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yf "- . VruorwrA ELECTRIC AND PowEn CoxvAwy,

: Rxcnw oxn,Vzmoxx xi20261 --

T

March-20, 1980

s

Mr. Harold R. Denton,iDirector Serial No. 252/030780Office of Nuclear Reactor Regulation' LQA/WRM:rab

~

. Attn: ~ Mr. Olan D.-Parr, Chief.' ~ Light Water LReactors Branch No. 3' Docket No.'50-339

- Division of Project Management'

U. S. Nuclear Regulatory Commission .

. Washington, D.C. 20555

' Dear Mr. ! Denton':~

We have received the request for additional information forNorth Anna Unit 2 from'Mr. Olan D. Parr,: dated March 7, 1980,~ pertaining'

to achieving cold shutdown using safety grade equipment.

Enclosed are our responses to the questions received.- If youhave.any questions, please contact this office.

Very truly yours,

-h. M,,J$WZ .

C. H. StallingsVice President-Power Supply

and Production Operations

l .

i Attachment-j..

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8003'210107~

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JQUESTION 1':: JPfovide safety-grade steam generator dump. valves,: operators,~ . air _and power supplies which meet.the. single-failure criteria.s

. -

. .

: Provide a commitment to demonstrate the ability to manuallyW .t'

. |'

ioperate the atmospheric steam _ dump _; valves and demonstrate.

| theJab111ty to conatunicate' with the control room while doing-- ,

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'.. .c 1 RESPONSE:

'Esch North Anna ~ steam generator'is. provided. with one safety grade seismically

- .. supported atmospheric.. dump . valve (PCV-MS-201A', B, C). . Control air is_

,

supplied;to the~ atmospheric' dump valvescfroa the Instrument Air System,

which is fautomatically backed. up by:the Service Air System. : Air is delivered' '

|to the.' valves through a seismic qualified 2-inch header from the Auxiliary-s

; ,.

The;2-inch header is reduced to a 3/4-inch seismic qualified header,in.-

-Buildin8.-

.the Hain Steam Valve House. The.3/4-inch header. splits and supplies each

of the valves through individual check valves. Located between the checkc

. Evalve.and the respective atmospheric dump valve ~ is a connection to a backup '

.

-supply. tank-(2-IA-TK-4A, B,-C)-for'.each of.the' dump valves. The seismic"

,

3, . qualified tanks each have a' volume of.-16.7 ft at 110.psig. The tanks are

1 maintained'at pressure by the instrument air header. The check valves pre--

,

; vent loss of air from the tanks back through the' instrument air header should

'the Instrument) Air System be we depressurized. ' Electrical power to the

, electropneumatic| controller, which" controls _ the valve position, is provided' to each. valve from separate channels of uninterruptable safety grade powar

,

from independent station batteries.

' The most.'115titing single failure would be the loss of one main steam line_

: atmospheric dump _ valve. (This could be caused by the loss of 'the~ electrical,

ichannel which supplies power to one' atmospheric dump; valve. This situation,

- - 3 ,'would prevent' operation of Lone atmospheric dump valve from' the control room.,

. J ? Two" valves would still be available to control cooldown.-? ,

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The Main' Steam Valve House.is:a seismic qualified Class-I' structure which'' - :

[ [has four;1evelsibeginning at' ground level. - The first level:contains the

L air |; tanks [for the atmospheric dump. valves an'd miscellaneous valves. In

, ' ' . . - . . .~

.

. .

,

: the second level 'are ~ the main steam trip valves 'and the third level contains

5 the main steam non-return valves. ' Loc'ated -in the fourth level are the steam--'

, generator code safety' valves, atmospheric dump valves, .and the decay heat -_

release: valve.. If.? required, the atmospheric dump valves could be operated_

,

' locally in the main steam. valve house using a handwheel which is accessible

to operating:1.ersonnel.;- Commukication with the control room is auilable

;using either the page. party system or hand held two way radios. The ability~~

[~

to manually operate the atmospheric steam dump valves will be demonstrated,

,

? prior to completion of the power ascension' test program.-

M

The other cause of failure of one atmospheric dump =valire would be_ a-

f

. mechanical fsilure'~ of the . valve. In'this case the operating personnel could

circumvent the single ~ active failure as follows:i

u

.y .

. L(a)' : Bring the plant down to the RHR cut-in conditions via the decay-

iheat release'line. :If. th'is cannot be done, North Anna will

fproceed as in (b)...

1 .

|(b)? Alternatively, the failed atmospheric 1 dump valve could be isolated'

Iby:an isolation . valve up stream of the dump valve. ' The d"mp

-- valve could then be repaired or, replaced if required.i

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M[s c' ~ ! QUESTION /2: ' jProvide the-cap' ability stoicoolldownito the RHR cut-in point-' jin lessLthan'36Lhours assuming the mostjlimiting single..

_

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'~,.

, L failure 'and: loss of.Loffsite power orf show that1 manual'' ' '

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'

(actions [insidelor outside- containment or -return to hot~

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~ (standby.until"the manual' actions or maintenance can' be . 179~ : "-

_

fperformed to' correct the=failurejprovides'an acceptable'E ;%' ..'

.

;

A_ -alternative.-g.,

*~

lRESPONSE:> \.sz-<

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A ^ * tThe!RCS:isCeapable |of being cooled via natural convection. _ Diab .o. Canyon --

" ' ~ 'f and Salem are prototypical,of " North Anna,' and; tests conducted at Diablo~

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g'D( Canyon.would- demonstrate the. ability to cooldown to RHR initiatien onE,j .

h M, )naturalconvection.;'Thetime'11mitof-36to48.hourstothe-RHRcut-in'

- 1 point currently suggested.seems reasonable, barring unforeseen: diffi ,4, 3

_ _cculties,:but prototype testing at Diablo' Canyon will verify the time'

.

