ML20127P847
| ML20127P847 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 02/28/1967 |
| From: | Hall W, Newmark N ILLINOIS, UNIV. OF, URBANA, IL |
| To: | US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20127P840 | List: |
| References | |
| CON-AT(49-5)-2667 NUDOCS 9212030139 | |
| Download: ML20127P847 (12) | |
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N A T H A N M . 'N E W M A R K sit vatsov L Ason Avony. U n s A N A. ILLIHois CON 3ULv1NG ENGINEERING SERVICES D Rt. r T Report to AEC Rcgulatory Staff ADE00ACY OF THE STRU"TURAL CRITERI A FOR THE MONTICELLO NUCLEAR GENEPATING PljsNT UNIT I NORTHERN STATES POWER COMPANY Minneapolis, Minnesota (D,c ,.c t No. 50-203) b; N. M. Neve.o r k a nd W. J. Hall february, 19C7 1
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. . a ADE0W,CY OF THE STRUCTURAL CRITERI A F OR -THE :
MONilCELLO NUCLEAR GENERATING PLANT UNIT I l f
by. l N. M. Nei .na r k and W. J. Hall
-?
INTRODUCTION .
This report is concerned wi th the adequacy of the contelnment structures and components for the Manticello Nuclear Concrating Plant Unit l.. q cesigned for a net electrical output o f a b o u t 4 7 2 M.'e , for which application ,
I f or a const ruct ion perTJt and operat ing license has been made to the U. $. '
t Atomic Energy Comis s ion by t he Nor t hern S tates Power Company , Minneapolls , .
e i
Minnesota. The facility is lo:ated ?? milet downstream from St. Cloud. :
Minnesota, end-abaut 3 miles' northwest of the village of - Monticello, Minnesota.
on the south bank of the Mississippi River. ,
Specifically, this report is concerned with the design crittrla.that determine the ability of the cr itary and secondary containnent systems. to withstand a design earthquait of 0.009 nax imum transient ground acceleration-- f sin.ultaneously with the other loads f orming the basi's of the contal,nment desico. The facility also is to be des i gned t o wi ths tand a- max imum ear thquakc ~
of at least 0.179 ground acceleration to the extent of -insuring saf e shutdown anc containment.
This report is based on inf ormat ion and cri ter ia-~5et f orth' in .the facility Description and Safety Analysis R' port e (FDSAR) and supplements l thereto as listed at the end of this report. ' A lso, we have part icipa ted in e l.
dircussinns with-the AEC-regulatory staff concerning!the design of this-unit.
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DESCRIPTION OF FACit ITY Monticello Unit I is describec in the FDiAR as- a certplete- nuclear pcw.cr valt to be licensed for operation et pon.cr le ve ls up to approximately--
1409 MWt (4 72 MWe net). The unit will be a single cycle, forced circulation, boiling water reactor that produces steam for direct use in the steam turbinc.
In must respects the design will be essentially identical to that for Com none.ee l t h Ed i s on 's Dr escen Un i t 2 and the Millstone Nuclear Power Station.
The pr imary containment sys tem, which houses the reac tor vessel .
and the rec ircula t ion system, consists of a drywell, vent pipes ,and a torus shaped stru:ture which contains a pool of water for pressure suppression purposes, the center of-the torus lies $11ghtly below the bottom of the drysell. The drywell is a steel pressure vessel with a lower spherical portion about 07-ft in diameter and a cylindrical uoner portion about '10,ft in-diameter, the over-all height is approximately 105 f t .
The reactor building provides secondary containment for the system when the pr imary containwnt is in service and serves as the primary containment s t rut ture dur ing pe r iods v. hen t he pr irra r y conta inment ~ ls open inr servicinti.
