ML20234D133
| ML20234D133 | |
| Person / Time | |
|---|---|
| Site: | 05000000, 05000214 |
| Issue date: | 08/31/1964 |
| From: | Koffmann E LOS ANGELES, CA |
| To: | Case E US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20234A777 | List:
|
| References | |
| FOIA-87-40 NUDOCS 8707070110 | |
| Download: ML20234D133 (17) | |
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P. O. BOX 3669 TERMIN AL ANNEX I
LOS ANGELES. CALIFORNIA 90054 t
p%-@. L i
August 31, 1964
.l Mr. Edson G. Case Assistant Director U. S. Atomic Energy Commission Division of Reactor Licensing Washington, D. C.
20545
Dear Mr. Case:
i Enclosed for your information is a copy of Stone and Webster's latest discussion of the containment stress problem, "The Strength of Nuclear Reactor Containment Structures", dated August 10, 1964.
Sincerely, C/vR
~
E. KOFFMANN Senior Nuclear Engineer MF:cjm Ice attached Enclosure b
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PDR FOIA THOMAS 87-40 PDR un suna s
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August 10, 19 k id.
Mys;,
e nMQsf THE STFtENGTW OF IGCLEAR RE/CTOTt CONT!@
METGU NUCLEAR PLAI?f - UNIT NO. 1.
LOS _GGEIES D,Q@TEENT OF FATER AND POWER I.
GEIGRAL In the design of convontionci structuros, it is customary to use prescribed " permissible unit stresses" with-out spoeific considorction of the implied structurcl behavdor in occh design.
Thus tho vclucc of pornissibio unit stresses given in codes of practice roflect group judgments regarding.
cecaptable behcvior and "cafcty" for entire eleccas of conven-tional structuroc subject to conventional londingc.
Dcponding upon tho validity of tho ecsuced loading and upon soveral t
l vericbles effecting the strength, any particulcr conventional t
structure designed to such critoric ncy be rational, over-designed, or underdecigned.
However, boccuse the critoric have been conservatively specified, thoro vill be few instances i
of undordecign so corious as to rosult in fcilure..
Huelocr rocetor contcine:,nt structures cz.n not bo 4
eleccified as "cenventiencl."
In the design'of such struc-
/
'ucas, one can not assuco that cny particulcr criteric for unit i
- rcases cro cyprcpriato unlocc they r'eficct c consideration the structurcl behavior that is cppropr).cto for those M
particular structures.
To cdopt c set of permissible stress criteric vithout such consideration een load either to a design which is unnecessarily costly or to e design that, is unsefe.
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preberibcd permissible unit stresses for conventional bg.L,
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structuros serve to assure safety and to prevent excessive @'
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distortions under service locding.
Since such limits on~
^
permissible stress cre prescribed for general use in the design of broad cle.cses of structures, one ncy e::pect con-servative levels of permissible stress.
Such is, in fact, the case.
III. LOADINGS FOR MUOLEAR REA050R CORTAII?,iEUT STRUOTURES One ecn not properly sepercte the choice of per-nissible stress levels fron the nctter of loadings.
If it is as possible to defino loads which can not possibly be exceeded,,
I one is justified in proscribing stress levels which inply a i,
1 stroncth.only slichtly groctor then these defined loads.
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tho other hand, if the defined loads cre uncertcin and acy be l
substantially enesededi, the corresponding unit stresse s must I
be so prescribed as to inply strengths well in excess of
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design loads.
In addition, cnd npcrt fron considerations of
(
safety, ono cust be sure that the prescribed unit stress levels:
.~
do not inply excessive distortions under service load condi-p tions.
It is useful to start by listing the kinds of loadings I
to which nucicar conteinnent structures will be subject.
These acy include:
a.
Hornal opercting loads j
b.
Wind l
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m.
h b
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a Incident internc1 pressure hf!hp c.
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Test pressure (15 per cent cbove incident pressurab e.
Long-torm lec1: rate tost et incident pressure f.
Ecrthquche accalarctions We are concerned here with c massive type of construction cnd the gravity forces associcted with the mess.
4 of the structurc not only arc of significant magnitude, but must bo included in every load combination.. The wind forces associtt6d with c::tremely high (unlikely) wind velocity cro negligiblybac11 in con?crison with certhqucho cecclera-tion forcos.
