Regulatory Guide 7.6

Stress Allowables for the Design of Shipping Cask Containment Vessels

ML13350A219
Person / Time
Issue date:	02/28/1977
From:	Office of Nuclear Regulatory Research
To:
References
RG-7.006
Download: ML13350A219 (4)

REG"LATORY COMMISSION'" n e l eibruaryh1977

) .(ou@ U.~...INUCLEAO

..G

• . .

• OFFICE OF STANDARDS :DEV ELOPM ENT-

REGULATORY GUIDE-7.8 STRESS ALLOWABLES FOR THE DESIGN

OF:SHIPPING. CASK CONTAINMENT VESSELS

'

A. INTRODUCTION

aind thev allowthe use, of superposition in stimming loaiding týffcfls. De~sign stressVtlutsfor ifltefsitiesar dL usel.

Se.'tions 7 a.35:and ,,1136 Of 10 CFR Part 7.. h-bCauseLestablished naterial this use ist

-in',Iih4 th 1E'.d. C and,.bccause this impproach is

,...ackaging..of Radioactive .NMtaterial for Tranisport. shear stress the~or-...'h;i6 h*.s

... : Tr *: tnsport of Rad~ioact*ie.Mieria U~nder*. "t bh"huni aeon icUd hI

i niaxixmunif Certa.un Condiiihn.C:.establish* reqirementst sh0,"n to .he iacnserv ivL cSt mainttcLfthe stress"

• ominitns tha-iUep istic de orn~a* re it v

" Oi.ekaAsusd:i6? tr'amsp0r. radi'active materials,;-:z ,

, ,-must."mt:under~normal- and.hypothettcal',accident. ,to,,cxerimntal. ..data- " "" -'= - , . ." "

sign criteria ac-  :' '," ...-. :

"*i!!=? :0h * iti5sUTis

,:::: uid niostmib es' d

.con

• . .ceptah.to itions.This gudd

.the.,N.RCstaforuse

-

the rteistructuraC, . 'In current designs for the t*a nent isselsol vessels of-type B fuel casks. the nature or *i y.c.l i t d pressure analysiso*.f th:Icontainment loads and the contain* ,,,i (stainle.s

p ickages: used to transpo rt irradiated nuclear :fuel.

steel) re such tha c rle fracture ru not MAlternativedesign criteria may"be used if judged ac, Thermal ratchetting considered to p I P let

.cptah!-,by the NRC.staff in meeting the structural Iau. I ficulies in cyindrical requirementsofli§7L.35 and 71.36of 10CFR Part 71. is nol consi ere

B. DISCUSSION

I*N o' ' "ions 3 vieldint. and 7 ensure that failure

. ket, 'e;tt~r ined ntr,*,.t. hlid At nresent. there are no desien standards thatican ticcur. Secondarv stresses (i.e.. stiesse:

.he directly used toevaluate the structurhl integrity orf:Affil

• 0..,; the -contairieinnt

....radiated How-vcr.

ruecls. radiated.fuel. %lessels"Section of shippingcaksfrr AIl or~he. A E ""-T~l' ieidingar 'ni s unrestrained Ni-ldbng-hut. are :considered in not considered nsiee tooc's cause H eergro Boiler*and Pressure Vessel Code.* n a fatiuu and shakedow n .mnlmls

• ments.for thi design of nuclear power nit. corm of S J.* lOf "r tion d Regulatory csnt Position 4cmtr ensures that Positio fatigue failure

5nensure.,

nents. "The staff has.adaptcd pbrtions eria oe notoccur and Reulat Position the ASM*E.Code to'form acceptabled

.. for shippiing c, k containment.:vessels. In I.I guide. . that- the structureswill shake down to elastic behavior mcask containment Vest :after afew c\ cles. Both of these positions deal only thc'ded6ign* criteria for.s fined in 10 CFR Part ..ithehstress rane of normal operation. A reduc-

• .st~ls ~r..normal conditii (

71). are'.similar Ntgcdictr, r ia-in Section III of tion. in the aIIowitble stress for-lire exceeding.10' -cv- the ASME.Co fo 'as. components under nor- : ces is specificd:in, Reulator, Position 4 since:use of

• al condj* n and I de ign criteria for.* accident the~ 10:Cvclycvalue for greater lives* mnia not preserve cases.

condit'fr those for-faulted  :)

conditions

': *

an amdequate design margin  : for all inw the ý'

Co a, ..

