ML20211M902

Proposed Tech Specs 3.7.2 Re MSIVs

ML20211M902
Person / Time
Site:	05200003
Issue date:	08/31/1997
From:	WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
To:
Shared Package
ML20211M896	List: ML20211M902 NSD-NRC-97-5340, Provides Argument as to Why Completion Time for Restoring Inoperable MSIV Should Be 8 H for Restoring Rather than 72 H,Per Re Comment 4 on Ssar Chapter 15.W Status for Open Item Tracking Sys 4464 Is Confirm-W
References
NUDOCS 9710150174
Download: ML20211M902 (13)

Text

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4 Maia Stcan Icc10tica V31v 3 (MSIVs) 3.7.2 3.7 PLANT SYSTEMS 3.7.2 Main Steam Isolation Valves (MSIVs)

LCO 3.7.2 The minimum combination et Elves required for steam l!1ow isolation shall be OPERABL1 APPLICABILITY: MODE 1 MODES 2, 3, and 4 except when stes.u flow is isolated.

ACTIONS CONDITION REQUIRED ACTION i

COhirLETION TIME A. One MSIV inoperable 8

A.1 Restore valve to 2d hours in MODE 1. OPERABLE status.

E B. on. or mor. of tw.

turbine stop valves B.I Restore volvt% n huis and its associated ggg g3, turbine control valve, --' ' a-

_'-6 2 ... k a ;

_'. e; . _in ,

turbine bypass velves, main steam to auxiliary steam header valve, or moisture separator reheat supply steam control valve inoperable in MODE 1.

(continued) 9710150174 971003 PDR ADOCK 05200003 A PDR

@ AP600 3.7-5 apoi #.e.cosuem coemi 08/97 Amendment 0

e Maia 5tcan Iceletion V31v03 (MSIVs) e 3.7.2 ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME

h. Two NSIVs inoperable 8.1 Se in NODE 2. 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> in NODE 1.

8 One NSIV inoperable and one or more of the turbine stop valves and its associated turbine control valve, four turbine bypass valves, main steam to l . auxiliary steam header valve, or moist %

• separator reheat su e,'ly steam l

control valst inopirable f4 NODE 1.

E Required fatior. and associated Cotepletien Time of CondJc.ioqsAof6 not met-(continued)

AP600 3.7-6 08/97 Amendment 0

e Maia 5tcan Iss10tico VC1vc3 (usIVs)

, 3.7.2 ACTIONS .(continued)

CONDITION REQUIRED ACTION COMPLETION TIKE

)k . Que or two usIVs [b.1 Isolate associated steam 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> inoperable in MODE 2, flow path.

3, or 4.

IdiD

........ NOTE--------

l Separate Condition Ip. 2 Verify flow path remains Onco per 7 days entry is allowed for closed, each usIV.

QB one or more of the turbine stop valves and its associated turbine control ,

valve, four turbine bypass valves, main steam to auxiliary steam header valve, or moisture separator reheat supply steam control valve inoperable in MODE 2, 3, or 4.

{U Required Action and lt.1 Se in MODE 3. 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> associated Completion Time of condition g &MD not met.

l'2

, se in MODE 4 with RCS 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> cooling provided by the RNS.

@ AP600 3.7-7 08/97 Amendment 's soo,wsow, osom nr oesnr

Nais stcan Ics1ctica V31vcs (NsIVs)

, . 7.2 SURVIILLAMCE REQUIREMENTS ,

SURVEILLANCE FREQUENCY i

i gR 3.7.2.1 ..................N0TE..................

.i Only required to be performed prior to entry into NODE 2.

Verify NsIV closure time a 5 seconds on In accordance an actual or simulated actuation signal. with the Inservice l Testing Program sR 3.7.2.2 .................. NOTE..................

Only required to be performed prior to entry into NODE 2.

Verify tur: sine stop, turbine control, In accordance turbine bypass, main steam to auxiliary with the steam header, and moisture separator Inservice reheat supply steam control valves' Testing Program closure time a 10 seconds on an actual or simulated actuation signal.

