ASTM E2230-22

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation:E2230 −22
Standard Practice for
Thermal Qualification of Type B Packages for Radioactive
Material
This standard is issued under the fixed designation E2230; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 This practice defines detailed methods for thermal
2.1 ASTM Standards:
qualificationof“TypeB”radioactivematerialspackagesunder E176Terminology of Fire Standards
Title 10, Code of Federal Regulations, Part 71 (10CFR71) in
IEEE/ASTMSI-10International System of Units (SI) The
the United States or, under International Atomic Energy Modernized Metric System
Agency Regulation SSR-6. Under these regulations, packages
2.2 Federal Standard:
transporting what are designated to be Type B quantities of
Title 10, Code of Federal Regulations, Part 71
radioactive material shall be demonstrated to be capable of
(10CFR71), PackagingandTransportationofRadioactive
withstanding a sequence of hypothetical accidents without
Material, United States Government Printing Office, Oc-
significant release of contents.
tober 1, 2004
1.2 The unit system (SI metric or English) used for thermal
2.3 Nuclear Regulatory Commission Standards:
qualification shall be agreed upon prior to submission of
Standard Format and Content of Part 71 Applications for
information to the certification authority. If SI units are to be
Approval of Packaging of Type B Large Quantity and
standard, then use IEEE/ASTMSI-10. Additional units given
Fissile Radioactive Material, Regulatory Guide
in parentheses are for information purposes only.
7.9, United States Nuclear Regulatory Commission,
1.3 This standard does not purport to address all of the
United States Government Printing Office, 1986
safety concerns, if any, associated with its use. It is the
2.4 International Atomic Energy Agency Standards:
responsibility of the user of this standard to establish appro-
Regulations for the Safe Transport of Radioactive Material,
priate safety, health, and environmental practices and deter-
No. SSR-6 (IAEA SSR-6 Revised)International Atomic
mine the applicability of regulatory limitations prior to use.
Energy Agency, Vienna, Austria, 2018
1.4 This standard is used to measure and describe the
Advisory Material for the IAEA Regulations for the Safe
response of materials, products, or assemblies to heat and
Transport of Radioactive Material (2012 Edition), No.
flame under controlled conditions, but does not by itself
SSG-26, (IAEA SSG-26)International Atomic Energy
incorporate all factors required for fire hazard or fire risk
Agency, Vienna, Austria, 2014
assessment of the materials, products, or assemblies under
2.5 American Society of Mechanical Engineers Standard:
actual fire conditions.
Quality Assurance Program Requirements for Nuclear
1.5 Fire testing is inherently hazardous. Adequate safe-
Facilities, NQA-1, American Society of Mechanical
guards for personnel and property shall be employed in
Engineers, New York, 2001
conducting these tests.
1.6 This international standard was developed in accor- 2.6 International Organization for Standards (ISO) Stan-
dance with internationally recognized principles on standard- dard:
ISO 9000:2000, Quality Management Systems—
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom- Fundamentals and Vocabulary, International Organization
for Standards (ISO), Geneva, Switzerland, 2000
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee. ISO 13943Fire Safety – Vocabulary, International Organi-
zation for Standards (ISO), Geneva, Switzerland, 2017
This practice is under the jurisdiction of ASTM Committee C26 on Nuclear
Fuel Cycle and is the direct responsibility of Subcommittee C26.13 on Spent Fuel
and High Level Waste. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Jan. 1, 2022. Published April 2022. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 2002. Last previous edition approved in 2013 as E2230–13. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/E2230-22. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2230−22
3. Terminology 4.3 The regulatory thermal test is intended to simulate a
30-min exposure to a fully engulfing pool fire that occurs if a
3.1 Definitions—For definitions of terms used in this test
transportation accident involves the spill of large quantities of
method refer to the terminology contained in Terminology
hydrocarbon fuels from a tank truck or similar vehicle. The
E176 and ISO 13943 (Fire Safety – Vocabulary). In case of
regulations are “mode independent” meaning that they are
conflict between Terminology E176 and ISO 13943, the
intended to cover packages for a wide range of transportation
definitions given in Terminology E176 shall prevail.
modes such as truck and rail.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 hypothetical accident conditions, n—a series of acci-
5. Significance and Use
dent environments, defined by regulation, that a Type B
5.1 The major objective of this practice is to provide a
package must survive without significant loss of contents.
common reference document for both applicants and certifica-
3.2.2 insolation, n—solar energy incident on the surface of
tion authorities on the accepted practices for accomplishing
a package.
package thermal qualification. Details and methods for accom-
3.2.3 normal conditions of transport, n—a range of
plishing qualification are described in this document in more
conditions, defined by regulation, that a package must with-
specific detail than available in the regulations. Methods that
stand during normal usage.
