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GB/T 41024-2021: Load combination and design criteria for structural analysis of spent fuel transport cask
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Load combination and design criteria for structural analysis of spent fuel transport cask
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GB/T 41024-2021
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Basic data | Standard ID | GB/T 41024-2021 (GB/T41024-2021) | | Description (Translated English) | Load combination and design criteria for structural analysis of spent fuel transport cask | | Sector / Industry | National Standard (Recommended) | | Classification of Chinese Standard | F73 | | Word Count Estimation | 13,171 | | Issuing agency(ies) | State Administration for Market Regulation, China National Standardization Administration | GB/T 41024-2021: Load combination and design criteria for structural analysis of spent fuel transport cask
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Load combination and design criteria for structural analysis of spent fuel transport cask
National Standards of People's Republic of China
Structural Analysis of Spent Fuel Transport Containers
Load Combinations and Design Guidelines
Load combination and design criteria for structural analysis of
spent fuel transport cask
This electronic version is the official standard text, which is reviewed and typeset by the Environmental Standards Institute of the Ministry of Ecology and Environment.
Published on 2021-11-01
2021-12-01 Implementation
Ministry of Ecology and Environment
State Administration for Market Regulation
ICS 13.300
F 73
release
directory
Foreword...ii
1 Scope...1
2 Normative references...1
3 Terms and Definitions...1
4 Load combinations...3
5 Design Guidelines...7
Load combinations and design criteria for structural analysis of spent fuel transport vessels
1 Scope of application
This standard specifies load combinations and design criteria for structural analysis of spent fuel transport vessels.
This standard applies to the structural analysis of spent fuel transport containers, the total activity of radioactive contents is greater than 3000A1 (special radioactive materials),
Greater than 3000A2 or 1×10
The radioactive material transport container of Bq can be implemented by reference.
2 Normative references
This standard refers to the following documents or clauses thereof. For dated references, only the dated version applies to this standard.
For undated references, the latest edition (including all amendments) applies to this standard.
GB 11806-2019 Regulations for Safe Transport of Radioactive Materials
3 Terms and Definitions
The following terms and definitions apply to this standard.
3.1 Terminology
3.1.1
stress intensity
The combined stress is based on the equivalent strength of the third strength theory and is specified as 2 times the maximum shear stress at the given point, i.e. the algebraically maximum at the given point
The difference between the principal stress and the algebraic minimum principal stress (positive for tensile stress and negative for compressive stress).
3.1.2
primary stress
Any normal or shear stress resulting from the applied load, which is necessary to satisfy the law of equilibrium of external or internal forces and moments.
The fundamental property of primary stress is that it is not self-limiting, and when the primary stress greatly exceeds the yield strength, it can cause failure or at least general deformation.
shape.
3.1.3
secondary stress
Normal or shear stress due to constraints of adjacent materials or due to constraints of the structure itself. The basic properties of secondary stress are
Self-limiting, localized yielding and minor deformations can satisfy conditions to induce stress, a single action of which will not produce the expected failure.
3.1.4
primary membrane stress
Average primary normal stress over the thickness of the solid section.
3.1.5
primary bending stress
The primary normal stress component distributed linearly along the thickness of the solid section.
3.1.6
alternating stress intensity
The alternating stress intensity altS is defined as the intensity of the alternating stress at all possible stress states (i and j),
One-half of the largest absolute value in the sum.
3.1.7
fatigue fatigue
Local and permanent damage increment process occurs at a certain point of the structure under cyclic loading conditions, after sufficient stress or strain cycles,
The accumulation of damage can cause cracks in the material, or the cracks can further propagate to complete failure.
3.1.8
stability shakedown
There is no continuous cycle of plastic deformation. When the deformation stabilizes after several load cycles and the subsequent structural response is elastic, the structure will
settle down.
3.1.9
containment boundary
The assembly of packaging components used to contain the radioactive material is a physical barrier to prevent the loss or dispersion of the radioactive material during transportation
barrier.
Note. The metal part of the containment boundary of the spent fuel transport container generally includes. inner cylinder, primary sealing cover, penetration sealing cover and connecting bolts, etc.
3.1.10
criticality safety components
Parts other than the containment boundary that may affect the criticality safety of the container during transport.
3.1.11
other safety components
All structural parts that perform other safety-related functions of the transport container, with the exception of containment boundaries and criticality safety-related parts.
