ML20024B465

Forwards Jj Happell 800306 Memo Re B&W Positions on Potential Nrc/Acrs Questions Re Comparative Features of Mulheim Kaerlich Plant & Domestic PWRs

ML20024B465
Person / Time
Site:	Crane
Issue date:	03/18/1980
From:	Taylor J BABCOCK & WILCOX CO.
To:	BABCOCK & WILCOX CO.
References
TASK-06, TASK-07, TASK-6, TASK-7, TASK-GB GPU-0263, GPU-263, NUDOCS 8307080788
Download: ML20024B465 (18)

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J. H. Taylor, Manager, Licensing (2817)

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Suej* Comparison of BW Cose'stic and Germsn MSS

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March 10,1973 Date

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Ref:

J. J. Happell to J. H. Tcyice dated !! arch 6,1560, subject:

BG Positicos on ACRS Fellow Memorandum.

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A copy of the referenced letter is attached for your infomation. This information should be very useful in the event t: tat questions should 4

arisa at future NRC or ACRS meetings regarding the comparative fet h t es of the rulheim Xaerlich plant and our domestic FWRs.

This comparison was made strictly for oJr backup information and not as a result ofa d! rect request from the ACRS or NRC.

There is one furthtr area which it would be interesting to gather

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comparatively infomation and that involves the ICS fell power supply I

area. This of course comes up as a result of the Cr/stal P.tver event

!8 and if further infor=ation in this area becomes available it will be distributed.

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J. J. Happell w/o attach.

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EEM ksitions c1 ACRS Fellow Ikrorandun Marc'h f.1930 l

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Refa mnces: (1) Latter. John G., Stempelos to Meyer 3ander, Cossible Suggestices for the 11 corpora;.fon of Ger:*.an Pk'R Ideas in U.S. PWIs",

I h' Decester 6, 1979.

q II (2) 1.etter. J. H. Taylor to E. A.1:ocack, "Differatoces Se:wem

}h Gr.rcany and U.T. P.4R1". January 29, 1920.

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Tf.is is in respcase t.) > cur request 11 Riference (2) to prepre C3V ;,0sitions (l

c:n(erning Mr. Steirrelos' sug estions in Referarce (1). The attach:.a<sts to this htter crovik the inforr.ation rt! quested.

• • e have ahs fr.cluded a sum:.ary In this lector tnd a table of contents '.o facilitate 1ccating each detailed es %

cor:::ent. In the attachunts. Apprepriate pcccier.s =f the att ched have :aen V

diseases with th;se on distribution with <sterisks (*) after tSeir neres.

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' l A su:viary of tht results cf m.r review of each state.ent in Mr. Ste. peles' letter is as fc11ows (see attachments for =are details):

(1)* Leaktightness of Containn.ents - B&W sees to need for chance in design pnticsophy, alth ugh per:sIssable site boundary doses might te reconsidered (1:wer in Germany).

(1)

Containment Size Study - Very probably not cost beneficial for T;3! portient no opinion en auxiliary building strangement (an AE shculd be centacted).

(2)

Diverse Containt;ent Isolation Signals - 85M c:nsiders current cractice to be essentially cquivaient in that tvis different ; Pes 2ure :Ignals are used in U.S. plents, (2) j Spray System Effectiveness - A s; ray systen exists on !!? but mitigating

,e,a have insufficient informati:n to deffr.e basicffects are osas A Spinai.

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,,, - ger ga s reascns except M< designers have tend c :: ard a g,. en Stur.i.... TWS s wes passive

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Containcent Sucp Pucping - B&W agrees that aute=atic. sump pu: Ping shculd r.ct be permitted.

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. Closed Loop AFWS - 83 considers the F.X design to be worthy of consideration l'

for future U.S. piants.

ot ali German plants utili:e closed loop design.

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(3) Reduced Loop Effects

- B*N agrees that closed loop AF.iS reduces the (Using Closed Loop APdS) potential for offsite doses.

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.i (4) liultiple Cedicrted ECCS - Concli l!