have been shown by experience to lead to successful qualifi-
cation are emphasized. Possible problems and pitfalls that lead
3.2.4 regulatory hydrocarbon fire, n—a fire environment,
to unsatisfactory results are also described.
one of the hypothetical accident conditions, defined by
regulation, that a package shall survive for 30 min without
5.2 The work described in this standard practice shall be
significant release of contents.
doneunderaqualityassuranceprogramthatisacceptedbythe
3.2.5 thermal qualification, n—the portion of the certifica- regulatory authority that certifies the package for use. For
tion process for a radioactive materials transportation package packages certified in the United States, 10 CFR 71 Subpart H
that includes the submittal, review, and approval of a Safety shall be used as the basis for the quality assurance (QA)
Analysis Report for Packages (SARP) through an appropriate
program,whileforinternationalcertification,ISO9000usually
regulatory authority, and which demonstrates that the package defines the appropriate program. The quality assurance pro-
meets the thermal requirements stated in the regulations.
gram shall be in place and functioning prior to the initiation of
any physical or analytical testing activities and prior to
3.2.6 Type B package, n—a transportation package that is
submittal of any information to the certifying authority.
licensed to carry what the regulations define to be a Type B
quantity of a specific radioactive material or materials.
TEST METHODS
4. Summary of Practice
6. General Information
4.1 This document outlines four methods for meeting the
6.1 In preparing a Safety Analysis Report for Packaging
thermal qualification requirements: qualification by analysis,
(SARP), the normal transport and accident thermal conditions
pool fire testing, furnace testing, and radiant heat testing. The
specified in 10CFR71 or IAEASSR-6 shall be addressed. For
choice of the certification method for a particular package is
based on discussions between the package suppliers and the approval in the United States, reports addressing the thermal
issues shall be included in a SARP prepared according to the
appropriate regulatory authorities prior to the start of the
qualification process. Factors that influence the choice of format described in Nuclear Regulatory Commission (NRC)
Regulatory Guide 7.9. Upon review, a package is considered
method are package size, construction and cost, as well as
hazards associated with certification process. Environmental qualified if material temperatures are within acceptable limits,
temperature gradients lead to acceptable thermal stresses, the
factorssuchasairandwaterpollutionareincreasinglyafactor
cavity gas pressure is within design limits, and safety features
in choice of qualification method. Specific benefits and limi-
continue to function over the entire temperature range. Test
tations for each method are discussed in the sections covering
initial conditions vary with regulation, but are intended to give
the particular methods.
the most unfavorable normal ambient temperature for the
4.2 The complete hypothetical accident condition sequence
feature under consideration, and corresponding internal pres-
consists of a drop test, a puncture test, and a 30-min hydro-
suresareusuallyatthemaximumnormalvaluesunlessalower
carbon fire test, commonly called a pool fire test, on the
pressure is shown to be more unfavorable. Depending on the
package. Submersion tests on undamaged packages are also
regulation used, the ambient air temperature is in the –29°C
required, and smaller packages are also required to survive
(–20°F) to 38°C (100°F) range. Normal transport require-
crushteststhatsimulatehandlingaccidents.Detailsofthetests
ments include a maximum air temperature of 38°C (100°F),
and test sequences are given in the regulations cited. This
insolation, and a cold temperature of –40°C (–40°F). Regu-
document focuses on thermal qualification, which is similar in
lations also include a maximum package surface temperatures
both the U.S. and IAEA regulations. A summary of important
for personnel protection of 50°C (122°F). See Appendix X3
differences is included as Appendix X3 to this document. The
for clarification of differences between U.S. and international
overall thermal test requirements are described generally in
regulations.
Part 71.73 of 10CFR71 and in Section VII of SSR-6. Addi-
tional guidance on thermal tests is also included in IAEA 6.2 Hypothetical accident thermal requirements stated in
SSG-26. Part 71.73 or IAEA SSR-6, Section VII call for a 30 min
E2230−22
exposure of the entire container to a radiation environment of 6.6 While 10CFR71 or SSR-6 values represent typical
800°C (1475°F) with a flame emissivity of 0.9. The surface package average heat fluxes in pool fires, large variations in
heat flux depending on both time and location have been
emissivity of the package shall be 0.8 or the package surface
observed in actual pool fires. Local heat fluxes as high as 150
value,whicheverisgreater.Withtemperaturesandemissivities
stated in the specification, the basic laws of radiation heat kW/m under low wind conditions are routinely observed for
low package surface temperatures. For high winds, heat fluxes
transfer permit direct calculation of the resulting radiant heat
as high as 400 kW/m are observed locally. Local flux values
flux to a package surface.This means that what appears at first
areafunctionofseveralparameters,includingheightabovethe
glance to be a flame or furnace temperature specification is in
pool. Thus the size, shape, and construction of the package
reality a heat flux specification for testing. Testing shall be
affects local heat flux conditions. Designers shall keep the
conducted with this point in mind.