The reactor building together with the stanoby gas treatrent system and a 290 it stack provide the secondary c an ta i nme n t b'a r r i e r . The. secondary _
containment building is described 'in Sect ion V-? of the FOSAR Vol. I as cons is t ing of pour ed-in-p lace re inf orced conc re te ex te r i or wa l l s. up to We
- ref ueling floor , with e steel structural f rame with insulated metal siding-4
' located above this f loor . .The sioing is to be installed with sealed joints. ,
Section II-5 nf Ref . I and L F igs .11 -b-3 through !!-5-5 indica te that becron eAists et about elevation 600 or 870 et the olant site, and l- that ,ibout 0 % fo f t of predo9 nahtly tranular scciments with.interbedded I -
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layers of lacustrire clay and glacial till overlie the bedrock. On 'he i
besit of the elevations given in Fig, 1-4-7, i t appears that present f l ans {
call for the foundation to rest at abSut elevation 690 on the overburdsen, same 3 0 - d ') ft obove bedroca. :
i i 50VRCES OF STRESSES IN CONTAINMENT STHUCT URE Is'C TYPE I COMP 0NEUT5 ;
Tht containment system, which includes the drywell, vents, torus, and penetrations, i s to be designed for the follawing conditions, as noted in Section V-l of Ref. 1; pressure suppression chamber, internal design pressure, +50 psig, external detign pressure, +2 pilg; drywell internal -!
design pressure, +b6 psig, external design pressure, &2 psig; design tempera- {'
ture of drywell and pressure suppression chamber, 761'f. ;
Is noted in Sec t i on V-3 of the TDSAR, t he seismic desi.gn ci the- '
orimar, conta inn 4 nt system, which is classified as'either a Class T--Critical' i t r uc tur e or Clat s 1--Cr i t ica l Equipment , is to be based on dynamic ' analyses using acceleration response spectrum curves for the specified design and ,
maximum carthquates. As i s nnted later in.this report, the spectra are not ;
necessarily used in the design process,. however. ;
, All structures will be designed to withstand a wind velocity of 100 mph wi th gus ts of 110 mph, and where failure possibly could affect.the ,
-r operation and function of the primary containment and ' reactor primary system,- .{
the design is to be made to insure that saf e~ shutdown can be achieved,
- considering the effects of possible danage arising Irom a short-term tornado loadinn with winds'un to 303 mph.
The reactor builcing, which comprises the se c on'da ry . con t a i nme n t r
n s ten a lan ; wi th' the s tocJano gas t r ea t me n t system, is listed as a Class 1-- '[
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4 Critical Structure. The reactor building is to be designed to withstand an internal necutive pressure of 0.25 11.. of water with respect to the outside atmosphere in neutral wind conditions. It is also designed to be able to withstand 7 in, of water (about 1/4 psi) without pressure relief. The structure is to be designed f or seismic loadings combined with the other applicable functional loadings (dead load, operating loads , snow load, wind load, etc.).
Tne Class I--Critical Equipnent, which includes the nuclear s team '
supply system, and reac tor cooling and s tandby systems, as well as a number of other items, as listed in Sect ion V-3 of FDSt.R, are to be designed to- .
withs tand the same seismic f orces and other applicable loadings as noted carlier for the primary and secondary con t a i nne n t systems. '
t COMMEN75 ON ADECUACY OF DESIGN i
selsnic Des ion' Cri ter ia -- ke agree wi th thu approach adopted, I which is identical in principlc to that adopted f or. Dresden Unit 2, namely j that of a basic design f or a design earthquake with provision that a-safe L shutdarn can be rade f or a max imur ca r t hqua ke somewhat- larger-- than t he-design earthquake. Ve are in agreement with the 0.069' design earthquake +
and 0.129 ma> 1 mum earthquake criteria as given by the applicant in the FOSAR. >
provided that the f oundations of Class ! structures and equipment restEon -l sound rock or.an otherwise firm base. The boring data available in the FDSAR and Amendmerit s sugges t that a f oundation at elevation about 888-890 will rest on quite soft material, if the foundation'is placed-at this-level ,
we recommend a des i gn f or a 0.159 nes imum ear thquake wi th f urther provis ion that soccial pr ecaut ions br taken to insure that liquefaction of the supDorting i ..
