ML20247F323
| ML20247F323 | |
| Person / Time | |
|---|---|
| Issue date: | 03/31/1989 |
| From: | NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | |
| References | |
| TASK-MS-527-4, TASK-MS-804-4, TASK-RE REGGD-07.008, REGGD-7.008, NUDOCS 8907270125 | |
| Download: ML20247F323 (6) | |
Text
_ __ . _ _ _ . _ _ _ .
U.S. NUCLEAR REGUI.ATORY COMMISSION R; vision 1
- g. March 1989 C g/pg) *****
REGULATORY GUIDE OFFICE OF NUCLEAR REGULATORY RESEARCH REGULATORY GUIDE 7.8 (Tasks MS 527-4 and MS 804-4)
LOAD COMBINATIONS FOR THE STRUCTURAL ANALYSIS OF SHIPPING CASKS FOR RADIOACTIVE MATERIAL A. INTRODUCTION can be used in addition to parts of $$ 71.71 and Section 71.71, " Normal Conditions of Trans- 71.73 of Part 71 to fully delineate thermal and me-chanical load combinations for purposes of structural port," and Section 71.73, " Hypothetical Accident
) analysis. This guide should be used in conjunction Conditions," of 10 CFR Part 71, " Packaging and Transportation of Radioactive Material," describe w th Regulatcry Guide 7.6, " Design Criteria for the Structural Analysis of Shipping Cask Containment
. normal conditions of transport and hypothetical acci-dent conditions that produce thermal and mechanical Vessels," for the analytical structural evaluation of the heavy (i.e., weighing several tons) casks used to loads that serve as the structural design bases for the transport irradiated nuclear fuel.
packaging of radioactive material for transport.
Regulatory Position 1.1 of this guide addresses Initial conditions must be assumed before analy-initial environmental conditions. The external ther-ses can be performed to evaluate the response of mal environmental limits for which a shipping cask structural systems to prescribed loads. This regulatory must be designed are stated in 9 71.71 as being guide presents the initial conditions that are consid-100*F (38'C) in direct sunlight and -40*F (-40'C)
(' ered acceptable by the NRC staff for use in the struc-in shade. The regulations specify that these two nor-tural analysis of Type B packages used to transport mal conditions are to be applied separately from the radioactive materialin the contiguous United States.
other normal conditions. For the other conditions of Any information collection activities mentioned 9 71.71 and for the hypothetical accident conditions, in this regulatory guide are contained as requirements this guide' presents a range of ambient temperatures in 10 CFR Part 71, which provides the regulatory ba. from -20*F (-29*C) to 100'F (38'C) as a part of sis for this guide. The information collection require, the initial conditions. In the contiguous United States, ments in 10 CFR Part 71 have been cleared under there is a 99.7 percent probability that any hourly OMB Clearance No. 3150-0008. temperature reading will fall within this range.1 Regulatory Position 1.3 addresses initial pressure B. DISCUSSION conditions. The pressure inside the containment vessels and neutron shields of irradiated fuel shipping To ensure safe structural behavior of shippm.g casks depends on several factors. These factors casks used to transport radioactive material, specific include prepressurization of the vessels, the cask load conditions must be established that will encom-pass the' static, dynamic, and thermal loadings that may be experienced by the casks during transport. 'M. D. Gens, The Transportation and Handling Enworunent, SD-DC-72-1386, Sandia laboratories. Albuquerque, New Mexico, This regulatory guide presents initial conditions that septetnber 1972.
LTSNRC REoUIAToRY OUIDEs The guidos are issuird in the following ten broad divisons:
Regulatory Guides are issued to desertbo and make available to the pub-t i e a ion , to lines s 1. Power Reactors 6. Products staff in evaluating specific problems or postulated accidents, or to pro. 2. Research and Test Reactors 7. Transportation vios guidance to applicants. Regulatory Guides are not substitutes for 3, Fuels and Materials Fao)11 ties 8. occupational Hentth regulat6cns, and compliance with them le not required. Methods and 4. Environrnenta' and Siting g. Antitrust and Financial Revlow y solutions different from tho a set out in the guides will be acceptable If 5. Materials ano Plant Protection 10. General they provide a basis for the findings requisite to the issuance or continu-
[ ance of a permit or heense by the commission.
