ML20062F140

Discusses Possible Dangers of LOCA in Containment Purging During Normal Plant Oper.Requests Either Commitment to Limit Purging or Justification for Continuing.W/Encl ANO: 7812080207

ML20062F140
Person / Time
Site:	Prairie Island
Issue date:	11/28/1978
From:	Schwencer A Office of Nuclear Reactor Regulation
To:	Mayer L NORTHERN STATES POWER CO.
References
NUDOCS 7812150061
Download: ML20062F140 (6)

Text

-.. -

t 76-Qfr2 -

l

(

p ** "%,?

UNITED STATES t

NUCLEAR REGULATORY COMMISSION f

j {bj-[q, j WASHINGTON, D. C,20555

1. q

.....a

.; A...

\\

/

November 28, 1978 L

Docket Nos. 50-282 and 50-306 l

Northern States Power Company i

4 ATTN:

Mr. L. O. Mayer, Manager Nuclear Support Services 414 Nicollet Mall - 8th Floor i

Minneapolis, Minnesota 55401

{

Gentlemen:

.[

RE:

CONTAINMENT PURGING DURING NORMAL PLANT OPERATION i

A number of events have occurred over the past several years which l

directly relate to the practice of containment purging during normal plant operation. During recent months, two specific events have occurred which have raised several cuestions relative to potential failures of autenatic isolation of the large dianeter purge pene-trations which are used during power operation. On July 26, 1978, the Northeast Nuclear Energy Company reported to the NRC such an i

event at Millstone Unit No. 2, a pressurized water reactor located in New London County, Connecticut. On Septenber 8, 1973, the Public.

t Service Electric and Gas Company reported a similar event at Salem l

Unit No.1, a pressurized water reactor located in Salem County, New Jersey.

Ouring a review of operating procedures on July 25,197S, the licensee l

discovered that since May 1, 1978, intermittent containment purge i

operations had been conducted at Millstone Unit No. 2 with the safety actuation isolation signals to both inlet and outlet redundant containment isolation valves (48 inch butterfly valves) in the purge inlet and outlet penetrations manually overridden and inoceracle.

The isolation signals which are recuired to automatically close the purge valves for containment integrity were manually overridden to allow purging of containment with a hich radiation signal present.

The manual override circuitry designed by the plant's architect / engineer defeated the high radiation signal and all other isolation signals to these valves. To manually override a safety actuation signal, l.

the ccerator cycles the valve control switch tc the closed position and then to the open position. This action energized a relay which blocked the sa#ety signal cnd allcwed manual oceration indecendent of any safety actuation signal. This circuitry was designed to permit reopening these valves after an accident to allow manual i

coeration of certain safety equipment.

i

?

7812150061

t

-2 On September 8, 1978, the staff was advised that, as a matter of routine, Salem Unit No. I has been venting the containment through the containment ventilation system valves to reduce pressure.

In certain instances this venting has occurred with the containment high particulate radiation monitor isolation signal to the purge and pressure-vacuum relief valves overridden. Override of the containment isolation signal was accomplished by resetting the train A and B reset buttons. Under these circumstances, six vilves in the containment vent and purge systems could be opened with a high particulate isolation signal present.

This override was performed af ter verifying that the actual containment particulate levels were acceptable for venting. The licensee, after further investigation of this practice, determined that the reset of the carticulate alarn also bypasses the containment isolation signal to the purge valves and that the purge valves would not have auto-natically closed in the event of an emergency core cooling system (ECCS) safety injection signal.

These events and information gained from recent licensing actions have raised several concerns relative to potential failures affecting the purge penetration valves which could lead to a degradation in containment integrity and, for PWR's, a degradation in ECCS pe rfo rma nc e.

Should a loss-of-coolant accident (LOCA) occur during purging there could be insufficient containment backpressure to assure proper operation of the ECCS. As the practice of containment ourging during ncreal operation has become more prevalent in recent years, we have required that 3pplicants for construc* ion permits or operating licenses provide test results or analyses to cemonstrate the capability of the purge isolation valves to close against the dyramic forces of a design basis LOCA.

Some licensees have Technical 5:ecifications which ;rchibit purging during plant operation pending demonstration of isolation valve coerability.

In light of the accve, we recuest that you provice within 30 days of receipt of this letter your commitment to cease all containment purge during operation (hot shutccwn, hot standby, startup and pcwer oceration) or a justification for centinuing purging at your facilities. Specifically, provide the following information:

1 I

l 1

3-4 t

(1) Propose an amendment to the plant Technical Specifications based upon the enclosed model Technical Specification, or (2)

If you plan to justify limited purging, you must propose a Technical Specification change limiting purging during operation to 90 hours0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> per year as described in the enclosed Standard Review Plan Section 6.2.4, Revision 1.

.Your justification must include a demonstration (by test or by test and analysis similar to that required by Standard Review Plan 3.9.3) of the ability of the containment isolation valves to close under postulated design basis accident conditions. Within thirty days of receipt of this letter, you are requested to provide a schedule for completion of your' evaluation justifying continuation of limited purging during power operation.

(3) If you plan to justify unlimited purging you need not propose a Technical Specification change at this time.