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i f oandatlori neaterial cannot occur, and thut the foundat1on bc .l
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des igot d anains1 any 5ignificant settl&ent or tipping. A good ioundatlon- l design is of - paramount' impor tanc.e to the succest.f ul per f ortnance of Clar,s ! !
S t ruc ture s and er uipment - under car thquake loading,- We note that the US C f,G$ j e
report (Ref. b) concurs in these recommendations, flthough no rwntion of this fact is made in the FDSAR and Amendraents t that we have teen, we assume that interaction loadings between the reactor ;
builcing substructure and the surrounding soll will be considered in the l i
desion of the substructure for both static and dynamic fooding conditions.
The response acceleration spectre for the design earthquake of
- 0.000 (as recomncaded by the applicant in the FDSAR) is presented as F1 9. 6-$. ;
end it plotted therein to an arithrnttic scale which ma es it difficult to read, >
cspecially i ti the high-frequency (Iow pe r l od) r e g ion.t. . from the discubsion .l piesented in V>1ume 1 of. the FD$ A R and in resonnse to Oucs tion' ?.8 in An.end-tent 4 Le are led to believe that the acceleration response spec t ra correspond [
to-the Tal t car thquau of , July ?), 19b?, NCP W, except in terms of amplitude, .
which has been scaled. A replot of the spectrum on a log scale in terms of period.-but or i thme t Ic. scale f or ret panse ac celerat lon, has -been presented as fi 9 2.0-! in Amendment 4 Plotting these-two spectra on tripartitc e
toporithm paper,-which facilitates ccnparison of the " acce lera t iori, ve loc i ty . s a nd ' d i s p l a c eme n t response spectra, reveals some dif ferences in the two spectra, ,
especially i n t he h i gh-f rer,uenc y region. ' Also, when one compares the shape of the spectrum to the m-are commonly accepted response spectra, as for exampic~
that ior the El. Cent'ro carthquake, there seems - to be some major dif f erence: in( ,
the response values obtained, particularly in the f"id-frequency range from-i .-
about "
S ys t hrough 3 or a cos , which ray be the range of considerable i-I n
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importance-in many cases In design. The reasoning for the select. ion of-the 4 i
Taft carthquake is still not clear to us, especially in view of the fact i l
that this particular plant may be founded on rather soft granular foundation material, layered with cioy and till, sene distance above'bedroc~. In the 1 case of i tems which have periods of D.3 seconds or greater we recommend that the designers employ a higher input consistent with that used In previous-designs of this type, corresponding to the shapa of the El C2ntro response spectrum scaled to the appronriate acceleration. If the designers wish to i
use o spectrum which has en even higher response in the high-f requency region, ;
as i t a; pears may be the case f or the Taft record proposed, we will not object to this, f or this.is indeed conservative.
l The discuss ion on page !!-Ci-4 of the FDSAR Val. I Indicates that' i if computeri7ed methids of dynamic ana lyt is are used the ma there t ica l model' s may bc subjected to on crcuraion through the Taft carthqunac.- w: rec oatmcod that, if t h i t-method of analysit is crployed, the time-history record employed be such that it will be in agreement with the response spectrum values as outiined abnve throughout the entire f~recuency range, namely that-which would 1 carresonnd to a scaled El Cerit ro type exc itation, in Secti3n V-3 it is noted that the ver t ica l accelera t ion is ast,umed '
to be caual to tw3-thirds t he hor i t on t a l ground acceleration, and that for the design of Clan ! s truttures and equip ncnt the mu lmum horizontal acceleration and the max imum ver tica l accelera t ion are considered to occur sitnul taneous ly, an6 where applicable, stresses are'added directly. We interpret this statement :
in the app l icat ion - ti mean t ha t ~ the s t resses aris ing f rom the car thquake. in
- both tne ver1ical -and hor ironta l direc t ion, and which occur 5imul taneously at a particular location, wi ll Le added di rec t ly to the stresses ar.;5ing from the i
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other applicabic loadings,--including pressures and temperature-stresses arising f rom an accident. On the as s umn t i on that this interpretat ian Is cOrre !, he ConCcr in the aDproach.
