ML22277A745
| ML22277A745 | |
| Person / Time | |
|---|---|
| Site: | 07103097 |
| Issue date: | 08/03/2022 |
| From: | Boyle R, Shaw D TN Americas LLC |
| To: | Division of Fuel Management |
| Garcia-Santos N | |
| Shared Package | |
| ML22277A716 | List:
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| References | |
| A33010, L-2022-DOT-0008 | |
| Download: ML22277A745 (25) | |
Text
Non-proprietary version Formulaire : PM04-4-MO-6 rev. 03 Orano NPS SAFETY ANALYSIS REPORT Unrestricted Orano CHAPTER 2.1 STRUCTURAL ANALYSIS FCC4 Prepared by Checked by Identification :
DOS-19-021166-011-NPV Vers. 1.0 Page 1 / 25 TableofContents Statusofrevision 2
Summary 3
- 1. Purpose 5
- 2. Inputdata 5
- 3. RegulatorycomplianceoftheFCC4packaginginroutineconditionsoftransport 5
- 4. RegulatorycomplianceoftheFCC4packaginginnormalandaccidentconditionsoftransport 8
- 5. References 22
- 6. Listoftables 23
- 7. ListofAppendices 24
0 orano
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Status of revision English version French version Date Purpose and record of revisions Prepared by / Verified by Old reference: DOS-13-00081778-100 0
0 04/2012 First issue Revision of safety analysis report TFXDC 2158 rev. H Addition of Appendix 2.1-9 Additional details added to Appendix 2.1-13 (revision of document FFDC05071 Rev. C) 1 1
10/2016 Modification of document Increase in the mass of the package, to 5500 kg Addition of an evaluation of the strain rate of the claddings during ACT Additional information added to Appendix 2.1-6.
Addition of an analysis of the impact of damage to the doors after a 1 m drop onto a bar at the maximum temperatures of NCT New reference: DOS-19-021166-011 1.0 1.0 04/2019 Update of Appendix 2.1-6 justifying the strength of the Zy-4 claddings from -40°C to °C at strain rates representative of the dynamic loadings during the drops Minor corrections 2.0 10/2020 Added possibility to have a Chrome coating thickness up to 30 µm on the zirconium alloy cladding.
Revision of Appendix 2.1-6 3.0 05/2021 Addition of the impact of the variations in the mechanical properties of shells and screws between -40°C and +°C, according to the new Appendix 2.1-14 Addition of reference FDE-07-02717 Rev. A Additional information added to Appendix 2.1-11 Update of the package tie-down and consideration of the cumulative stresses 4.0 See 1st page Consideration of the update of the S9 welds length (Appendices 2.1-4 and 2.1-5):
Addition of the proof of the non-impact of the S9 welds length modification on the tie-down and fatigue analyses Update of the results of the lifting and stacking analyses Brand names AFA 3G, M5, M5Framatome, Q12, MONOBLOC, TRAPPER, AGORA, HTP, HMP and ROBUST FUELGUARD are brands or registered brands of Framatome or its subsidiaries, in the USA or in other countries.
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Summary The purpose of this Chapter is to analyse the conformity of the FCC4 package in routine, normal and accident conditions of transport by demonstrating compliance with the requirements of the regulations
<1> applicable to type IP2 packages loaded with fissile materials.
This analysis includes:
regulatory compliance of the FCC4 packaging under routine conditions of transport with package tie-down and lifting, regulatory compliance of the FCC4 packaging under normal conditions of transport with the description of the regulatory tests relating to normal conditions of transport: spray test, stacking test, perforation test and free-fall test from 0.9 m.
regulatory compliance of the FCC4 packaging in accident conditions of transport with the representative nature of prototype 2, regulatory drop programmes for prototype 2, drop test results (for prototype 2) and strength of the rod boxes. The cumulative effect of the drops in normal and accident conditions of transport is also analysed.
Tie-down modes Nos. 1 and 4 are evaluated by numerical calculation to validate the stress levels reached in the outer shells for these 2 tie-down modes in each direction by means of numerical calculations. The stress levels associated with strap tension are combined with the unit longitudinal and transverse accelerations due to transportation and demonstrate the absence of damage to the package model. These stresses are used as input data for the fatigue analysis which considers the cumulative stresses associated with transportation at 1 g, handling and stacking. This analysis shows that the estimated minimum lifetime is 8,321 years for tie-down mode n°1 and 37 years for tie-down mode n°4, at the rate of road transports per year for the FCC4 packaging, which is consistent with the lifetime of the FCC4 packagings.