Regulatory Position 8 places a limit on the extreme The desit criteria :.presented hcre arc based rance of.tht tot ilstresses due to initial fahrication primnarily on lin ear elastic analyses. Linear.. elastic and the norial: opr ating and accident states ol" the analyses are simpler than truc elastic-plastic analyse

s. containment vesseL

"'Copies may be obtained; from. the American. Society or Mechanical Engineers, United Engineering Center. 345 East 47th The followking terms are presented with the delini- Street. New York. N.Y. 10017.

tions used in this guide:

-1 , 111:-Slwict..9lv I IN Ot,:t.'-.'

14.1~ icfJ;.'tt.

UNCREGULATORY G IDES, t~i C~lnik'tn 011411IdW

.,2blA-1-1D~  !";--11S1 thu~itr ie l! iý" ~totE jiý

,git,,meine! tiaks~e a uiart~.t the pulcmethodss~ faluly o40tt4ih"llI

.iii ffl ttvttilIn, th

e. to

4 fl4in aliln Slc ii ittn Gublern.

Rt,

1tS t otttJet4 lt

1. I'owl,- flea Jtu% I.. Pttoijur wilth tt14Cm isno, rftwified.

a'! nut ast.etit uvts fto re 0 4 llt tons, antl 0.tintI.iflrp 2. Rnse..11t It,%.Tlst R,,ictms 7. T ,s~~ttc, dif1levent front thousi%410nutin itte,?quitil" will ile .IVcet.t .de I

'l v1,1 tiltsoulno4s 3., Fuets ntrolMaim ,,ts F itte a ocuil.outn.t11 tI~novie I t,,u In, the Instltitjs mln~us~tp 4tho a~~, tim sulatee or conflniiunce 9, Anfn,,ttstH'

A .bif .th . 4, Env,,tinnwntatl anti Sitirnl

.

at peri or jw., Ir itm Coirmivor, -

Otatidi encautav.id at all Corntnnts an'l %urfgvittris Inimpntfltewtflit%- iti ttiev-

.14

0 . fim. and.rpotle.

to 1,41lectri" Inom to

,nflf.ix:t.,u, o t*-4. tlnnt orniwrrv.

ti1av.

Ho 'w Cotl

-nimiatS

.C4 1t n cieihls on th is q idjif d R...ttess It,Is~nifle. 1r-o1nýIII-W

men!,t 0n .40 *tunslntiidtt t i ii-0 t swet lml4.1 Ii timtli

4ti ll 4wr SIt.

%As,,rh 116v, Iii4.!~w,'it tt,, , ilIthlefittS

t 41 .

205!bg. Alttrit-ri U,. ,twt . ofit Dot T11i.111en 11:.1,oo,,

W.0st~o

.. U.C, ., -

nett.autt ott tt,. t.4 eil tor an .6irv s.it,.

I. Stress intensity' is defined as twice the maximum 8. Containmeni vessel is defined as the receptacle shear stress and is equal to the largest algebraic dif- on which principal reliance is placed to retain the ference between any two of the three principal stres- radioactive material during transport.

ses.

C. REGULATORY POSITION

2. A primary stress is a stress that is necessary to satisfy the laws of equilibrium of forces and moments The following design criteria are acceptable to the due to applied loadings, pressure loadings, and body NRC staff for assessing the adequacy of designs for (inertial) loadings. Primary stresses are not self- shipping cask containment vessels in meeting the limiting because local yielding and minor distortions structural requirements in §§71.35 and 71.36 of 10

do not reduce the average stress across a solid sec- CFR Part 71.

tion.

