ML20094P159

Application for Amends to Licenses NPF-37 & NPF-66,changing TS 3/4.7.5 & Bases Section 3/4.7.5 for Ultimate Heat Sink

ML20094P159
Person / Time
Site:	Byron
Issue date:	03/31/1992
From:	Schuster T COMMONWEALTH EDISON CO.
To:	Murley T NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM), Office of Nuclear Reactor Regulation
Shared Package
ML20094P163	List: ML20094P159 ML20094P167
References
NUDOCS 9204070259
Download: ML20094P159 (18)

Text

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. . Commonwealth Edison 3

4- -

Zf :1400 Opus Place -

• ' v - Downers Greve, IHinois 60515 e

March 31,- 1992.

Dr, Thornas E. Murley, Director .

' Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555--

- Attn: Document Control Desk

Subject:

Byron Station Units 1 and 2.

Application for Amendment to Facility Operating Licenses NPF 37 and NPF-66 Appendix A. Technical Specifications NELC_Dache1Nasm50-A5 Land _50:355 -

Dear Dr. Murfey-Pursuant to 10 CFR 50.90; Commonwealth Edison proposes to amend Appendix A, Technical Specifications of Facility Operating Licenses NPF-37 and NPF-66. The proposed amendment requests changes to Specification 3/4.7.5 and the Bases Section 3/4.7.5 for the Ultimate Heat Sink.

The description, impact, and bases of the proposed changes are contained in ,

. Attachment A. The revised Technical Specification pages are contained in Attachment - '

B. =The proposed changes have been reviewed and approved by both on-site and off-site review in accordance with Commonwealth Edison procedures. Attachment C describes Edison's evaluation performed in accordance with 10 CFR 50.92(c), which has determined that no significant hazards consideration exists. An Environmental

- Assessment has been pmformed and is included as Attachment D. Attachment E contains figures referenced by the text of the submittal. - Attachment F provides a list of-Byron /Braidwood UFSAR sections which are being revised as a result of the Design Basis Reconstitution process for the Byron Station Ultimate Heat Sink.

Due to the complex nature of submittal, we offer to meet with your siaii, at

your convenience., to present the basis of the submittal and to answer any questions.

Commonwealth Edison is notifying the State of Illinois of our application for this amendment by transmitt.!ng a copy of this letter and its attachments to the designated State Official.-

.920407o259 920331 p

M ADOCK 05o00454 l u-ZNLD/1645/1 eon f901

Dr. Murley March 31,1992 To the best of my knowledge and belief the statements contained here are true and correct, in some respects, these statements are not based on my personal knowledge but upon information received from other Commonwealth Edison and contractor employees. Such information has been reviewed in accordance with Company practice and I believe it to be reliable.

Please direct any questions you rnay have concerning this matter to this office.

Respectfu!!y, _

(f -

&WtLf f,c i (hka~phD

Terence K. Schuster Nuclear Licensing Administrator Subsg ibed and Syorn to before me _ _ _ _ . ~ ,

thisgZ[/da of ffj'tch ,1992. ..

o=ciC!AL SEAL'

, sANoaA c.LARA .

(/ xe_, : - ' .J N"AMY Fi?. STATE D " L CS k

- ' otary Put$1t vy cevv 35 > E8 "ES C *)'

m.m a n w w =:x Attachments: (A): Description and Impact of the Proposed Changes (B): Proposed Technical Specification Changes (C): Evaluation of Significant Hazards Consideration (D): Environmental Assessment Statement (E): Figures (F): List of Affected UFSAR Sections cc: W. Kropp - Senior Resident inspector. Byron A. Hsia - Project Manager (Byron), NRR B. Clayton - Branch Chief. Region lli Office of Nuclear Facility Safety - IDNS ZNLD/1645/2

ATTACHMENT A DESCRIPTION AND IMPACT OF PROPOSED CHANGES

Background

The ultimate heat sink (UHS) consists of two essential service water (SX) cooling towers and the normal makeup, safety related makeup and backup makeup systems.

A simplified general arrangement drawing is provided as Figure 1 in Attachment E.

The drawing depicts the tower design and its interconnections with the rest of the SX sp.;em. Each of the two safety related mechanical draft cooling towers consists of a water storage basin, four fans, four riser valves and two bypass valves. Normal  ;

makeup to the cooling towers is provided from the non safety-related circulating water system with the safety-related emergency supply of makeup water provided by the  ;

diesel-driven SX makeup pumps located in the River Screen House The diesel-driven '

SX makeup pumps auto-start on low level in their respective basin. Loss of both the normal and safety-related makeup supplies due to natural phenomena such as a tornado. flooding or loss of SX makeup pump suction (due to a seismic event concurrent with low river flow) can be c,ircumvented by use of the backup deep-well makeup pumps.

