 3. The FSAR -loads are. therefore equal _to 61% of the Auxiliary Building - Battcries Capacity and therefore there-is approximately. a 40% margin within the battery. ~ 884.5 Amp-hr./ =1440 Amp-hr. =.61'x 100 = 61% capacity ~ '4.

It'should.be:noted that while a battery is being constantly

- discharged, even at a varied rate, the relationship of. amp-hrs > discharged to specific' gravity is a straight line. This is verified by the manufacturer. Therefore, specific gravity. at the 100% capacity-line of 1440 AH can either be calculated or obtained by extension _of the actual test data line, which 'is done in our ~ L ' case. The average beginning and ending spec?fic gravities for 10 service tests exactly duplicating the FSAR loads were 1.216 and j- -1.163, respectively. l.

5. _The FSAR Discharge Rate on Specific Gravity vs. Percent Discharge Graph was plotted (Figure 2) by drawing a~ line beginning at 1.216,

. the specific gravity value at 0% discharge, and ending at 1.163, ~ the specific gravity where the battery is 61% discharged. Extending;the straight line to the 100% discharge point (1440 AH)

gives. a specific gravity of-1.128.

L

6. 'The. Specific Gravity.vs. Percent Discharge Graph also has a line drawn depicting the eight -(8) hour rate from manufacturer's data, i-

'This represents the battery's rated discharge capacity and is ' included to. exemplify the straight line relationship of amp-hrs discharged to specific: gravity. i E: ,....,- - -.... _.,, _,,.-.. -,--,_,-,, _,,,. m...,....,--,,,,..,, - _,,_..

Supporting.Information For Battery Margin Page 2

7.. The specific gravity range required to deliver the FSAR load is equal to:

1.216 - 1.163 =.053 (from actual test data as plotted). 8. If we want-to determine the minimum beginning specific gravity, we start from the lower specific gravity limit of 1.128 which represents 100% discharge (at FSAR rate). We then add the specific . gravity range required to meet FSAR loads-(1.128 +.053 = 1.181). 1.181 is the minimum specific gravity to start from where battery capacity would be equal to the FSAR assumed loads. ~ 9. With the existing minimum specific gravity of 1.190 we can meet the FSAR loads with a margin of 10%. This margin is determined by subtracting the minimum specific gravity (from 8 above', from the APCo existing minimum value of 1.190 (1.190 - 1.181 =.009). This is the difference between the minimum FSAR value and the existing acceptance value. The capacity margin provided by the existing acceptance value is determined by dividing this difference (.009) by the battery capacity specific gravity range from 0% discharge to 100% discharge [.009/(1.216 - 1.128) = 10.02%]. This is the margin of battery capacity with existing Technical Specifications.

10. Similiarly, for the APC0 proposed average specific gravity limit of 1.195, the margin of battery capacity is; (1.195 - 1.181)/ (1.216 -

1.128) = 16% margin.

11. The Auxiliary Building Battery manufacturer concurs with this

. calculational methodology. .D6 i

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