Mns regarding number of trains and dedication can e.o be reached via a cost / benefit study, syste:t i

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,l interaction stady and considerarten of the com; arable

<l,1, reliability of operating versus acn-operatir.g eqi.ip-t ment.

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Core F?ocd Capacity - Aediticnal catteity is due to Ger:an desNg1 criteria that M 7

'a33!Eonal rat tures be assumed. Sasic capacit/ is atout g.

the same es a U.S plant.

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(5) l FORY Positico Indication - Std* agraes that f aive ;csf tfon or flow indicatico is l

g desiracle.

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!I AIVS - BW f.cosiders a diverse trip system to be the most appecpriate so?utien. -

t iS) in (5) d Fuel Elwent Storage - IX locaticn of pool may be cost teneficiel d2e *o site condi tions. f.ot recc :r. ended for the tyi.ical U..S. plant.

!U (7)

Off-Gat Traat ent - Pabably the result cf 1cter Ga ran site bou.-dary cea.e Ifnits ii sd

'tp~g during creration. Suggest an AE de asW to cc.:::t,t.

(S)

F C1&ssif* cation of.tTc - AP4 syst'e s are safety reade c1 conparable U.f.. plants f:

(sace as !X cla*sificatien).

(8)

Saf6ty Atlated Valve !bnitoring - Equivalent systems are required on U.S. plaats 1:

(R.G. 1.47).

! h, (ii) SG Water Level - Sinilar provisions are planned for U.S. plants.

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(10) Rate of Flux Change Trip - Bl.W feels that the benefits are not sufficient to i

1 warrant a change in present U.S. plants. It should be evaluated for use in future P.PS systems.

4 Additional sumary cor=ents are:

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(1),Certain of fir. Stempeles' cornents (such as classification of AF4 systems a :d sump pu= ping) appear to be oriented toward a cceparison of the early tecn cicpy THI-2 ;1 ant with the LX plant which is c:nsidered a relatively current tccr.ec.ogy Plant.

The tiSS used in the MX plant is very sinflar to the TVA (Zellefente) snc

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WPPSS (2;P-1/4) units and.would be. ore corpar'able to these plants.

Cn the Other hand, *he THI-2 site is probably core cc parable with the M/. site than !*PPSS Or TVA, and on this basis it is appropriate ccxparisen.

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I (2) Differences exist between Ger: an a.-d U.S. design critaria. It is probable that one major ressen for these differences is a recognitien that site coccittens i

.h-fer typical Ger an plants tend to be core restrictive than for cc: parable U.S.

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In general, Cercan sites are smaller and closer to urcan populatica

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centers and heavily traveled traffic routes, including air corridors, than

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Happell te Taylor 8W Positions on ACRS Fellow Memorandum

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i typical U.S. sites. It is questionable whether a comparable U.S. plant would

' hh he currently licensable at the HK site without the addition of special features.

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One conclusion that might be drawn is that Cor.cn design criteria takes greater recognition of urban siting than comparable U.S. criteria.

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(3) The lower offsite dose Ifmits applicable in Germany p1=y an (=portan't par

• in design. This I's exemplified by the MK contain=ent design, off-gas system and 3j!

the closed loop ARI system.

h; these same features, However, all German nuclear plants da not have I

(4) The variation of acceptance criteria (cr MK as a function of the number of j

failures assumed in ECCS systems during an event is an interesting c:ncept.

This approach allows the HX plant to have about the same total capacity in 4

j their 4 train F.CCS systems as U.S. plants have in 2 trains by "recogni:ing the I:

lower probability of cultiple failures.

I This Approach gives greater reliability t

at lower cost than if each of the 4 trains had to be full capacity.

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(5)

SW encouragts' and supports AC!ts efforts in comparirg U.S. and foreign tec.nology.

i As we have noted above. and in the attached. Sa'J agrees with a number of Mr.

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Stempelos' conw.ents. There would also be. erit in a for=al program to cor::sare current U.S. and foreign design require =ents. Such a program, however, shculd l!

recognize differences in typical siting conditions bett.een Europe and the 0.5.,

t and should be perforced on a cost / benefit ratto basis with apprcpriate c:nsidera-i4L tion of potential offsetting effects between increased redundancy and aut: ation I

{,f (as typified by the HK design) and the increased potential for adverse system interactions.