For the ma>inum carthcarse and safe shutdown, it is noted in-l Secticn V-3 that the functional load stresses combined with the carthquake .
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s t res ses prot >ab ly do not exceed yield stress; hwever, where calculations f i nd i r.a t e that a structure :ar Diec,e of equipment are stressed beyond yield, on anal, sis 4:111 be made 13 determine its enerp bsorpt ion capac i ty end a review will be made to-insure that en,- resulting_ deflections or distortions will not prevent proper functioning of the structure or piece of equipment.
The same type of statement i s' traide f or the tra> imum ea r t hquake. Thesc' eriteric appear reasonable to us as t one, as t he des ign leads to assurance that t h( shutdown can be achieved under t he maximum earthquale conditions.
A table of damping co f f icients ib given on patje 11-6-!.. It is
. n u t e r, thcrein that. for the "reactar-building (mas s i ve cons t ruc t ion wi t h mnn, c ros s wa l ls and cou lpment anc providing on y secondary containment)"
a darw i ng va l ue of 5 percent is specified. Furthor elaboration on this point is given in anner to Question 2.5 of Amendment 4 'Ar. a result of i tecent-considerations on our par t and by ot hers, we would be in agreement eith t his value f or cases in which working stresses are no more than about.
one-half the yield point and in which there may be considerabic cracking af.sociated with the concrete structure. In the event that the concrete is nut ttressed to that level where it is considerably cracked, we would recommend a value of 2 or 3 percent as being more reasonabic.
fiso listed therein is a value of 10 percent critical-damping for pround roc sing modes of vibratlon. Wo.would' agree, particularly when
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8 Structures are founded in or upon a soft base material, that the evidence indicates that - f ounda t ion ac t ion counled wit h st ruc tural ec t ion leads to larger equivalent damping values. On t he bas i s of i nformation currently l asailable to us at present we would be reluctant to ass'ign a'value as high l es 10 percent and would reconmend a value of perhaps 7,5 percent as being ,
acolicable under the noximum carthquake conditions-unless there is some ;
further j ust if icat ion ava!!able f or assigning a higher value. I Although no statement i s made t o thi s e f fec t , we ass ume that the domping t actors c ' ted ir Table 11-0-3 are te be employed f or both 'the design .;
and max irt,um ca r thqua ke loading conditions. ' '
1 in connection with the secondary containment as provided by the reactor building, statements in Section V-2 indicate that the $1 ding is to ;
be i nstalled with scaled joints. The insurance provided agalntt leaka ge is not clear to us f or cases involving design or maximum earthquake loadings, ;
and we believe deserves further consideration.
8 On page !!-6-5 the s ta terent is made that Clabs !! structures and equipment shall be designed on the basis of a minimum scisnic horizontal
- coefficient of 0.10 with a one-third allowable increase in basic. stress.
F ur t he r amp l i f i ca t i on on this approach is provided in. answer to Question 2.8 of Amendnient 4 wherein the applicant shows that-this app 6oach is conservative when considered -in connection with the basic design earthquake proposed by the applicant. In accordance with the discussion presented we believe'the.
-oach is acceptable f or the _ par t icular des ign carthquake loading selected this facility.
Wi th ref erence to c ranes ,- f ur the r elab' ora t ion on the des ign .of
-the_ cranes i s presented i n ansbcr t o C ue t t i on 2. 9 of Amendmen t 4 On the 4
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basis of the philotophy described therein, that clamps and bumpers will be provided to' prevent the trolley and bridge f rom being di%placed durinn ;
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carthquake excitation. we believe that the design will be satisfactory, i The design of the stack is described in more detail 1.'. answer to Cues t i on 2,10 of Mendmen t 4, anc we are in agreement with the criteria t
det : r ibed there concerning the poss ibili ty of danace should the stac*. fail, _
i and the r-ethod of anclytis to be followed in the design -f or poss ible car th--
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cuase loading. We recommend that the damalng to be employed in the design ,
f be c>nsistent with the strrss levels that are expected, and a damping value on the order of 2 or 3 percent be used unless significant cract.ing is envisioned in the response of the stack, which we expec t would- not be the cato.