In early 1991,it became apparent that saveral UHS design assumptions were indeterminate or different 1 rom those previously assumed in the UFSAR and UHS des!gn analysis. Consequently, a design basis reconstitution effort for the UHS was undertaken and completed in 1992. This design review and re analysis was required to determine the cumulative effect on SX cooling tower performance. The review considered the following items:

a. The regulatory requirements were reviewed to determine the limiting design basis accident (DBA) and the number and type of postulated equipment failures. For design purposes, the worst case accident scenario considered for the Byron Station UHS is a large break Loss of Coolant Accident (LOCA) coincident with a Loss of Offsite Power (LOOP) on one unit, and the concurrent orderly shutdown and cooldown from maximum power to Mode 5 of the other unit using normal operating procedures. This event alsu includes consideration of the most limiting single active failure. This particular series of initiating event, coincident event, and single active failure is consistent with regulatory requirerrhnts and with the design basis event presented to the NRC in Reference 2. The irdividual scenarios detailed the various initial flow alignments, fans out of seivice, and single active failures. For each scenario, an analysis case which described the initial conditions, flow distribution, the energy transport, and the available e Juipment was developed. The scenarios are as follows:

1) ContainmenLSpwfurnp Epilure The smgle failure of a containment spicy pump was chosen to maximize the peak heat load on the UHS. This failure maximized the peak hr 't removal rate by the four operating reactor containment fan coolers (RC. ,s). The UHS towers were not functionally af,'mted by this failure.

ZNLD/1645/3

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2) CooUng_ToweLEaafailute

. The single failure of a tower fan affects the heat removal capability of a tower cell. This f ailure was considered in addition to the two cells that were assumed to be out of service (OOS) initially. Technical Specifications allow two fans OOS without being le an action statement. The accident unit containment heat load on the UHS for this failure corresponds to that generated from 4 RCFCs and 2 containment spray system (CS) pumps operating.

3) DieseLGenerator.Eailure The single failure of an emergency diesel generator affects UHS heat load, system flows and tower performance, The accident unit containment heat load on the UHS for this f ailure corresponds to that generated from 2 RCFCs and 1 containment spray pump operating. The SX system flows correspond to one SX pump operating on each unit. In addition to the 2 out of service cells,2 additional cells were affected by the diesel generator 1 allure.

4) EstentiaLService_WateWump_Eailure The single failure of an accident unit usential service water pump reduces overall system and tower flow rates. T1e towers were not functionally affected by this failure. The accident iit containment heat load on the UHS for this f ailure corresponds to that generated from 4 RCFCs and 2 containment spray pumps operating.

The analyses performed for all the above scenarios verified that the peak basin temperature remained below the design temperature of 100" F. Other f ailures considered resulted in either lower heat input to the tower, no effect on the tower's heat removal capability, or were enveloped by the above limiting f ailures.

These scenarios provided the basis for SX system flew and tower cell flow calculations, containment mass / energy release calculations, tower performance calculations and the overall basin temperature calculations.

b. Previous UHS performance calculations assumed a steady state heat load of 67 MBtt{hr 124 MBlu/hr from the non-LOCA unit plus 43 MBtu/hr from the LOCA onli) . The new steady state heat load from the two units is 103 MBtu/Hr (72 MBtu/hr from the non-LOCA Unit plus 31 MBtu/hr from the LOCA Unit). This results in a greater demand on the SX cooling towers. 3

c. Several changes were made in the analysis assumptions which resulted in an increased rate of energy transport into the SX system from the LOCA unit containment. The reconstitution study maximized the accident unit containment heat load to the UHS by:

Postulating scenarios with 4 RCFCs and either 1 or 2 CS pump (s) operating (the maximum number of RCFCs running. assumed previously was 3)

J l .MBtu/hr = million Stu per hour ZNLD/1645/4

i ,

E

• Assum;ng hi0har SX water flowrates to the RCFCs

• Assuming highor air flowratos to the RCFCs and Assuming earilor switchover to containment recirculation phaso and t correspondingly earlint RhR haat loads for casos where 2 CS pumps are

( oper ating.

The analysis resultod in greater LOCA unit contamment integrated heat loads of ap aroximately 25% for the first two hours after accidert initiation and an increase in _OCA unit containment peak heat load to 830.8 MDtu/hr. Thoso increased heat loads woro used for constavatively ovalu ting UHS tower periormance and

, do not affect previous UFSAR Chapter 6 containment anatyses,

d. The worst case meteorological wet bulb temperature for the Byron Station area is i

82'F for a 3 hour3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> aeriod, as determined in the UFSAR 30 year climatological record sear.,h. It s at the worst meteorological condition for which Regulatory ~

E Guide 1.27 states that the UHS must be capablo of performing its cooling function for the critical time porlod (i.e during the design basis ovent LOCA/ LOOP on ono unit and the Non LOCA unit shutting down), the effect on the cooling tower's

. ability to reject the design heat loads was considered for the reconstitution analysos utilizing the highei wet bulb temperature of 82*F rather than the arevl<>usly assumed tower design value of 78*F. The effect of raising the set aulb temperature was a resultant decrease in the cooling tower perfortnance.

i ii e. The previous analysis utilized a single bounding scenario which assumod 48,000 hl a

gpm flowing from two SX pumps to a single tower with 4 cells operating and each j cell receiving an equivalent share of the total flow. The assumption of 48,000 gom for the case where the two pumps are operated in paral!e', on a given unit, was in error and provided too high an estimate of system flowrate. The design basis raconstitution effori utill:ed a calibrated computer model of the SX eystem a tu determine SX pump and individual tower cell flow rates for various postulated accident scenarios.