You must, however, provide the basis for purging and a schedule for 4

responding to the issues relating to purging during normal operation as described in the enclosed Standard Review Plan Section 6.2.4, Revision 1, and the associated Branch Technical Position CSS 6-4 As discussed in these documents, purging during nornal operation may be permitted if the purge isolation valves are capable of closing against the dynamic forces of a design basis loss-of-coolant accident. Also, basis for unlimited purging must include an evaluation of the impact of purging during operation on ECCS performance, an evaluation of the radiological consequences of any design basis accider.t requiring containment isolation occurring during purge operations, and an evaluation of containment purge and isolation-instrumentation and control circuit designs. Within thirty days of receipt of this letter, you are requested to provide a schedule for cenpletion of your evaluation justifying continuation of unlimited purging during pcwer operation.

Pending completion of the NRC staff review of the justification for continued purging in (2) cr (3) above, ycu should commit to either cease purging or limit purging to an absolute minimum, not to exceed 90 hours0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> per year.

I y

y m-.y-

. The staff believes that ooth the Millstone and Salem events resulted from lack of proper management control, procedural inadequacies, and possible design deficiencies. While the containment atmosphere was properly sampled and the purging (venting) discharges at both facilities were within regulatory requirements, the existing plant operating procedures approved by the licensee's management did not adequately address the operability of the purge valves anJ the need for strict limitations on (or prohibition of) overriding a safety actuation closure signal. The requirements for valve operability were not discussed and the related Technical Specifi-cations were not referenced in the procedures. Design deficiencies probably contributed to the events as the safety actuation bypass condition is not annunciated nor is a direct manual reset of the safety actuation signal available. Consequently, we have developed the position specified below to assure that the design and use of all override circuitry in your plant is such that your plant will have the protection needed during postulated accident conditions.

Whether or not you plan to justify purging, you should review the design of all safety actuation signal circuits which incorporate a manual override feature to ensure that overriding of one safety actuation signal does not also cause the bypass of any other safety actuation signal, that sufficient physical features are provided to facilitate adequate administrative controls, and that the use of each such manual override is annunciated at the system level for every system impacted.

Within thirty days of receipt of this letter, you are requested to provide (1) the results of your review of override circuitry and (2) a schedule for the development of any design or procedural changes imposed or planned to assure correction of any non-conforming circuits. Until you have reviewed circuitry to the extent necessary to verify that operation of a bypass will affect no safety functions other than those analy:ed and discussed on your dockets, do not bypass that signal. Our Office of Ins:ection and Enforcement will verify that

. you have inaugurated administrative controls to prevent improper manual defeat of safety actuation signals as a part of its regular inspection program.

Sincerel g(flO L

I A.

chwencer, Chief Operating Reactors Branch #l Di <1sion of Operating Reactors

Enclosures:

1.

Model Technical Specification 2.

Standard Review Plan 3.

Brancn Technical Position CSB 6-4 cc: w/ enclosures See next page 1

Northern States Power Company 6-cc:

Gerald Charnoff, Esquire Shaw, Pittman, Potts & Trowbridge 1800 M Street, NW Washington, D.C.

20036 Sandra S. Gardebring Executive Director Minnesota Pollution Control Agency 1935 W. County Road B2 Roseville, Minnesota 55113 The Environmental Conservation Library Minneapolis Public Library 300 Nicollet Mall Minneapolis, Minnesota 55401 Mr. F. P. Tierney, Plant Manager Prairie Island Nuclear Generating Plant Northern States Power Company Route 2 Welch, Minnesota 55089 Joclyn F. Olson, Esquire Special Assistant Attorney General Minnesota Pollution Centrol Agency 1935 W County Rcad 52 Reseville, Minr.esota 55113 Robert L. Nybo, Jr., Chairman Minnesc a-Wisconsin Boundary Area Comr.ission i

619 Second Street Hucson, Wisconsin 54316 Clarence D. Fierabend USNRC P. O. Bcx 374 Rec Wing, Minnesota 55C66 i

i f

s NUREG 75/C87 J.sp ng 'o, c

c' U.S. NUCLEAR REGULATORY COMMISSION tm 3

STANDARD REVIEW PLAN W T j#\\....j OFFICE OF NUCLEAR REACTOR REGULATION SECT 10m 6.2.4 CONTAINWENT If0LAi!CN SYSTFM

1. EV!EW 4ESPON5191LITIES Prtsary - Containment Systems Branch (CSB)

Secondary - Accident Analysis Branch (AAB)

Instrumentation anc control Syste. Sranch (IC5B) g eenanical Enginearing Branch (MEB) w Structural Engineering Branch (SEB)

Reactor Systems Brancn (R58)

Po.er Systems 3 ranch (PSB)

I.

ARE AS OF afvlE's The design njective of the containment isolation system is to allow the normal or ceer-gency passage of fluids tnrougn the containment boundary.hile oreserving the ability of

• ne boundary to prevent or limit the escape of fission products that may result from sostulated accidents. This SRP section, therefore ts concerned witn tr a isolation of fluto systems.nich renetrate the conta'nment boundary, includir,9 the design and testing requireme.s for isolatie barriers and actuators. Isolation barriers include valves.

closed otptrq systems, and blino flanges.

[

The C58 reeie.s the information presented in the aoolicant's safsty analysis report (SAR) regarding containment isolation provisions to assure conformance with the requirements of General Cesign Criteria $4. 55. 56 and 57.

The CSB review covers the follo.ing aspects of containment isolation:

l.

The deitgn of containment isolation provistens, including; a.

The nuacer and location of isolatton valves. i e.. the isolatton valve arrange-ments and the pnysical location of isolation valves with *espect to the containment.

e Th. actuation and control features 'or isstatton valves.

i c.