I. The values for material propertie

s. design stress

3. A secondary stress is a stress that is self-limiting. intensities (Sil), and design fatigue curves for Class I

Thermal stresses are considered to be secondary components given in Subsection NA of Section III of stresses since they are strain-controlled rather than the ASME Boiler and Pressure Vessel Code should be load-controlled, and these stresses decrease as used for the materials listed in that subsection. For yielding occurs. materials not listed there, the method discussed in Article 111-2000 of Subsection NA should be used to The bending stress at a gross structural discon- derive design stress intensity values. ASTM material tinuity, such as where a cylindrical shell joins a flat properties should be used, if available, to derive head, is generally self-limiting and is considered to be design stress intensity values. The values of material a cecondary stress. However. when the edge moment properties that should be used in the structural at the shell and head junction is needed to prevent ex- analysis are those that correspond to the appropriate cessive bending stresses in the head, the stress at the temperatures at loading.

junction is cons'idered to be a primary stress. The bending stress at a joint between a rectangular shell 2. Strain-rate-sensitive material properties may be and a flat head is unrestrained by hoop effects and used in the evaluation of impact loading if the values will be considered to be a primary stress. used are appropriately considered in a dynamic time- dependent analysis and can be suitably justified in the

4. Primary membrane stresses are the average nor- license application.

mal primary stresses across the thickness of a solid section. Primar.1 bendingk stresses are the components When strain rate sensitivity is considered in the of the normal primary stresses that vary linearly structural response to a combination of static and across the thickness of a solid section. dynamic loads, the static portion of the stresses and strains should be analyzed separately using static

5. The alternatingstress intensity. Salt- is defined material properties and should meet the static design as one-half the maximum absolute value of S 12, S,)., criteria. The total stress and strain state resulting S'I. for all possible stress states i and j where oa., a02 from both static and dynamic loads should meet the and u 3 irc principal stresses and design criteria for which strain-rate-sensitive material rroperties (e.g., yield strength) are substituted for static values.

SC2= (Oi - frlj) - (o2i - '2j)

3. Under normal conditions the value of the stress S!3 = (a - a2j )" (03i - a3) intensity resulting from the primary membrane stres- Sit. (3i - a3j)-(ali - Or1j) ses should be less than the design stress intensity, Sm, and the stress intensity resulting from the sum of the

• 1, etc., follow the principal stresses as their direc- primary membrane stresses and the primary bending stresses should be less than 1.5Sm.

tions rotate if the directions of the principal stresses at a point change during the cycle. 4. The fatigue analysis for stresses under normal conditions should be performed as follows:

6. The phrase stresses caused b ' stress concentra- tions refers to increases in stresses due to local a. Salt is determined (as defined in the "Discus- geometric discontinuities (e.g., notches or local ther- sion"). The total stress state at each point in the nor- mal "hot spots"). These stresses produce no mal operating cycle should be considered so that a noticeable distortions. maximum range may be determined.

7. TIpe B quantitv isdefined in §71.4(q)of 10CFR b. The design fatigue curves (Figures 1-9.0) of Part 71. Normal conditions of transport and Section III of the ASME Boiler and Pressure Vessel hypothetical accident conditions are defined in Appen- Code should be used. These curves include the max- dices A and B, respectively, to 10 CFR Part 71. imum mean stress effect.

7.6-2

c. Salt should be multiplied by the ratio of the m n Trnax. 0 F

modulus of elasticity given on the design fatigue Low Alloy Steel 2.0 0.2 700

curve to the modulus of elasticity used in the analysis to obtain a value of stress to be used with the design Martensitic Stainless Stec 2.0 0.2 700

fatigue curves. The corresponding number of cycles Carbon Steel 3.0 0.2 700

taken from the appropriate design fatigue curve is the allowable life if only one type of operational cycle is Austenitic Stainless Steel 1.7 0.3 800

considered. If two or more types of stress cycles are Nickel-Chromium-Iron 1.7 0.3 800

considered to produce significant stresses, the rules for cumulative damage given in Article NB-3222.4 of Section III of the ASME Boiler and Pressure Vessel Code should be applied.

c. The temperatures do not exceed those listed in the above table for the various classes of materials.

d. In the analysis of high cycle fatigue where the number of cycles exceeds 104 cycles, the ASME

design fatigue curves should be extended using a 4%

decrease in the allowable stress per decade, starting d. The ratio of the minimum specified yield from the IO0 cycle value. High cycle fatigue could be a strength of the material to the minimum specified potential problem due to vibration during transpor- ultimate strength is less than 0.80.

tation.

e. A value of 4 should be used as the maximum 6. Buckling of the containment vessel should not stress concentration factor in regions where this fac- occur under normal and accident conditions.

tor is unknown.