possible differences between the hypothetical accident and
6.3 Two definitions of flame emissivity exist, and this
actual test conditions in mind during the design and testing
causes confusion during the qualification process. Siegel and
process. These differences explain some unpleasant surprises
Howell,2001,providethetextbookdefinitionforacloudofhot
such as localized high seal or cargo temperatures that have
soot particles representing a typical flame zone in open pool
occurred during the testing process.
fires. In this definition the black body emissive power of the
4 6.7 For proper testing, good simulations of both the regula-
flame, σT , is multiplied by the flame emissivity, ε, in order to
tory hydrocarbon fire heat flux transient and resulting material
accountforthefactthatsootcloudsinflamesbehaveasifthey
temperatures shall be achieved. Unless both the heat flux and
were weak black body emitters. A second definition of flame
material surface temperature transients are simultaneously
emissivity, often used for package analysis, assumes that the
reproduced, then the thermal stresses resulting from material
flame emissivity, ε, is the surface emissivity of a large,
temperature gradients and the final container temperature are
high-temperature, gray-body surface that both emits and re-
reported to be erroneously high or low. Some test methods are
flects energy and completely surrounds the package under
better suited to meeting these required transient conditions for
analysis. The second definition leads to slightly higher (con-
a particular package than others. The relative benefits and
servative) heat fluxes to the package surface, and also leads to
limitations of the various methods in simulating the pool fire
a zero heat flux as the package surface reaches the fire
environment are discussed in the following sections.
temperature. For the first definition, the heat flux falls to zero
whilethepackagesurfaceissomewhatbelowthefiretempera-
7. Procedure
ture. For package qualification, use of the second definition is
7.1 Qualification by Analysis
often more convenient, especially with computer codes that
model surface-to-surface thermal radiation, and is usually 7.1.1 Benefits, Limitations:
permitted by regulatory authorities.
7.1.1.1 The objective of thermal qualification of radioactive
material transportation packages by analysis is to ensure that
6.4 Convectiveheattransferfrommovingairat800°Cshall
containment of the contents, shielding of radiation from the
also be included in the analysis of the hypothetical accident
contents, and the sub-criticality of the contents is maintained
condition. Convection correlations shall be chosen to conform
per the regulations. The analysis determines the thermal
to the configuration (vertical or horizontal, flat or curved
behavior in response to the thermal conditions specified in the
surface) that is used for package transport. Typical flow
regulations for normal conditions of transport and for hypo-
velocities for combustion gases measured in large fires range
thetical accident conditions by calculating the maximum tem-
are in the 1 to 10 m/s range with mean velocities near the
peratures and temperature gradients for the various compo-
middle of that range (see Schneider and Kent, 1989, Gregory,
nentsofthepackagebeingqualified.RefertoAppendixX3for
et al, 1987, and Koski, et al, 1996). No external non-natural
specific requirements of the regulations.
coolingofthepackageafterheatinputispermittedafterthefire
7.1.1.2 Temperaturesthataretypicallydeterminedbyanaly-
event,, and combustion shall proceed until it stops naturally.
sis are package surface temperatures and the temperature
Duringthefire,effectsofsolarradiationareoftenneglectedfor
distribution throughout the package during normal conditions
analysis and test purposes.
of transport and during thermal accident conditions. In
6.5 For purposes of analysis, the hypothetical accident addition, maximum pressure inside the package is determined
thermalconditionsarespecifiedbythesurfaceheatfluxvalues. for both normal and accident conditions.
Peak regulatory heat fluxes for low surface temperatures
7.1.1.3 While an analysis cannot fully take place of an
typicallyrangefrom55to65kW/m .Convectiveheattransfer
actual test, performing the thermal analysis on a radioactive
from air is estimated from convective heat transfer
material transportation package allows the applicant to
correlations, and contributes of 15 to 20% of the total heat
estimate, with relatively high accuracy, the anticipated thermal
flux. The value of 15 to 20% value is consistent with
behavior of the package during both normal and accident
experimental estimates. Recent versions of the regulations
conditions without actually exposing a package to the extreme
specify moving, hot air for convection calculations, and an
conditions of the thermal qualification tests described in
appropriateforcedconvectioncorrelationshallbeusedinplace Section 6. Qualification by analysis is also a necessity in those
oftheolderpracticethatassumedstillairconvection.Afurther
cases where only a design is being qualified and an actual
discussion of heat flux values is provided in 7.2. specimen for a radioactive materials package does not exist.