Those on distribution are requested to contact the writer before :'. arch 14 with any last minute comments on the contents of this letter or attachments.

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.i, Attachments.

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0. W. Berger*

E. A. Idomack 4

ii J. A. Bohart i

A. i.. Jenkins*

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G. J. Brazil 1*

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Stempelos Coment k

Page 1

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Containcent Leaktightness 1

Containment Size Study 2

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Dives se Containment Isolation 3

Spray System Effectiveness 3

i Containment Sump Pu::: ping.

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3 ffultiple Dedicated Closed Loop AFMS 4

Effects of Loop Event 5

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Multiple Cedicated ECCS 4

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Core Flood Tank Capacity 6

5 PORY Position Indication 8

i ATWS i

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Fuel Storage Pit Location 9

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Of f-Gas Trea tment 10 I

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AFWS Classification 11 Safety Related Valve S.tatus ;bnitoring 1

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Progrant.ed OTSG Level 1

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' Rate of Flux Change Trip (Diverse)

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fr 884 POSITION O'l STE*;PELO TO bet:0ER LETTER 12/6/79 i

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"(1) The HK containcient is a steel sphere designed for an internal press.;re of j

84 psia. The steel sphere is located v:f thin a concrete building. A large. strong.

l 1eakproof building should be the first step in designing a reactor plant. If the additional space afforded by the choice of a large contair.sent is properly utill:ed.

a considerable savings in dollars and man-rea will occur during maintenance c:t-ations.

The idea of space for caintenance may apply to auxiliary buildings as t; ell. 7:e degree of space utilization for different containcants (e.g., Cherokee.'Perkins, and Oconee Plants of Oake Power) can be studied to determine whether the large containment

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really aids maintenance and survelliance."

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StW Position:

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Introduction:==

This recc.rendation references (1).1ctktishtness of containcants I:

and (2) suggests that a study of con:1; rent size be serfor ec j;

to determine if larner sizes will rence c:an-ren execsure aca il facilitate maintinance.

(1) Containrent Leaktightness j d*,-

Soth the !!K plant 'and comparable U.S. plants are designed to caet desi;n leak

il rate require =ents which are depencent pri=arily u;on site conditions and r

permissable offsite doses. In this sense, both FK and comparable U.S. ;14nts are acceptably " leak tight" in that they =cet required acceptar.ce standarcs.

N The MK containment is. designed for a greater degree of leaktightness because

,1 of unique site conditions. The h*K site is ses11, with a large population tensity close by. The site is also borcered by the Rhine River an'd a railreac whicn

#j both carry a large amount of heavy traffic. Under these conditions, tne *

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'f plant had to be designed for an exceptional degree of leaktightness to ceet the Geman requir: ment for an essentially zero dose at the ' site boundary foliening a design basis event. It is very probable that a U.S. plant designed to the same site requirements wculd have to exhibit a similar degree of leaktightness in order to be licensed.

j Pemissable offsite doses during both nor=al operating and accident conditions are considerably Icwer in Germany than in the U.S.

B&W does not sete the need f r an arbitrary tightening of leaktight ess st:rdards on U.S. nuclear plants. While maximum 411cuable post-accident doses as the site i

.j bcundary might be reconsidered, the required leak tightness of a given c0-tain-

.f cent structure should centinue to be a func' tion of related site ccnditions and conservative off-site dose limits.

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!!a te: The radiation leakage at it!!-2 was not a functica of containment Itakti;htness, y

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(2) Contalement Size Study I

j US Contafar:ent St.W questions idsether incr eased contain ent size would shcw an attractive

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l cost /t.anefit ratio with re ard to Reactor Coolant System arrangere:t. Oc. a ct j

Reactor Coolant Systess have cany advantages with res;ect to reduced water inventory, less saleiding voluce, and 1 ewer everall capital and operating costs.

