ML20128F355
| ML20128F355 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 12/04/1969 |
| From: | Hall W, Newmark N NATHAN M. NEWMARK CONSULTING ENGINEERING SERVICES |
| To: | |
| Shared Package | |
| ML20125A422 | List:
|
| References | |
| FOIA-92-198 NUDOCS 9212080317 | |
| Download: ML20128F355 (12) | |
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I J A 1 H A l .' f.: N ". W M A R K ;
CON 7ULTit!G N N : ' T ;af NG L P,%'#C C G 1114 CIVIL CNGINCEiN' C CUILDINC. -
URBANA. ILLINOl') 61001 REP 03T 10 AEC RELULAIORY STAFF Clt THE ADt00ACY Or THE S1hUCTURAL DESI0fl FOR li!LLSTONE flVCLEAR POWER $TATION UNIT 1 AfC DOCKET No. 50-245 by ,
6 N. 11. Hewmark I ,.
W. J. Hall RgCElVED "
' AICMC INERGY CONF.USS10 ACRS 9
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4 December 1969 9212000317 920611 '
LAWRENC92-198 PDR .
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ADEQUAC f Or IhC ! ff40CIURAL DESICN
, TOR HILLST0ld NUCLEAP, PNEh STA110N U11T I by N. H. Hm.tr.or t and V. J. Hall INTRMC r!_0N This report on the Hillstone Nuclear Power Station Unit I was prepared on the basis of: (1) Review of the Final Safety Analysis Report l (FSAR) and anendments thereto as submitted by the applicant, and as listed l
l at the end of this reporti (2) a visit to the site on September 10, 1968 and discussion of the facility in a neeting on September 11, 1968 in New York City with representat Ives of the appilcant, the AEC Division of Reactor Licensing and the npplicant's architects end engineers; and (3) discusslor,a of the facility with the AEC Regulatory Staff.
The Hillstone Nuclear Power Station Unit 1 is designed for a maximum output of 2,011 HVt (652 Hwe net) and consists of a single cycle o forced circulation bolling water reactor producing steam for direct use in.
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a steam turbine. The unit in ecst respects is slmtlar In concept, but not
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i in size, to Dresden Unit 2. The application .for an Operat ing License hes .
been made by the Connecticut Light & Power Corpany (CL&P), the Hartford l-L Electric Light Company (HELCO), Western Massachusetts Electric Company (WHECO),
and the Hills tone Point Company (Millstone). The f acility is located on the north shore of Long Island Sound in the town of Waterford, Connecticut, and about 3.2 miles WSW of the town limits of New London, Connecticut.
Hillstone Nuclear Power Station Unit I was designed for a Design Basis Earthquake (DDE) of 0.179 maximum horizontal ground acceleration and for
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2 an Operat ing Bas is f arthqu..ke (OSC) of 0.079 m:41 mum hor izontal ground acceleration. Ihr vertical certhqusk? excitat ion was assured to occur s imultaneously, and was tol:en as two-thirds of the magnitude of the corresponding horirontal excitation.
The crlterlo applicable to the design of Millstone Nuclear Power Station Unit I vare reviewed by us at the cons truct ion permit s tage; we have not in general included herein comments on toples covered in the earlier report.
COMMENTS ON AQLQUACY Or DE510N farthquake Hara_r_d The earthquake horard proposed and agreed on originally for Mllis tone I cons idered an ODE of 0.079 max, ground acceleration and a DBE of 0.179 The ratlo between these values is not in accord with pres 6nt seismic criteria which require that the OBE be at least one-half the Intensity of the CBE, The purpose of the present criterla is to insure that t ,$e earthquake induced notions and stresses are consistently related to the allowable stresses and/or motions for the two earthquake hazards considered, taking into account the appropriate damping f actors and other appropriate condit lons , and that the norgin of safety is not lower than It should be for those items of structure or equipment whose design is most critically
Hence it is cf the most urgent i mpo r t a nc e , in considering the
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adequacy of the Mills tone Unit No. 1, that emple margins of safety exist for the OBE design conditions to make up for the f act that the OBE values originally used are approximately twenty percent lower than the values that would now be used in the design of a new plant to be. consistent with the DBE values, which are regarded as being appropriately conservative.