1 l

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1 l

AP600 3.7 8 08/97 Amendment 0

, . _ . .- . . - . _ _ _ _ ~ . _ - .

Main 8t:Em Ico1Ctic3 V01v:s (MSIVs)

, B 3.7.2 8 3.7 PLANT SYSTEMS B 3.7.2 Main Steam Isolation Valves (MSIVs)

RASES RACKGROUND Each main steamline has one safety related MSIV to isolate steam flow from the secondary side of the steam generators )

l following a high energy line break. MSIV closure terminates l flow from the unaffected (intact) steam generator.

One MSIV is located in each main steam line outside containment. The MSIVs are downstream from the main steam safety valves (Hssys). Downstream from the MsIVs, main steam enters the high pressure turbine through four stop valves and four governing control valves. Closing the MsIVs isolates each steam generator from the other and isolates the turbine bypass system, and other steam supplies from the steam generator.

The MSIVs, turbine stop and control valves, turbine bypass valves, main steam to auxiliary steam header valve, and moisture separator reheat supply steam control valve close on a main steam isolation signal generated by either low steam line pressure, high containment pressure, Low Teoide or high negative steam pressure rate. The MsIVs fail closed on loss of control air or actuation signal from either of two 1E power divisions.

Each MSIV has an MSIV bypass valve. Although these bypass valves are normally closed, they receive the same amargency closure signal as do their associated MsIVs. The MSIVs may also be actuated manually.

A description of the MSIVe is found in the SSAR, section 10.3 (Ref. 1). Descriptions for the turbine bypass valves, main steam to auxiliary steam header valve, and moisture separator reheat supply steam control valve are found in the 88AR, Section 10.4 (Ref. 6).

APPLICABLE The desi.gn basis of the MSIVs is established by the SAFETY ANALYSIS containment analysis for the large steam line break (SLB) inside containment, discussed in the SSAR, Section 6.2 (Ref. 2). It is also affected by the accident analysis of the SLB events presented in the SSAR, Section 15.1 (Ref. 3).

(continued)

)AP600 B 3.7-7 08/97 Amendment 0

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Mais Stcan Icsictica valves (MSIV3) e B 3.7.2 1ASES APPLICA3LE The design precludes the blowdown of more than one steam SAFETY ANALYSES gwnerator, assuming a single active component failure (e.g.,

(continued) the failure of one NSIV to close on demand).

Design basis events of concern for containment analysis are SLB inside containment with the failure of the associated MSIV to close, or a main feedline break with the associated failure of a feedline isolation or control valve to close.

At lower powers, the steam generator inventory and temperature are at their maximum, maximising the analyzed mass and energy selease to the containment. Due to reverse flow and failure of the NSIV to close, the additional mass and energy in the steam headers, downstream from the other NSIV, contribute to the total release. With the most reactive rod cluster control assembly assumed stuck in the fully withdrawn position, there is an increased possibility that the core will become critical and return to power. The core is ultimately shut down by the boric acid injection delivered by the Core Makeup Tanks (CMTs).

The accident analysis compares several dif ferent SLB events against different acceptance criteria. The large SLB outside containment upstreau of the NSIV is limiting for offsite dose, although a break in this short section of main steam header has a very low probability. The large SLB inside containment at hot zero power is the limiting case for a post trip return to power. The analysis includes consideration of scenarios with offsite power available, and with a' loss of offsite power. With offsite power available, the reactor coolant pumps continue to circulate coolant for a longer period through the steam generators, maximising the Reactor Coolant System cooldown. The reactor protection system includes a safety related signal that initiates the coastdown of the reactor coolant pumpe early in the large SLB transient. Therefore, there is very little difference in the predicted departure from nucleate boiling ratio between cases with and without offsite power. Significant single failures considered include failure of an F. sty to close.