.

'

.H' t.requir'ed for this operation.' '

,

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,

"' ,~ '_ North Anna, since;it has'only'one RHR suction line containing two safety-., ,-.-i

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Egrade! series valves for: tie-in of.the: RCS. to the RHR, might be constrained~

' * ~.. . ; . . . .

~ tbyc the mechanical failure of' one of these- valves to open to: af feet ' the-

.

finalltiein.'

. In this . case the cooldown by. natural . convection would be1 :

v.

_

continued as Lfar as pos'sible below- the -3500F--450 psig ' normal tie-in. point,^

_

- - the RCS ,would he 'depressurized as far ~as practica1', efforts would be made-^

-

.

t to openj the stuck valve . (via handwheel, ; thermocycling,' etc.), while steam3._:x - , r --<,f

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< dump via the steam 'generatorslis -. continued.. . -

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. :The' probability |of a fallureJof.one of these valves:(MOV-2700 andL4 ip y +

q ,J M.0V-2701) 3s t extiemelyf remo te'.'These valves are powered' from. dif ferent12, .i q +

,w .m ~

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, , ' ' " { emergency powerstrains.. Failurinof either-power' train or of either valve''J ,

p[: ,' ,- ..

W operator, could prevent; initiation 1of RHR cooling'~ in :the normal manner from -a--

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. _.* ?f.L the fcontrol room. O_ In -the : event of such a failure,! operator action' could '.m ,.

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]N' .beitaken to open'the affected valve manually._.The; mechanical failure ~

j of(theidisciseparating;f rom the.st'em:has been investigated '(WCAP-9207)-,

~.and 51ts probabiliby has b'een' found t'o.be in the- range 'of 10-3. to 10-4 per:~

~

",

Lyear. 2The' probability of~an earthquake larger thAn the'0BE at North Anna;

iis[10j2|to-10-3 per year.: The combined ~ probability.of valve at'em failure co-,

fincident with the earthquake:is 10-5.to 10-7 per year, so. low that it ne'ed not be' ' J'

,

considered 'in;_the ' single f ailure analysis.: .Inithe ' event of such a failure' -

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ithe plant would remain'1n a. safe hot standby condition with heat removal-

'- ;via' the steam generators.

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- f .QUESTIONi3 D Provide the capability to depressurize the~ reactor coolant~

'

isystem with only'. safety-grade systems assuming:a: single-~

,

J failure and ' loss fof offsite power or show that manual ~~

-

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i actions inside or ~outside' containment or | remaining at hotc

U * istandby..until manual ~' actions or repairs are. complete pro--: vides an acceptable alternativer-

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RESPONSE:7

sm

^ t. $he reactor-coolant" system;is normally'depressurized.by means of the-

.

pressurizer auxiliary spray, -_ fed ' through a single. valve HCV-2311, - from

the' d'ischarge of the centrifugal'' charging pump (s). Should this 3-inch'."

: valve ffail':to open following .a seismic event every effort would ~ be made =

'.to''open itivia portable compressed gasicylinder,; or 'by maintenance, 'and '* ~

. -

.if these attempts fail: system pressure could be reduced by blowing thei. ; '

~

. -pressurizer down-through'one of the two parallel power-operated relief>r

valves provided for this pyrpose (PCV-2455C or PCV-2456). The power->

- operated relief: valves are seismic Category I.and meet the applicable.

IEEE-279, standards..

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g 4._ , [ QUESTION:4:E'iProvidelthe capability; for borating with.only, safety-grade '.''' n" ;/ systems 'a'ssumingia single 1 failure and Lloss of offsite power_

'

_C , _ : c:6 iorfahow:that manual. actions inside or outside c'ontainmentiors'~

'7

.2

~'% remaining at hot-standby until. manual action. or repairs are*

s

? ~ completed provides anfacc'eptable alternative'.; , ,

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, MRESP'ONSEij' ~ 'i

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sThe normal?methodItio heavily. borate. the Ndrth Anna RCS is to take suction'-

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.

. . . . . . .,:

. ,C ;for:the,chargingL pump (s) f rom: thel 12, percent boric' acid solution' of; the~

,,

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a j

Kboric acid storage tank (s)jia|the boric acid transfer pumps and the+.

:c% ( _ :n'ormal charging}1ine.;?This(is'a' safety grade route.- An alternate method _,

. of' boration is to -align'~theidischarge. of.' the borie- acid Lpumps, as above,;,

. .;..' ,e,, .. . . . ..

. . .

. . iand' align the discharge of one ' centrifugal charging pump with the RCS-'~

~

'- | through the Boron Injection Tank (Normal safety injection piping to the

*' RCS)'. ;

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Should a single failure of a common italve 'in the normal charging line'<

| (occur, every; effort wodid_(be made to open it via har.dwheek.etc, and if-

,.

.