The positions of ' solation valves for ecrmal clant operating condttions (includ-leg snutdemn), post-accident conditions, sa1 in the event of valve ocerator power failures.

L IPe salve actuation signals.

The ca;ts #3r selecttor of closure t**es of isolation.alves.

i USNRC STANDAR0 Revitw pt.AN s

c

• , m.

.e o.a....

, s 7

.m...e....em.c........

i

.m..e

.m.

o.

e.

c..

c.

c

..a.a i,. e.

c

-. n.

. a a

_ e e

..e 9

M r

.b h

.P

. 1

.$..S.

...S g g g.g gg gg.ggg agg g$gggghg

..g.f C...be

.*, g 1

e.s.

Z 8h

..1.b.q) $ u p,..gm

,9 C em.

osa.* e.

r A Sc M i

ev. 1 i

, - ~, -

Connect directly to the contair, ment atmotptere Should te provided alth 15olatI0n valves as folfowt.

I/

s.

One locsed closed isolation valved inside and 3re locked CIG5ed isoletton valve outside Containment, or tsotation valve inside and one loCred Closed isolation valve out-L.

One automat:C side Containment; er inside end one automatic isolation v41ve$#

C.

Ore IcChed closed Isoletton valve outnide Contalement, or d

One 4Jt0matiC ilolet1CA e4Ive iniide'and one tutte4 tic igoldtiQn eglve outllde Contatrietnt.

I C#6er4I Cesign Crtterton $7 requireg that lines that peeeteate (Pe prteary Cor.*4tn-

• ent bou der / and tre nelleer dort Of tTe re4Ctor CColent grei$are Coundary nor n

ConrieCted direttly to t*e Contate. ment 4tmosprere Shculd te provided sitt. 4t le45t 2ne loCued Closed, remote-menual, 3r automatic isolation v4tve /outside containment.

).

De gereral deligP Criter'4 Gerett Containment (golation p*ovtgtong for lineg pere.

• reting tre primary CGnt41nment Coundary thet dif fer f rom the esplicit egquireeents 4

af General Celign Criterta 55 and t6 if tre basis for 4CCeptacility is defined.

following are guidelines for 4CC*Dtable alternate Cont 41ntent 16ol4 tion Drovision%

for Certain CI455e5 of lifel:

4 Segul4 tory Guide i Il detCritel 4CCept4 Die Coetainment t $o14t90n proviticng for I n s t rue'e n t lines.

In ejdttion, instrument lires that 3re closej Coth (n$ide and Gutside CGnt41reent, 4rg.3egtgned to eithstead the Drellure end temggrature candi t t uns 's t ic.t og a ;oS S-Of-Cootent 4CCident, trd are Oe$ lined to withstand Tyr49fC *'*4 Cts, are accepticle enthout l$oI4ticn valvet.

D C )n t 4 ) nme r t fgoletton provis10ng for linel in engineerej $4'ety features or eogineered $4fety *eature-related Syl*emt may include "e*ote**4044) v4Ive%, but provisions snoubs :e e4ce to detect possicle leasage fr:m inese !tnes cutstce Cgntainment.

I C.

Contalement isolation provistens for lires in systems needed for 54fe shutdown of the plant (e. g., I'Culd 33llon System, reactor Core ' solation Cooling System, and tgotgtton Condenger gygtem) eay inCjyde reeste-e49,41 v41weg, ;ut provision

$noul1 te voce to detect constele letsege from trese Itaet outs tde Contalement e.4:.es try 2e* ired 4$ sealed Close3 Dere?ert (See item il.3.f)

1. teel

' age 1 i p3 f a t e s i

se o,.4: 'd vn,CCentacle autesat'. 'soist:;n,si.e fo tnis

'4 1

c',..~eC.

,41.,

tir ef

.,n 6,

.4*)

f, The rechanical redundancy of isolation devices,

~

The acceptability of closed piping systems inside containment as isolation q

barriers, 2.

The protection pr9vided for santainment isolation provisions against loss of function from mtssiles, pipe.hto, and earthquakes.

3, The environmental conditions inside and outsice the containment that.ere considered in the design of isolation barriers.

3.

The design criteria applied to isolation barriers and Diping.

5.

The provisions for detecting a possible need to isolate reSote-manual-controlled systems, such as engineered safety features systens.

6.

The design provisions far and technical specifications pertaining to oper3Dility and leakage rate testing of tre isolation carriers.

1.

The calculation of containeent atmosphere released prior to isolation valve closure for lines that provide a direct path to the environs.

PSB has primary responsibility for the qualification test prograi for electric valve ocerators, and the [CSB has primary responsibility for the qualification test program for the sensing and actuatien instrumentation of the plant protection system located both ins'de and outside of containment. Tee "EB nas review resconsibility for the avalifica-tion test program to cemenstrate the performance and reliacility of containeent isolation valves. The MES and 3EB have review resoonsiDility for mechanical and structural design j

of the containment isolation provisions to ensure adequate protection against missiles, pipe

. hip, and earthquakes. The AAB reviews the radiological dose consequence analysis for the rel+ase of containment at.mosomere prior to closure of containment isolation valves in lines that provide a direct path to the environs. The R$8 reviews the closure time for contairment isolation <alves in lines that provide a direct path to the environs, with respect to th* prediction of nset of accident 'nduced #uel failure.