Nun erous calculations were performed to evaluate the timo dependent basin temperature responses. Theae calculations iricluded sensitivity ans to avaluato the off.act of varying the fractions of flow and energy to the towers Ly 4 t'N. The results of the calculations venfied the basin temperature does not excma 10C" under the worst case accident ecenario.

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i 2hlD/:645/5 g . .. Aa --

Description of the Proposed Chegos Reference 100cuments time Design Basis Reconstitution effort for the Byron Ultimate Heat Sink (UHS). As a result of this effort, Technical Specification 3!4.7.5 and the Bases for the cpecification are bein0 revised to clarify the current UHS design and to praserve the assumptions used in the current UHS analyses. The Updated Final Safety Analysis Report (UFSAR)is being re"ised for the came reasons. A !!st of affected UFSAR sections is provided in Attachment F. In addition, other changes to the Specification are proposed that did nut result directly from the d sign basis reconsutution.

The marked up Technical S ocification pages indicatin0 the proposed changes are E 3rovided in Attachment B. discussion of each change follows. The changes have aeen classified intu 6 groups: 1) SX f an operation and SX pump discharge temperaturo Limitin0 Conditions for Operation (LCO), 2) SX f an o 3eration Action Requirements,

3) UHS cooling tower basin level switch operability, A) addition of the provision that Specification 10.4 M not applicable to the SX makoup pump Action Requirements,

5) editorial changes, and 6) Tochnical Specification Bases rewrito.

1. Essential Sorvico Water Fan and Tomperaturo Limiting Condition for Operations (LCO)

Description and Dasos.of.the Current Requiroment The current Technical S aecification 3.7.5.b requires four Essential Service Wafor System (SX) fanc operaale with only one unit operatir.g. With both units operating,3 fans with power supplied from each unit are required to be operable for a total of six fans. LCO 3.7.5.d requires the SX pump discharge temperature to be less than 80'F with less than 4 f ans running in high speed or less than 98~F with all f ans running in high speed.

The current Technical Specification fan operability requirements are based on the original cooling tower analyses which determined the SX pump discharge water temperature remained less than 98'F. Therefore, the analyses verified that the temperafure of the water inventory within the UHS basin remains less than the design maximum value of 100" F. This 100~ F temperature limit is specified to assure: 1) the maximum Reactor Containment Fan Cooler inlet teraperature assumed for the contalnment heat removal safety function is mair'tained; and 2)

, the inlet 'emperature assumed for equipment coolers serviced by the SX System is not exceeded. The original analyses considered a time dependent LOCA heat load that peaked at about 100 seconds at a value of 556 MBlu/hr, utilized the thermal capacity of the essential service water and assumed the following: 1) an

) initial SX pump discharge temperatura of 90'F,2) 78#F ambient wm oulb temperature, and 3) four cooling tewer cells available to accommodate the d9 sign basis acciaent heat load (References 2 & 3). Six of the eight cooling tower cells were required to be operable during two unit operation. A single active f ailure of the emergency diesel generator was postulated to cause the loss of two cooling tower f ans, leaving four cooling tower cells available to remove the design basis heat load.

t ZNLD/1645/6

Description arr.f Bason of titoBoquestod Ibviulon Technical Specification LCO 3.7.5.b is being revised to require 6 f ans operable in the high speed mode with either one or both units in Modo 14. The revision also removes all unit specific fan requirements. The essential service water pump discharge tomperaturo limit in LCO 3.7.5.d is being reduced from 98'F to OG' F.

Unchanged is the statement that whon the SX pump dischar00 temportaure is between 80~F and its upper limit (06" F in this proposal), then the required operable f ans must be running in h;gh speed. The 90*F SX pump discharge tempstature limit with all operable six f ans running, assures that the inliial cold water basin temperature assumption used in the basin temperature calculations for this mode of tower operation romains va!!d. The proposed number of fans tmd temperature limit requirements are based on the results of calculations perforrned for the reconstitution effort. The calculations perfonned are explained in dntall

' below.

Time dependent basin temperature calculations woro performeri to dolormine the temperature response for the essential service water system. The results of the calculations verified that the basin temperaturo does not exceed 100'F under the postulated accident scenarios. The basin temprature calculations used the following a3sumptions!!nputs:

a. The rationalo for inillal cold water basin temperature was as follows:

1. Both the current and 3ropased Specifications (la not enquire any fans running in high speer when the basin temperature is less than 80'F.

Thorofore, a group of aingle f ailura scenarios were analyzod assuming an initial basin temperature of 80'F and assumina no fans were initial y running. These scenarios did not take credit for DHS heat transier to the atmosphere until post LOCA operator actions were initiated to open riser valves and stari f ans. Durin0 the initial chase of those calculations the thermal capacity of the water present in 11e SX System and cooling

. tower basin was solely relied upon to accept heat. Figure 2 depicts the basin temperature responso for the worst caso scenario starting at an

) initici basin temperature of 80*F, that of a single cooling tower fan failure.