.- these fail?an alternate' boration path would ~be used, , admitting the 12 per-.-. '

''

< . . ,

RCS via the .Boren Injection Tank (Safety -, n Tcent- boric. acid. solution to the. ,-

*,

.,

,

LInjectiion Ro' te) or via the RCPIsaal-injection lines. There'are also~

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safety-grade fl h : paths.s:

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! QUESTION: 5': fProvid'e'a commitment-to perform a. natural, circulation test'

' (including the worst' single | failure) to demonstrate the~

'-

ability to- cool ddwn and depressurize Lthe : reactor coolant' =c-

' system f and to demonstrate L that boron mixing ia suf ficient under.

such' circumstances. -As an. alternative to a test at North~

' Anna provide justification of why, the proposed' Diablo Canyon'

: natural circulation test is prototypical'of North Anna and.

21s bounding.- Any justification should include ' reasons why' ' steam generator.cooldownLand upper head'cooloff for North.

: Anna will be accounted 1for in the Diablo Canyon test. Pro-< -

Evide a conniement to run the natural circulation test atNorth Anna prior to;startup -following first. refueling ofUnit 2 if the Diablo Canyon test is not completed or does,not< provide satisfactory results during the first fuel cycleat North: Anna Unit 2.-

RESPONSE:

North Anna Unit -2 and Diablo -Canyon Unit 1 have been compared in detail to

ascertain'acy differences between the two plants that could potentially,

t affect. natural circulation flow and attendant boron mixing. Because of the

similarity between the. plants, it was concluded that the natural circulation.

capabilities would be'similar, and, therefore, the results of prototypical

natural circulation' cooldown tests being ' conducted at Diablo Canyon sdll be

representative of the capability at North Anna.~

The general configuration of the piping and -components in each reactor coolant

-loop is the :same in both North Anna and Diablo Canyon. Both plants have~

.

Hodel' 51 steam generators and Model 93A reactor ' coolant pumps, Land the eleva-P

E - L tion head represented by these components and the -system piping is the same in

both plants. :

E?To compare the. natural circulation capabilities of North Anna -and Diablo Canyon,

'the hydraulic ' resistance coefficients were: compared. , The coefficients were't

' ; generate'df on a per loop _ basis to permit such a comparison between a' three loop _

:and a four loop plant.-LThe-hydraulic resistance coefficients applicable to

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~ :ndrmal flow conditions.are as follows:u. -I

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~~ fDiablo Canyon' Unit'l North Anna Unit 2

|7.6 x 10-10 ft/(loop spm)2 10.4iReact rlCore & Internals-. 36.8~ 29.6Reactor Nozzles-- 4

24.0 30.0i RCS Piping.

114.4~ 119.6.Steam Generator.; TOTAL, LOOP 182.8. 189.6

,

(182.8)1/2North Anna' Flow.Rati "" *189.6 -Diablo Canyon-,

LThe general arrangement of the reactor core and internals is the same in

North Anna and Diablo Canyon. . The coefficients indicated represent the re-- , '

As exhibited, the difference betweensistance seen byithe flow in one loop. -~

_

-tre internals of.a three loop and a four loop plant results in a higher-

; coefficient.for North Anna.

.

-The reactor vessel outlet nozzle. configuration for both plants is the same.*

The radius.of curvature between the vessel inlet nozzle and downcomer section.

.

-

of the ves'sel on the two plants is different. Based on 1/7 scale model

testing performed by Westinghouse and other literature, the radius on the

vessel nozzle / vessel downcomer' juncture influences the hydraulic resistance

-of-the flow turning from the nozzle to the downcomer. .The Diablo Canyon-

| vessel inlet nozzle ~ radius is. significantly smaller than that of North Anna,-.

as reflected-by the higher coefficient for Diablo Canyon.

f

The coefficient of resistance for the RCT piping in-North Anna is higher than _~

,

that 'for: Diablo ~ Canyon;because of; the -loop isolation valves.- This is the only

'significant, difference between the piping in the .two plants since the reactor

. coolant. pumps 1are the same. and both plants have pump weirs.x .

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JDetails of the'-specific' steam' generator' units.were also compared.to ascertain'~ *, , ,

iany: variation (e.g., primary volume, tube heikht, tube diameter) ;that .could+

I'

. affect natisral circulation capability by changing the effective elevation of-

;the heat sink or,the hydraulic resistance seen by the primary; coolant. It~

a was concluded' that-t'here areino' differences in the original design 'of the

,N : steam: generators'infthe two plants:that would affect the natural circulation

-. e . . ..

.: characteristics. The higher coefficient indicated for North Anna reflects the

| increase in resistance that resulted from assuming that 100 tubes in each:'

steam g'enerator are plugged. -(Thelactual number is 94)..

As indicated, the difference between the total resistance coefficients for.

- ,the two plants"is' insignificant. It is expected' that the relative effect of

the coefficients would be the same'under natural circulation conditions such

-that the natural circulation loop flowrate for North Anna would be within*

;two percent of that for Diablo Canyon.''

,

i

.

The coefficients provided reflect the' flowrate and associated heat removal

' capability of an' individual loop in the plant. The comparison, therefore,.

,

!does not.take into consideration the number of' loops available nor the core

- heat'to be removed. An' evaluation of the North Anna Steam Dump and Auxiliary.

- Feedwater' Systems has-been: performed;to demonstrate that cooling can be~

' provided via all three st'eam generators following the most. limiting single -,

. factive failure,' i.e., , the failure of an atmospheric relief valve.'

',

~

[It can.;therefore, be concluded that the results of the natural circulation_

b deooldown' tiests performed at:Diablo Canyon will be representative of the '

I c:d n'atural circulationiand[ boron mixing capability of;the North, Anna plant.- _Th'e..,

I results of these : tests .will be/ reviewed for applicability. A natural.