E2230−22
7.1.1.4 Whiletoday’sthermalcodesprovideausefultoolto conduction and radiation. Natural convection in the gap is
perform the thermal qualification by analysis producing reli- usually neglected. Drum type packages usually have an inte-
gral thermal shield.
ableresults,thelimitationofanymethodliesintheexperience
of the user, the completeness of the model and accuracy of the
7.1.2.5 Thepackagecontentsandtheirheatgenerationshall
input data. Since in these analyses the heat transfer is the main
beconsideredinthemodelpreparation.Theimpactlimiterand
phenomenon being modeled and since it is mostly nonlinear,
the thermal shield insulation properties will result in slightly
thethermalcodeusedshallbeverifiedagainstavailabledataor
elevated temperatures during normal conditions of transport
benchmarked against other codes that have been verified. In
due to the resistance to heat flow from the package. Thus the
addition, limitations of analyses for determining the thermal
package interior has higher temperatures than the surrounding
behavior of a package include as-built package geometry, real
ambient temperature.
material properties including phase changes and destruction of
7.1.2.6 When creating the model and selecting the nodes, it
insulation, and real fire characteristics, including actual con-
is important to represent all materials of construction and
vection. Code software used shall be managed in a manner
components essential to containment in the model. Fig. 1
consistent with the appropriate QA methodology outlined in
shows a typical nodal network/finite difference model with
NQA-1 or ISO 9000 as appropriate.
node selection for temperature information on a package with
7.1.2 Model Preparation—This section describes the vari- animpactlimiter.Additionalnodeswillneedtobecreatedand
ousaspectsathermalmodelshallincludeandthemethodology utilized for an accurate Finite Element Analysis or Finite
of preparing a representative model. Difference Analysis model.
7.1.2.1 A common approach to analyzing a package is to 7.1.2.7 The mesh selected in the model for temperature
model the package as a drum or in a cylindrical configuration. profile analysis in the thermal portion of the hypothetical
This approach considers the package as an axisymmetric accident analysis shall be varied depending on the temperature
gradients. The finest mesh is located near the outer surface of
circular cylinder (outer shell) with a constant internal heat
source.Anothercommonapproachistomodelthepackagesas the package where the steepest temperature gradients occur.
The mesh size is increased as temperature gradients decrease,
a finite length right circular cylinder with an impact limiter
which usually occurs as the distance from the surface in-
(which also acts as a thermal insulator to the package). The
creases.Atestforpropermeshsizeistorefinethemeshfurther
outer shell will surround a cylindrical structure that contains
and demonstrate that no significant change in calculated
the content heat source.
temperatures results from the refinement.
7.1.2.2 Thermalprotectionofatypicalradioactivematerials
7.1.2.8 Thermo-physical Properties of Typical Materials:
package includes the impact limiters placed at the ends of the
(1)The thermal properties of the materials of construction
package and the thermal shield surrounding the cylindrical
need to be defined and documented as they are critical to
section of the package. The impact limiters consist of a
achieving meaningful results from the analysis. Properties of
low-density material, such as polyurethane foam, wood, or
the various components involved are often obtained from
other organic material enclosed in a steel shell, hollow steel
reference materials but all sources are to be verified for
structures or aluminum honeycomb design structure. The
reliability by determining that the properties were measured in
low-density configuration impact limiter usually has a low
accordance with accepted standards (that is,ASTM) and under
effective thermal conductivity.
an accepted quality assurance program (that is, NQA-1 or ISO
7.1.2.3 Thelowthermalconductivityimpactlimiterreduces
9000).
the heat transfer from the ends of the cask during normal
(2)Thematerialpropertiesusedneedtocoverthetempera-
conditions of transport, and into the ends of the cask during
ture range of the conditions being analyzed. If materials have
hypotheticalaccidentconditions.Analysisoftenshowsthatfor
propertiesthatchangewithtemperature,theyshallbemodeled
polyurethane foam impact limiters, the foam burns during a
withtheappropriatevariableproperties.Notethatuncertainties
hypotheticalaccidentandoff-gasescreatingpressurewithinthe
in the temperature dependence of material property data
impact limiter structure. This, along with the thermal expan-
increase with the variation of temperature from “room tem-
sion of the materials is to be considered in order to provide for
perature.”Additional testing is necessary for any material that
the worst case conduction/insulating properties. Credit for the
does not have well defined material properties.
insulating properties of the impact limiters shall be taken only
(3)Parts that are small or thin, or both, and do not have a
when structural analyses can demonstrate that the limiter
measurable affect on the overall heat transfer rates are often
remains in place under hypothetical accident conditions.
omitted from the model. Typical examples for this are thin
7.1.2.4 The thermal shield of radioactive waste and spent
partsthathavehighthermalconductivityandarenotseparated
fuelpackagestypicallyisastainlesssteelshellsurroundingthe
by air gaps from other components of the package being
cylindrical structural shell of the package. A gap is created
analyzed.Thinpartsseparatedbygaps,however,actasthermal
between the thermal shield and the structural shell of the
radiationshieldsthatgreatlyaffecttheoverallheattransferrate
package. Because of the low conductivity of air contained in
and shall be considered.