2. Scenarios were analyzed assuming an initial basin temperature of 88"F. Existing administrative controla for the UHS require unit shutdawn if the tower bcsin temperature is over 88'F. In these scenarios, UHS heat removal was crodited immediately followbg the event because present administrative controls require six tower f ans running in high speed when tha basin ten perature is greater than or t equal tu 80^F. Dependent upon the scenario, the f ans not subject to a

/ single active f ailure, would either remain running or auto reenstgize 7 with the respective diesel generator output breaker auto-closure.

ZNLD/1645/7

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3. Scenarios were analyzed using the proposed SX a discharge temperature Technical Specification limit of 96' In F.pum t lose scenarios, UHS heat rernoval was credited immediately following the event j because the proposed spec,tication and administrative controls will require six tower fano runnin0 in high speed when the basin i temperature is greater than or equal to 80'F, Dependent upon the j scenario, the f ans not subject to a sin 0l e failure, would auto reenergize ,

with the respective diesel generator output breaker auto closure. The 1

oeak basin temperature was determined to occur for the case of n ,

dalled cooling tower f an, in combination with two previounty OOS fans.

This case resulted in only G f ans running in high speed. The heat load l for inis case (Figure 4), corresponds to that generated with 4 RCFCs  !

and 2 CS this case.purnps. Figure 3demonstrate The calcuiations depicts thethat basin the temperature peak basin response for 1 temperature does not exceed 100'F.  ;

i

4. S:enarios were analyzed usin0 the existing SX pump discharge l temperature Technical Specification limit of 98'F. In these scenarios,  !

UHS heat removal wac credited immediately followmg the event because administrative controls require six tower fans running in high

_ speed when the basin temperature is greater than or equal to 80"F.

Dependent upon the scenario, the f ans not subject to a single active  :

fallure, would auto reener0ize with the respective diesel generator  ;

output breaker auto closure. A series of engineering calculations ,

demonstrates that with an Inillal basin tempetature as high as 98'F the  :

design basis accident scenario would result in a peak SX temperature  ;

of 100.5'F. It would remain above the design limil 100*F for less than 10 minutes, ,

b, Cooling tower cold water basin level was assumed to be at the Techn! cal Specification minimum of 50% This conservatively provides the minimum '

dval!able Volume of water inventory in the VHS basin and for the SX system 4

to serve as a heat sink. Basin levels above 50% provide additional volume that would increase the thermal capacity of the water inventory and result in a lower peak basin temperature, i

c. Inlllally, the essential service water system was assumed to be aligned in the normal operating configuration of one pump operating por unit, the pump discharge train crosstle valves open, the pump discharge enK-crosstle '

valves closed and the return header croastie vaves open. The norma!!y operating heat exchangers and coolers were assumed to receive flow.

d. It was assumed that two cooling tower cells were initially out of service and -

the corresponding riser valves were closed since current requiremente of Technical Specifications allow this. The scenarios considered either one

' cell out of service on each tower or two cells out of service on one tower, depending on whichever was the most limiting. ,

ZNLD/1645/8 I ,

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o. Tower bypass valves were assumed to be closed.

f. When operator actions were required in the main control room, it was  ;

assumed the<;e actions occurred 10 minutes following safeguard signals.

This caused a ten minute delay before heat romoval via the f ana began. i The 10 minute delay allowed the main control room operatcr to reach the  :

a >plicable step in the Byron Emergency Procedures and complute a lpnment of fans and riser valves on the cooling tower. This was a L reasonable ascumption because all actions are achlovable from within the control room, the actions apaear early in the emergency procedurou, and no locai operator action is requ red.

g. The two essential service water pum as on the accident unit were assumed [

to operate following ths LOCA basec on auto stad signals, unless the single  !

active f ailure prevented ene pump from starting. The non accident unit pump that was running Initially was assumed to remain tunning. It was ,

assumed that only one non accident unit SX pum? was running in the post accident mode since the non running pump woukl not receive an auto start -

signal.

h. All safety related essential service water system heat exchangers and coolers were assumed to be aligned for service based on ESF sl0nals created by post LOCA conditions, j

l. The flows to the individual tower cells were determined based on the system alignments under different accident scenarios. The data was used to .

determine the amount of flow and energy going to each of the cooling towers. l J. The steady state heat loads of 31 MBlu/hr from the accident unit and 72 -

MDtu/hr for the othar unit were used. These steady state heat loads were '

added to the LOCA tJnit containment heat loads to obtain the total heat load t

n the UHS for the basin temperature calculation. The LOCA energy piofiles for various single failure modes were obtained from a calculation

• performed by CECO. As an example, Figute 4 graphically represents the transient UHS total heat load generated from 4 operating RCFCs and 2 operatiry CS pumps. This calculation provides the highest integrated head load over an 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> period. Th9 corresponding response of basin temperature is shown in Figures 2 and 3.

g k. An amblerit wot bulb temperature of 82*F was utilized for the analyzed I cases.

I. Tower perdormance was modeled using a computer program developed by Environmental Services Corporation (ESC), modified to specifically represent the Byron cooling towers, in all of the cases, the cooling tower ,

performance curves were generated using a flow slightly higher than the

< average tower cell flow. This method gave a conservative estimate of the ,

tower performance since the tower performance decreases with- '

l cooling' increa sing flow, assuming a constant number of cells in service.

ZNLD/1645/9

. Several of the asnumptions utillred in the calculations were inherently a a conservative. These co_nservatisms, while not being quantitatively analyzed, provide additional rnargin to the 100"F SX system basin design temperature.