!(~ j]I This guide was issued after consideration of comments received 'frorn th9 public. Comments and suggestions for 4.. gw,,,i as in these copies of issued guides may be purchased from the Govemment Printing office at the cu, rent GPo price. Information on current GPo gr6ces may be obtained by contacting the Superintendent of Documents. U.S.
gu6 des are encouraged at all times, and guldes will be revised, as ap. Govertwnent Printing office, Post office Box 37082, Washington, DC propriate, to accommodate comments and to reflect new information or 20013-7082, telephone (202)275-2060 or (202)275-2171.
inexperience, Written comments may be submitted to the Regulatory Publications issued guides may also be purchased from the Nationai Technical Infor-Branch, DFIPS, ARM, U.S. Nuclear Regulatory Commission, Washing- mation Service on a standing order basis. Details on this service may be inn, DC 20555.
obtained by writing NTIS, 6225 Port Royal Pood. Springfield, VA 22161, 8907270125 090331 PDR REGGD -
07.008 R PDR
ternperature distributions associated with the ambient 1. GENERAL Y NITI A L CONDITIONS TO temperatures and the decay heat of the irradiated UE USED FOR BOTH NORMAL AND fuel, and kny gas leakage from such fuel. IlYPOTIIETICAL ACCIDENT CONDITIONS Regulatory Position 1.5 addresses the possibility 1.1. All initial cask temperature distributions that fabrication and installation stresses may result should be considered to be at a steady state. The nor-durir g cask construction. These stresses depend on mal and hypothetical accident conditions should be many different processes and should be considered considered to have initial conditions of amb!ent tem- i when evaluating the casks. perature at -20*F (-29"C) with no insolation and of l Regulatory Position 1.6 states that the values for ambient temperature at 100*F (38*C) with maxi-imtial conditions given in this guide are maximums or mum ins lation. Insolation should be in accordance minimums. However, intermediate values could pos- with paragraph 71.71(c)(1). Exceptions to the above sibly create a more limiting case for some cask de- are made for the cold environment normal condition signs. For example, a seal design might be more sus- (which uses -40'F) and for the thermal accident ceptible to leakage at a pressure less than the maxi- condition (which considers the higher thermal initial mum internal pressure, or a local structural response condition but not the lower one),
might be greater during an impact test if the weight of 1.2. 'Ihe decay heat of the radioactive material the contents were less than the maximum. should be considered as part of the initial conditions.
Sections 71.71 and 71.73 of Part 71 outline re- Generally, the maximum amount of decay heat (
quirements for packages used to transport Type B should be considered for the hot environment and no quantities of radioactive materials. However, some of decay heat should be considered for the cold envi-these requirements do not pertain to irradiated fuel r nment. These conditions should include the insola-shipping casks because of the massiveness of the tion considerations of Regulatory Posmon 1.1. In ad-casks or because the requirements are not structurally dition, the free-drop and vibration parts of the nor-significant to cask design. Casks that are designed to mal conditions and the free-drop and puncture parts transport one or more commercial fuel assemblies f the accident conditions should consider the cases weigh many tons because of the large quantities of f maximum decay heat with an ambient temperature structural and shielding materials used. This massive- f 100*F (38"C) and of no decay heat with an ambi-ness causes a shipping cask to have a slow thermal ent temperature of -20*F (-29'C).
response to sudden external temperature changes 1.3. The internal pressure used in evaluating nor-such as those that might be produced by quenching mal and hypothetical accident conditions should be after a thermal exposure. The NRC staff feels that consistent with the other initial conditions that are the water immersion test of s 71.73 and the water being considered. Minimum internal pressure should spray test of S 71.71 are not significant in the struc- be taken as atmospheric or, for designs where inter-tural design of large casks. Therefore, they are not nal pressures are less than atmospheric. the appropri-discussed in this guide. (Note, however, that these ate negative value.
conditions may be significant to criticality and other nonstructural aspects of cask design.) 1.4. For commeteial nuclear power plant fuels, the release of all the pressurized gases inside the irra-Similarly, the corner drop and the compression diated fuel should be considered in determining the tests of 9 71.71 are not discussed because they per- maximum resultant containment vessel pressure.
tain only to lightweight packages. The penetration 1.5. Fabrication 2 and installation stresses used in test of 9 71.71 is not considered by the NRC staff to evaluating transportation loadings should be consis-have structural significance for large shipping casks tent with the joining, forming, fitting, and aligning (except for unprotected valves and rupture disks) processes employed during the construction of casks.
and will not be considered as a general requirement.