the gap, the heat resistance of the gap greatly reduces the heat
(4)When a material phase change or decomposition is
transfer rate during both normal conditions of transport and expected to occur, the analysis shall consider replacing the
hypothetical accident conditions. Heat transfer across the gap
material properties with conservative values. For example,
betweenthethermalshieldandstructuralshellismodeledwith polyurethane begins to decompose at 200°C (400°F), and the
E2230−22
FIG. 1Example of Node Selection When Modeling a Package
analyst often considers replacing the polyurethane properties (which is equivalent to the total insolation specified in
withthoseofairatthesametemperature.Notethatthethermal 10CFR71.71(c)(1) of 800 g-cal/cm for a 12-h period), 96.92
2 2
properties of polyurethane are similar to those of air and W/m (200 g-cal/cm for a 12-h period) for non-horizontal flat
2 2
actually the polyurethane properties are not critical since the surfaces, and 193.83 W/m (400 g-cal/cm for a 12-h period)
use of polyurethane results in a nearly adiabatic, that is, well for curved surfaces. Ambient temperature shall be 38°C
insulated, surface during hypothetical accident conditions. (100°F). Note that insolation depends on the shape and
(5)Radiation heat transfer occurs at the outer surfaces of a orientation of the package surface. A transient analysis of the
packageandalsointhegapbetweenthethermalshieldandthe normal conditions of transport can be performed instead of a
structural shell. Therefore, the consideration of the surface steady-stateanalysis.Thermalloadsforatransientanalysisare
emittance of these surfaces is critical to the model. Emittance different from those discussed in this paragraph.
values of the package exterior surface for the fire are specified (2)Inaddition,representativeinternalheatgenerationshall
in the regulations. be considered when preparing the model to determine the
(6)The analyst shall be familiar with the how the code temperature distribution of the package.
models radiation and, in specific, surface emissivity or absorp- (3)The model shall address external natural convection
tivity (also treated by some codes as reflectivity or albedo). In and radiation boundary conditions and temperature property
general,conservativesurfaceemittancevaluesaretobeusedin variations.
the analysis, that is, emittance value of 0.9 or unity (black (4)The temperature distribution of the package is assumed
body) for fire conditions, and an emittance of 0.8 shall be symmetric about the vertical axis and its horizontal mid-plane.
assumed for the outer surfaces in accordance with regulations. The heat transfer model needs to be defined, for example,
Package interior gap surfaces might be assumed as manufac- two-dimensional axisymmetric heat transfer (radial and axial).
tured for pre-fire conditions. Use of other than conservative The model shall address insolation on the package surfaces.
values shall be justified. Radiation heat exchange at the package interior surfaces shall
7.1.2.9 Model Preparation for Normal Conditions of Trans- be addressed.
port Thermal Evaluation: (5)Heattransferwithinthecontentsofthepackageisoften
(1)A steady-state analysis for normal conditions of trans- omitted in the special case where the heat generated in the
portthatfollows10CFR71.71shallassumeconstantinsolation contents is uniformly applied to the interior surfaces of the
of 387.67 W/m on horizontal flat surfaces exposed to the sun package. It is possible to use the package symmetry in the
E2230−22
modeltofacilitateevenheattransferconsiderations.Spentfuel pletelylost.Thisassumptionprovidesaconservativeapproach.
packages require special consideration as the bulk of the heat These two cases envelop the best and worst case scenarios
during the hypothetical accident thermal evaluation.
generated by the contents is transferred radially to the packag-
ing due to the large aspect ratio and the impact limiters on the (5)Underlying assumptions shall be documented and in-
clude:
ends of the package.
(6)The inside containment vessel temperature causes the
Enclosure radiation
External radiation
internal pressure to be elevated above atmospheric pressure.
Natural convection
Theinternalpressureatsteadystateareestimatedbyassuming
Insolation
the atmosphere contains dry air at an appropriate pressure and Internal heat dissipation
Internal convection
temperature when the package is closed. If the package
containswater,assumethatatsteady-statetransportconditions
7.1.3 Example of Package Model:
the air is saturated with water vapor. The internal pressure is
7.1.3.1 For demonstration purposes, consider that the ex-
equal to the sum of the dry air and the vapor pressure of water
ample package (see Safety Analysis Report for the 10-135
at the temperature of the environment within the containment
RadwasteShippingCask,1999)isasteelencasedleadshielded
vessel for normal conditions of transport. The stresses due to
cask intended for solid radioactive material (see Fig. 2).
pressurization of the package need to be addressed as part of
Overall dimensions are 2.85 m (112 in.) diameter by 3.3 m
the structural analysis.