Note. Secondary sealing structure and its bolts, lifting device (lifting trunnion), etc.
3.1.12
packaging
One or more containers and any other components or materials within the container required for containment and other safety functions.
3.1.13
package
The package submitted for transport and its radioactive contents collectively.
3.2 Symbols
Salt--alternating stress strength, MPa;
Sa--allowable amplitude of alternating stress intensity component, MPa;
Sm--design stress strength, take the smaller of 1/3 Su and 2/3 Sy, MPa;
Sn--primary plus secondary stress strength, MPa;
Sy--the yield strength of the material at the corresponding temperature, MPa;
Su--the tensile strength of the material at the corresponding temperature, MPa;
A1, A2--Radionuclide limits (according to the regulations in GB 11806-2019).
4 load combinations
4.1 Basic regulations
In this standard, the loads that need to be considered for structural analysis under different conditions required by GB 11806-2019 are superimposed according to the most unfavorable situation.
The load combinations of the containers under initial conditions, normal transport conditions and transport accident conditions are given, see Table 1 for details.
4.2 Initial Conditions
4.2.1 General requirements
Loads at initial conditions shall be the basis for normal transport conditions and transport accident conditions, which shall be compared to normal transport conditions and transport incident conditions, respectively.
The loads under these conditions are combined for structural evaluation of the vessel.
4.2.2 Initial temperature
The initial temperature distribution of the container should be in a steady state. The initial temperature of normal transport conditions and transport accident conditions should consider the ambient temperature -40 ℃
No sun exposure and ambient temperature 38 ℃ with sun exposure. Sun exposure should meet the requirements of GB 11806-2019.if the most
Low temperature lower than -40°C or maximum temperature higher than 38°C should be considered separately. The heat resistance test conditions in the transport accident conditions do not need to consider the low temperature initial
initial condition.
4.2.3 Decay heat
The initial conditions should also take into account the decay heat of spent fuel assemblies. The maximum decay heat should normally be superimposed at higher ambient temperatures and should be considered
Considering the solar exposure requirements in GB 11806-2019, the decay heat can usually not be considered in the case of low temperature.
4.2.4 Internal pressure
4.2.4.1 The internal pressure of the vessel mainly depends on the following factors. the pressure of the inert gas refilled in the vessel, the temperature change of the vessel and the spent fuel
Leakage of all gases within the cladding. The internal pressure of the vessel should be reasonably combined with other initial conditions. The minimum internal pressure shall be atmospheric pressure, for less than atmospheric pressure
In the design of pressure, the value of internal pressure should be negative.
4.2.4.2 The release of all gases in the spent fuel assembly shall be considered to determine the maximum internal pressure of the vessel.
4.2.5 Assembly stress
When evaluating a vessel, the stresses arising during the assembly and installation of the vessel (including joining, forming, assembling and aligning, etc.) should be considered. If not
Subsequent measures to remove these stresses should be taken into account when determining the maximum vessel stress. It should be considered a stress free state prior to assembly.
Note 1.Assembly refers to the assembly of the main components of the container. including the inner cylinder, gamma shielding layer, outer cylinder, etc., but does not include the manufacture of individual components.
Note 2.Assembly stress should include stress caused by interference fit and boundary shrinkage caused by lead solidification process, but not including sheet forming, welding
Residual stress caused by etc.
4.2.6 Others
When performing structural analysis, the following loads should be considered separately and do not need to be superimposed on each other.
4.3.2 Heating
The conditions of the container in still air with an ambient temperature of 38 ℃ and the sun exposure specified in GB 11806-2019 should be considered. as transport
The vessel has a mechanically assisted cooling system which shall be considered ineffective during structural evaluation under heated conditions.
4.3.3 Cold
Consideration should be given to the condition of the container in still air at an ambient temperature of -40 °C and without sun exposure. At the same time, it should be considered that the container has no internal thermal load
and minimum internal pressure, the possibility of coolant freezing and its effects should also be considered.
4.3.4 External pressure increase
The effect on the vessel structure should be evaluated when the external pressure is increased to 140 kPa.
4.3.5 External pressure reduction
The effect on the vessel structure should be evaluated when the external pressure is reduced to 60 kPa.