L eircul'ation cooldown test' will(.b'e performed; at North . Anna Unit:2 prior to-

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f r.w A if 5st) fuel cycle:at-North Anna'Nnit|2.;-

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W. - d ESTION-|'6i= jCommit to providing -specific. procedures for cooling down'

using natura1Ecirculation and-submit-a'summaryfof *.hese.-L

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^ > .~ RESPONSE:1_ ~~

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Is sQUESTION .7:'- Provide ~ or require a s'eismic Category I AFW supply for at.

least 4 hours at Hot Shutdown plus. cooldown . to the:DHR~

,. system cut-in based o'n the longest 1 time,(for only onsite or-

' Poffsite' power and assuming the. worst' single failure), orshow that:an adequate alternative seismic Category I source

,

- will-be~ available.'

.

' RESPONSE:

The pumps, drives; piping and 110,000 gallon condensate storage tank ~of'

the Auxiliary Feedwater System are all seismic- Category I. The normal AFW

is supplied from the 110,000 gallon condensate storage tank, which is

missile protected. Operation of the AFW pumps (two motor driven pumps.

and'one turbine pump)' provide residual heat > removal for up to 8 hours.

'

; .usingLthe 110,000 gallon condensate storage tank. The AFW pumps are located

..in the Auxiliary Feedwater Pumphouse outside.the containment. The two

-motor driven AFW pumps are connected. to independent buses of the

. Emergency: Power System. In the event that only one pump is available to,

' supply feedwater'following a loss of offaite. power,-there is adequate

(capacityLto cool |down the reactor. Emergency sources of water supply are4

|provided from the Fire Protiection or Service Water Systems. . -If further

: condensate is~ required it can b'e supplied by means of gravity. from the.

[ 300,000 gallon storage tank...

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SQUESTIUN 8': :Identifyf and disc'uss safety grade CVCS instrumentation needed-

'' :for . operator information during shutdown.

~

RESPONSE:9

^'

,JThe'following[is;atabulationfof'theCVCS: instrumentation.neededforoperator

I finformation duringlshutdown:-

-

1.. Boric Acid Tank' Temperature

:(Non-seismic).,

, .

' 2 .~ Boric Acid Tank Level-(Seismicfqualified transmitters).

- 3. ' Charging Flow (normal path)' (Safe ty ' quality)

I4. . Charging Flow'(secondary path)<

-(Safety quality) *

.

'5. -Charging Flow-(tertiary path, safety injection lines)(Safety' quality)

.

.

6. Pressurizer Auxiliary' Spray Valve HCV-2311Position Indi:ator:(Non-seismic qualified).''

.:, .

7. Pressurizer Pressure' ' (Safety quality).

,

:8. -Pressurizer Temperature(Non-seismic . ' qualified)

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._ Liquid samples may be drawn-from thecletdown. lines, from..the hot legs and--

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,Lthe: cold' legs'of'the RCS loop, from.the Pressurizer ~ liquid and vapor space,s

'

- Land from:theLRHR pump' suction and discharge., , ,

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.The. operators'can determine that flows'are taking place in:the desired'

~

m ;r. ,

.: routes by1 observation:of combinations 'of. valve positions, pump operating'

- - '!1ights, ' levels,' L flow, instruments, temperatures' and pressures. ,

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s - The following is a more| detailed scenario for!the cold shutdown problem.''

' COLD SHUTDOWN ' SCENARIO ' (Assuming loss of 'all' non-seismic ' Category I equipment)- y.- ..

The safe shutdown design basis of North Anna is hot standby. The plant can be.,

:

maintained in a safe hot standby condition while manual actions -are taken to-'

permit achievement of. cold shutdown conditions following's safe shutdown earth .

quake:with loss of offsite power, Under such conditions the plant is capable

of achieving RHR initiation conditions -(approximately 350 F,--450 psig) in,

approximately 36|to.48' hours,-including-the time required for any manual.

-. actions.: To achieve and maintain cold shutdown, four key functions must be

c

- performed. These arei(I)' circulation of the-reactor coolant,'(II) removal of.

residual heat, (III) boration and makeup, and (IV) depressurization.'

,

f

IL '' Circulation of Reactor Coolant

Circulation of .the reactor coolant has two stages in a cooldown from hot,

i standby to cold shutdown. . The first stage is from hot standby to 3500F.

.During this stage,. circulation.of the reactor coolant is provided.by.L

natural circulation with the reactor core as the heat source and steam

-generators as the heat sink.c Steam release from the steam generators is>

|-- initially via the steam generator safety. valves and occurs automatically as

L .a resultLof turbine and reactor trip. > Steam release for cooldown is via_u-

the main steam atmospheric steam dump valves ~which can be operated manually

with'their handwheels. The main steam atmospheric steam dump valves are..

--accessible for -local' operation.; The status of each steam generator canL .-' be monitoNed using seismic qualified instrumentation located in the Control,

Three separate' channels for>both steam generator pressure and'. Room.-a

' ~

.

,- water? level.are available.--

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''A 'couldown rate of 50 F:per hour. can.be-maintained during the entire. cooldown0

..

,. hen'all three| atmospheric; relief: valves are available.--In the; event of aw

s' ingle failure of one1 valve,La '50 F per h ur cooldown rate can be maintained'

until approximately the last. half ihour of the cooldown, when a' rate of 40 F

.~per| hour;can .be maintained. - Using two atmosphetic' relief valves and the decay,

? heat" release ' valve., a cooldown. rate of 50 Ff per hour can be maintained during~

entire cooldown.\-

The backup; air,supp1'y tan'ks are designed to maintain sufficient operating

pressureLauch'that enough time is'available for a ruptured' air line to.be._

ilocated isolated, and theLinstrument air header restored..