. Some of the majoLconservatisms are.

1) Basin level was assumed to be at the Technical Specification minimum of 50% The basin is normally maintained at 82% level, which would provido additional water inventory heat capacity,

2) No credit was taken for ambient heat dissipation in passive coolin010W0f cells (i.e. those cells with riser valves open but the fans off). Any cooling that occurs from these passive cells or from fans running in low s aced would fudher limit basin temperature hence providin0 mere marg n to the maximum allowed basin temperature.

3) The 80"F basin tem >orature calculations which bound operations of the tower at s 80T bas n temperature assumed 10 minutes for operator action to align riser valves and start the fans in high speed. The fans will be running in high speed earlier than the analysis assumed when stmted in accordance with emergency operating procedures.

4) No credit wa9 taken for the cooling contribution from the makeup flow of any of the makeua systems. The makeup system for the UHS takes a suction from the Roc s River or from the deep well system,

5) More f ans than assumed in the analysis are usually maintained functional.

The time dependent basin temperature calculations were performed using the fan operability requirements 3roposed in LCO 3.7.5.b. Initial basin temperatures ranging from 80*F to 98': were used to analyze the post accident basin temperature response following a variety of postulated failures. The scenario that provided the highest peak basin temperature was when there were 4 operating RCFCs,2 operating CS pumps and a single f ailure of an SX cooling tower f an (worst case scenario). The peak basin temperature remained under 100'F with an initial basin temperature of less than or equal to 96'F for all scenarlos evaluated.

The SX pump discharge temperature limit of 80*F, with less than 6 f ans running, assures that adequate thermal capacity is available in the SX water inventory to absorb the initial heat input prior to oporator action to open risers and start the

) cooting tower fans. Operator action in the Contral Room is assumed to occur at ten minutes after the event initiation. In that time, SX basin temperature is assumed to increase until the operators have re aligned the coolin0 tower.

Two assum'!d failures that directly affect tower functionality are a single SX f an failure or a single emergency diesel generator (EDG) fatlure. Failure of any SX fan (starting with 6) will result in 5 fans remaining to dissipate the heat from the

' postulated accident. For these scenarios, the remaining f ans are sufficient to remove the full LOCA heat. Faiko of an EDG could result in a total of only 4 tans being available (assuming 2 initially OOS and loss of 2 more f ans), if an EDG were to fail on the LOCA/ LOOP unit, on1y one SX pump would be running to cool the essentialloads, m addit!on, one RCFC train would not operate as a result of the EDG failure. The fans of the affected RCFC train would remain do9nergized and the RCFC discharge check dampers would close. The resultant heat removal from the LOCA containment would be approximately one half of the value calculated for cases where all 4 RCFCs fur.ction. For these scenarios any 4 SX fans are sufficient to remove the LOCA heat.

ZNLD/1645/10 v . _ _ ___ ___ _ . _ d

. For cassa where basin temperature is >80*F but <90'F, calculations essumod that the tot ulrod operable fans v ore initWly running in high speed, Tho same number of inns as discussed for each nt tho casos above are requirod, Tho difference is that with the temperature above 80'F, the fans need to be running, impact of IIm Proposed _Clutnge The proposed changes for the LCO in conjunction with the original LCO requ rements reflect the conditions and assumptions of the design calculations.

With this.nowly defined sp3cification, the UHS will always be in a conditbn to perform its specified function assuming' a worst caso single active f aiiure and under worst case environmental conditions With the basin temperatur9 loss than 80"F, no fane need to be running initially because the calculations have shown there is sufficient time for the operators to manually start the f ans during a design basis limit!ng accident scenario and still koop SX cooling water temperatmos under the 100"F limit. With basin temperatureo above 80'F and less than or equal to 90'F, f ans running in high speed are needed immediately at the onset of the design basis limiting accident scenatio. Consequently, the LLO iequires fans to be running in high speed when basin temperatures are in this rango,

2. Essential Service Water Fan Action Reqdrerrmnts Description andBaeos of CurtontBequirement

Technical Specification 3.7,5 Action b requires that if one of the f ans required in the LCO combination is inoperable then it must be restored within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or the unit must bo shutdown; The UHS could periorm its specilled function under the design basis limiting accident scenario if a single active f ailure is not assumed.

Only 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> of continued operation are allowed in this degraded condition.

Tachnical Specification 3.7.5 Action (d) requiros the appropriate unit (s) to be in Hot Standby in 6 houro and in Cold Shutdown in 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> if an ossential service water pump discharge temperature exceeds the LCo limits of Specification 3.7.5.d. At Byron Station, pump discharDe temperature is the only installed indication that conservatively reflects the UHS basin tamperature. Since both units' SX pumps take suction from each of the UHS basins, this action requirement, In effect, would require both units to shutdown if both units woro in 3 Modes 14. Exceeding the basin temperature limits would put the units in a condition outside its design basis analysos; consequently, an immediate shutdown is iequired, Dascription and Bases of the.BequestedBevision Technical Specification 3.7.5 Action b is being revised to require that if only 5 fans are operable in thu hl0h speed mode (LCO 3.7.5.b), then within one hout verify that the remaining fans are capable of being poworod from their respectivo diesel generator, Rostore at least G tans to operable status in 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or shutdown the units.