The acceptability of the lifting arrangements of the containers for 14-foot assemblies is verified in accordance with the RCCMR Code or the KTA Safety Standards.
The results show that the structure meets the criteria for excessive strain and plastic instability with minimum margins of 43% for the weld seams and 36% for the bolts (essentially due to pre-load).
Given that the number of cycles is less than 20,000 ( deliveries per year for years), the fatigue analysis is not carried out in compliance with the KTA 3905 requirements.
The state of the package after the regulatory tests relating to normal conditions of transport (spraying, free fall, stacking and penetration) is as follows: the enclosure of the package sustains only localised deformations with no impact on the spacing between packages, and the state and the distribution of the contents within the enclosure remain unchanged.
There is no dispersal of the radioactive contents on completion of the regulatory tests for normal conditions of transport.
The frame-door assembly suffered some damage during the mechanical tests for accident conditions of transport. The constriction of the cavity and tearing of the doors may be attributed to the cumulative result of the two drops onto a bar which targeted the same point of impact on the door containing the assembly.
The results of a vertical drop, carried out using prototype 1 - FCC3, were extended by the demonstration of the correct behaviour of the balsa wood shock absorbers (Appendix 2.1 completed by the study presented in Appendix 2.1-13). The verification of the strength of the bolted connections on the shells is presented in Appendix 2.1-11. The analysis is carried out over the temperature range of NCT and takes into account the cumulative effect of NCT and ACT drops.
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Appendix 2.1-14 includes an analysis of the mechanical properties variations of shell and screw steels between -40°C and +78°C, which demonstrates the negligible impact of the temperature range concerned on the energy absorption capacities of materials (shells and screws), and so the not very significant influence on the drop behaviour of the packaging.
Finally, the calculations performed on the rod boxes validate the behaviour for a static radial loading of g (maximum value observed during the drop tests for prototype 2). The support provided by the wedging system during an axial drop from m was also justified, with a deferred impact of the internal fittings. The volume of the fuel rod bundle cannot therefore expand.
The condition of the package on completion of the regulatory tests, under ACT as mentioned above, was as follows: the package enclosure suffered localised, permanent deformation, which had no effect on the safety of the package.
There is no dispersal of the radioactive contents on completion of the regulatory tests for accident conditions of transport.
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- 1.
Purpose The purpose of this Chapter is to analyse the conformity of the FCC4 package in routine, normal and accident conditions of transport by demonstrating compliance with the requirements of the regulations
<1> applicable to type IP2 packages loaded with fissile materials.
This analysis is largely based on calculations for routine conditions of transport and normal conditions of transport and on tests representative of accident conditions of transport.
- 2.
Input data The packaging is described in Chapter 1.4 of this Report and the radioactive content is described in Chapter 1.3 of this Report. In particular, the mechanical characteristics of the materials contributing to the structural strength of the packaging are given in these chapters for a temperature range from
-40 °C to +78 °C. The demonstrations were carried out for a maximum packaging weight of 5,500 kg, or more if indicated.
- 3.
Regulatory compliance of the FCC4 packaging in routine conditions of transport 3.1.
Package tie-down The normal behaviour of the package is verified in routine conditions of transport when these tie-downs are in place. The tie-downs considered are as follows (described in Appendix 2.1-1 and whose parameters are defined in Appendix 2.1-2):
Tie-down type 1: container with 2 straps placed in proximity to the inner hole of the lifting box Tie-down type 4: container with 4 straps: two straps placed on the upper half-shell reinforcement, in proximity to the inner reinforcement angle bar of the lifting box, and two straps placed on the upper half-shell reinforcement, in proximity to the central reinforcement angle bar.
For the tie-downs detailed above, the packaging integrity is verified, considering the following transport cases:
Case 1: filled FCC4 packaging: Transportation of a single filled package, unstacked Case 2: empty FCC4 packaging: Transportation of 3 packages, stacked in two levels.
These two cases cover the tie-downs defined in Appendix 2.1-1.
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The analysis in Appendix 2.1-2 determines the stress levels reached by means of numerical calculations in different configurations for each tie-downs defined above. In a conservative approach, the stress levels reached for different loading cases from Appendix 2.1-2 are combined, that is to say:
For case 1:
Component Progressive nb.
