ML19221B284

For Comment Issue of Reg Guide 7.8, Load Combinations for Structural Analysis of Shipping Casks

ML19221B284
Person / Time
Issue date:	05/31/1977
From:	NRC OFFICE OF STANDARDS DEVELOPMENT
To:
References
REGGD-07.008, REGGD-7.008, NUDOCS 7907200158
Download: ML19221B284 (5)

Text

.#g @ N I G g %.U.S. NUCLEAR REGULATORY COMMISSION May 1977 H

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.t!M) REGL LATORY GJDE

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OFFICE OF STANDARDS DEVELOPMENT REGULATORY GUIDE 7.8 LOAD COMBINATIONS FOR THE STRUCTURAL ANALYSIS OF SHIPPING CASKS A. INTRODUCTION Regulatory Position C.I.a of this guide mentions ensironmental initial conditions. The external ther.

Appendix A. " Normal Conditions of Transport,"

mal ensironmental limits for which a shipping cask and Appendix B.

"flypothetical Accident Con-must be designed are stated in Appendix A of its ditions." of 10 CFR Part 71," Packaging of Radioac-CFR Part 71 as being 130"F(54 C)in direct sunlight tne N1aterial for Transport and Transportation of and -40=F (-40 C) in shade. These limits are applied Radioactise N1aterial Under Certain Conditions."

without any additional loading. For the other condi-describe normal conditions of transport and tions of Appendix A and for the hypothetical acci-hypothetical accident conditions that produce ther-dent conditions, this guide presents a range of am-mal and mechanical loads that serse as the structural bient temperatures from -20'F (49 C) to 100 F design bases for the packaging of radioactise material (3PC) as a part of the initial conditici. In the con-for transport.

tiguous United States there is a 99.7 percent probability that any hourly temperature reading will f low ever, initial conditions must be assumed faH within this range (Ref.1).The insolation data before analyses can be performed to evaluate the provided in the Internationa. Atomic Energy response of structural systems to prescribed loads.

Acences safety standards (Ref. 2) have been adopted This regulatory guide presents a set of initial condi-fo'r this guide because thev have sufficient conser-tions that is considered acceptable by the NRC staff vatism when compared with other solar radiation for use in the structural analyses of type B packages data (Ref. 3).

used to transport irradiated nuclear fuel in the con-tiguous United States. The values in this set supple-Reculatorv Position C.l.c mentions initial pressure ment the normal conditions and the hypothetical ae-conditions. I't should be noted that the pressure inside 6

cident conditions of the regulations in forming a the containment vessels and neutron shields of ir.

more complete basis from which structural integrity radiated fuel shipping casks depends on seseral fac-may be assessed.

tors. These factors include pre-pressuritation of the sessels, the cask temperature distributions associated B. DISCUSSION with the ambient temperatures and the decay heat of the fuel rods, and any gas leakage from the nuclear ensure safe structural behasior cf shippmg i s fuel rods ~

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casks used to transport irradiated nuclear fuel.

specifie 'oad conditions must be established that will Regulatory Position C.I.e states that the values for encompa s the static dynamic, and thermal loadings initial conditions gisen in this guide are maximums or that may he experienced by the casks during trans-minimums. Ilowes er, intermediate values cot '1 pos-port. This.egulatory guide presents initial conditions sihly create a more limiting case for some cask that can be used in addition to parts of Appendices A designs. For example, a seal design might be more and B of 10 CFR Part 'l to fully delineate thermal susceptible to leakage at a pressure less than the max-and mechanical load combinations for purposes of imum mternal presture. or a local structural response structural analysis. It is intended that this guide be might be greater during an impact test if the weight of used m conjunction with Regulatory Guide 7.6, the contents was less than the maximum.

" Stress Allowables for the Design of Shipping Cask Containment Vesselsf for the analytic structural Appendices A and B of 10 CFR Part 71 outline re-esaluation of the heavy (i.e., seseral tons in weight) quirements for packages used to transport type B casks used to transport irradiated nuclear fuel.

quantities of radioactise mateiials. Some of these re-USNRC REGULATORY GUIDES a

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e. The intern.I pressure used in evaluating normal caa. howeser, because of the heasmess of the casks and hypothetical accident conditions should be con-or because the requirements are not structurally sistent uith the other initial conditions that are being ugmEcant to eask design. Casks that are deugned to considered.

transport one or nmre commercial fuel assemblies w eich many tons because of the large quantines of

d. The release of all of the pressurized gases inside structural and shielding matenah used. This the fuel assemblies should be consi6ered in determin-m a s-sneness causes a shippmg ca k to bas e a slow ther.

mg the maumum containment sessel pressure.