A direct costparison of the 2 design with co= parable U.S. plants on the basis of size alone is not conch:sive. Unlike U.S. plants, a is designed to 1 :1t;de the spent fuel storage poc: inside the RS pressure boundary. The M 2eac:.or j

Coolant System is also arranged identically to comparable it.'t. plants, whi h indicates that there is ne additional rcom between RCS c: ;cnents for maf :arance I{i 4

operations. Finally, the.* t containcent struct.:re includes a significar.: a.ount d

of safety equipment inside the contain ent building but e. sternal to the steel

'4 pressure boundary. Cn co=::ar&ble U.S. plants, such safety eqaipcent is nce-ally located in an ad.facent auxfila.y butiding. This latter fact wuld imply, at f;

least, that there cay possibly be less room for maintenan:e in the a plan: than q

in U.S. plants.

l Auxiliary Buildine B&'d has no concent on the ; potential cost / benefit ratio of utilizing lar'ger

,h aux 111ery buildings to red.,ce man-rem exposure and facilitate maintenance.

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Whether such changes would show an attractive cost /ber.efit ratic could :ss: he co: rented upon by an architect engineer.

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Note: The capital costs of a nuclear plant are extre ely sensitive to RCS water t

't Inventory. i.arger invent.:ry requires larger contain ent volu e,.-cre s.-f elding volume, longer pipihg runs.... In general,.. ore of eter/ thing is required, right down to wire tr.d insalation.

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- Diverse Containment Isciation 51snals f(.

- Spray System Ef fectiveness

- Containment Sump Purpjng 5tercelos Corrent

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"(2) The MK containcent has diverse isolation signals. The Ger=ans believe that j f the containment spray system complicates the ECCS and is ineffective. The saray system is operator actuated at MK and is not required for licensing. Fumpir.g of

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the containcent sump must be deliberately performed by the operator in the l'.4 design."

B&W Position:

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==

Introduction:==

This com.ent c: vers (1) diverse sienals, (2) containrent ssery, and

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(3) containment su=o pueoing.

l-(1) Diverse containment Isolation Sionals 2

j" All comparable U.S. plants incorporate, or should incorporate, both high containment pressure and low RCS pressure contain ent isolation signals, f,.f These trips would be adequate for ;ostulated LCCA events. Steam line break events would result in isolation based upon the high centainment press.-e and/or the containment purge activity signal. 30% considers current U.S.

practice to be equivalent to HK design for these events.

alI (2) Spray System Effectiveness B&W does not knew the basic reascns why the c:ntainment spray systema are not considered effective except that MK designers have tended toward a passive l l approach to centainment design. We do know that the MX design utill:es a containment spray system but does not include the effe:ts of spray act::n when l

defining post-accident pressure and tem;erature conditions. On this basis, the systen does not need to be safety grade and is not required for licenskg. 21*l has insufficient informaticn at this time to ecc.ent on the relative erits and

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demerits of the MK spray system design philosophy.

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(3) Containment Sueo Pumpir.o B&W agrees, based upon the TIII-2 event, that aut:matic transfer of c:r.tair.r'ent i

sump water to the auxiliary building should not be permitted. The tra sfer should be manually actuated and interlocked with contaircent is~ latice. sige.als i

o to prevent transfer of activity after an event.

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The MK plant has r:ultiple dedicated Auxiliary (e=ergency) Feet. eater Ostems.

i The closed loop system bleeds stea.n from the steaan generators into auxiliary a

condensers.

Potentially radioactive steam is not bled to the at;nos;rere.

.'i The effects of a loss of power may not be as pronounced in the smaller audliary

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condensers as does occur in the large =ain turbine condenser.

Steam :ence::ed in these auxiliary condensers flows by gravity to the feedpu=p suction."

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I' 8&M Position:

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Introduction:==

This cocinent ccncerns (1) s:vltiple dedicated closed 1'com ra systems, and (2) effects of a loco event.

I iN (1) Multiple Cedicated Closed tooo api $

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' The cles.4d loop AFWS on the !1K plant is the result of Icwer alloutie eff-site

[ D-doses in Germany and more restrictive !*K site ccnditions (i.e., srall :f te,

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large nearby population centers, and adjacent heavy traffic en the Rhi a p.tver

• p and nearby main railroad ifne). The design criteria of the AF.;S is to ;revent e-

.i-all discharge of steam from the secondary system to reduce cosas at the site boundary to essentially zero.