The non-safety related turbine stop or control valves, in combination with the turbine bypass, main steam to auxiliary steam header, and moisture separator reheat supply steam control valves, are assumed as a backup to isolate the steam flow path given a single failure of an MSIV. The safety analyses do not differentiate between the availability of o

(continued)

)AP600 5 3.7-8 08/97 Amendment 0

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Naic stcan tosiction V21v03 (MSIV3) i B 3.7.2 EASES APPLICABLE the turbine stop valve or its series control valve. Either RAFETY ANALYhES the turbine stop valves or its associated turbine ccLtrol (continued) valve are required by this LCO to be OPERABLE. These l valves, along with the turbine bypass, main steam to auxiliary steam header, and moisture separator reheat supply steam control valves are considered as alternate downstream valves.

The MSIVe serve a saf ety related function and rammin open during power operation. These valves operate under the following situations:

a. Nigh energy line break inside containment. In order to manimise the mass and energy release into containment, the analysis assumes that the MSIV in the affected steam generator remains open. For this accident scenario, steam is discharged into containment from both stoma generators until the unaffected loop MsIV closes. After NSIY closure, steam is discharged into containment only from the affected steam generator and from the residual steam in the main steam header downstream of the closed MSIV in the unaffected loop. Closure of the MSIV isolates the break from the unaffected steam generator.

b. A break outside of containment, and upstream or downstream from the MSIVs, is not a containment pressurisation concern. The uncontrolled blowdown of more than one steam generator must be prevented to limit the potential for uncontrolled RCS cooldown and positive reactivity addition. Closure of tac NSIVs or alternate downstream valves isolates the break, and limits the blowdown to a single steam generator.

c. Following a steam generator tube rupture, closure of the MsIVs isolates the ruptured steam generator to minimise radiological releases.

d. The NSIVs are also utilised during other events such as a feedwater line breaks however, these events are less limiting so far as MSIV OPERABILITY is concerned.

The MSIVs and the alternate downstream valves satisfy Criterion 3 of the NRC Policy statement.

(continued)

AP600 3 3.7-9 08/97 Amendment 0

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. -_ _ _ _ . _ - ~___ _._ _ _____. -- - _ . _ _ _ _ _ -

Maia StCan IGalction V01v 3 (MSIV3)

, B 3.7.2 RASES (continued)

LCO This LCO requires that one MSIV in each of the two steam lines be OPERABLE. The MSIVs are considered OPERABLE when their isolation tipos are within limits, and they close on an isolation actuation signal.

This 140 requires that four turbine stop valves or their sesociated turbine control valve, four turbine bypass valves, one main steam to auxiliary steam header isolation valve, and one moisture separator reheat supply steam control valve be OPERABLE. A valve in considered operable when its isolation time is within the safety analysis isolation time limit of 10 seconds and it closes on an MSIV actuation signal. The turbine bypass valves and main steam to auxiliary steam header isolation valve are alternatively considered OPERABLE when closed and administrative b?

maintained closed with automatic actuacion blocked as appropriate.

This LCO provides assurance that the MsIVs will perform their design safety function to mitigate the consequences of accidents that could result in of fsite exposures comparable to the 10 CFR 100 limits or the NRC staff upproved licensing basis.

This LCO provides assurance that the design and performance of the alternate downstream valves are compatible with the accident conditions for which they are called upon to function (Ref. 5).

APPLICABILITY The MSIVs, turbine stop or associated turbine control valves, turbiue bypass valves, main steam to auxiliary steam header isolation valve, and moisture separator reheat supply steam contrcl valve must be OPERABLE in MODE 1 and NODES 2, 3, and 4, except when steam flow is isolated when there is significant mass and energy in the RCS and steam generators.

Therefore, these valves must be OPERABLE or closed. When these valves are closed, they are already performing their

. required function.

! In MODE 5 or 6, the stems generators do not contain much energy because their temperature is below the boiling point of water; therefore, the MSIVs and alternate downstream valves are not required for isolation of potential high energy secondary system pipe breaks in these MODES.

4 .