ACCforasrE CRITER!a The general design cri*eria establish requirements for isolation carriers in lines pene-trating the primary containment coundary. In general, two isolation carriers in series are reouired to assu e that the isolation ' unction is satisfied assuming any single r

icti e fatlure in t*e contatament ' solation provisions.

?>e design of the centairment isolation provisions.411 ce acceptable t3 CSB if the fal? ewing criteria are sattsf ted-1 General Design Ort teria 55 and 5s require that lines that penetrate the primary cort-tainment Doundary and either are part 3f the reactor Coolant pressure boundary or Sev. !

S.2.3=2

/

34 k

4.

Isolation valves outside containmen should be located 45 close to the containment

\\

as practical, as reTJired by Ceceral Design Criteria 55, 56, sno 57 5.

The position of an isolation valve for normal and shutdo.n plant operating Conditions and post-accident condittons depends on the fluid system function. If a fluid system does not have a post accident function, the isolation valves in the lines should be automatically closed k'orengtneeredsafetyfeatureorengineeredsafety feature-related systems, isolation valves in the Ifnes may remain ccen or be openea.

The position of an isolation valve in the event of power failure to the valve operator should be the " safe

• cosition. Normally this position would be the post

• accident valve position, All power-operated isolation valves should have position indication in the matn control rooe.

6 There snoulJ te itversity in the parameters sensed for the initiation of containment isolatton.

t system lines.nich orovice vn open pg'r Jrem the containment to the envirens shoul 3 be equipped.ith radiation monitors tr.at are capable of isolating these lines spon a high radiation signal. A nign radiation signal should not te considered one of the stverse containment isolation parameters 9.

Containeent isolation valve closure trees anculd te selected to assure rapid isola-tion of the contatnment following po,tulated Acetdents. The valve closure time is the time it teses for a power operated valve to De in the fully closed position after the actwator power has reached the operator assembly; it does not include the time to reach actuation signal setpoints or instrument delay times, which should be constcered in cetermining the overall time to clcse a valve, System design cara-Otittles snowlJ Oe constJereo in establishing valve clasure times. For lines.hicn crewtee an open cath f rom the containment to the environs; e.g., the containment purge ano vent lines, isolation valve closu e times on tre order of 5 secords or r

less may t,e eccessary The closure ttees of these valves should be establisted on the basis of minimiting the release of contatraent atmosphere to the environs, to ett';ste the offsite radiological consecuences, and assure tnat emergency core cooling system (ECCS) effectiveness is not degenced by a reduction in the containeent b4cepressure analyses of tne radiolcgical conse*6ences and the ef f ect on the ccctairnent tickeressure due to tre release of contathment atmosphere should te orce + Jed to justify tre selected valve closure time.

Additicnal guidance on the design and use of contatement purge systems =nica may te used during the normal

~

pi ent ecerett ag modes ( t e., startup, po.er operatten. kot staracy and not snutdown) is proviceq in grenen ecnatcal Positton 058 6-4 (8ef 9).

For olents sacer review for cuerating 1+ ceases or slants foe.nien the Safety Evaluation deport for construc-tion permit apolication.as issued prior to July 1,1975, the methods described in se: tion 3. :tems 9 1 a, e, d. e, f, and g, 8.2 through 3 4, and 8.5.0, c. and 3 of Brancn Technical positten 6-4 snould te teoleeented. For tnese plants. BTP !tems B.

c and 9 $ a, regarcing tre site of tre curge system as(d sur*ng normaa plant SLerttion and 'Pe justif'c 3 Mon 2y acceotaDie dose Conseoye*Ce analysis, may De 6 2.4*5 Oev. 1

d d.

Contalement isolation provisions for lines in the systems identif ted in items b and C normally consist of ore isolation valve inside and one isolation valve ietside ;ontstrment If it is not pract1 Cal to locate a valve testde contain-Sent f f9r essaple, t>p

,41 * *4f ts gerie r eater 45 5 result of an acctdent),

both velves may be loc ated cutside containment.

fur this tspe of evolition valve arrangement, tte valve nearest tne contaireent and the osping Let.een the contalrment ard the valve should ce enclosed in a leas-tight or controlled leasage housing, If, in lieu of a housing, conservative design of the piping and valve is assumed to preclude a Dreach of piping frtegrity, the design stculd confore to the recutremeats of 54P section 3.6.2.

Design of the valve and/or the piping ccepartseat should provide the capabilit/ to detect leauage f rcm the valve shaf t and/or Donnet seals and terminate the leakage, e

Contatr*ent isolation provtsions for f i es in engineered saf ety 'esture or ergineered safety feature related systems normally consist et too isolation valves in series. A single isolatten valve will be acceptaD e it it ca9 be

[

i sho.n that the system reliability is greater with only (ne isolation valve in the line, the system is closed outstoe containment, and a llegle active fatlure can be acccmmodatej eith only one isolation valve in the line.

The closed system outside containeert sLould be protected from missiles, designed to selssic Category I standards, classtf ted Safety Class 2 (Ref. 5), ard should have a design temperature and pressure estiaq 4t least equal to that for the containment. The closed systes outsice Containment should be leak tested, unless it can ce shc n that the systes integrity is being maintained du ing r

normal plant operations. Fef this type of isolation valve arrangement the valve ts located outside contatnment, and the piping between the containeeat and the valve shoald te enclosed in a leak tight or controlled leaka;e nousing.

If, in lieu of a houstng, conservative design of the piping Snd valve is assumed to preclude a creacn of piping integatty, the design should conf orm to the requireeents of !qP section 3.6.2.