Comparable U.S. plants use cultiple dedicated AFU systems, but they car.st be

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considered to be closed loop systems. During abnormal events invc!ving loop

,p heat removal is accomplishsd using safety grade moculating atmos;heric :sep,

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',3 valves; these are redundant and si:ed to conservatively rec:ve de:ay hast.

j,p These valves discharge steam to the at:osphere. Steam may sisc te disc::seged p

to the atmosphere during r.on-loop conditions on U.S. plants, de:cnding :on

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the extent of load reduction and acount of bwpass that is provicec to tre main

- t condenser.

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B&W considers the !!X closed Icop arrangecent to have a nur.ber of acvantages over

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comparable U.S. practice:

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(1) The potential for activity release to the atrosphere would te elf inated

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primary to secondary SG tube leakage.This is of particular significance in p j.,

,I Such a criteria would have f ;crtant safety and public relations value since the potential for activity release

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(2) The ascunt of primary to secondary tube leakage that exists in a p::

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both before and after an event. would beccee a much less sensitive factor In evaluating the offsite dose consequences and would provida :re 'lexi.

bility in defining p,ermissable ;ost-event acticns.

As an exa ;le, taring the TMI-2 event, steam generater 3 was isolated on the sec:riary tif e because of suspected tube leakage and was, therefore, not available as a stkup r. eat sink.

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(3) A closed loop AFVS would conserve secondary inventory duri. g 5: s.'utdown and post-accident coa.diticn:. *!!th a suitable heat sir.k a<allable, ccoling could be maintained indefinitely with essentially no 1 css of sec:ncary 4

coolant and with no steam release to the atmosphere.

C:rparacle U.S. nuclear

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plants are somcwhat Itcited in this respect by the capacity of aedilable

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water storage facilities to make up for steara lost to the ataosphere I

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.t In susnary, S&*J feels that further review of the t-:X design for possible g

appifcations to future domestic plants is warranted.

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(2) Effects of loco Event i

. 'U This cosaent is assuced to mean that the potential discharge of activity 3,

Ej' through atsosphere du=p valves is eliminated if a closed loop AP.J5 is utilfred.

I 84W agrees with this conclusion.

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• (4) The fE plant has.wltiple dedicated ECCSs. The accu:rulator (Core Fice: Tank) capacity in the I:X plant is over 3 times es large as in the corresponcing 'J.2. plant."

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Lj SW Position:

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==

Introduction:==

This co ent concerns (1) multiple dedicated ECCSs and (2) core flood m

.l tank capacity.

1 (1) !*.sltiple Oedicated ECC5s

.sj The redundancy incorporated in l'X systems is the result of differing design i i, criteria that apply in Germany. In sus =ary, pertinent Cerman criteria require j.;f that:

(1) One train of a given ECCS syste= be considered incperative as the result g l* j, 5

of a single random active failure.

{.F (2) An additional train assumed to be out-of-se vice for maintenance.

(3) The initiating event may involve one of the remaining ECCS trains; (for

, i; example, failure of a nozzle where the ECCS connects to the RCS).

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Applying the above criteria has resulted in four redundant trains in ea:n MX ECCS system. each with 1/2 to 1/3 capacity. It shculd also be noted

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acceptance criteria in Germany is a function of the nu-ter of failures. i.e..

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a acceptance criteria. It is for this reascn that a single train of 1/2 to 1/3

[e capacity is considered acceptacle in the event all of the above criteria should i

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actually occur during an event.

l German design criteria also requires that all ECCS be dedicated.

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e Comparable U.S. design criteria results in two redundant. train syste=s s.hich I

do not have to be dedicated.