Thus the offect of wind forces can be eliminated from the locd combinations of interest.
1 Since an incident is judgsd to be a rare occurrence,
-)
r the effects cre correspondingly rcrc.
Nevertheless, the entiro purpose of the containment structure is to contain the radioactive gescous products of such tn incident.
The important point to noto is that the pressure ces'ociated with
~
an incident hcs besn nost ecnservctively determined.
In other I
vords, given en entrencly unlikely ac1 function of the recotor itself, the ctrimum conceivcbic overpressure is the design valuo stipulcted for the incident condition.
Note first that the assumed recetor cc1 function is c::trene cnd therefore t
unlikely, and second that the pressure associcted with this unlikely cvont hcs been cost ecnzarvctively determined.
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sure) is expected to occur only once in the life of the stree,
n, ture.
A long-tern lock rate test ct 100 per cent of incident' pressure no.y be conducted sovercl tices within the life of the s.tructure.
The prcGosed contcircent structure is located in an crea 12cro certhquate cccc,leretions ncy lead to significant icads.
The scrthquche eccolarctions chosen for design, how'-
PQ rcECnt 0;;t Cns Oc;;inc. for the proposGd locations.
b GV&r For the cbovo-deceribcd cen?cnents of loeding, the fd11owing conbinctions warrant conciderction:
1.
Operc. ting locds on structure plus strength test i
pressure m
8 J
2.
Opercting loadc on structure plus incident prosaurc plus certhqucha 6
3, Operating loads on structure plus long-tern lech re.tc test ct incident pressure plus I
- e. m-s, %w.c.,~,. s.
.c It should be notsd thtt the only difference between conbina-
~'
tiens 2 cnd 3 is zhet in combination 2 rc.dioactivo products cnd hect cre released ans;.dc the contcincent structure, while in conbirction 3 they are not.
Thorofore, conbinction 3 will not be ncntioned further in the discussion which follows.
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IV. DI: SIT:ZD STRUCTUFJ.L ESIi1VIOR FOR !!UOLEAR CONTAIIGIEUT 4Ek,3f, STRi0TURE t w%..E Firct, cnd of percrnount importcnce, tha structure A must rcacin vc?ortight under incident conditions.
For the co itonplated type of construction (hecvy reinforced concrete Shell with plcto stcol linces), rupture of the liners could occur in tho vicinity of c crech in the concreto shell only-if that crack vero enlcrged in consequence of cpprecicble',
yield strain in the reinforcing bars.
Note that the liner picto is ductile ctccl cnd it should be cble to bridge a very 1crge crcck without cu3ture; ncycrtheless, it is more conservative to escurs thct the bridging ccpcbility of the liner plcto is uncsrtcin end to decign the reinforcing bars.
i n
O for c stress levol below yield.
Thus it is cppropricto-thct the reinforcing steel be docicnad for elcstic behcvior under the locd conbinction essocicted with c recetor incident, By this necns one provents 1crge-width cracks in the concrete shell, ncintains the intecrity of the. liner plates and, incidentally, avoids paths of significant direct r diction through the concrete chall, Under the tost pressure condition, the recetor is shut down cnc there is no possibility of c reactor incident and no rcdiction hcztrd.
Still it is necessary to avoid rupture of the liner platec. Accordingly, for any loading i
conbinction including test pressuro, it is desircble thct the k
d em S
.-..,-._.e-N9 i
n 7
\\-
reihforcin;; stool be designed for elcstic behavior.
By this m.
ccans, rupturo cf the lincr plates is preventsd and any cracks */10h occur in the concrete shcIl during tost pres-suro vill close when the pressu"O ic renoved.
For cc.rthquche accclerctions, incident pressure, or tect pressure acting clono 3 the behavior of the reinforcing-
.stcol is enpected to be olistic cince elestic behavior has s
boon ccccpccd ce c design critorien for the conbined loadings.
In cddition, the structuro vill be chectod to ensure that under certhqucko cnd cpornting locds clon0 the avercge bar stress-3 1*cycis rill roncin bslow 20,0g0 psi and that under incident,
proccu~e and operating los.ds clono, tho avercgo bcr stress i
C icvois vill rencin bolcu 26,700 psi.