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}/ebelievethat in general the design of this platit is governcd Ly the DCC conditions, and that there is enough of a norgin of saf ety to insure that the slightly low OBE values that were used d.o_ not_ _impair the safety of the plant, pynamhcAnalysisofStructures from the materials presented in the FSAR and amendments thereto, -
It appears that three methods of dynamic analysis were enployed for major structures an noted next.
T!w History - The answer to Question Vll.A.10 indicates that the drywell, reactor bu,Ilding, ventilation stack, rad waste building / control room, and condensate storage tank, were analyzed by the time history method. The jescription given in the amendments to the r$AR Indicate that the solution in this case is based on a classical norml node approach, and' the time history of response is computed for each uncoupled mode by numerical Integration. Subsequently the modal responses are combined at each Instant of time, and the maximum values are determined for use in the design process.
The answer to Ques tions VII. A.9 and VII. A.10 s tates that a 12 sec.
interval of the Taft N 69 W earthquake, nornellzed to a ground acceleration ,
of 0.079, was used. The answer to Question B-1 of Amendment 18. Indicates that a s lmt lar approach was crployed - for the Des ign Bas ts: Earthquake analyses.
The answer to Question VII. A. ll . in Anendment 17 Indicates that the response spectrum resulting f rom the nornot ized Taf t time history in all-cases fell above the snoothed response spectrum which had been provided as criteria at the tlne of the Preliminary Safety' Analysis Review, which is acceptable.
The damping values which were used with the analyses-are given in the answer to Question VII.A.14.1 and appear acceptable.
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lo On the basis of the Inf ormt lon rude ovallable to us , we believe that tra t irv-his t ory.- "e t hod n us< d cons t itutes a reascnably conservot ive design approach. Iri A~rndrent if> tbc applicent conf irre that all of the
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- the Cl3si ! l t e rm anal yzed by/t ic.e-bls tory me thod were anal yzed f or, and are capable of res is t ing within allcuble limi ti., both the Des ign Bas is f arthquak e es well as the Operating Basis farthquake.
Res pont c & cctrem - The answer to Questlon VII.A.10 Indicates that t he gas turbine building, Isolat ion condenser, LPCI pump, conta inment hea t e xchange r, suppres s ion chamber, recirculation loop piping, and reactor pressure vessel were des igned by the smoothed response spectrum method of analysis. A descrIpt lon of the response spectrum txthod used is presented in Amendment 18.
The applicant Indicated therein that " Method !" Involves calculat ion of moment s and s t r es s es from the resultant (s qua re root of sum of squares) of the modal inert ial f orces , and " Method II" Irivolves the s tandard nodal response approach of calculat ion of the values of moment, shear, etc. , for each mode and corrbining these appropriately, as, for example, by taking the square root of the sums of the squares of the modal response values. When several of the frequencies lle close together, however, even this approach may not be conservat ive and d irec t s urmut lon f or the corresponding modes rray be more appropr late. In some cases Method I can give unconservat ive results unless the direct ions of the resultant ine r t la t f orces are care f ully chosen.
5 Complete check calculations are required to demonstrate that the response jructrum ruthed of analysis as used in all cases is conservative, it appears from the results of the calculations rcported on page 103 of Ate ndre nt 18 that the earthquake Injured stresses in the recirculation piping are relatively snall, and hence the design achieved can be considered as reasonably acceptable. The maximum stressos for the recirculation loep piping are given In Amand. Tent 19 for one case, with a breakdown of the sourcos of stress presented in Anendnent 21. Although this breakdown does not IdentIf y the details of the method of analysis used, it helps to demonstrate the conservatism of the des ign. :
Equivalent Static Coef ficient Hethod - The answers glven to Questions VII. A.2, A.3, and A.4 f or pIptng Indicate that a rigorous dynamic analys ts I
was not perf ormed for the main steam line piping and apparently neither for.
nost of the other pIptng. 'Instead, a static anslysis using equivalent static coef ficients to account for the seismic excitation, was employed.