5. The stress intensity, Sn, associated with the range of primary plus secondary stresses under nor- 7. Under accident conditions, the value of the mal conditions should be less than 3Sm. The calcula- stress intensity resulting from the primary membrane tion of this stress intensity is similar to the calculation stresses should be less than the lesser value of 2.4Sm of 2 Salt; however, the effects of local stress con- and 0 .7Su (ultimate strength): and the stress intensity centrations that are considered in the fatigue calcula- resulting from the sum of the primary membrane tions are not included in this stress range. stresses and the primary bending stresses should be less than the lesser value of 3 .6Sm and Su.

The 3 Sm limit given above may be exceeded if the following conditions arc met (these conditions . 8. The extreme total stress intensity range between can generally be met only in cases where the secon- the initial zero stress state, fabrication, normal opera- dary bending stresses are a substantial portion of the tion. and accident conditions should be less than total stress): twice the adjusted value (adjusted to account for modulus of elasticity at the highest temperature) of a. The range of stresses under normal condi- Sa at 10 cycles given by the appropriate design fatigue tions excluding stresses due to stress. concentrations curves.

and secondary bending stresses yields a stress inten- sity, Sn, that is less than 3 Sm.

A value of 4 should be used as the maximum b. The value Sa used for entering the design stress concentration factor in regions where this fac- fatigue curve is multiplied by the factor Ke, where: tor is unknown.

Ke = 1.0 (Snr < 3 Sm)

9. In some cask designs. shielding materials apply (I-n) (Sn _I loads through differential thermal expansion or supp-

=1.0+ n(m- ik3Sm 1 _(3 Sm<Sn< 3 mSm)

ly additional strength to the containment vessel. In such cases, shielding materials that have low yield

=1n (Snn -. 3 mSm) strengths (e.g., lead) may be structurally analyzed us- Sn is as described in a. ing an elastic-plastic technique while the inner shell is analyzed by a linear elastic analysis. When uranium is The values of the material parameters m and n are used for shielding and is needed to add strength to the given for the various classes of materials in the fol- containment vessel, the fracture behavior of the lowing table: uranium shielding should he considered.

7.6-3

Ii .D0

J. IMPLEMENTATION

sions regulahtions., the design criteria described herein

%,ill be used bh the starr mter October I .1977. in as-

1I,-pUrp'os o N his section. is to provide infornma-

16n,:.ppIIýl Ints:- rardingj the N RC

lien ezs

.se.sing the. adequacy or designs.

"LI 0l" packages for shipping ur coiltainnient:.,ces- irradiated fuel with

'0

respect to the structural rcquiremcnis in *71.35 and stahrt~. plan wror Lil.i n. this regulatory guide.

7.1-36 .of I..CI"R. Part771. Whenoralternative criteria licensee .roposed...ti.applicant should I w.-.cpt in thl%L t.s case in h~ich thL dfplpic nt 'or icnu proposes .mndmet.ptatl ahk letrilativt method. denitinrtr tl*t tl'heir use satisfies the: requirements t'or conilpI\ ing;wtth ,pecified portions ol*.tht Conmris% of -§,7 T3 5mAnd 71 36 o 110 CF R Part .71.

I

I.J)NITED STATES

• NUCLEAR REGULATO11Y COMMISSION

INAS H IN rTON; D. C. 20555 POSTAOE AND FEEs PAID

• NUCLAR RC.ULA.ORV

• OFFICIAL BUSINESS COMMISSION

PE~NALTY IFOR PRIVATE USE. S300

0