Design of the valve and/or the otptng compart.sent shGb'.4 provide the capanility to detect leavage frce tre valve shaft and/or donnet seals and terminate the. leakage.

f 5esled cicsed carriers may to used n plac) of autcmatic fsolation vahes.

$esivo c'osed ostriers 'rclude 31ird flanges and sealed closed isolation valves

-nic% *ay to closej manual valves, closed re*cte-man al valves, and closed u

Sutcmatic valves =nich remain closed after a loss of coolant accident. Sealed CIDsed tsoletton valves should De u der 40miFistrative control to assure that a

they cacnot ce tradverteetly opeeet A0ministrative control tr.cludes techanical devtces to 6eal or loca tne valve closed. or to prevent po=e* f*;9 telnq sup-plied to tre valve operatse.

L 4elief valves way be used as isolation valves provided the relfef set point is greater then 1.$ times tne containment design pressure.

I i

dev, I 6.2.4*a 1

61 U,

esign of tre contaireeet ' solation system 15 acceptac!e if provtsions are mace isolate ffuta systems t > al to tre Ccerst r 'n t e "atn centrol room to ano...en t0 that 4t4 ecutsped with remote man;al tsolation valves.

Suc*i provisions may include irstrt, rents to measure fic,. rate, 0,et.ater level, te*De*4ture, pressure, and eajintion level.

Provisions should be ma e in tre cesign of the containment isolation system for j

12.

o.)erability testing of tre contalement isolation valves and f eakage rate testing of The isolation valve testing program should be consistent the isolation barrices, Tre acceptance criteria

.ith tnat preposed for Jtrer engineered saf ety featJres.

for the leakage rate testing program for containment isolation barriers are presented in SRP section 6.2.6 he t an s e areas of review identified in subsection 1 of this SEP section as teing the Oraeches. tPe sCceDlance Criteria ar:0 their eethcds of applicati)n

• e4cr'i'tilit/

3' Ct'er C""la t"ed i* the 9P sect 10"s ;orre sponding to those branCPes.

jr*

1;I 8EliE. XCCE:UGfi 4, crocchres fesc*?ted tete. Decvide ;uidav e on revtew of the contitemer.t isolation Tre revie er selects and tegnagites material from the revle. procedures as may svstem.

De GOtr,0riate for a particalar ctse. Portions of the +evig. My Oe CCne on a jeeeric Dasts for asCects of Contatnment isolation Cotrsnen to a class of contalerents, of by i3coting tre results of previous reviews of plants.itn essentially the same containeent isolation provisions.

the secondary revie. Drancaes will provide input Upon request ' rom tre primary rew t e.er, fer tne aress of revie. stated in si.osection 1.

The crimary revie.er cotains and uses issa e taat tnts review orocedure is corelete.

s sc h input is requ(-ea t3 r

I*e CSB determtres tPe acce0tability of the CCntainment isolation system Oy CCmQaring CPe De ustem 3esign cr+ter}a to tre ces*qn equiremests fer en engineerea safety 'eatc*e.

isolation pro-wslity staNsrds ind the se? smic cos t4n classif tcation of t*e contaseme*t v s'005, 'nc'satrq tre piptng ceaetrating tre containfrent, 3re coroared to Regulatory a :es 26 ena r 29, res; ectr.ety.

• re 53 also ascertains tant no single 'tutt can prevent isolation Of tre containrent.

N s is acccmolisrec ej revie.ing the centainment isolatien provtsions for each 1:ne met-it:rg tre containment to :etermine taat t.o tsolation barriers in se-ies are provided, sed o cchjurctten.Its t;e DSB *)y c. vie ir; the oc.er sources to tre valve acerators.

l ne :53 revie s tre informat en in tae Saa justif tng certai ment,s3 ration provisions f

.m n stffer ' rom the e.ciicit -e w re,ents of General :esign :r'te-ia 25, 56 and 57.

Ne CSE judges the accectaciltty of tnese :entaineent tsolatten crovisions oised or a

maarison witn the accepta'ce criterta given in sucsectton H l

l Rev. 1 6.:.s.7

4

=alved if the appitCant Commits to limit the use of the purge system to less than 90 bcurs per year.ntle the plant is in the startup, pc.er, hot stancby and hot shutdown modes of operaticos. This Coweitsent should te incorporated into the Technical Sr.,ecifications used in tre operation of tre plant.

The use of a closed system inside Cont #tneent as one of the isolation barriers will f

De acceptable if the design of the Closed systee satisfies the following requirements:

The systte does not Communicate with either the reactor Cool.it system or the a.

containment atmosonere.

t the system is protected against 1tissiles and pipe = hip.

C The syste* ts :esignated seisitC Category !.

1 The systell is Classified Safety Class 2 (def. 5).

e.

Ine systelt is designed to withstand temperatures at. east equal to the Contain*

l ment, de s in*I temperatu e.

r f.

The system is designed to withstand the esternal pressure from the Containment structural 4CCeptance test.

g.

The system is desigred to eithstand the loss of-Coolant 4CCident transient and enviroceent.

Insofar as CSB is Concerrej eith the structural design of Containment internal structures and piotag systems, tre protection of isolation barriers against loss of function from missties, pipe = hip, and earthquakes will be SCCeptaDie if isolation Darriers ce located tenind misstle bare +ers, pipe

• Nip was Co/isidered in the design I

of pipe restraints and the location of p* Ding penetratino the containment, and the tsolation barriers, inC!uding the piping between isolation valves, are cesignated seisetC Category !,

i.e., designed to withstand the effects of the safe shutdc.n earthquane, as recommendeJ Dy 4egulatory Guide 1.29.