4.3.6 Vibration and fatigue
4.3.6.1 The structural evaluation of the container under normal transport conditions shall consider vibration and shock loads. Includes small incentives for container-vehicle systems
Vibration loads generated; intermittent generation at joints and turnouts during railway transportation, as well as speed bumps and potholes during road transportation
Impact load. Repeated pressurized loads and any other loads that affect mechanical fatigue of the vessel should be included in the analysis.
4.3.6.2 Fatigue analysis may be carried out separately for different load combinations of containers under normal transport conditions, and the evaluation should be based on the most unfavorable initial
conditions and is consistent with a reliable spectrum of lifetime in normal shock and vibration environments. Table 1 lists the worst-case scenarios.
4.3.6.3 Other factors that may cause thermal fatigue should be considered. These factors should include those encountered during spent fuel loading and unloading
Thermal transients, and the interaction of the tethering system with the thermal expansion of the vessel.
4.3.7 Stacking
4.3.7.1 Unless the shape of the package can effectively prevent accumulation, it should be subjected to the higher pressure load of the following two tests for 24 h.
By.
a) equivalent to 5 times the maximum weight of the package;
b) Equivalent to the product of 13 kPa and the vertical projected area of the package.
4.3.7.2 The load shall be applied evenly on two opposite sides of the package, one of which shall be the bottom of the package on which it would normally rest.
4.3.8 Penetration
4.3.8.1 The package shall be placed on a rigid, flat, level surface that will not move significantly during the test.
4.3.8.2 A rod with a diameter of 3.2 cm, a hemispherical end and a mass of 6 kg should be allowed to fall freely and fall on the cargo in the vertical direction.
The center of the weakest part of the bag. Thus, if the penetration depth is deep enough, the containment system is impacted. The rod shall not show signs of being tested
deformed.
4.3.8.3 The drop height from the lower end of the rod to the expected point of impact on the upper surface of the package shall be 1 m.
4.3.9 Free fall
4.3.9.1 The target for free fall is defined as a flat horizontal plane target. After the target is impacted by the container, its anti-displacement ability or anti-deformation energy
The increase in force did not result in a significant increase in the damage of the specimen.
4.3.9.2 The spent fuel transport container shall be evaluated for falling on the target at the height listed in Table 2, and the impact surface of the container shall be the expected
At the position where the greatest damage is caused to the container, the test target shall meet the requirements specified in 4.3.9.1.Consideration should also be given to the maximum weight of the contents of the container and
Impact on shock when minimum.
4.4 Loads under transport accident conditions
4.4.1 General requirements
The loads under transport accident conditions shall be combined in accordance with Table 1 according to the initial conditions specified in Section 4.2.in the spent fuel transport container
When carrying out structural analysis, the same container shall be subjected to the Free Fall Test I,
Free fall test II, heat resistance test; or apply free fall test II, free fall test III, heat resistance test in sequence. The samples are subjected to various
The sequence of the free-fall test should follow the principle that after completion of the mechanical test, the damage to the specimen will cause the specimen to fail in the subsequent
The most severe damage occurs in the heat test.
4.4.2 Free fall test I
4.4.2.1 The container shall fall freely on the target so as to cause the most serious damage to the container, from the lowest point of the container to the height of the upper surface of the target.
Should be 9 m. The test target shall meet the requirements specified in 4.3.9.1.The maximum and minimum weight of the contents should be considered.
4.4.2.2 In order to determine the maximum deformation part of the container after the free fall test I, the top,
Deformation of top, lateral, bottom, bottom, and over-gravity impact points. If the design of the container causes a certain tilt angle direction to drop to the container
The more destructive, the impact of these angled drops should also be evaluated.
4.4.3 Free fall test II
The container should fall freely on a rod firmly upright on the target to allow the most serious damage to the container. Expected shock from container
The height from the point to the end face of the rod shall be 1 m. The rod shall be made of round solid mild steel with a diameter of (15 ± 0.5) cm and a length of 20 cm,
If a longer rod will cause severe damage, a rod of sufficient length should be used. The tip of the rod should be flat and level with rounded edges
corners with a radius of no more than 6 mm. The test target shall meet the requirements specified in 4.3.9.1.The maximum and minimum weight pairs of contents should be considered
impact of this condition.
4.4.4 Free fall test III
The container should be subjected to a dynamic crush test, that is, the container is placed on the target, and a 500 kg object is allowed to fall freely onto the container from a height of 9 m.
cause the most serious damage to the container. The weight shall be a solid low carbon steel plate of 1 m × 1 m and shall fall horizontally. steel plate
The edges and corners of the bottom surface are arc-shaped, and the radius of the corners is not more than 6 mm. The drop height is the distance from the bottom of the board to the highest point of the container. For testing
The target shall meet the requirements specified in 4.3.9.1.