(130 in.) height. It consists of two (2) concentric carbon steel
cylindrical shells surrounding a 89 mm (3.5 in.) thick lead
7.1.2.10 Model Preparation for Hypothetical Accident
shield. The 13 mm (0.5 in.) thick inner shell has a 1.67 m (66
Thermal Qualification:
in.) internal diameter and the 25 mm (1 in.) thick outer shell
(1)The effects of the hypothetical accident thermal condi-
has a 1.93 m (76 in.) outside diameter. The base is welded to
tions on the package need to be evaluated. The hypothetical
theshells.Thetopofthepackageisprovidedwithprimaryand
accident thermal conditions are defined in the regulations. The
secondarylidsofasteppeddowndesignconstructedoftwo75
various test conditions shall be applied sequentially, which
mm(3in.)thickplatesjoinedtogethertoforma150mm(6in.)
means that the thermal test follows the drop and the puncture
thick lid. The lids are secured with bolts. Lid interfaces are
tests.The reduction of the insulating capabilities of the impact
provided with high temperature silicone gaskets.
limiter caused by the free drop and puncture test shall be
7.1.3.2 The initial temperatures are determined from the
consideredintheanalysisofpackages.Incaseswheredropand
normal conditions of transport assuming a 38°C (100°F)
puncture damage to the impact limiters cannot be modeled in
ambient temperature with insolation. Fig. 3 shows typical
sufficient detail, two cases are analyzed to envelope the
steady-state temperatures under these conditions and an as-
performance of the impact limiters during a fire.
sumed 400W heat generation from the contents of a typical
(2)Theinitialtemperaturedistributioninthepackageprior
package. For packages with large thermal mass, or fully
to the fire shall be that determined for either the normal
enclosed by a thick insulating medium, such as polyurethane
conditionsoftransport(38°Cwithinsolation)[SSR-6,§728]or
foam, a 24-h average insolation value is often used to deter-
that determined for the case of defining the type of shipment
mine temperatures of interior components.
(exclusive or nonexclusive) from 10 CFR 71.43 (g) [10 CFR
71.73 (b)]. Usually, undamaged packages lead to higher 7.1.3.3 Two impact limiters are located at the top and
bottom of the package. The impact limiters are 10-gauge
pre-fire temperatures because package insulation is undam-
stainless steel shells filled with rigid polyurethane. The inner
aged. However in cases where damaged conditions lead to
surfaces of the body and the lid are clad with 12-gauge
higher pre-fire temperatures, those temperatures shall be used
stainless steel. The exposed portion of the cask body is
instead.
provided with a 10-gauge stainless steel thermal shield. A 6.4
(3)The thermal conditions imposed on the package during
mm (0.25 in.) gap between the cask body and the thermal
hypothetical accident conditions are that the package, with the
shield is maintained by spacers. A potential issue during
initial temperature distribution as determined above, is sub-
thermal qualification is the manufacturer’s ability to maintain
jectedtoafireof800°C(1475°F)foraperiodof30min.After
uniform gap width and potential effect of gap variation on the
the 30-min period, the source fire is assumed extinguished and
thermal results. The effect of gap widths in the as-
the ambient temperature reduced to 38°C (100°F). Any
manufacturedpackageshallbeconsideredanddiscussedbythe
ongoing combustion that continues after the fire shall be
analyst.
accounted for in the analysis. Flames of the ongoing combus-
7.1.3.4 Fig. 4 shows the predicted temperatures of a typical
tion are not allowed to be extinguished. In addition to the
package after 30 min following the initiation of the flame
natural convection to the ambient air and radiation to the
environment for the cask with the impact limiter attached.The
environment, the package shall be subject to insolation during
model was created using TAS of Harvard Thermal.
the post-fire cool-down.
(4)To determine the effect of the reduced insulating
7.1.3.5 After 30 min, the ambient temperature is reduced
capabilities of the impact limiter, two cases are analyzed. The from 800°C (1475°F) to 38°C (100°F) and, consequently,
first one assumes that the free drop and puncture tests had
the package begins to lose heat to the environment by natural
minor effects in thermal performance of the package during a convection to the still air and radiation to the environment.
hypothetical accident. The second case assumes that the However, the temperature in some regions of the package
insulating capabilities of the impact limiter have been com- continues to increase for some time due to heat conduction
E2230−22
FIG. 2Typical Package With Impact Limiters at Steady State (Using TAS)
NOTE 1—Temperatures are in °F. Note that in the original figure, colors were used to represent temperature variations.