Feedwater: to'the steam generators is provided from the Auxiliary Feedwater

-

-System'using the seismic' qualified 110,000 gallo'n condensate storage tank as

, th'e primary source and two separate Seismic Category. I piping sub-systems.~

.

:T The first sub-system is composed of two motor driven auxiliary feedwater pumps,

each powered'from'a different emergency; power train. The,second sub-system

,' incorporates.a steam turbine driven pump. Emergency sources of water are-

-

.

provided from the Fire Protection or Service Water. Systems. The operation of

If the Auxiliary Feedwater System can be monitored using seismic qualified

' instrumentation located in'the Control-Room.. There is an indication'of the:

flows into each steam gener'a'or, and pump operating status lights for the.t'

motor driven pumps.1 There are two indications in the' Control Room for the~

level'.in.the 110,000 gallon condensate storag'e: tank. There~is a local.indicatior.

.for suction = and discharge ' pressure for the. turbine driven AFW pump. Assuming'

fri; tithe plant is shutdown from-full power.and maintained at hot standby.for04|two. hours before'cooldown is initiated, and that the RCS is then= cooled to 350 F.at-

_ La : rate ;of--50 F/ hour, the quantity of auxiliaryf eedwat'er. required is approxi'- |o '

f

'

imatelyL92,000 gallons.i j+

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, iThe second stage of ' reactor coolant circulation is fran 350 F to cold shut-

.Edown.' During this fstage, circulation 'of. the reactor coolant is provided by^

* - : the Residual; Heat Removal pumps.,

- .

'

.

_

II. ' Removal of' Residual Heat

: Removal of residual heat also has two stages in a cooldown from hot stand-,

by jo: cold shutdown. The first stage is from hot | standby to.350 F.

~

During this stage, the steam generators act as the means of heat removal-

from 'the reactor coolant syst'em. : cInitially, steam is released f rom the

steam generators via the steam generator safety valves to maintain hot~

' standby conditions. When the operators are ready to begin the cooldown,.

?the' main steam line atmospheric steam dump valves are slightly opened by-

~

. local operation with their handwheels. As cooldown proceeds, the operator

will' occasionally adjust these' valves .to increase the amount 'Sey are

. open. - "This allows.a reasonable cooldown rate to be maintained. Feedwater

e makeup to the steam generators.is provided from the Auxiliary Feedwater~

' System. .The Auxiliary Feedwater System has the ability to remove decay*

' heat [by. providing feedwater. to all three steam generators for extended,

J !.perio'ds of operation. -Communications for these actions will be by use~

,

~ f hand -held ' two way radios, : the . station Gaitronics system, or by sound-oa

powered' sets..

~

.The second stagefisifrom 3500F to cold shutdown. During~this stage the-~

> Residual Heat'. Removal (RHR) System is brought into operation. The'

, . , -

~

1 Residual ~ Heat Removal' Heat Exchangers'~in the RER system act as the means..

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Lof-heat removal!from the' Reactor' Cool' ant System. In'the-RHR Heat1e

. .-

, . Exchanger :the residual' heat is transferred to the Component Cooling 1.

.

System which' ultimately transfers the. heat.to the Service Water System..

:. .

. The Component Cooling and the Service Water systems are both designed

to seismic Category 1. The'RHR system includes two Residual Heat Re- .

moval Pumps and.two Res' dual Heat Removal Heat Exchangers. Each RHRi

,_ Pump is powered from different emergency power trains and each RHR Heat

- < . . . .

* .| Exchanger is cooled by a different. Component Cooling loop. If any:*

component ,in one .RHR loop becomes' inoperable, cooldown of the plant is -

not compromised;j owever, the time for cooldown would be extended,'

h

s

The operation of the _RHR system can be monitored using seismic qualified

I instrumentation in the Control Room.- There is indication of the pump.

I: ' discharge flow,' the pump operatiing' status and the Component Coo 11. g'

,

flow from the discharge of the RHR Heat Exchangers.

. ..

'III. Borationiand Makeup.

^ Boration is accomplished using portions of tha Chemical and' Volume Con-

.tro1~ System.(CVCS). Boric acid 12 we. % from the Boric Acid Tanks,,

'(each of which' has two redundant emergency powered heaters) 1* supplied'

. . ,

~ to the suction of the Centrifugal Charging Pumps.by the Boric Acid'

~ Transfer Pumps.'. The Centrifugal Charging Pumps inject the borated water'

Lt into the Reactor Coolant System via the normal charging and reactor coolant

~

' pump seal injection flow paths. The three- Boric Acid Tanks, four Boric ~-

1 Acid Transfer Pumps,'and the associated piping are of Seismic Category 1'

~

_

'' design.: ..There is . sufficient boric acid 'espacity in one tank to provide

. - I for a cold shutdown for one unit with the most reactive rod withdrawn.-..

NJ UThe Boric ' Acid Transfer Pumps are each powered from different emergency- -

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1 :. S Qs he Bosic Ackd^ Tank level can be mon 1tored to verify.* ~

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Q the'operabil'ity of the.boration pori: ion of the.CVCS. : For this, credit is. . 2

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. .. . .

,

? M ,taken for operator. action in usingia portable differential pressure.g _ -, n'.