ZNLD/1645/11

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l During operations with a unit la Modes 14, emergency diesel Generator (EDG) l inoperability on the unit susceptible to the DBA LOCA' LOOP, is constrained by Technical bpecification LCO 3.0.1.1 which provides maximum allowed outa00

, timos (AOTs) for either a single EDG (72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />) or two EDGs (2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />) inoperable. Af ter this AOT is used, the subsequent action specified is for the affected unit to achieve Hot Standby conditions in G hours and Cold Shutdown in the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />. The existing action requirements of Specification 3.8.1.1 assure a limned this of unit operation is allowed for conditions involving inoperable EDGs.

Dudng a DBA LOCA/ LOOP on one unit. or only a LOCA on one unit, calculations show that 5 SX fans are necessary to dissipaie the energy assuming all ESF equipment functions. Four SX Fans are necessary to dissipate the energy when unavailability of an EDG, in conjunction with an offsite power loss to the LOCA unit, results in approximately one. half containment heat iriput.

The "EDG requbement' of Action 3.7.5b assures that possible concurrent reliance on the actions of LCO 3.8.1.1 does not result in an unanalyzed condition, while continuing to operate under the provisions of this action. It is important that at least 4 f ans are powered from their respepthe einergency diesel generators since the analyses for one half containment heat input assumed 4 fans are running in high speed either at the onset of the accident (for scenarios analyzed at 90"F) or at 10 minutes into the event (for the scenarios analyzed at 807) Present emergency procedures start f ans with supplied ESF power either from Station Auxiliary Transformers (SATs) or emergency diesel generators. No credit is taken for cross tying the ESF buses to provide an emergency power supply for any f ans, although this could be done if it were necessary. In conclusion, the additional requirement of an EDG being operable for each f an telled upon assures the minimum number of fans are available to safely shutdown the plant assuming a DBA LOCA/ LOOP on one unit ar'd a concurrent safe shutdown of the 4

opposito unit.

No change to Technical Specification 3.7.5 Action (d) has been requested.

Impact otthe Proposed Chango The proposed Action Requirement b is consistent with LCO Action Requirement development methodology. When observing the conditions of this actbn requirement the UHS can still perform its specifiwd function for the design limiting accident scenario: however,it cannot meet the single active failure requirement.

The 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> allowed outage time has not changed. Since AOTs and limitations on the degree of eqabment inoperabl.ity are specified, the operation allowed by this action statement s consistent with accepted methods. l. aquipment is degraded beyond the limitations of Action 3.7.5.b, then Specification 3.0.3 applies

3. UHS Cooling Tower Basin Level Switch LCO, Action Requirements, and Surveillance Requiremente Description and Basos.of the Current Requiremont There are currently no explicit operability requirements for UHS cooling tower basin level switches. Byron Station conservatively interprets the current Action 3.7.5.c to mean that when a basin level switch fails, the automatic start signal to the essential service water makeup pump is not operable, and thmefore the makeup pump is considered inoperable. This is very conservative because the makeup pump is still functional and can be started manually either from the main control room or locally. The control room bacin level indication is not related to the level switches that auto-stait the makeup pumps. Therefore, operators have levelindication if a level switch were to fail.

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Descriptkm and Bacos of.the Roquwtod Revision A new requirement is proposed in specificetion 3.7.5.e in require two operable

. UHS cooling tower basin level switches. The corresponding action stat 9 ment would require within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> that, with one switch inoperable, the switch be restored or both basin levels be vorified > 82% within the next hour and overy 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> therealtor. Othnrwise, the reactor murt be in at least Hot Standby withh the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in Cold Shutdown within the followinn 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />. If both switches are inoperable, the action statement requires, within one hour, either restore one switch and follow the first action requirement, or verify both basin levels are > B2% overy 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. T he shutdown requirements would be the same as above. Alco included is the requirement to provide a special report to the Commission if any of the switches are inoperable for greater than 30 days. A surveillance inquirement is also proposed in 4.7.5.g explicitly requiring that the UHS cooling tower basin level switches bo demonstrated operable by the performance of a channel calibration at least once per 18 months.

The new besin level switch operability requirements provide an alternate method to maintain the sequired UHS cooling tower basin level when a basin level switch is inoperable, preventing essential selvice water makeup pump automatic start on low basin leve;. With an inoperable basin level switch, basin level is increased to a point that a surveillance can adec uately ensure that the bas ln low level limit of 50% is maintained. Dunng this per od the makeup pumps would be manually started if required to maintain basin level.

The proposed Action e., which iaises level to 82%. is similar to the actions for one essential service water mhkeup pump inoperable (Action c.2), high Rock River water level (Action f 1 & f.2), low Rock River level (Action g.2.a & g.2.b), and a ton ado watch (Actions h.1 & h.2).

The basis for this action was provided in an application for amendment to Facility Operating Licenses NPF-37 and NPF-66 transmitted in a letter from R.A.