(continued)

AP600 B 3.7-10 08/97 Amendment 0

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4 M3in stcan teolctica Vc1voc (MEIVs) g B 3.7.2 Ad With one MSIV. :: _, .-':r _: .;.. su uio. .. y . 1... sud it: ;____ int ' :.iin; ;;rra.wl 1.^ .., tuziin; i;;1::, _in rt: r t - -" ' ' ' - ; e4peesr-L._ ;.. . .y l . s . vu , v. . i____e

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:;;.~. e t .. - inoperable in

//75# action must be takere to restore OPERABLE status MODE within 1,@% hours. Some retairs to the valved can be made with the plant hot. Th+ D hour completion Time is reasonable considering the low probability of an accident occurring durigg this time period that would require a closure of these valves. With a single MsIV :: - in L.,

i__inti:1 . 1 :: inoperable, the safety function, isolation

1. gg kg'

of the steam flow path, is provided by the :---ini ,

OPERABLE vr.1ves, but can not acccesmodate a single failure, l

i

' The l} hour Completien Time is reasonable considering the -

low probability of an accident during this time perion that would require a closure of the steam flow path. The assumptions and criteria of the accident analyses are l preserved by the ability to automatically isolate the steam flow path.

l '- ": ,The b hour completion Time is than

{ that normally allowed for containment isolation valves j because the MSIVs are valves that isolate a closed system penetrating containment. These valves differ from other containment isolation valves in that the closed systam provides a positive means for containment isolation.

AP600 B 3.7-11 08/97 Amendment 0 aoun.creo.cueoso702 rotows7 w -

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Main steam Iceletica v:1vec (MsIve)

D 3.7.2 BASES (continued)

ACTIONS b With eewa#G4M,--ow any number of the turbine stop valves and its associated turbine control valve, turbine bypass, main steam to auxiliary steam header isolation, or moisture separator reheat supply steam control valves inoperable in MODE 1, action must be taken to restore OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. Some repairs to the valves can be made with the plant hot. The 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> Completion Time is reacenable considering the, low probability of an accident occurring during this time period that would require a closure of these valves. With a c' ;1: ""r? __ _L backup isolation valves inoperable, the safety function, isolation of the steam flow path, is provided by the remaining OPERABLE valves, but can not accommodate a single failure.

The 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> Completion Time is reasonable considering the low probability of an accident during this time period that

• muld require a closure of the steam flow path. The assumptions and criteria of the accident analyses are preserved by the ability to automatically isolate the steem flow path.

addit , th 72 hou Comp lon i rest th no 1 1 ed or o a so t al ocau the Vs a valve tha sola a el ed my one at g on i t. e a vos to fr o e co ainmen isola on es i tha ec sed sy em p v s p ti mean for ta at - lati b [e.gg %eom bfoyd on GNf0GN voivt inoffohR volve5 With two MSIVs inopattable in MODE 1 or if the MeeV can not be restored to OPERABLE status h in accordance s

with Required ActiorgA.1 the unit must be placed in a MODE in which the LCO does not apply. To achieve this status, the c it must be placed i MODE 2 Yithin 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and Condition D would be enter'd. e The Completion Times are reasonable, based on opergting experience, to reach MODE 2 and to close the inIan orderly manner and without challenging unit systems.1 b.1andb.2 vak5 \er b.\ #

Condition h is modified by a Note indicating that a separate Condition entry is allowed for each MSIV.

(continued)

AP600 B 3.7-11 08/97 Amendment 0 l

a

M Main Steam Iccictio2 Valv30 (MSIV3)

B 3.7.2 BASES -

ACTIONS b.1andb.2 (continued)

Since the MSIVa are required to be OPERABLE in HODES 2, 3, and 4, the inoperable MSIVs may either be restored to OPERABLE status or closed. When closed, the MSIVs are already in the position required by the assumptions in the safety analysis.

The 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> Completion Time is consistent with that allowed in condition A, and conservative considering the reduced energy in the steam generators in MODES 2, 3, and 4.

For inoperable MSIVs that cannot be restored to OPERABLE status within the specified Completion Time but were closed, these inoperable valves must be verified to be continually closed on a periodic basis. This is necessary to ensure that the assumptions in the safety analyses remain valid .