FIG. 3Initial Temperatures for Transient Analysis for a Typical Package With Impact Limiters (Using TAS)
from surrounding regions of higher temperatures. These local partially, for the lack of pre-fire insolation. For packages to be
temperatures will continue to increase until the content tem-
qualified under both U. S. and international regulations, this
perature exceeds the temperature of the surrounding package
effect shall be addressed and quantified for the regulator.
components. The rate at which the package cools will be
7.1.4 Additional Information to be Reported:
reduced as insolation is applied during the cool-down time. If,
7.1.4.1 The results of the analysis shall be tabulated to
aspermittedintheU.S.(10CFR71.73(b)),pre-fireconditions
summarize the maximum temperatures resulting from the
are determined without the insolation specified in 10 CFR
hypothetical accident condition for each material of construc-
71.71, then initial package surface and contents temperatures
tion. In addition, graph(s) shall be included showing tempera-
will often be lower than the steady state temperatures reached
ture as a function of time for representative and critical/unique
with insolation after the fire. If package temperatures without
locations on the container during a hypothetical accident. The
insolationareloweratthestartofthefire,initialfireheatfluxes
to the package surface will be higher, compensating, at least
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NOTE 1—Temperatures are in °F. Note that in the original figure, colors were used to represent temperature variations.
FIG. 4Temperatures After the 30-Min Fire on a Typical Package With Impact Limiters Attached (Using TAS)
interval selected shall be long enough to show all component data and retrieve results through a number of menu driven
temperatures descending with time. An example is shown choices. Some older codes require entry of data in the form of
below in Fig. 5. an input file, without the benefit of a GUI, and rely on a
7.1.4.2 Changes in the internal pressure shall be addressed. third-party graphics program to plot results of an analysis.
The internal pressure typically increases during the hypotheti- Some heat transfer codes require the use of a separate code to
cal accident due to heating of contents. Chemical decomposi- determine radiation form factors, which are then used by the
tion of the packaging materials and package contents shall be thermal code to treat enclosure radiation. The results of the
considered and appropriately addressed. thermal analysis are often used by the structural analyst to
7.1.4.3 Considerationofthermalstressesduetobothnormal perform thermal or pressure-induced stress analyses.
conditions of transport and hypothetical accident conditions 7.1.5.4 Thermal codes shall be qualified for package evalu-
shall also be included in the analysis. ation by verification, benchmarking, or validation. A code is
7.1.4.4 Post-firesteadystatetemperaturesshallbeanalyzed. verified by comparison of the results with the results of
Any resultant damage (for example, smoldering or melting of appropriate closed form solutions.
aneutronorgammashield,orboth)orchangeintheemissivity 7.1.5.5 Sample Problem Manual for Benchmarking of Cask
ofthesurfaceofthepackageshallbeevaluatedwithrespectto Analysis Codes (Glass, et al, 1988) describes a series of
the impact on the post-accident “normal” temperatures. problems, which have been defined to evaluate structural and
7.1.5 Analysis Conduct: thermalcodes.Theseproblemsweredevelopedtosimulatethe
7.1.5.1 General-purpose heat transfer codes exist for per- hypothetical accident conditions given in the regulations while
forming the thermal analysis of packages for the transport of retaining simple geometries. The intent of the manual is to
radioactive materials. These codes model heat transfer phe- provide code users with a set of structural and thermal
nomena (conduction, convection and radiation) for multidi- problems and solutions which are used to evaluate individual
mensionalgeometrieswithlinearandnon-linearsteady-stateor codes.
transientbehavior.Theymodelvariousmaterialswithtempera- 7.1.5.6 Acodeisbenchmarkedbycomparisonoftheresults
ture dependent isotropic and orthotropic thermal and other with the results of other qualified codes. An alternative code
physical properties, including phase change. validationmethodistocomparethecoderesultstoresultsfrom
7.1.5.2 These general-purpose codes treat constant or time- package design-based test data or hand calculations performed
dependent spatially-distributed heat-generation sources, enclo- under qualified QA programs.
sure radiation and boundary conditions including temperature 7.1.5.7 Any code selected to perform the thermal design
and heat flux. analysis of a radioactive material transportation package shall
7.1.5.3 Most commercial FEA codes have thermal solvers be subject to the QA program requirements for nuclear
and provide pre- and post-processors. The pre-processor is facilities as prescribed in ASME NQA-1 or software require-
used to create package geometry and generate a mesh for the ments of ISO 9000 as required by the certifying authority.
package, while the post-processor provides results in a graphi- 7.1.5.8 Several thermal analysis codes are available to
cal format. Pre- and post-processors are often in the form of a licensees of radioactive packages to perform the qualification
graphical user interface (GUI) which allows the user to enter analyses.Thisdocumentisnotintendedtodescribethevarious
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FIG. 5Example for Temperature as a Function of Time for Selected Locations on a Sample Container
During a Hypothetical Thermal Accident
thermal codes in detail, but a few are mentioned and briefly surfaceisheavierthanair,andsubjecttodisplacementbyvery
described in Appendix X4 for the reader’s benefit. Codes not low velocity air currents. The effect of wind is minimized by
mentioned in Appendix X4 are often equally adequate to enclosing the pool within a ring of 6 m high wind fencing.