From the tabular Infornation presented in the answers to the questions cited, as for exanple Table VII. A.4-1 of Amendment 17 It appears that the approach. >
adopted leads to conservative values of stress. It is noted in the answer to Question VII. A.4 that "the stresses in all Class I piping systens 'are wl' thin, the allowable stress l'Imits as set forth in B31.1.0-1967." An additional entry to Table VII. A.4-1 is given on p. 10 of Amendment 19, and covers the
- core spray system. It will be noted there.that the seismic stress comprises 7
a nojor portion of the total stress, f
Two points were noted in reviewing this portion of the analysis :-
namely, (1) that in considering the vertical: carthquake excitation-It appears l
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6 that a constant coef f1cient of 2/3 of 0.079 or 0.179 for the OBE and DBE respectively tere used without ac:111fication; cnd (2) there 15 no indication that the loadings were placed on adjacent spans of piping in directions to lead to the cbsolute maxiirum stress ing conditlen. However, in view of the short lengths of the pIptng spans, and the high frequency range in which most of this piping would be expected to f all, it is believed that these coefficients _
and analyses will not lead to stresses that are seriously greater than those that were calculated. On this basis, we believe this aspect of the design is marginally satisf actory.
The description of the procedures that were employed in determining the placement of the hangers , s tops, anchors, etc., and their des ign appear ,
acceptable.
Cont a i nma nt _ Dns l qn The containrent des Ign for the Hillstone station is of the conventional steel drywell and torus type. A substantial amount of detailed Information concerning the design is presented in the form of copies of detailed certified drawings in Appendix 13. The text noterial includes conwent on f abricat ion procedures, welding details, and a general' description of the erection, testing, field Installations of penetrations and nozzles, and a general review of the basis of the containment des Ign.
Included is a description of the seismic loads and seismic coef ficients used for the des ign of the drywell. From the Infornation presented in.
Amendme nt 17, It is evident that these coef ficients were determined f rom a t ime his tory method of analys is.
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On page XII-l.13 It is noted that for the Design Basis Earthquake a f actor of 2.4 t itres the Operat ing Bas is Earthquake shears and nonents were used. This ratio corresponds to 0.17/0.07, the ratlo of the 00E to the OBE, and seers reasonable If the loeding conbinations are conpa rable.
Reactor Suy ort Structqrs The answer to Quest ion VII. A.6 In Amendnent 17 discusses the_ reactor support structure design. The response given there suggests that because the
" proof load" on the bolts is greater than the rnaximum tension any bolt will be subjected to, the f riction force will be available. Later discuss lon in the same reply suggests that the term " proof load" used there really refers to the applied clamping load and suggests that the f riction will be ef fective at all times for all loading conditions. From the Infornution presented in the summary table and the discussion, it appears that this aspect of the design is satisf actory.
Class i St ructures and Eculpment located within Class II Structures In responding to questions on the problem of Class I structures and equiprent located in Class II structures the applicant has supplied -
Infornation concerning the specific Items of Class I equipnent housed in Class II structures in Amendment 14 Specif ically, on Page !!!-2 It is noted that "An evaluation of the Class !! structures ho, sing Class 1 -
eq uipme nt Indicates that these structures have the capabil !1y of reeting Class I requirements, except for a few items. Modif icat ions will be made, where necessary, so as to insure the proper f unction of the Class I (quipment."
b An explan,ation of this point 15 made in the reply to Question B-4 of Ar.c od rw n t 16. This expl4 rat ion appN rs sat is f actory.
To_rus A?!anbly and SurtIrn N a d e r_
A discussion of the design procedure followed f or the torus and suction header 15 presented in the answer to Question VII. A.I. It is dif ficult to f ollow the presentation given there, but on the basis of the Infornation -__
presented there and in the answer to Question 0-5 of Anendment 18 the design appears satisfactory.
Floodlna of Critical Purans and HStors due to fallure of Cupnression Charher The discussion in Amendnwnt 15 suggests that the possible leakage of coolant would be handled by adequate pumping capacity, but the response to Ques tion VII.B.9 in Acendment 17 notes that the corner rooms will be protected with water-t tght doors which will preclude inundation of critical ECCS e qu'pment. We concur In this approach.