The 7 day Completion Time is based on engineering judgment, and is considered reasonable in view of MSIV status indications available in the control room and other administrative controls which ensure that these valves will continue to be closed, b.1 and b 2 If the MSIVs cannot be restored to OPERABLE status or closed within the associated Completion Times of Condition % the unit must be placed in MODE 4 with normal residual heat removal system in ser, rice where the probability and consequences of an event are minimized. To achieve this status, the plant must be placed in at least MODE 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, and in MODE 4 with normal residual heat removal system in service within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. The allowed Completion Times are reasonable, based on operating experience, to reach the required unit conditions from full power conditions in an order.y u nner and without challenging plant systems.

SURVEILLANCE SR 3.7.2.1 7 REQUIREMENTS The MSIV closure time is assumed in the accident and containment analyses. This surveillance is normally performed upon returning the plant to operation following a refueling outage. The MSIVs should not be full stroke tested at power, since the resulting plant transient is (continued)

AP600 B 3.7-12 08/97 Amendment 0 J

Main Stcan Iceletica valv:0 (MSIva) s B 3.7.2 e

BASES SURVEIt'.ANCE SR 3.7.2.1 (continued)

REQUIREMENTS significant when the plant is generating power. A partial valve stroke (typroximately 10%) is performed during plant operation and has minimal perturbation on plant operations but ensures the freedom of valve movement. The MSIVs surveillance tests a;te perfonned in accordance with the Inservice Testing Program.

The Frequency is in accordance with the Inservice Testing Program. The minimum Surveillance Frequency to demonstrate valve closure time is based on the refueling cycle. The Frequency was concluded to be acceptable from a reliability standpoint.

This Surveillance is modified by a Note that allows entry into and operation in MODES 3 and 4 prior to performing the SR. This test is conducted in MODE 3 with the plant at operating temperature and pressure, in accordance with the Inservice Testing Program. This allows a delay of testing until MODE 3, in order to establish conditions consistent with those under which the test criterion was generated.

SR 3.7.2.1 Locause the MSIV closure time is assumed for steam flow isolation in the accident and containment analyses, the l

alternate downstream valves must meet the PSIV closure time.

This Surveillance is normally performed upon returning the plant to operation following a refueling outage. The alternate downstream valves should not be full stroke tested at power, since the resulting plant transient is significant when the plant is generating power. A partial valve stroke (approximately 10%) is performed during plant operation and has minimal perturbation on plant operations but ensures the freedom of valve movement. The surveillance tests for the turbine stop and turbine control valves, turbine bypass valves, main steam to auxiliary steam header isolation valve, and moisture separator reheat supply steam control valve are performed in accoadance with the Inservice Testing Program.

The Frequency is in accordance with the Inservice Testing Program. The minimum Surveillance Frequency to demonstrate valve closure time is based on the refueling cycle. The Frequency was concluded to be acceptable from a reliability standpoint.

(continued)

AP600 B 3.7-13 00/97 Amendment 0 ao0Wecespecu6030702 r07.cet F97

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Main Steam IGc10 tic 3 Valv00 (MSIVc)

B 3.7.2 a

BASES

• SURVEILLANCE BR 3.7.2.2 (continued)

REQUIREMENTS This surveillance is modified by a Note that allows entry into and operation in MODES 3 and 4 prior to performing tte SR. This test is conducted in MODE 3 with the plant at operating temperature and pressure, in accordance with the Inservice Testing Program. This allows a delay of testing until MODE 3, in order to establish conditions consistent with those under which the test criterion was generated.

REFERENCES 1. AP600 SSAR, Section 10.3, " Main Steam System."

2. AP600 SSAR, Section 6.2.1, " Containment Functional Design."

3. AP600 SSAR, Section 15.1, " Increase in Heat Removal by Secondary System.'

4. AP600 SSAR, Section 10.2, " Turbine Generator."

5. NUREG--138, Issue 1, " Staff Discussion of Fifteen Technical Issues Listed in Attachment to November 3, 1973 Memorandum from Director NRR to NRR Staff.*

6. AP600 SSAR, Section 10.4, "Other Features of Steam and Power Conversion Systems."

e Q.

C AP600 B 3.7-14 08/97 Amendment 0 soon.cmo.cuecao7oa ror ceirer gg -