10 fre destqn riteria applied to Cceponents performing a containment isolation function, j

including the isolation terriers and the piping tetween them, or "e picing bet-een the Contatrment sad the outermost isolat'on Darefer, are aCCeptacle i' l

Group B avality standards, as defined in Regulatory Guice 1.26 are applied to a,

the C0econents, un'ess the service f1ncticn dtCtates that Group A Quality standJrds be applied.

D.

Ihe C0mOonents are Oesignated sets.mic Category in 4CCor$ance with Regulatory Guide 1.29.

5.2.4-6

e<.

1 1

l have remote-manual isolation valves in Systems naving a post-acef dert safety function maf f%e CSB reviews the provistons made to detect the lires penetrating the containment.

to allow the cperator in the esin control leakage f ece these I tnes outs tde containment ar.A teasaqe detection provisions may reom to isolate the system tr ain should leasage occur,

(

tr,clude instrumentation f cr measuring system flow rates, or the pressu e, temperatu e, l

r r

in areas outstde the containment such as valve rooms or engi-l I

radi ation, er.ater tevel the CSS Cases its acceptance of the leakage detection provisions r.eered safeguards areas, identify the Ifnes that described in the $AR en the cacability to detect leanage 4n0 should be Isolated.

The C!B determines that the containment isolation provisions are designed to allow the This information should be taDulated isolation Darriers to be individually leak tested.

to tre saf ety analysis *eport to f scilitate the C5B review.

The C5R determines from the cescriptive information in tre SAR that provisions have been containment isolation systes to a11c= periodic operability made in tre lesign of the isolation system. at testing of tre po.er-c;er sted isolation valves and the contairment the operating license stage of review, the C$8 determines that the content and intent of testing of contain-proposed technical specifications pertaining to operability and leak ment isolation JQuipment is in agreement with reQuireme ts developed by the staff, n

A

!V EVAtOATION F thC t NG5 should o,coort concluding statements similar the Information provided and the C58 revtew to the f ollowteg, to be included :n the staf f's safety evaluation report-of the containment isolation system for the (plant nate) has "The scope of review l

i s

tecluced schematte dra tngs nFd descriptive inf ormation for the iso ation prev sion The revte. nas also fluid systems.hicn penetrate the containment bourdary.

for included the applicant's preccsed cesign bases for the containment isolation Drovi-siens, sod analyses of the functional capacility of the contairment isolation system.

ime basis f or t$e st af f's acceptance has teen the conformance of tre centainment isolation provisions to the Commission's regulations as set fertn in tre Gerecal and to applicaete equiatorj gutdes, staf f technical pr.sttiens, and Cestan Cetteria, (Scecial preolems or enceptions that the staf f tames industry codes and standards.

to specific contatement isolation provisions or the functional capatility of the containment isointion system should te discussed. )

coactudes tnat t*e containment isciation system cesign con +cres to 31f "The staff industry coces and standards, acclicaele eequ ations, guides, staff positions, and i

snd is.iccept.ne:e

• 4Eff4ENCE5 v.

1 13 Cf4 Part 50, accead+i 4 Gereen! *esign Criterion 54 'Pioing Systems Peretrating ant r r* eat 2ev 6. 2. 4 -9

I The C58 reviews the position of isolation valves for normal and shutdown plant operating conditions, post accident conditions, and valve operator power failure conditions as listed in the SAR.

The position of an isolation valve for each of the acove conditions depends on the system function. In general, power-operated valves in fluid systems which do not have a post accident safety function should close automatically. In the event of power failure to a valve operator, the valve position should be the position of greater safety, nnich is normally the post accident position. However, scecial Cases may arise and these will be considered on an individual basis in determining the acceptability of the prescribed valve positions. fhe CSB also ascertains from the SAR that all power-operated isoittion valves have position indication capability in the main control room.

The C58 reviews the signals obtained from the plant protection system to initiate contain-ment isolstion. In general, there should te a diversity of parameters sensed; e.g.,

abnormal conditions in tre reactor coolant system, the secondary coolant system, and the containcent, which generate containment isolation signals. 51nce plant designs differ in th6s regard sed many different corbtnations of signals from the plant Drotection system ara used to initiate containment isolatien. tPe C5B consf oers the ar*Pqe*ent proDosed on an individual basis in determining the overall acceptability of the containment tsolation signals.

The CSB reviews isolation valve closure times.

In general, valve closure times should be less than one minute, regardless of valve siIt.

(See the aCCeDtance Criteria for valve closure times in subsection !!. ) Vahes in lines that provide a direct path to the l

enyteens, e.g., the containment purge and ventilation system lines and main s,eam lines for direct cycle plants, may have to close in times much shorter than one minute. Closure times for these valves may De dictated by rsdiological dose analyses or ECCS performance censiderations. The C5B will request the AAB or RSB to review analyses justifying valve closure times for these valves as necessary.