cul response to sudden esternal temperature change such as thos that m:ght be preduced h3 quenchmg

e. It is the intent of this guide to specify discrete in-ster a thermal esposure. The NRC staff feek that the itial conditions ' hat will serve as bounding cases for water unmeruon test of \\ppendix 3 and the water structural response Maximum or minimum s alues of spras test of -\\ppenda A are not upmficant in the imtial conditions are gnen. Howeser, if a larger structural deuen of laree casks. Therefore, thes are structural response is suspected for an initial condi-not dncmsed m' t h:s c uide. I Note, how es er. that these tion that is not an extreme (e g-an ambient

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condmons mas he uemficant to criticahts and other temperature bet w een -19 F (-28T) and 99 F nonstructaral asnects of cask design )

( F C )). intermediate initial conditions should also be considered in the structural analysis.

Su mlarly. the corntr drop and the compression tem ef \\ppenda -\\ are not discussed be:ause they

2. %rmal Conditions of Transport pertam oni) m hghtw eight packaces. The penetration test or \\ppenda \\ is not considered bs the NRC Each of the following normal conditions of trans-statf to hase strustural s:gmficance for large shippmg port is to be apphed separatch to determim its effect skstescent for mprotected uhes and rupture on the fuel cask.

s dn W and u:H not be considered as a ceneral re-ouire ment-N"' C'nironment-The casi should be struc-turally evaluated for an ambient temperature of C. REGULATORY POSITION lM 154'C) in stiH air and with maximum insola-tion (see Table 1). If the cask has auxiliary coohng Iht load condaions enen here are considered ae.

9stenn for the contamment or neutron shicid fluids, certable to the N RC sialf 'or use in the =aktical these systems should be considered to be inoperable strastural cuh.ation of shippmc casks used to trans.

during the hot environment condition.

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pct type B quantities of irraduted nuclear fuels.

b. Cold ermrmiment-The cask should be

1. General Initial ('onditions 'I o Be I sed for Hoth et aluated for an am bient temperature of -40 F Normal and 11 pothetical \\ecidtnt Concitions

(-40^C) m still air and with no insolation. The case of 3

maximum fuel heat load and maximum internal pres-

\\h imtui cask temperature d:stribution should sure should be conudered in addition to the case of a

he conWered to be at steady state The not uland no internal heat load The possibility and conse-hy pot heucal accident condmons should e con-quence of coolant freezing should aho be considered udered to hne imtial conditmns of embient temperature at -20T (-NC) with no insolation and

c. hmn es terna/prenure-The cask should be et unhient temperature at 100'F (NC) with the es aluated for an atmopheric pressure 0.5 times the maumum msolation data gnen m Table 1. Excep.

standard atmospheric pressure.

tions to the ahose are made for the hot ensironment and cold ensironment normal conJitions tuhich use

d. Fibratimi and latiene-The cask should be mher steads state s alues) and for the thermal acci.

es aluated for the shock and vibration ensironment dem condalon Iwhich conuders the hicher thermal normalk incident to transport. This environment in-imtul condmon but not the lower onej cludes the quasi-steady sitratory motion produced by small excitations to the cask-sehicle system and h.

Thu deca) heat of the irraduted fuel should also intermittent shock loads produced by coupling, he cowdered as part of the mitial conditions.

switching, etc., in rail transport and by bumps, (icneraH). the mnimum amount of deca) heat potholes, ete-in truck transport. Repeated pres-should he conudered m combmation with the ther-suri/ation loads and any other loads that may con-

' ul em ironmental conditions of Regulatory Posinon tribute to mechanical fatigue of the cask should be In adJmon, the tree-drop and sihration parts considered.

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ot the norm il condmons and the free-drop and punc-ture parts of the mdent conditions should consider Factors that may contribute to thermal fatigue the

'se of no desas heat and the cask at -20'E should aho be considered. These factors should in-L s

0( ) These mitiai ther yal condit:ons are sum-clade the thermal transients encountered in the marized m Fable 2.

loadmg and unloading of irradiated nuclear fuel.

9 158 239 x

e. Free drop-The cask should be evaluated for a length as to :ause maximum damage to the cask. The one-foot free drop onto a flat unyielding surface. The cask should contain the maximum weight of contents cask should contain the maximum weight of contents and should hit the bar in a position that is expected to and should strike the impact surface in a position that indict maximum damage.