Thoco conditions vill be ch0ched in the ccco of chic pcrticulcr design. in order to scticfy previonc cc=citaontc.
It chculd be cnphasized, l
houover thct it is believed thoco criteric cre unduly con-l[
4 servative3 cnd should not bo included cs general criteria for futuro desigac.
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tcined for c long pericd of tin ic the condition of norcal i
operct:.ng lende on the strnctura, i.e., self-weight and norncl tonpercturo gradicnte.
For thic condition, it is desired i
that strsca lovals be within the s1cstic rcnge and that such e_,_,, s: -,,..., r,..,. u
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conbinctions, it cppocrs virtuc11y cortcin (but sub.iect thai {
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... L l;' hf.Q check cnclysis) thtt the decired behavior under the normal TrPjM'~
o?orcting. condition will be cchieved.
V. E00XEEDED UKIT STESS 1.EYZLS TO ACHIEVE DESIRED IRiuvIOR OF WCCLPAS 00PE.I'zEET STRUOTUf ES Thus fcr we hevo indicated only that the reinforcing bcr unit strescos should be in the elcatic range in order to achieve tho-desired behtvior 1. under operating loads plus strength test prossure, 2. ur_ der opercting londs plus a
incident plus ocrthqucho accolcrctions.
Soforo etcting the liniting unit strcsc lovels to be uscd sc proportioning critoric, a bricf discuccion of the structurcl interaction O.
.sI v) of linc? plctcs and reinforced concreto shell is necessary.
The inner liner picto ic c:pocod 'to internal cnbient condi-s tions and its interception vill dcpend upon the conditions postulcted to prevcil inside the contcir cat.
The outer licar picto is enbedded bot'.; con the popcorn concrete and the L
reinforced coserete; thus its full participation is cocured.
Under the strength tost precsure cpplied to tho inner liner, i
both plctos cro ccting.
It chculd bc noted that tho' steel for the liner plctes hcc boon deliberately chosen for ductility cnd that the yield strength cf thic ncterial (32,000 psi) is
~
relativcly low.
In contrccts the steol reinforcing bars 4
l i
g
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- n.,:--
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4 T
d5 ns*
/
'4
(._
hr.vp h.
a guaran.; sed.inicua 7.ield. Otrongth of 40,000 psi; 8 @g.
g thei. cctual yicld ctrongth vill be about 43.000 psi.
- TheiR, n
"f production *. rill be cloccly controlled, with tensile tests o'il 1
.g ovary hott pro 6uced for this pr.rticulcr project.
With the e.bovo in vicw. the following unit stross levolc arc believed to be censerv. tive and such as to produ00 the provicualy 6efined 6ccirtblo behavior of the structuro.
tlc cracs levolc cpecified be. Low cre to bo applied to the followinJ two decicn conditiens:
0 erctinc locds plv.c strength tost pressuro.
1.
?
,s m
v3crat_nt;,.Loacc p.:.us incident pressure plus c:.
c:d :,htuahc.
Th' S u ccc lovcl critorie. to be c.pplied are as follows:
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forcin.g barc shr.11 not c:.:cced 32,000 psi.
This a:!-
critorion is introducsd to provido t very high dcgrec of strety with respect to bursting of the wcils.
Such brcratin; could c:.11y occur if tho vertical or horicental n rJorane forco cor?lotely l
devolc?c6 the yicld resictnnco of the corre-l cponding inner r!.2d outer layers of reinforcing bars.
In vicu of the concorvatively chosen load-
_n3 vclucc n un:.; ctress criterion of 32,000 psi would be c.ppropri.to cven if the actur.l' yield c
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forco not taken by the embedded liner plate, %a0MG1,
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not excead 32,000 psi.
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Iloto that the especity.of the concrete to take cbccr has boon disregarded because of the probable.resence:
p
... __w of* horizontal and vertical cracks.
These cracks v111~be very tangentl&1 sncilandthenogloctofconcretdchearresistanceiscon-servativo.
Roto also that the chocon levels of bar unit stress aro voll within the elastic rango.
Service load stress lovels of 32 000 psi ofton are encountered in conventional 3
reinforcod concreto' construction and the wall behavior at s'uch tar stroco levels is 'expoeted to be satisfactory.