4.4.5 Heat resistance test
The maximum designed internal heat release rate of the container subjected to radioactive contents in the package and the rate specified in Table 4 of GB 11806-2019
Under the specified sun exposure conditions, it is still in thermal equilibrium at an ambient temperature of 38 °C. In addition, these parameters are allowed to be tested before and
Have different values during the test, but are taken into account when evaluating the package response curve later.
Heat resistance tests include.
a) Expose the vessel for 30 min to a thermal environment that provides a heat flux at least equivalent to that under completely static ambient conditions
The heat flux density of the hydrocarbon fuel/air flame to give a minimum average flame emissivity of 0.9 and an average temperature of at least 800 °C,
The specimen is completely engulfed by the flame such that the surface absorption coefficient is 0.8 or the package is exposed to the specified flame which actually has
the absorption coefficient value.
b) subjecting the container to the maximum design internal heat release rate generated by the radioactive contents in the package and specified in Table 4 of GB 11806-2019
Under the specified sun exposure conditions, exposed to an ambient temperature of 38 °C for a long enough time to ensure the temperature of each part of the sample.
to or near the initial steady state. Furthermore, these parameters are allowed to have different values after heating is stopped, but
be taken into account when considering the packet response curve. During and after the test, the specimen shall not be artificially cooled, and the material of the specimen shall be allowed to
Burn naturally.
4.4.6 Water immersion
The container shall be submerged for not less than 8 h in a water depth of at least 15 m which will cause the most serious damage. carried out analytically
evaluation, the vessel shall be subjected to an external gauge pressure of at least 150 kPa.
4.4.7 Enhanced water immersion
Intensive water immersion test for spent fuel transport container packages containing more than 105A2, the package should be submerged a lot at a depth of at least.200 m
in 1 h. For evaluation by analytical calculation, the vessel shall be subjected to an external gauge pressure of at least 2 MPa.
5 Design Guidelines
5.1 Basic regulations
5.1.1 The structural design criteria are based on linear elastic analysis, the basic assumption of which can be applied to the superposition principle to determine the effect of load combinations on the vessel structure.
However, some other safety-related components can adopt appropriate nonlinear methods according to the actual situation.
5.1.2 The containment boundary, critical safety-related parts and other safety-related parts shall be made of materials that meet the standard or technical
It corresponds to the specified material properties, design stress intensity, design fatigue curve, etc. When performing structural analysis, the material property values should be based on the corresponding temperature.
degree selection.
5.1.3 During the design of the vessel, in addition to meeting the structural safety assessment criteria specified in this standard, it should also meet the requirements of criticality, shielding, and containment.
capacity and other safety function requirements.
5.1.4 For the spent fuel transportation container whose main material is carbon steel and low-alloy steel, additional requirements such as low temperature fracture toughness shall be considered at the same time.
5.1.5 This Section does not apply to the spent fuel transport container whose main material is ductile iron.
5.2 Design Guidelines for Containment Boundary Structures
5.2.1 Limits of stress intensity of containment boundary structures under normal transport conditions
5.2.1.1 The stress strength value of the overall primary film should not be greater than the design stress strength Sm, and the primary film plus primary bending stress strength should not be greater than the design stress strength Sm.
1.5Sm.
5.2.1.2 The fatigue analysis shall be carried out as follows.
a) Salt shall consider the total stress state distributed at each point during normal operating cycles to determine the maximum extent.
b) When the cyclic load does not exceed 106 cycles, the design fatigue curve in the standard specification may be used. When the load exceeds 106 cycles, the
Take the Sa value from the applicable design fatigue curve for the maximum number of cycles defined by that curve.
c) Salt should be multiplied by the ratio of the modulus of elasticity given on the design fatigue curve to the modulus of elasticity used in the analysis to obtain a correlation with the design fatigue
Stress values to use with the Lau curve. When only one working cycle is considered, the appropriate design fatigue curve can be selected from the corresponding
As the allowable life, if there is significant stress caused by two or more stress cycles, the accumulated stress should be considered.
cumulative effect.
d) When the structure is discontinuous, an appropriate stress concentration factor should be used. When the coefficient is unknown, it usually takes a value of 4.