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y y: ) * H bdicator.which can b's. connected'to the level signal: lines from the Boricx

~Ac'id. Tanks. ~'

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. Makeup, in excess of that provided as 12 wt. % boric acid is provided.u -

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"_. from the' RSfueling. Water. Storage; Tank |(RWST), which contains 2000 ppa"s

,

,

i.

x borated. water.lusing Centrifugal Charging; Pumps and the same. injection

.j 41 flow pathe aslescribed forlboration.. .Two motor operated ' valves, each |'

2 powe' red fNom different emergency power- trains ~and connected in parallel,^ '

,,

will'tranafer'the ssction of the charging pumps.to tho' RWST. ' Makeup- '

-

:from the RWST can be monitored using . seismic qualified ins rumentation in the'

1

.- . - g.

' : Control Room. . Separate redundanti channels of RWST . il indication..

: exist.., ,

n

j3

~

IV.. Depressurization'S

-Depressurization.is? ccomplished using portions of the Chemical and Volumeii~$', ,

,, ' Control System (CiCS). - !Either 12 wt. % boric acid or refueling water can

b'e used"as' d'escribed for depressurization with the flow path being from"'

i.. u34.'. ~

. ^ the Centrifugal Charging Pumps to the auxiliary spray valve in the.

y( ~ Pressuriser. . The three|Centrifug'al Charging Pumpsiare of Seismic Category~

g_o

[1 JI.3 IThe'powersupplies'for[theCentrifugalChargingPumpsare'the' emergency~

'

7w --

-,,

['s, b" busaasLH ~ and J.which are backed up by. the emergency | diesel generstors.'~ & ' - ._~, .

. .

.

.

! ,' q x LThe motors for~ pumps.2-CH-P-1A and 2-CH-P-1B are powered from busses(, R (HJandlJ1respectively. ' Charging pump'2 CH P 1C may have its' motor' powered- - - -

,. ,

: , y .. _.'

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( - dfromfeither:H or~ J bus.S The twol sets of switchgear for. charging pump C -'

! ..,

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,

%g f @ 'are{ electrically [ interlocked with cell switches {and the control switches Eo- ,,

*

'' 'y . .,.., . . . . . . . . . .

p, .f j 1 prevent ~ inadvertenti i simultaneous' closing 'of both breakers, thus : assuring,

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train separation 'between the H and J busses.. In addition, th$ J bus-~

switchgear will'not have automatic. operating features and during'

normal plant operation will be. in the "re.cked-out" position.

>.

_ The pumps can be operated from and their operating status monitored in"

,

'the Control Room. The'depressurization of the reactor coolant syecem.can

be monitored using' seismic qualified instrumentation in the Control Room.'

Available to the operator.are three channels of-P'ressurizer pressure,'

,

three channels of Pressurizer ' level and two channels of reactor coolant-'

' pressure (wide. range).,

Maintainina RCS Temperature and Pressure Without I.etdown

. In performing the cooldown, the operator will integrate the functions of heat,

!

. removal, boration and makeup, and depressurization so that these functions

can be accomplished without letdown from the-reactor coolant system. Boration,

cooldown, and depressurization will be accomplished in a. series of short steps

arranged to keep Reactor Coolant System temperature.and pressure and Pressurizer

level in the desired relationships; however, to demonstrate that boration and.,

1

Edepressurization can.be done without letdown, a simpler scenario can be used.-

cFirst, the operators borate the u.CS to the cold shutdown conditions, taking

.

advantage of th'e ' steam space available in the pressurizer. Second, thei

,operators use the~cooldown contraction to lower the pressurizer water level.

l . Finally,'the operators use auxiliary spray frora the CVCS.to depressurize the-

' plant to 425 psia. .

' .The~assumediinitial conditions 'following plant trip are: .*

'

DRCS. Temperature =~5470F.RCS Pressure = 2250 psias

L Pressurizer Water Volume = 350 f t3 '.

L Pressurizer ' Steam' Volume = 1050 f t3'

,

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To. calculate if -boration can be accomplished without letting down and without,,

,

:taking'the plant water solid, worst case conditions of end of life'and maximum~

. peak Xenon were assumed. These result'in a requirement for 420 cubic-feet of

12 we. % boric acid at 1650F to reach cold shutdown conditions. When added

to the RCS, ' the boric acid would be heated ' to 5470F and would e 'and' to 550

cubic feet. Since this volume is less than the 1050 cubic feet available in'

the pressurizer st'eam space, boration to cold shutdown concentrations can-be

accomplished without letdown,' without taking the plant water solid, and without

cooling down. *

The cooldown' from 5470F to 3500F decreases the volume of water in the RCS by

approximately 1340 cubic feet. ' Some of this contraction is used to reduce the(-

.- pressurizer water level to the no-load water level (following the increase

caused by the boration) and the remainder is compensated for by makeup from the

refueling water storage tank..

To . calculate if depressurization can be accomplished without letting down and

without. taking the plant water solid, it was assumed that the Pressurizer was -~ ~

at saturated coaditions with 350 cubic feet of water,1050 cubic feet of steam,

0and'the Pressurizer metal, all at 653 F '(2250 psia). It was further assumedoi

'

that no additional water would be removed from' the Pressurizer by the cool-e

L - down contraction. : With these assumptions, and including the effect of heat

input: from. the' Pressurizer metal,'it was determined that spraying in approximately.

660 cubic. feet of 165 F. water would produce saturated conditions' at 425 psia

: (450 F) with a' water volume of 1180 cubic feet and a steam volume of 220 cubic

Efeet.

_The results of the calculations described above ' demonstrate that boration and

.