VI. Syg?Iiv 0F DESIGN AED CHECK UIALYS7
)
C In several places in the previcuc discussion, it has been noted that partictler c=0.nptions will be s'.$. ject to a check to encure that tho;. cr+. valid.
In other inatancss, it has boon noted that ertain invc'stigations voald be er.rried out for this particultr design duo to previous concitconts, cven though it is believed thtt those casos aro unduly con-1 ccrvet!vc.
A cucc.: cry of principal critoric was discussed at I
the AEC ctaff hearing of Ju.ly 30, 1964, end ic-included below for information:
A.
Doci n Analysed S
1.
Operating conditions (gravity plus thornal Gradientc) plus strength test precauro.
f
a g..r 12. -
A Embedded liner.
U
- u. m c.
XX.XXXXXXXECXX noting
,M d b.
w
.s ;
b.
Mr.ninn:2 bar stress not to onceed "i 4 *, ,
Z:
32 000.nsi S
'2.
Opercting conditions plus incident pressure plus ecrthqucho plus' all thornc1 effects.
c.
Lincr plctcc ceting b.
M ninum bc.? stress not to enceed 32,000 pc1 S.
Chcek Anclyses 3
Opercting conditions (grcvity plus thermal l
grcdients) plus earthquako.
i 1
l c.
Liner plctos e.cting b.
Averngo bcr stress not to eneced.
20 000 psi 3
' +. Sc1f-vcicht plus incident pressure (without thcrac1 offects).
e o
c.
Liner pictc 'rcsistence not considered b.
Avorege bar stress not to exceed 26,700 psi 5.. Operating conditions plus incident pressure plus cll thcr.ani eff0 cts.
c.
Liner pletos ccting b.
Avoragc bar ctress not to enceed 26 700 psi s
6.
Opcreting conditiens (grevity plus thereci
.credionts).
c.
Linor p12tos ccting b.
Average bcr strccs not to enceed 20,000 psi 4
g I:
)
c e
a=
_..A
-e%--,.-
im-a e
/
13
~
IV VII. DISCITSSIOH OF DESIGP PRESSURE CASES
'lN In the staff nocting of July 30, referred to just' 4
cbove, pcrticular concern ucs opressed cbout the philosophy bchini criteric '+ cnd $.
For thct rocson, the following i
rdditional discussion is presented.
l N.
.1.
Strens Lnvra.n I
Under the loediag conditions on the reactor contc1cnont structurc resulting fron tho acrinus credible incident', without ecrthqueta, the averego stress in the steel rcinforcins rods on any section through.the structure, i.e.,
t'ao ucnbrane stress. will not execed 26,'/00 psi.
This stress level is squel to 66 2/3 por cent of the minimum gucranteed I
yic1d strcngth of the rods cnd was crrived ct after conside'rc-mV i
tien of 'the truc fcilure criteric cnd the procodent established by cristing Codos.
3.
Fn<.b n. o c r< ^.e M e Ouo fciiuro criteric., ca rcssed in terms of stress,
~
cro gencrc11y concidered for proccurc vsssels undo of ductilo plcte uttcricls such cs c:rbon s:cel.
l.
Yicld strass or t
"I,4 ting stress cbove which relctively itrgo pitstic dofornction ncy teko ple.ce ui ncut r:pprecichlo chango in stress.
2.
Ultinctc stress or the limiting stress cbove which frr ctra.ccy result.
It is 1:.gcrtent to note thct in c nctorici uhich is inhcrantly ductilo, cnd the w.
s usum
-___-___m.m_____:___m__
7,3 e.3
.~
...t
.j -
_a_.
14.
m L
ductility of ifaich is not inhibited by circumstances 3 -
s I.
.m;
+
m, crisinc out of the design, large plastic deformations will hcvc tchan plecc before this level of stress is rocched.
Thercfore, if 1crgo defornctions are to bo
- c. voided, this critorion, ultinato stress, is l
cisnificant only if restraint conditions provont ductilo action.
C.
Enir. tim Oc60 P?orisionc
' The ASIG Cods for Unfired Pressure Vessels and cupplcnontcry Codo enccc '.citten for cdtptation to stoel.
recctor conte.innent veccc10 sot linits of cenbre.no stress at the leccer vclue of 1.1 tincs 621/2 por cent of the yield I
l V,m ctrongth or 1.1 tinos 25 per cent of the ultinate tensile strength.