Unless subsequent steps are taken to eliminate these C. REGULATORY POSITION stresses, they should be considered in determining the maximuin resultant vessel stress.
The load conditions given here are considered acceptable to the NRC staff for use in the analytical structural evaluation of shipping casks used to trans- 2 Fabrication means the assembly of the major components of port Type B quantities of radioactive materials. the casks (i.e., the inner shell. shielding. outer shell, heads. ctc.)
Table 1 lists the load combinations that should be but not the constriction of the individual components. Thus, used. Analyses should combine the 1mtial conditions
.. the phrasefabncation stresses includes the stresses caused by in-
.terference fits and the shrinkage of bonded lead shielding dur-with both the normal conditions and the hypothetical ing solidification but does not include the residual stresses due accident conditions. to plate formation, welding, etc.
- 7. 8-2
i Teble 1 Summary of Load Combinations for Normal and N~ Hypothetical Accident Conditions of Transport Ls .
, Applicable Initial Condition Ambient Internal Fabrication Temperature Insolation Decay Heat Pressure 2 Stresses 8 ,
l 100*F -20*F Max.1 Zero Max. Zero Max. Min. .
NORMAL CONDITIONS (Analyze Separately)
{
/^
Hot emironment: ,
100'F ambient temp. X X X X
)' Cold emironment:
-40*F ambient temp. X X X X Increased external pressure: 20 psia X X X X X Minimum external pressure: 3.5 psia X. X. X X X
[" Vibration and shock 4: X X X X X l \ normally incident to the -------------------------- -----------------------------
mode of transport X X X X X Free drop: X X X X X 1-foot drop --------------------------------------------------------
X X X X X
\
l ACCIDENT CONDITIONS
- (Apply sequentially) f
!- Free drop: X X X X X 30-foot drop ------------------------- ----------- ------------------
X X X X X n.
Puncture: X X X X X d op onto bar -----------.- -----------------------------------------.
X X X X X Thermals:
fire accident X X X X X 1See Regulatory Position 1.1.
p 2See Regulatory Positions 1.3 and 1.4.
- [
t l
t 3See Regulatory Position 1.5.
- See Regulatory Position 2.5.
5 Evaluations should be made 30 minutes after start of fire and at postfire steady-state conditions, n
l 7.8-3
t 1.6. It is the intent of this guide to specify dis. Although there are a number of different load crete initial conditions that will produce bounding combinations that could occur during normal trans-cases of structural response. Maximum cr minimum port and for which separate fatigue andyses may be values of initial conditions are given. However, if a performed, this evaluation should be based on the larger structural response is suspected for an initial most unfavorable initial conditions for the specific condition that is not an extreme (e.g., an ambient design consistent with a credible spectrum represent-
} temperature between -20*F (-29'C) and 100*F irg the life-cycle for normal shock and vibration envi- 1 (38'C)), intermediate initial conditions or other ronments. Table 1 identifies the cases that the staff $
combinations of initial conditions should also be con- believes are the most unfavorable.
sidered in the structural analysis.
2.6. Free drop - The cask (assuming a weight of
- 2. NORMAL CONDITIONS OF TRANSPORT ver 30,000 pounds (13,600 kg)) should be evalu-ated for a 1-foot free drop onto a flat unyielding sur-face; it should strike the surface in a position that is Each of the following normal conditions of trans- expected to inflict maximum damage. Impacts with port is to be applied separately to determine its effect maximum and minimum weights of contents should on the fuel cask. These nor'nal conditions are also to be considered. ;
be combined with all the initial conditions as shown 3.
in Table 1. HYPOTHETICAL ACCIDENT CONDITIONS The following hypothetical accident conditions 5 2.1. Ilot environment - The cask should be are to be applied sequentially to the same cask in the structurally evaluated for an ambient temperature of order indicated (dropped, then punctured, then ex-100*F (38'C) in still air and with maximum insola- posed to fire) to determine the maximum cumulative tion .(see Regulatory Position 1.1). If the cask has effect. These hypothetical accident conditions are mechanically operated auxiliary cooling systems, also to be combined with the initial conditions as these systems should be considered to be inoperable shown in Table 1.
during the hot environment condition.