5.2.1.3 The primary and secondary stress strength Sn should not be greater than 3Sm, and its calculation is consistent with the calculation of 2Salt, but the factors considered in the fatigue calculation
Partial concentrated stress is not included in this stress range.
5.2.1.4 When the following conditions are met, the primary stress plus secondary stress may be larger than the 3Sm limit (these conditions are usually only
Only occurs when the thermal bending stress accounts for a large proportion of the total stress).
a) The stress intensity Sn resulting from the stress range under normal transport conditions, excluding the stress caused by stress concentration and thermal bending, shall be
not more than 3Sm;
b) The value of Sa used to design the fatigue curve is multiplied by the factor Ke.
Salt and Sa are the allowable amplitudes of alternating stress intensity and alternating stress intensity components, respectively; the material property parameter value m of different material categories
and n values are detailed in Table 3.
a) The temperature does not exceed the temperature of various materials listed in Table 3;
b) The ratio of the specified minimum yield strength to the specified minimum tensile strength of the material is less than 0.8.
5.2.1.5 The shear stress intensity value on the section subjected to pure shearing shall not be greater than 0.6Sm;
The degree value should not be greater than Sy.
5.2.1.6 For bolts, the stress strength value of the primary film should not be greater than 2/3 Sy, and the primary film plus primary bending stress strength should not be greater than Sy.
5.2.2 Limits of stress intensity of containment boundary structures under transport accident conditions
5.2.2.1 The stress strength value of the overall primary film should not be greater than the smaller of 2.4Sm and 0.7Su; the primary film plus the primary bending stress strength
It should not be greater than the smaller of 3.6Sm and Su; the average primary shear stress of the section subjected to pure shearing should not be greater than 0.42Su.
5.2.2.2 The plastic analysis method is allowed to be used for the structure of the containment boundary part, and the structural evaluation can be carried out according to the maximum strain not exceeding 5%.
The effect of plastic deformation on the seal shall be assessed.
5.2.2.3 For bolts, the stress strength of the primary film should not be greater than the smaller value of Sy and 0.7Su; the primary film plus the primary bending stress strength
Should be no greater than Su.
5.2.3 Other design requirements of the containment boundary structure
5.2.3.1 No buckling of the containment boundary structure shall occur under normal transport conditions or transport accident conditions. in design dimensions and load
When loaded, the eccentricity should be calculated using appropriate coefficients. Buckling analysis can be used to ensure that the material does not deform erratically and that the vessel is fully
Meet the linear elastic analysis requirements in this specification.
5.2.3.2 The ultimate total stress of initial state, manufacturing state, normal transportation conditions and transportation accident conditions shall be less than 2 times the
The adjusted value of Sa after 10 cycles given by the Lau design curve (the adjustment was used to calculate the elasticity of the model at the highest temperature). appropriate
The stress concentration factor is used for the calculation of structural discontinuity. When the stress concentration factor is unknown, it usually takes a value of 4.
5.3 Design criteria for critical safety-related components
5.3.1 Limits of stress intensity of critical safety-related components under normal transport conditions
5.3.1.1 For the hanging basket, the overall primary film stress intensity value should not be greater than the design stress intensity Sm, and the primary film plus primary bending stress is strong.
Degree should not be greater than 1.5Sm.
5.3.1.2 For the hanging basket, the pure shear stress shall not be greater than 0.6Sm; the bearing stress shall not be greater than Sy.
5.3.2 Limits of stress intensity of critical safety-related components under transport accident conditions
5.3.2.1 The stress strength of the overall primary film shall not be greater than the smaller value of 2.4Sm and 0.7Su, and shall not exceed 0.7Su;
The primary bending stress strength shall not be greater than the smaller of 3.6Sm and Su, while not exceeding Su.
5.3.2.2 The shear stress of the section subjected to pure shearing shall not exceed 0.42Su.
5.3.2.3 The plastic analysis method is allowed to be used for some structures of critical safety-related components, and the structure can be carried out according to the maximum strain not exceeding 5%.
structure evaluation.
5.4 Design criteria for other safety-related components
5.4.1 Limits for stress intensity of other safety-related components under normal transport conditions
5.4.1.1 The stress strength value of the overall primary film should not be greater than the design stress strength Sm, and the primary film plus primary bending stress strength should not be greater than the design stress strength Sm.
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