The C58 determines the acceptaoility of the use of closed systems inside containment as isolation barriers by comparing the system designs to the acceptance criteria specified in subsection !!.

l 4

fne "EB and 5EB nave review responsibility for the structural cesign of the containment internal structures and pioing systems, 'rcluaing restraints, to assure trat the contain-ment ' solation provisons are adequately orttected against missiles, pipe whip, and earth-tuates. The CSB cetermines that for all containment isolation provtsions, missile pro-tectice and protection against loss of function from pipe whip and earthquakes eet design f or,s i ce r t ti ons.

Ih* CSB *eviews the system drawings (w91Ch 59ould s*ow the loca-(

• tans af itsslie bareters relative to the containment isolit1Cn provtsicrs) to determine that tre noletton provisions are protectes from missiles. The CSS slso *ev' ens the 1el'Q9 Triteets applied tc tFe C3nt3 N ent (SClation provisions to determtne that pr3teca ti3n against 4)Mamic ef fects, such as D ye whip and earth 3uanes, mas Considered in the i

(

l design Ibe CSB will requept tre "E9 to review the design adequacy of picing and dal ses foe entC6 conservative design is assumed to preclude possible creach of system integetty in lieu of prQviding & Ieat tight 94u549g l

8ev-6.0.4 4 i

BranCn Techn'tJI Position CS8 6-4 CONTAINMENT o'JRGING OURING NCRMAL PLANT 0*f 4Af!CNS 4.

BACsG2CONO This branch technical position pertains to system lines.hf Cn Can provfde an Cpen path from the containment to the environs during normal plant operation; e.g., the purge and vent itees of the Contai9 ment purge system. It supplements the position taken in SRP section 6.2.4 wnile the containment purge system pros!Jes plant Cperational f ?en tetlity, its design must Consiaer tre importance of Sinittling the release of Contairtent atmosphere to the enttrons following a ocstulated loss *of-coolant accident, theref9re, plaat oesigns must not rely en its ase on a routine tasts.

The need for purging has not al=ays egea anticipated in the design of plants, and there-fore. design criteria f or the C ntairment purCe system have not been fully developed.

The purging esperience at operating pla9ts varies consideraDiy from plant to plant. Scme plants do not purge during reactor operition, some purge intermittently for short periods and some purge Continuously.

Ite Containment purge system has been used in a variety of =ays, for example, to alleviate Certain ocerational problems suCn 45 escess Air leakage into the Contairsent f rom preumat1C l

Controllers, for reducing the airtoree ICttwity within t'.e Containment t0 facilitate perscerel access 2aring react:r 70=er 0;eration, and for Controlling the C09taf ereet pressu e, temperature ard relattie umidity. Mcwever, the purge and went lines provide a

r an acen path from the cantainment to the environs. Should a LDCA OC: e dur+ng Cortaiarert pu g'ng aren IP.9 reactor is it DC=er, tPe calculated Accident doses s*.ould te eithin r

10 CFR 100 guideltae values TPe 512+ng of the purge ind went Il es in most plants has taen Dased on tne need to control the Containment S t.mosDnere 1J'1 *q

• e' vel i ng operat ions. This need has resulted in very large lines penetrating tre contairment (about 42 inCPes in diameter). Since these lines are normally tre only ones provided that will permit some degree of Control tPe Containment at?csDPere to facilitate personeel access, some plants have used over trem for Containte9t purgtmq duriag normal plant operation. Under swCh Conditions, CalCJlated accident doses could Oe st;ntficant. IPerefsre. the use of t.9ese large Contain-meat pu ge and weet Itres should Oe restricted to cold shutdc n Canditions and refueling r

30 erat' ors.

E-

I l

4 ; 4 11 i

2.

10 CFR Part 50 Appencts A, Geaeral Design Criterion 55, " Reactor Coolant Pressure Boundary Peretr ating Conta t ament,

• 3 10 CFR Part 50, appeacl= A, Gea,es1 Oesign Criterion 56, "#eimary Containment (sulation.'

4 10 CFR Part 50, accendix A, General Design Criterion 57, " Closed System Isolation valves "

5.

Regulatory Guide 1.141, " Containment isolation Provisions For Fluid Systems."

6.

Regulatory Guide 1.11. " Instrument Lines Penetrating Primary 8eactor Containment."

7 Dequlatory Guide 1.26,

• Quality Group Classifications and Standards for 'nater,

5tess. and Radioactive-Weste Containing Coroonents of Nuclear Pc er plants."

9.

Geg;1 story Guide 1.29, '5etsmic Cesign Classification."

9 Brinen Technical Position CSB 6-4, " Containment Purging Duricq Normal Plant Opera-tions," attached to this 53P section.

l r

sev, t 6.2.4 13 f

1

The containment isolation provisions for the purge system lines should meet the d.

standards appropreste to eng1reered safety features; f.e., Quality, redundancy, testability and otner iccreprt ste cet teria.

Instrumentatlon and control systems provided to isolate the pu ge system lines r

e.

containment should be independent and actwat?d Cy diverse parameters; e.g.

pressure, safety injectten actuation, and contairment radtation level, If energy is reoutred to close the valves, at least two diverse sources of energy shall te provided, either of =nich can affect the isolation function.

Pu ge system isolaticn valve :losure times, including instrumentation celays, f-r should not enceed five seconds.

4 Prnvisicos should be nade to ensure thtt isolation valve closure =111 not te prevented cy deDris.nich could potenttally cecome entrained in the escaD'nq air and steam.

should not be relied on for temperature and numidit/ control witnsn 2.

The purge systra.

the containment.

3 Provisions should be Sade to mintel2e the need for purging of the containment by provioing containment atmosonere cleanuo systems itnin the containment.