Tornado pes 1qn Criterla The tornado design criteria are described in answer to Question !!I. A.4 of Ane ndme n t 15. The celteria given there, including consideration of a tornado with a rotationa) velocity of 300 mph and a translational velocity, of 60 nph, are in line with similar criterla employed for other plants with the exception that It, appears the tangential and translational velocitles are not superlmposed to yleid a net translational velocity of 360 mph. In this respect, then, the design may not be quite as conservative as that in f
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9 other slmtlar plants currently being constructed, although it naets the criteria originally proposed. Also, it is noted in the discussion that the stress limitt enployed with the torncdo design were yleid point for steel and 8'/4 o f ul t i r.a t e strength for concrete. These two stress criterla are not ccm,mrable as regards reserve of avalloble strength.
Se twle CrItgrla f or Equipr;nt Pr ec u rn rm n t , inf ludino Critleal in'.trem ntatlon _
and Controls The answer to Question A-ll of Amendrent 16 and A-7 of Amsndment 18 Indicates that this this topic has been considered. However, the detalls of the analyses and types of tests to be perforiwd need f urther clarlfication.
We recontend that this be a follow-up ltern at a later tine.
,J ny k e structure It is noted in the answer to Question IV.1 of Anendment 17, A-16 of Ane ndne nt 10, and B-3 of Amendment 19 that the intate structure neets Class I selsmic criteria. Just as in the case of the tornado des ign, however, the 1
two s tress criteria of yleld for reinforcing steel and 0.85 fl for concrete used in this des Ign are not comparable as regards reserve of available strength.
Torslonal Effects ,
The answer to Question Vll. A.15 and B-7 of Amendment 18 suggests that torsion will have little ef fect upon the contalnnent structures. In fact, accidental torsion input arising from earthquake excitation, and more part icularly f rom anomalles in the propagation of the carthquake ground motions, is unaf fected in any way by the stif f ness of the s tructure involved.
The configuration and stifth of the structures affects the stresses that the structures see, but has no e f f ect upon the accidental tors lon which can occur whether the building is synnetrical or unsynnetrical.
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, The ef fects of accidental torsion have rot been considered in the analysis of the building or cenntet ing elemnts. iksn e r , t he s e e f f ec ts are probably small in this c6se.
Dr m p 3 1 of Fr..L L g h It is Indicated in the answer to Question VII.B.4 that the analyses pertalning to the dropping of fuel casks into fuel storage fill pool will be provided before 12-1-69. The answer to Question A-10 of Amndment 18 does not adequately consider the ef fects on the f uel pool structure to insure the adequacy of the design to preclude an accident arising from such an incident. However, this is a generic consideration and we understand that CRL 1s also following this item.
SUMMARY
COM4F NTS Af ter a review of the FSAR and the amendments and other eterial x
made available to us, we believe the design is probably adequate in terms of provision for saf e shutdown for a Design Basis Farthquake of 0.179 mulmum horizontal ground acceleration and to withstand otherwise the effects of an earthquake of 41 percent of this magnitude. However, on the basis of the inf ormat ion mde available to us, it is our opinion that the existence of a' positive margin of safety in the design rests on judgment rather than fcct i
proved by analys is.
We have noted in our report several items which should be handled as f ol low-on I tems. .
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- 1. Final Saf e ty Analys is ficport , Volt. 1, 2, crid 3, and Aner.dmnt s 8, 9, 12 through 19, and 21, Millstone Nuclear Pewer Stat len Unit 1, 1968 and !
19691 l 1
- 2. "Millstona Point IJ'sclear Station f orthqu:Au Analysic; Reactor Dullding," i John A. 01uw and Atso:.3 July 19%. (Report reforenecd in FSAR, but l transmitted Inforrr. ally ) -
- 3. " Adequacy of the Structural Criterla for the Millstono thscicar Pew:r -
Station" by il. M. Nevnerk and W. J. Itall, February 11, 1966, prepared .
under Contract No. A1(49-5)-2667.
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