perform thermal qualification of packages to regulatory re-
7.2.1.3 The intention of a pool fire test is to subject the
quirements. No comparison or evaluation of codes is provided
prototype package to an environment that is representative of
in this document.
conditionsfoundinatransportationaccidentfire.Notethattwo
differentenvironmentsareunderconsiderationhere.Thereisa
7.2 Pool Fire Testing
hypothetical accident condition or regulatory hydrocarbon fire
7.2.1 Benefits, Limitations:
environment, described in the regulations, and an actual pool
7.2.1.1 Pool fire testing has been the traditional testing
fire environment, which is created at 1 m above a pool of
methodbywhichapackageisqualifiedtothethermalaccident
burning liquid hydrocarbon fuel in calm wind conditions.
environment set forth in the regulations. In the test, the
Packages that are designed to withstand the regulatory hydro-
prototype package is placed 1 m over a pool of fuel whose
carbonfireareconsideredtofunctionsafelyinatransportation
lateral dimensions relative to the package meet the require-
accident. The actual pool fire environment is a convenient
ments stated in the regulation. When atmospheric conditions
means for testing packages and is usually very different from
arequiescent,thefuelisignitedandthepackageisengulfedin
the hypothetical accident conditions as discussed below.
thefireplume.After30min,thefuelisconsumed,thefiregoes
7.2.1.4 The hypothetical accident condition environment
out, and the prototype package is left to cool down naturally.
specified in the regulations is usually reduced to a schedule of
7.2.1.2 Aconvenient method for forming a pool consists of
heatfluxabsorbedthroughthepackagesurfaceasafunctionof
floating a layer of jet fuel (JP-8) on water in a deep steel tub
the package surface temperature.Aheat balance at any instant
(see Fig. 6). The water provides a flat surface for the fuel,
in time on the surface of a package subjected to the regulatory
which ensures the fire burns out evenly over the whole pool
hydrocarbon fire gives:
area when the fuel is completely consumed. A deep tub (~0.7
4 4
m)providesenoughwatertomaintainaconstantfuelsubstrate
q 50.9·0.8·σ·T 20.8·σ·T (1)
absorbed environment surface
temperature which helps to maintain a constant fuel consump-
where:
tion rate during the fire. The packages are held at the required
q = heat flux passing through the surface of the
height above the pool surface with a stainless steel grill.
absorbed
package, kW/m ,
Structures are placed throughout the pool to support fire
-11
σ = Stefan-Boltzmann constant, 5.67 × 10 kW/
instrumentation that might include thermocouples,
2 4
(m K ),
calorimeters, heat flux gages, and gas velocity probes. The
T = temperature specified in 10CFR71, 800 + 273
environment
response of this instrumentation is used to provide evidence
= 1073 K,
that the required thermal environment has been met. Sheet
T = surface temperature of the package at any
surface
metal side ramps on the outside of the tub, and sheet metal
instant, K,
skirts on the grill provide fire plume stability. These are
0.9 = specified emissivity of flames, and
necessary because the fuel vapor immediately above the fuel
E2230−22
NOTE 1—Some features are to meet geometrical requirements, some stabilize the plume, and others provide evidence of supplying the required
environment.
FIG. 6A Pool Fire Test and Setup That Meets the Regulatory Requirements
support structures. In terms of flexibility and cost, there are
0.8 = absorptivity of package surface (minimum
obvious benefits over those associated with an oven or radiant
value).
heat facility.
7.2.1.5 This description of the hypothetical accident condi-
7.2.1.8 A second benefit is that the pool fire environment
tion environment is shown in Fig. 7. Note that in the equation
oftensurpassestherequirements,providingaconservativetest.
above, the “text book” definition of flame emissivity (see 6.3)
Fig.7showsthatthefluxfromapoolfiretoanengulfedobject
has been used to generate the plot. The regulatory heat fluxes
often exceeds the criteria by a factor approaching four.
are compared to a description of the actual pool fire environ-
Furthermore, the fact that the environment is a real fire shall
ment that has been determined from the response of thick wall
not be overlooked. The so-called second order characteristics,
passive calorimeters from which data have been gathered over
such as fire plume chemistry or non-uniform spatial and
the last 20 years in pool fires of sizes ranging from 1 to 20 m
temporalheatfluxes,affectpackageperformanceinunforeseen
in diameter.The wide range is due to minor variations in wind
ways; and subjecting a prototype package to a pool fire brings
conditions and calorimeter surface orientation with respect to
out deficiencies due to features that weren’t considered in the
the pool geometry.
design. Examples of this that have occurred in the past with
7.2.1.6 Note that in general, the pool fire provides an
packages in pool fires include unexpected seal response due to
environment that is more intense than that o
...