'depressurization'can be accomplished without letdown, without -taking the plant

water. solid,;and without taking full credit for the available volume created bye

,

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' the cooldown' contraction.'

y.

T A more detailed single ~ failure evaluation is presented below:

I. < Circulation of the Reactor Coolant-.

" A. -From Hot Standby Eo 350 P - Three reactor coolant loops and steam~

'8enerators are provided. The reactor' coolant system design and

physical layout assures sufficient ' natural ~ circulation. flow is

:available-to provide adequate Lore cooling, even with the use of any.

one of, the three' reactor coolant loops. There is no single failuree

~ '

that prevents the use of all three reactor coolant loops to transport

sensible and' d'ecay heat f rom the reactor core to the steam generators

via natural circulation m'echanisms'. Even with a single failure being

a main ' steam line ~ atmospheric dump valve (PCV-14S-201A,B,- or C) all

three reactor coolant -loops and steam generators can still be utilized.

The use of HCV-MS-204 in the Decay Heat Release Line insures that three

reactor coolant loops and steam generators are available for reactor

: core heat transport.

B., From .350 F to cold shutdown - Two RHR pumps are provided, either one

of which can provide adequate circulation of the reactor coolant.~-

Failure of one of-the.RHR suction isolation valves would require the

T va'1ve to be ~ deenergized and opened with its , handwheel. .

,

A -

II. - '~ Removal of Residual Heat

, _'A. From Hot' Standby to 350 F

: .:1.eMain steam line' atmospheric' steam dump valves - Three are provided

J(one per. steam generator); any one of which is' sufficient for~

:i residual heat removal.=. In the event'of a~ single' failure, twor.

' ~ This|however,- power operated relief valves remain.available.

does not prevent tlie availability or use of all three reactor_

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ccoolant loops and steam generators for cooling by'using thei

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Decay Heat' Release,Line (HCV-MS-204).:

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2. Auxiliary feedwater pumps - Two motor driven and one steam driven.

' auxiliary feedwater pumps are provided.~ In.the event of a single,

failure, adequate. pumps remain available' to provide sufficient

'f eedwater.' Each pump can be manually aligned to provide water~

'to all steam generators.

,

' 3. . Auxiliary feedwater flow contro1' valves - Air operated, fail open

> - valves are provided. In the even't of'a single f ailure of one.

flow contro1' valve (which effects flow to one steam generator from4

: either a motor driven pump.or the steam driven pump) auxiliary' ~

feed flow can still be provided to all three steam generators

from the other pumps by manual action.

4.1 Backup source - A backup source of auxiliary feedwater can Int.

provided to the suction of the~ auxiliary' feedwater pumps f. rom

either train of the Seismic Category I. Service Water System.

4

An additional non-safety grade backup source of water is' the~

'

Fireman.or the 300,000 gallon condensate storage tank.

.

i B. FromL350 F to'',00 F

' 1. - RHR Suction Isolation Valves MOV-2700 and'MOV-2701 (to RHR pump.,. .

' 2-RH-P-1A and to RHR pump 2-RH-P-1B) J ' Each valve is' powered from,

?Ja different emergency power train. Failure of either power train.' '

,

' could' prever.t.' initiation of RHR- cooling in the normal manner~

- from the control room.- -In the event of such a failure, the-

I 1 __ aff acted: valse can be opened with its' handwheel.~~

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Jheatifrom'the_RCS'until the RHR System _is available..

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Y ; .cdifferentiemergency. power train.;(In.the event of a' single' failure,- 1

- ?~ ._either, pump can provide sufficient R'HR flow.

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s_ c - N. RHR Heat. Exchangers' 2-RH-P kA andi 2-RH P- 1B - ~ If e'ither heat' '

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Pn , exchanger _is'. unavailable for'any. reason,tthe remaining heat ex-

: changer can provide | sufficient heat removal capability..-

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~ 4'.; RHR' Flow ' Control-Valve HCV-2758 - If this normally open, fsil'

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open-valve closes' spuriously,"RHR System cooling will be interrupted.,

- Sufficient RCS residual' heat' removal will be provided by utilizing*.

+ --the steam generators, main' steam line.atmo' spheric steam dump

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: valves and; auxiliary feedwater. system while th'e operator takes>

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' manual action to open the valve,,

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c51gRHRDischarge' Lines Isolation Valves MOV-2720A and'MOV-2720B --, ,

' Parallel 'and ' redundant paths thEough these valves' insure'' that if." ^ ' -

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|, a ; single. fsilure ' of. one ;of - these: valves cannot prevent RHRS coolingn '.y

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{',_' / flow f rom being directed ' to :the ' RCS. If.either.of these'normallys

[ ~d : closed. motor? operated. valves,:which are powered.from different| - !'

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'7.. = Service Water System .Two redundanti subsystems are provided for-

safdty related. loads. Either subsystem can provide sufficient'

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heat removal via one of :the Component Cooling System heat ex-: .

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, changers..

;III. Boration and Makeup

"A. -Boric Acid Tanks 1-CH-TK-1A, 1-CH-TK-1B, and 1-CH-TK-1C'

Three boric acid tanks are provided for the two reactor units of the~

s'tation. Each-tank contains sufficient 12 wt. % boric acid to borate

- one unit for cold- shutdown with the most- reactive rod fully withdrawn.