- e We f ind no details concerning specif ic attention to the strength- -
t en i n4 of areas around penetrationt of the containment, par ticularly in the orivary c on ta i nme n t area, the drp.clI, in the case of large penetrations especially, care should be taken to insure that these details will retain I the required *trengtb anc ductiiity under carthquake and service 1oading.
t Pr imary one secondary Containment Structure -- Tables of allowable stresset for the primary and secondary containnent design are presented on pag V-3-2 and V-3-3 of FOSAR Vol. I. These tables appear to be essentially s i rn i l a r to the tables presentec for Orcsden Unit 2_(Ref. 4); the tables appear ;
i to be in agreement with applicable codes, or in other cases appear to be .
reasonable to us.in general, However, there is one-point that needs clar_ifi-cation, namely the meaning of'.the com,ent in both tables cited relating-to
_ s e, f e shutd%n of the plant and the subsequent applicable f ootnotet. .i t is not-l' clear t3'u; 6.heth"r special s t res s c r i te r ia v i ll be erployed f or - Loading
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, 10 Condition ? or 3 respectively (f or -safe shutdown), or whether these ref erences
- apply to -the stresses -listed previous ly in the tables. In any event, although i
de believe clarif ication should tie (;iven to the point noted, in line with the pencrel c r i teria spec i f ied f or saf e shutdown, we believe that the design will ;
be adequate in this respect. I A study of the FD5 Aft documents indicates that the piping appears t o rice t the opplicable ASME and ASA Codt provisions, and no further comment .c is made herein on this matter, excent to note in connection with Table V-3-3 -i that Loading Condition 3 refers to a factor of "M.O.L. + 2 + $.L." This factor
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of 2 ^ 5.L. should be changed, we believe, to ref lec t the maxlmun. ear thquake I that is selected, wblch rnay not necessarily be twice the design earthquake nor twice the response values applicable thereto. The pipe penetration $ appear .i to be s irri lar to t he previ ou!. Dresden 2 des ign, and in accordance with dis-cussion in the FDSAft end Amendment 4, it appears that provisions have been ,
made to Mcomodate the jet f orces resciting f rom postulated ruptures' of any pipes within the containment. We also note and agree with the design approach followed for the main steam i sola tion valves as out lined on page 2.7-2 of '
Amencre n t 4 wherein the det.ign is carried out for scismic effects on these-values. as well as the appl.icabic piping.
CONCLUSIONS in line with the design goal of providing serviceable-structures comaonents with a reserve of strength and ductility, and on the basis'of' the inf orma t ion presented, we believc1 the cesign cr i ter ia out lined f or the -. i primary containnent. secondary containment, and Type i piping.can provide an acequate margin of safety for seismic resistance, i n reaching this, conclusion we assume that'the applicant will give f urther consideration to the several' i tems noted hercio concerning particularly the foundation design, i
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maximum earthcluate design level, the earthquake response spectra, the opolicable domping, and the enplicable stresses, especially for safe' shut-d o., n f o r the containment structures and piping.
REFERENCES I. "fa:ility Descr iption anJ Saf et y Analysis Report--Volume 1," Honticello Nuclear Generating Plani Unit i, Northern States Pwer Cornpany, 1960.-
- 2. "focility Description and Sofety Analysis Report--Volume !!." Montlcello Nu;lcar Generating Plant Uni t 1, 140rthern States Power Company. 1906.
- 3. "f oc i li ty Desc r ipt ion and Saf ets Ana lys i s Repor t--Amendment 4 '.' Mant icello Nuclear G.'neratino Plant Unit I, IDr thern States Power C amp o f , 1900,
- 4. "Adecuacy of the Structural Criterio.for the Orcsden fluclear Power Station-Unit 2." Report to the AEC Regulatory S taf f , by N, fi. Newmark and W. J., Hall,.
September, 1905. .
- 5. " Report on the Seismici ty of the Monticello fluclear Cencrating Plant' Unit 1,"-
U.S. Coast and Geodetic Survey, Ra;iville, Maryland, .
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