Decign acninu::. strosz, therefore, is cctablished 68 3/4 por ecnt of yicld strength or 271/2 per cent of
?
c ultincte strength, ifaichovcr value is lower.
The fcctor of 1.1 reflects ccacidorction of the tcnporary nature of the
~
pera: prsecr20 loading.
For c vecsci ncdo of pletc fcbriccted into a truo
- cnobloc structuro, both of thosc criteric cro pertinent.
The cpplice. tion of prcccure rccults in a genorcl state of bic.nir1 Otrces couplcd with conditions of tricniel stress at discontinuities.
Thaco conditions inhibit true ductilo de-
!crnction at cri.ticc1 points, and it ic desirable to provide e
4 m
i 9
mg.6
-n l
., mW
- g l.
- ,>;3.
- ~
y l
15
.i 2
.j.,e c acrgin of scfoty against gross yielding due to excessive %l;,,f4 p
pgl t
membrcno stress or frccture due to stress concentration atM, gp m,
points where ductility ocy to inhibited.
+u%y T
Tha steel beds in.the reinforced concrete contain-- ;
+
I-nc.nt structuro do not rourssent c monobloc structure but rcthor c frened structure in which a condition of bicxial or l
1 trinnici stress cannot onict in the bers.
Beccuse ductile bchevior of the ontire structure is thus escured, the useful locd which it een resist is limited only by the yield strength of the stoci cnd the conpressivo ctrength of the concreto..
The ACI Code (Bui'1 ding Codo Requirements for Reinforced
~
Concrote - ACI 318-63), ic cpplic:.ble to many details of l
.i n
decign cnd construction of c cpeciti structure of this. type.'
li V
l Houover,; it docs not speci:.ically cctcblish c stress level for the lond condition under consideration.
The Code recognizes l
l two goncral cpproaches to docign described cc " Working Stross" l
I (Part IV A) cnd "Ultincto Strength (Part IV 3).
L In Part IV A, tho vorhing strocs permitted for gravity locds pluc ten?crcry locds (wind or ecrthqucho forces) in reinforcing rods with c ninirnra yic1d of 40,000 poi is l
4/3 tinsc 20,000 psi or 25,700 psi.
In Part IV B, vorhing strosscc cra not established but instend riond fcctors" cre applied to the cotuc1 loads t'o determino the ultimetc loed which the structure nuct resist.
For reinforcing rodc with a l
yield point of 40,000 psi, the stress permitted undes 151tincte i
l f
l e=
e
.-m....
a
-.+.-_ee-,w=-
+=--'*e=
= * * *
,---...**M---
- W**
' ~ ' ' '
i
r m:m,
i
~
- 4., nep g.j kWVV 7 m?. J$guq? -
a g~ i f % p i *
- e
~
~
.t ;
g, s
%. H h wgte 16.
A v
mm w -
Ice.d in the stec1 is the yield strecs.
The load factorsczw-;
I
- .gf '
quiredverywiththenctureofthelond,andthefactor[fok decd locd is 1 5 This factor ves selected to establisi an approprieto mercin of scfety for c long-term lond, the ll
~
nagnitude of which can be established with recconab1e cer-teinty.
Since the uppor bound of the short-term internc1 i
I prcscure. load resulting from tho scxicum credible incident hcs boon established with auch certcinty, a 1crger factor
)
J uould not bc cppropricto for this condition.
Since a r
structure so designed would rocist 11/2 times the applied
.otding ct c stress in thoJbtcol rods of 40,000 psi, at design j
locding the stress vould bc 40,000 divided by 1 1/2, or t
li 26,'700 p si.
D.
C onclusi on s_
- t. !
The criteric discusced cbove scy be co=pered, as i
follows:
DesignHeb.brenoStressas Cr$ t_erio_n Per Cent of Yield Mclibn Unc1ccr Plent 66 2/3 8
AS'G 68 3/4 ACI 66 2/3 It ic belicved thet the propocad design strecs icvc1 is concorvativo.
A reinforced concreto containment structurc co decigned vill be et Icest cs scio es e stoel shell vescol designed in cccordance with the ASME Code.
k C,
e..
4.-.
...--w.-.,m.
A J