Provisions should te made for testing the availability of the isolation function and 4

the leakage rate of the isolation valves, individually, during reactor operation.

5 The following analyses should be performed to justify t*e containment Durge system destga:

analysis of tre radiological corsecuences of a loss-of coolant accident.

s.

An The snalysis should be done for a spectrum of urvak sizes, and the fasteurenta-tion and setcoints that =111 actuate the vent and ourge valves closed shoul.2 Oe identified.

The source term used in the radiological calculations sFould te based on a calculation unce* tPe terms of Appendia L to :etermine tne extent of fuel f at ture and t*e cencomitant release of fission products, and tre fission orcouct a:tivity in the primary coolant. A pre emisting todine soiks snould ce considered in Cetermining prieary coolant activity. The volume of containment in.htch fission products are mined should be justified, and t*e fission products frem tne aeove sources srould se assumed to ce released tnrough the ccen purge vahes du ing tre sanim m interval <eautred for valve c!asure The radiological r

u corsecuences snould ce nitnin to CF4 100 guidelf-s values.

b.

An analysis.ntc3 ce=onstrates the acceptacility of tre crovisions mace to crotect structares ano safetj-eetated equipment; e.g.,

fans, filters are duct-located seyono tre purge system tsolation sabes against loss of function

. ort, from t^e envirorment c eates Dy tae escaping air and steam, s

6,2.4 13 Rev.

a -

Ihe design and use of the purge and vent lines should te based on the premise of achieving acceptaDie calcJlated of f site ra3f olCg1 Cal Consequences and assuring that emergency Core cooling itCCS) ef fectiveness is not degrMed by a reduction in the containment Dackeressur9.

9arge system designs that are acceptacle for use on non-routine casts during normal plant operation on ce achieved t.y providing additional purge and went lines. Tee size o' these lines should be limited such that in the event of a loss-of-coolant accident, assunteg the purge and vent valves are open and subseque tly close, the radiological a

consequences calculated in accordance with Regulatory Guides 1.3 and 1.6 would not enceed the 10 CFR 100 guideline values. Also, the mautmum time for valve closure should not enceed five seconds to assure that the purge and vent valves would te closed cefore the onset of fuel failures following a LOCA.

ine site of the purge and vent lines should be acout eignt inches in diameter for PwR plants.

This line size may be overly conservative from a radiological vie = point for the Maru !!! B R olants and the HTOR plants because of containment and/or core design features.

Theref'r;. larger lire stles may be justified. However, for any proDosed line size, the applicant must demonstrate that the radiological consequences following a loss-of-coolant accident would be witn!n 10 CFR 100 guideline values. In summary, the acceptability of a specific line size is a function of the site meteorology, contatoment cesign, and radio-logical source term for the reactor type; e.g., 3'mR P%R or HIGR.

B.

BRANCH ffCHNICAl, DOSITION The system used to purge the contairm<nt for tre reactor operational modes of power operation, startup, hot standby and hot shutdown; i.e., the on-lif e purge system, shoul'd ce independent of the purge system used fo* the reactor operational modes of cold shutdown ed refueling.

1.

The on-lins purge system should be designed in accordance with the 'ollowing cetteria:

a.

The performance and reliacility v' the purge system isolation valves should te

ens istent.ith the operacility assurance program outlinec in MEB Branch Tecn-iical Position wf8 2 Pump and Valve Operability Assu ance program. (Also see r

SEP Section 3.9.3.)

The design basis 'or the valves and actuators snould i

include the euildup of containment pressure for the LOCA break spectrum, and the purge line and went line flows as a function of time up to and during valve closure.

5 The smtea # purge sna '.ert lires that say be used shoulo te limited to one surge line and ane.ent line, f*e size of the purge nna ent lines sheuld not eaceed accut eight inc*es in 31s*eter unless cetatleJ justification for larger line si:es is ornviced i

l Rev. 1 6.2.4-12 i

6 C0!!T?.INMENT SYSTE."5 CGitTAIN tEtiT VEitTILATION SYSTEtt (OPTIONAL *)

LIMITING CONDITION FOR OPERATION 3.6.1.8 The containment purge supply and exhaust isolation valves shall be closed.

APPLICABILITY: MODES 1, 2, 3, and 4.

r ACTION:

With one containment purge supply and/or one exhaust isolation valve cren, close tne c;en valve (s) within one hour or be in at least HOT STANDBY within tne next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTCOWN witnin tne follow-ing 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

SURVEILLANCE RECUIREMENTS 4.6.1.8 The containment curge su ply and exnaust isolation valves shall be determined closed at least once per 31 days.

I I

l

c.

An analysis of the reduction in the coetainment pressure resulting from the partial loss of containment atmospeere during the accident for ECCS backpressure determinat1on.

d.

The allowable leak rates of the purge and vent isolation valves should ce specified for the spectra of design basis pressures and flows against enich the valves must close.

e J

i b

i 2.4-14 I

l l

l

CC!iTAINME!1T SYSTEMS BASES 3/4.6.1.8 CCNTAINMENT VENTILATION SYSTEM The contain?.ent purge supply and exhaust isolation valves are required to be closed during plant operation since these valves nave not been der.onstrated capable of closing during a (LCCA or steam line break accident). Maintaining these valves closed during plant operations ensures tnat excessive quantities of radioactive materials will not be released via the contain..ent purce system.

T i

b STS 3 3/4 6-W e

+

-