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• :l 82 has mixed feelings concerning the Cart:an design criteria. On ene hand, it does appear that a four train arrangement effers additional reliabilit-and design flexibility over tv.o train syste=s (e.g.. adcitisnal syste-fai ures

,ij can be tolerated. scaller emergency diesels can be used; certain !(.C problems

.}4 would be eased). and the concept of relaxing acceptance criteria as a fur.ctiorr of the number of failures appears to be a reasonaole way of :ffsetting t*.e

.e, additional cost involved. On the other hand. i.e have no suostantive ressens to i

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seriously questien the adequacy of the two train systers used in the U.S.

With

• i regard to dedicated systems versus n:n-dedicated, there is e feeling a r2 U.S.

designers that a system that is exercised.!nten::itte st".y ce contin.;c;sl as ; art l

of a normally operating systen cay actually be eore reliable than a dati a ed systems.

SG feels that cost / benefit and system interacticn stuties are required tefore any conclusions can be reached in this area.

(2) Core Flcod Tank Cacacity The require.ent for four core ficed tanks is the direct result of the design criteria noted in item (1) above. It might be noted trat if the Cer an triteria

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• (5) The 11X PORY has a " pressure tap" direct valve position indication syste.

. p; Deta.ils of the system are unknown. The i4X plant includes tao AtlS safety vahes."

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Introddction: This consnent concerns (1) PCRY :osition indicatien and (2) At:5.

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(1) PORY Position Indication t

1 The MK plant uses pressure taps upstream and downstream cf the PORV to previde

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an indication of flow through the valve. The !!K plant also incluces previsions i

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':8 to automatically close the block isolation valve upstres:: of the FORY via the I

RPS in the event the PORY should fail to close.

8f.lf recoercends that equivalent prv ristons for valve position or ficw indication be included on all U.S. plants. f.irther. we recce.and that all currer.: ceceratica I

jl plants provide automatic isolatfor. to eliminate the requirer.ent for operater action In the' event a PORY should fail tr. close.

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B&W censiders the AT'45 event to be axtre=ely improtable and that preventive l il

.n measures (e.g., a diverse trip system) is the most appropriate resolution of I

this concern.

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.Intmduction: This co=nent concerns (1) the location of the TR fuel storace ::o1 inside containeent.

.i (1) Fuel Storace Pit location

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lhe location of th'e IK fuel storage pcol inside centain=ent is a form of 1

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bunkering and provides protection against potential plane crash accider.ts, I I[ ;[

large emplosions en the adjacent Tuiine River, and similar external events.

Considering the heavy traffic at the i!X site, the decision to include tr.e Il fuel storage facility inside centain=ent may have been cost beneficial. Such

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criteria wculd not be appropriate, however, for the majority of U.S. pia.ts which are re:notely sited and/or are outside heavy air traffic corridors.

!!f Storing spent fuel inside contair.=ent has the disadvantact of restrict * ; the ability to perform fuel handling operations related to s;Ent fuel shi;;i. g l ;g li and post-irradiation exa=ination (Pl!) activities to periods when the plant is not in operation.

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• (7)

The MX off-gas treatment systen employs a decer ta:Inatien vessel ar.d hoidays through activated charcoal filters (details unknotrn).*

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Introduction:==

This cce...ent concerns (1) differences in eff-cas trest:-ant facilities

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(1) Off-Gas Trea teent e: -

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As in the case of containment design fer leaktightr.ess (see 8*:t cceents cn Stempelos coe=ent (1)), the off-gas treatment facilities for P.X were dictated l ;t by lower permissable off-site dose Itaits and restrictive site conditicns.

It is very probable that a U.S. plant designed to caet the same corditions h.

wuld utilize a. similar or equivalent design. S?.3 tould suggast an architect

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engineer be requested to com.ent on design differer.ces bet'.scen !!X and cocparable U.S. off-gas treatment facilities.