Piping and the four safety grade boric acid transfer pumps are arranged

so that the two units can share two of the three tanks and if necessary

i hree''of- the four pumps.t

B. . Boric Acid Transter Pumps

-1-CH-TK-2C and 1-CH-TK-2D (Unit 2) - Two pumps are normally aligned

to 'each reactor unit. Each of these pumps ir, powered from a different-~

. emergency diesel power train. In the event of a single failure, either

pump;will provide sufficient boric acid flow.

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_ C. , Isolation Valve MOV-2350 -~.If valve MOV-2350, which is supplied fromj. -* , e

:' " - emergency power and is normally closed, cannot be opened due to power-

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; train or operator;Lfailureiit can be opened locally with its hand-

- wheel. . iIf valve MOV-2350 'cannot' be. opened with its handwheel, an '-,

alternate f' low path'is available via:a) air operated, fail open valve... g . -e .

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i'~ ~

FCV-2113A and a normally closed manual valve, b): the Boron ~ Injection.n

~ ' Tank ((BIT), s normal-safety -injection, routing, or c) the reactor--

3 - _ .

- _cooldnt pump seal. injection' flow (path.-

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;D.. Refueling Water Storage Tank. Isolation. Valves MOV-2115B and MOV-2115D -. '* ?~

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Each valve is powered from a different' emergency power train. -Only~

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one|of these normally closed motor operated valves needs to be opened.

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to provide a makeup flow' path from thel RWST to the centrifugal' charging~

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:_. Pumps.'

E.- Charging' Pump Su6 tion Isolation Valves MOV-2267A/B,.MOV-2269A/B, and''

2 / ~'^ .MOV-2 70A B -'In each set of valves, the 'A valve is powered from a

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different emergency power' train than the B valve. If one of these

normally open, motor operated valves closes spuriously, operator

action' can be used to: reopen the valve with its handwheel.

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. . F.[' Centrifugal Charging Pumps 2-CH-P-1A, 2-CH-P-1B, and 2-CH-P-lC -t

Pumps -1A and IB are powered from a different emergency power train.

Pump 1C c.an be. powered from either emergency power train. In the

event of.a single failure', any one pump can provide sufficient bora-

E tion'or makeup flow..

,

G.:: Charging Pump Discharge Isolation Valves MOV-2286A/B/C and'MOV-2287A/B/C.-~

.

In each. set'of valves, one valve is powered from a different emergency-

power train than the parallel valve.. If one:of these normally open,~

motor operated valves closes spuriously, operator action can be used-

'

-to reopen the . valve with its handwheel.,

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|H.f Normal 1 Charging Flow Control Valve FCV-2122 - This'normally open-valve:, ,

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' fails open on'lo'ss of. air or power. |If FCV-2122 closes spuriously,

-the charging; pumps-can operate on their miniflow. circuits until'

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ioperatoriaction'can open a bypass-valve-' ' '

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-I. ' Norma 1' Charging Isolation Va'1ves MOV-2289A and MOV-2289B - 1$ either.-

Jof these normally open, motor operated valves, each of which is'

Jpowere'd = from a different escrgency . power train,-| closes upuriously,,

operator ' action can be.used to reopen the valve with its hendwheel.

J. , Normal Charging Isolation Valve MOV-2310 - If the normally open. valve.,

~ closes spuriously, ,boration ~ could be accomplished by using the seal

injection path or using the safety. injection-boron injection tank

. path;

_

IG _ Reactor Coolant Pemp Seal Injection Isolation Valve MOV-2370 - If

this normally open, motor ' operated valve closes spuriously, operator~

action can be used to reopen the valve with its handwheel.

' L.; : Reactor; Coolant Pump Seal Injection Flow Control Valve HCV-2186 -'

This normally 'open valve fails .open- on loss of air or power. If~

:HCV-2186 closes spuriously, the charging pumps'can operate on their

miniflow circuits-until operator. action.can'open a bypass valve.

-

~

JM. Boron. Injection ' Tank Outlet Isolation Valves MOV-2867C/D - Each valve,

is powered from a different emergency power train; only one of!these :e

normally closed, motor operated valves needs to be opened.to pre--<

vide an; alternate path and source for.boration.~

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4, - IN. Boron Injection (Tank Inlet Isolation Valves MOV-2867A/B'- Each valve,

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zis powered from a' different: emergency power train; only one of these -- ''m-

[.normally closed,- motor operated valves needs to be opened to provide^

,' 1an altiernate. path and source for boration.,

...

IV.. Depressurizatio'n

i (A; . Auxiliary Spray Valve HCV-2311 - This.normally closed valve fails'

'

,

' closed on~1ossiof: air.or power. In this case, HCV-2311 can.be opened ~

by using'a~ portable nitrogen bottle. If HCV-2311 is stuck closed as -,

'a result of a single _ failure, the pressurizer power operated relief -4

'

_ ' valves can be used to depressurize the RCS.by discharging the

press'urizer to the pressurizer relief tank.

'

SB. 1 Charging Valve HCV-2310 .This valve fails open on loss of air or',

. power.: In this case, HCV-2310 can be closed by'using a portable'

nitrogen bottle.'- If.it!is atuck open, the redundant Seismic Category<

I pressurizer power < operated relief valves can b'e used.to depressurize~

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the'RCS by discharging the pressurizer to the; pressurizer relief tank., -

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C. RHR' Suction' Isolation Valves MOV-2700 and MOV-2701 - The RHR suction-

.

- isolation vilve motor" operators have.dripproof Class B insulation per,

,' NDIA= Standard's,Eparagraph MG1-1.20 and MG1-1;65. Failure ~of one' valve

. ;would require. operator. action to be deenergized and open'the valve'.with,

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