Chrzanowski to Dr. T.E. Murley dated May 24,1989. Technical Specification Amendment 32 was aparoved by the NRC as documented in the Safety Evaluation transmitted ay a letter from L.N. Olshan to T.J. Kovach dated Augut,t 15,1989. These amendments modified Technical S accification 3.7.5 to utilize the se!smict.Ily qualified deep well pumps in several nstances instead of the essential serv co water make up pumps to satisfy the design bases of the ultimate heat cink. Since the deep well pumps do not have an automatic start feature on low essential service water bas n level, a calculation was performed to determine an initial increased operating level, such that basin level would not f all beinw the Technical Spocification limit withir, a specified surveillance time interval.

The cciculation took into consideration basin inventory losses from evaporation, blowdown and drift for " worst 30 day" and " worst day weather condition periods, and a heat load on the tower that corresponds to power operation on one unit and normal shutdown on the other unit. Normal makeup was assumed to be lost.

This calculation datermined that if the basin level were raised to 80% and verified every two hours, a sufficient inventory of water would be available in the basin at the start of an accident which relles on cooling tower basin inventory for mitigation.

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During the porlod when tho casin lovel switches are inoperablo, there may be ovolutions that affect level beyond the evaporation, drift, blowdown and heat load requhements resulting from stmting or stopping an essential service water pump,

, changing riser valvo positions, er backwashin0 stralners. Of those evolutions, i bachwashing the strainers has the greatest impact on the UHS coollr tower basin lovel. An additional mar 0 l n of 2% was added to the Technical ocification basin level when the level switches aro inoperable to account for basi lovel changes during strainer backwashing. Therefore, basin level will be raised to a 62% At 82%, water level is above the basin overflow and the basins are ,

interconnected. The essential service water makeup pum s can be started as  :

roc utred. Increasing the basin lovel to > 82% and vmilyin lovel ovary 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> '

wil onsure that the water lovel remains above the Techni l Specification minimum of 50% i As part of the design reconstitution effort, an updated analysis was performed to determino the effect of increased accident heat loads on the evaporation rate and i the adequacy of the makeup system to rep!onish basin inventory. T hoso calculations evaluated the basin volume change as a function of time. The fire 1 calculation evaluated makeup from the Rock River using the SX makeup pumps )

starting with 60% initial basin lovol. A singlo active f ailuro caused ono SX  ;

makeup pump to fail. The calculation took into consideration basin loventory losses from blowdown, auxiliary feedwater supply, evaporation rate based on metaorological conditions for a worst 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period and heat load on the tower that corresponds to the bl0nest inte0 rated heat load for the first eight hour

_ period. Th,s calculation determined that adequato makeup capacity exists to replenish basin inventory.

A second calculation evaluated makeup frorn the deep well pum as. The accident scenario assumed the makeup from the Rock River is unavailab o due to low flow or level, basin levelis initial'y at 82%, and a single activo failure caused one doop well pump to fail. A two hour delay was assumed for the operator to start the deep well pump (s) locally and to align the systnm to deliver water to the basins.

The calculation used the same basin inventory losses as describod abovo. This calculation also datormined that adequate makeup capacity oxists to replenish basin inventory and that adequate inventory exists in the basin throughout the event to assure SX system operability.

Actions e.1.a and e.2.a state that the provisions of Specification 3.0 4 are not

, applicable. This allows modo changes while in the Action statement Ior the inoperable basin level switches. The basin levelis maintained al a conservatively hig11evel since automatic makeu? Is not available. Previous calculations domonstrated there was sufficiem time to manually initiate deep well makeup to the UHS. The same reasoning applies to the essential service walor makeup pumps. Considering that the essential service water makeup pumps have a greater capacity than the deep well pumps, level would recover more mpidly.

Since there is still redundant manual maknup capability to the basins and sufficient time before manual action is required, it is acceptable that the provision of Specification 3.0.4 is not applicable.

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impcciof.ttnProposed Chango The proposed change provides an alternate method to maintain UHS cooling

, tower basin level when basin level switches are inoperable. Tho altemate method is consistent with existing Technical Specification actions that replace automatic makeup capability with manual makeup capability. Based on design calculations the proposed alternate basin levels and surveillancu provide adequato measures to assure that basin inventory is available to support UHS and essential servico -

water operation for normal operation and accident conditions. Therefore the proposed change has no impact on plant safety.

4. Essential Sorvice Water Makeup Pump Action ihquiroments Description and Dasos of the Current Hoquhemonts The current Action Requirement for SX Makeup trains does not allow a mode change pursuant to Specification 3.0.4. ,

Description and Bases of the Proposed Hoquirements The proposed change to Action c.2 adds that the provisions of Specification 3.0 4 are not applicable. That is a unit can enter into an oporational mode with one essential service water makeup pump inoperable as long as the scme train deep well pump is operable and both UHJ cooling tower basin levels are greater than or equal to 82A This is consistent with the Techn! cal Specification 3.7.6 requirements of Actions f.1, g.2.a., arid h.1. Engineering calculations have shown that the UHS can periorm its specified function 1or the limiting accident scenario with both deep well trains aval able as the only source of makeup water.