3, Ilypothetical Accident Conditions is expected to indict maximum damage.

c. Thennal--The cask should be evaluated for a thermal condition in w hich the whole cask is exposed to a radiation environment of 1,475 F (800 C) with The following hypothetical accident conditions are an emissivity coeffici:nt of 0.9 for 30 minutes. The to be applied sequentially in the order indicated to surface absorption coefficient of the cask should be determine the maximum cumulative effect.

considered to be 0.8. The structural response of the cask should be considered up to the time when the

a. Free drop-The cask should be evaluated for a temperature distributions reach steady state. The free drop through a distanc(. of 30 feet (9 meters) possibihty and consequence of the loss of Guid from onto a flat unyielding horizontal surface. It should the neutron shield tank should be considered for strike the surface in a position that is expected to in-casks that use this design feature.

Diet maximum damage and should contain the max-imum weight of contents.

Tabie 2 summarizes the loading combinations In determining which position caus:s maximum damage, the staff currently requests evaluations of D. IMPLEMENTATION drop orientations w here the top and bottom ends, the top and bottom corners, and the sides are the :ask The purpue of this section is to provide informa-impact areas. The center of gravity is usu6y con.

tion to applicants and licensees regarding the NRC sidered to be directly above these in pact areas.

staff's plans for using this regulatory guide.

Howeser, evaluations of oblique stop crienta' ions are requested when appropriate.

This regulatory guide will be used by the staff after January 1,1978, in assessing the structural adequacy

b. Purrture-The cask should be evaluated for a of designs for irradiated fuel shipping casks with free drop of 40 inches (1 meter) onto a stationary and respect to the requirements in 10 CFR Part 71, sertical oild steel bar of 6 inches (15 cm) diameter N71.35 and 71.36. Alternatise methods that satisfy with it< top edge rounded to a radius of not more the requirements in the Commission's regulations will also be considered acceptable.

than G.25 inch (6mm). The bar should be of such ;

REFERENCES 1.

N1.B. Gens. The Transportation and Hand!ing En-Series No. b, Reetdations for the Safe Transport of wronment. SC-DC 13 86, Sandia Laboratories, Radioactise.t/aterials, 1973.

Albuquerque, New Niexico, Sept.1972.

3. Department of the Army, Research. Deselopment.

Test, and Esaluation of.tfaterial for Extreme Climatic

2. International Atomic Energy A gency, Safe y conditions. A R 70-38, N!ay 1969.

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" w,. 3

TABLE 1 MAXIMUM INSOLATION DATA Form and location Insolation for 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> of surface per day Flat surfaces transported horizontally:

Base None Other surfaces 800 gcal/crn- (2.950 Btu /ft-)

Flat surfaces not transported horitor aily:

Each surf ace 200 geal/cm2 (737 Btu /ft )'

2 Cun ed surfaces 400 geal/cm- (1,475 Btu /ft2 )*

• \\l:erna:n ci), a une function nu) be used. adopting an ahorptiencoefDesent and neglecting the ef!ccis of pess;bie ref'ection frorn ne:ghbonng ob;cets.

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TABLE 2

SUMMARY

OF LOAD COMBINATIONS FOR NORMAL AND HYPOTHETICAL ACCIDENT CONDITIONS OF TRANSPORT Applicable initial condition

\\mbient

=

Insolation Decas heat N.ormal or accident temperature u

o t

g condition 5

C.

=

l u

E I

- j O

o Y

Y W

W 9

R, 2

2 2

2 s.

O s.

c s.

/

Normalconditions liot ens f ronment -

130^F ambient temp.

x x

x Cold ens ironment -

x x

x

-40 F ambient temp.

x x

x Minimum external pressure -

x x

x x

0.5 atm.

x x

x x

. ibration & shockt -

x x

x x

Normally incident to x

x x

x 9

the niode of tran3puit x

x x

x Free drop x

x x

x x

1 toot dreo x

x x

x x

x x

x x

x Accideni conditions x

x x

x x

Free drop -

x x

x x

x 30 foot drop x

x x

x I'U nClu re -

x x

x x

x Drop onto bar x

x x

x x

x x

x x

x

'I hernialtt -

x

\\

x x

l'lTe accid CIlt I

s<e m i

• See Ih datory P s Ih' 1 L. ! c.in d C.1 d

+%ee Rega'..

ry P1 s' on (

d r "\\ 15tation cd fangue t + } s,g! u at t. T s sh o u d h t2 in n's.D TS "JIe5 a ff d " %Idr! 81f fire dild at ret-fire steady-state o'nd srs

, o Tro sT ATrs p

q N CLIAH R t ' t ; L A f r. fl y CO"*A 5 2 ( N V, A C t t *4 G T O N D C.'

555 P

7 f

F Paiu N

AM HE LATORY M

r' F F i C f A ( 6,,, 31%fSS c

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,ENALT Y f O A F 4 i V A T E V 5f. S EJO g

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