3.1. Free drop - The cask should be evaluated 2.2. Cold environment - The cask should be for a free drop through a distance of 30 feet (9 m) evaluated for an ambient temperature of -40'F onto a flat unyielding horizontal surface. It should
(-40 C) in still air and with no insolation. The case strike the surface in a position that is expected to of no internal heat load and minimum internal pres- inflict maximum damage. Impacts with the maximum sure should be considered. The possibility and conse- and minimum weights of contents should be quence of coolant freezing should also be considered. considered.
In determining which position causes maximum 2.3. Increased external pressure - The cask damage, applicants should consider impact orienta-should be evaluated for an external pressure of tions in which the cask strikes the impact surface on ts top end, top corner, side, bottom end, and bottom 20 psia (140 kilopascal).
corner and the center of gravity of the cask is directly 2.4. Minimum external pressure - The cask ver the point of impact. If the design of the cask is should be evaluated for an external pressure of such that an intermediate oblique orientation could 3.5 psia (24.5 kilopascal). be more damaging, the applicant should also evaluate the impact of the cask in those orientations. These latter evaluations should include impacting on appur-2.5. Vibration and fatigue - The cask should tenances that are part of the cask design such as be evaluated for the shock and vibration environment those used for handling, tiedown, or for other func-normally incident to transport. This environment in- tions during transport.
cludes the vibratory motion produced by small excita-3.2. Puncturc - The cask should be evaluated tions to the cask-vehicle system and also intermittent for a free drop of 40 inches (1 m) onto a stationary thock loads produced by coupling, switching, etc., in rail transport and by bumps, potholes, etc., in truck and vertical mild steel bar of 6 ir4ches (0.15 m) di-ameter with its top edge rounded to a radius of not transport. Repeated pressurization laads and any more than 0.25 inch (6 mm). The bar should be of other loads that may contribute to mechanical fatigue such a length as to cause maximum damage to the of the cask should be considered. cask; however, it should not be less than 8 inches <
Factors that may contribute to thermal fatigue * *) I ng. .
cad should hit the bar in a posi-should also be considered. These factors should in- tion that is expected to mflict maximum damage, and clude the thermal transients encountered in the load- impacts with maximum and minimum weights of con- <
ing and unloading of irradiated nuclear fuel from the tents should be considered.
cask and any restraint against thermal expansiori that 3.3. Thermal
- The cask should be evaluated may be provided by the tiedown system. for a thermal condition in which the whole cask is
- 7. 8-4
exposed to ' a radiation emironment of 1,475'F D.- IMPLEMENTATION -
-(800*C) with an emissivity coeffident of 0.9 for 30 .
P minutes. The surface absorption coefficient of the The purpose of this section is to provide informa-
. " to apphcants and licensees regarding the NRC
(' cask should be considered to be 0.8. The struct'aral
' response of the cask should be considered up to the staff,s plans for using this regulatory guide. -
time when the ternperature distributions reach steady - Except in those cases in which an applicant or state. The possibility and consequence of the loss of licensee proposes an acceptable alternative method fluid from e the- neutron ' shield tank should be for complying with specified portions of the Commis- 2
. considered for casks that use this design feature. sion's regulations, the NRC staff will use the methods described in this guide in evaluating applications for
, new package designs and requests for exi:; ting pack- 1
. Table 1 summarizes the loading combinations age designs to be designated as Type B packages for given above. all applications and requests.
l I
)
I 1
l 7.8-5
REGULATORY ANALYSIS A diaft regulatory analysis was published with the the final guide has not been prepared. A copy of the second proposed Revision 1 to Regulatory Guide 7.8 draft regulatory analysis is available for inspection (Task MS 804-4) when the draft guide was published and copying for.a fee at the Commission's Public for public comment in September 1988. No changes Document Room at 2120 L Street NW., Washington, were necessary, so a separate regulatory analysis for DC, under Task MS 804-4.
O l
9
- 7. 8-6 i
_ _ _ _ _ _ _ _ - - _ - - - - - - _ - - - _ - - - - - - - - - - - - - - - . - - - - - - - - - - - - - - - - - - - - -- - I
UNITED STATES , car cuss man NUCLEAR REGULATORY COMMISSION ent ^$$ * *555 o WASHINGTON, D.C. 20555 PERMf7 No G 67 OFFICIAL BUSINESS PENALTY FOR PRIVATE USE. 6300 O
O
_