The inter.t of Specification 3.0.4, in general, is to ensure that facility operation is not initiated with inoperable equipmont or systems. Exceptions to this provision are allowed if it can be demonstrated that the inoperable equipment does not affect plant safety, impact of.ttaPropwett Change This change has no impe:1 on p! ant and public safety. The backup deep well

train and increased basiri levei requirement provides sutlicient assurance, for the l maximum of 14 days that a train cf SX makeup may be inoperable, that adequate

! makeup flow will be available. The deep well makeup trains are seismically qualified and powered from an ESF bus. An allowance for the unit (s) to enter an operational mode, with one train of SX makeup inoperable and the compensatory

! actions of increasing the basin level and verifying the corresponding deep well train is operable, does not affect plant safety.

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5. Editorial Chan[ps The following changes are considered editorialin nature 10 correct, clarify or otherwise unclutter the Specification. These changes do not,in any way, affect the technical or regulatory requirements of the Specification,

a. The first sentence of Specification 3.7.5 is revised to state that thu ultimate heat sink shall be operable. T his is more accurate than stating that a'l of the LCO requirements are applicable to the cooling tower 3. In addition, there is one cornmon ultimate heat sink, not two independent sinks.

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b. proposed changes to LCO a. Action a, and Surveillance a express the cooling lower basin levellimit as apercentage. There is no reading available for " feat Mean Sea Level . This correspondin0 elevation is being moved to the Danes sectkm. No change to the operating limit is proposed.

LCO a is reworoed for consisteacy with the LCO format.

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c. The footnote is being deleted from LCO 3.7.5.d because it is no longer required. Th!s appfled during UHS cooling tower performance testing, which is now comp!ete. The corresponding asterisk is also deleted,

d. Specification 3.7.5 Action c revisions include correcting a punctuation error in the first line, and using the proper ca pitalization of " status" and

• MODE".

4 Mode should be capitalized because it is defined in the Technical Specifications; status is not, The proposed action verifies that both basin levels are greater than or equal to the limit for consistency with the other action statements, in addition, the last sentence will appear as part 3 to maintain a consistent format. An extraneous hyphen is be!ng deleted from "30. hours",

e. The word " continued"is being deleted from the Surve!ilance Requirements page because 11is the first page. The revision to Surveillance Requirement 4.7.5.d clarifies that f an operability must be verified in the high speed mode. Verifying high speed mode operation is also consistent with the LCO requirement to rnaintain the required fans capable of running in the high speed mode,

f. Changes in Surveillance Requirements 4 7.5.e.2 and 4.7.5.e.4 to add the words "at least" before "30 minutas" and "15 minutes"is a clarification. The diesel powered SX makeup pump shall be operated for at least 30 minutes and the deep well pumps shall be operated for at least 15 minutes; not operated for exactly 30 minutes or 15 minutes, respectively.

g. An additional change to Surveillance Requirement 4.7.5.e.2 deletes the requirement that the test signal be simulated. The low basin level test signal may be actual or simulated, allowing more flovibility in performing the t,urveillance.

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h. A surveillance that requires a visual inspectian to verify that there is no abnormal breakage or degradation of the fillinsterials in the UHS cooling

. The ideatical tower is being surveillanc9 added cunently requirement as Technical exists inSpecification Technical 4.7.5]dpecificabon 4.7.4.

and it will be removed in a futuro Technical Specification amendment being developed in response to Genetic Letter 91 13 " Essential Service Water System Failures at Multi Unit Sites" This change is proposed because the cooling tower is part of the Ultimate Heat Sink, and surveillance of the tower till materials is more appropriate in Technical Specificailon 4.7.5.

- 6. Technical Spocification Bados Description and Bases otthe.Cunent Hequkoment The current Dases for Technical Specification 3/4.7.5 is reviewed in the previous sections of this proposal. The f an operability and basin temaeraturo limits were -

selected to ensure that adequato cooling is availablu for crit cat safety related equipment and to ensure adecuate heat dissapation capability for a DBA contaipment heat load.

Description and Bases of the Requested Revision The Bases were re written to reflect the results of thn design basis reconstitution effort initiated for Byron's Ultimate Heat Sink. This study identified items that were indeterminate or different from those prevluusly assumed for the UHS in the UFSAR and UHS design analysis. These items affected the calcultited performance of the cooling towers during a postulated design basis accident.

The current Bases were re evaluated and revised based on calculations incorporating the limiting design basi 9 uvent with cortain postulated equipment failures. Discussion of basin temperature following a design basis tornado event has been removed from the Bases.

impact oltbe. Proposed. Change

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An ultimate heat sink design bases reconstitution effert and operability assessment process re-defined the design basis accident find identified new l limits. The new ilmits assure that the UHS I& capable of performing its two l- principle safety functions of dissipating decay heat energy after a reactor

shutdown and dissipating decay heat eaergy and containment stored heat energy l .. following an accidant. The bases were re written to incorporate only those items l applicable to Technical Spec!fication Limits.

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i References

1. January 9,1992 leller f om T.K. Schuster to Dr. T.E. Mutley, UHS Design  :

Basis Recons!1tution Final floport.  ;

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2. May 29,1987 lotter from K.A. Alnger to USNRC, Document Control Desk.  !

Essential Servico Water Cooling Towers.  ;

, 3. May 26,1987 letter from K. A. Ainger to USNRC, Document Control Desk, Essential Service Water Cooling Towers.  !

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