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"(8) The emergency feedwater syste::: for *4X is classified and designed as a safety g

systen. Consequently, all valves in the :~X system which can significantly affect

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the ability of the emergency Ri system to fulfill it's fur.ction and which -e.ay be repositioned either for operation or testing have cotor operators whicn at:1 be li,!

properly positioned by a R?S signal in the event of a syste actuation. This

!, ; ;l, signal,has priority so that even in the ;resence of a contradicting ;erational or test cos:nand, the action will take place. These valves, if im;ro;erly cicsed.

i. ; h would cause a safety grade alars in the ;t: control rec.s when coved from the opera-

!,E tional readiness position. In the I::t design, a status fr.dication lac; !s provided for each active safety co=;onent as a further aid in recogni-ing impec;erly ;:sitioned valves. In the absence of a protection systen command, the lamp is out. In the presence of a con:tand when the component is not in the co.~. anded conditicn, tl.e lamp blinks. Tlie lamp burns steadily when the component has achieved the c: r.ar.deo El ]1

,g condition."

81'J Position:

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Introduction:

This cos:. ant concerns (1) Classification of f.F'1 Syste. s and (2) 4 :

Safety Related Valve Status 'onitoring.

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The APJ systems on certain early vir.tage 'J.S. plants were not classified as

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safety grade. Current regulations require that all AP4 systems be safety jhcj grade on comparable U.S. plants.

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The APJ system on T;;I-2 was not classified as safety grade, but it does meet many of the requirements, such as being dedicated, redu.-dant, ;rovideo w! tin emergency power, etc.

't (2) Safety Kelated Yalve Status Monitories B&W feels that full conformance to the provisions of Ae-}ulatory Guide 1.47

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(which is required for all conte =porary domestic plants would provide status sonitoring systems equivalent to those of itx, although the "blin::ing-light"

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feature merits further evaluation as a possibly unique cathod of status annitoring, f.

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In order to better control scall break LCC/,s, the :X erergency feedwater system is prograc:r.ed to increase the stea:s generator sec:ndary inventory.

In the steam generator is centrolled at abcut 700 psia.

Pressare for a rapid tec:perature and pressure decrease for the primary side throu;n :leatThis p s

transfer to the steam generator.

i:i :I The saturation temperature for 700 psia is 50** F."

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Introduction:==

This coc=ent concerns (1) orenra-uning of stesn eenerator uater 'evel.

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(1) Prcor m.ed 0TSG Level

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A similar provision to increase the water level on the se:ondary side of t.*e steam generator is planned for the corresponding dccescic 3&

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Stempelos Coment

"(10) The HK plant has a flux rate of change trip which I ass:,::e is used when U '. '

. operating below the power range.

The cceparative U.S. plan: emplo/s excore detectors to sense a r.uclear power ichalance unich will Occar (ce a red wit.draval type accident.

This diverse c.ethcd of providing protection for the sane :ransient should be investigated.

6 Ba'l Position:

==

Introduction:==

This cocnent concerns use of (1) flux rate of chan:e as a dive-se trio.

(1) Rate of Flux chance Trip (Diverse) 4 The 8&'4 RPS uses a flux /a7 trip to protect against reac:fvity inserticas at low The flux /a7 trip senses that neutron power is substantially above thermal power.

Fcr slower accidents where this ichalance d:es not occur. the nigh power.

pressure trip will trip the reactor if core power exceeds energy removal rate.

i The HK design' requires diverse tri;s over the entire re-The flux rate of change trip (using ;or.ee range signals)ga of reactivi:y insartions.

U' will provide pr:tectica il down to a lower rate of reactivity insertiens than the fh.x :.T trip.

the flux rate of change tri his allows ji trip over the entire range.p to provice a diverse trip function to :he nigh pressure

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The B&'4 design meets all U.S. criteria. The German retairemant for diverse

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safety signals was the mafor reason for the flux rate of char.ge trip on F<.

Equivalent diverse trip functiens are provided en cc. : arable deeestic Ei.U plants t;

-.f via the flux /a7 and high pressure trios.

• hile the flux rate of enange

  rip is more sensitive than flux /4T for transients initiated fr:n very low power levels.

the of fference is not significant ercu 5 to warrar.t a chsnge in prese.: syste.ms.

The results of analyses with the flux /;aT trip and the high RC pressure : rip show good margin to the acceptance Ifmits. 'Je conclude, therefore, that changes to 3

the present domestic criteria are nc: t.a rran ted. The f:vx ra:e of change : rip should be further evaluated for any ::ew Ap5 designs on fut:;re plants.

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