(see Appendix 2.1-2)
Elementary load description Z
3 Self weight, full 6
Tie-down Z-X 13 Transport X+
Y 12 Transport Y-For case 2:
Component Progressive nb.
(see Appendix 2.1-2)
Elementary load description Z
5 Stacking Z-(tie-down efforts of a superposed 1/2 container) 1 Self weight, empty X
13 Transport X+
Y 12 Transport Y-The accelerations to take into account for the static analysis are detailed in the following table:
Mode of transport Longitudinal Transversal Vertical Road g
g down +/- g g
g down +/- g Rail g
g down +/- g g
g down +/- g g
g down +/- g Sea / River g
g down +/- g g
g g down +/- g
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The stress levels reached in the outer shell of the packaging are calculated below. In a conservative approach, the maximum stress levels at g, weighted by the accelerations from the table above, are combined. The maximum stress levels considered are those of the loadings defined below:
Cumulative Von-Mises stress Case 1 Case 2 Tie-down type 1 Tie-down type 4 Tie-down type 1 Tie-down type 4 Road (MPa)
Rail (MPa)
Sea / River (MPa)
The outer shell is made of carbon steel with a minimum yield strength of MPa (see Chapter 1.4 of this Report). At the maximum temperature of +°C obtained in normal conditions of transport (see Chapter 2.2), the yield strength of the outer shell is MPa (according to Chapter 2.1-14). The stress levels obtained are below this yield strength, even considering a cumulative action of these stresses.
The calculation model used for the tie-down analysis in Appendix 2.1-2 shows the S9 weld with a length of mm, which is longer than the one prescribed in the drawing of Chapter 1.4-1. In this analysis, maximum stresses are in the shells. The impact of the S9 weld length modification on the results obtained is negligible.
The stress levels determined in Appendix 2.1-2 are used as input data for the fatigue analysis presented in Appendix 2.1-3: the impact of the S9 weld length modification is therefore also negligible on the results of Appendix 2.1-3. The fatigue analysis considers the cumulative stresses associated with transportation at 1 g, handling and stacking. This analysis shows that the estimated minimum lifetime is 8,321 years for tie-down mode type 1, and 37 years for tie-down mode type 4, at the rate of road transports (a transport corresponds to one round-trip) per year for the FCC4, which is consistent with the lifetime of the FCC4 packagings.
The increase in the maximum mass of the FCC4 package of 1%, taking it to 5,550 kg, has no significant impact on the number of transport cycles nor on the stacking.
3.2.
Package lifting There are three possible lifting modes:
by means of the 4 lifting lugs welded on the upper shell, for handling the loaded or empty package and the lid alone during opening operations, by means of 2 sets of 4 lifting boxes, welded on the lower shell, for handling the loaded or empty package, by means of the fork-lift pockets provided under the lower shell.
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The acceptability of the FCC4 packagings lifting via the lifting lugs located on the upper shell, on one hand, and by the lifting lugs located on the lower shell, on the other hand, is verified in Appendix 2.1-4 by means of numerical calculations for a package weight of kg (increase of % in the lifting weight (5,550 kg) to take into account an imbalance in the load distribution and insofar as the lifting by chains is prohibited - see Chapter 1.7). The calculations cover strap angles between ° and °.
The acceptability of the container lifting arrangements is verified in accordance with the RCCMR code <2> or the KTA Safety Standards <3>.
The results presented in this Appendix show that the structure meets the criteria for excessive strain and plastic instability (see Paragraphs 6.2 and 6.3 of Appendix 2.1-4) with margins of 43% for the weld seams and 36% for the bolts (essentially due to pre-load).
Given that the number of cycles is less than 20,000 ( deliveries per year for years), the fatigue analysis is not carried out in compliance with the KTA requirements <3>.
- 4.
Regulatory compliance of the FCC4 packaging in normal and accident conditions of transport The analysis below addresses the compliance of the package model comprising the FCC4 packaging loaded with a maximum of 2 fuel assemblies or non-assembled rods in a rod box with the requirements applicable to industrial type package models loaded with fissile materials subjected to the regulatory tests in normal and accident conditions of transport.
4.1.
Description of regulatory tests The regulatory tests for industrial type packages loaded with fissile materials consist of the following sequences:
a) Spray d) Perforation a) Spray b) 1.2 m drop a) Spray c) Stacking f) 9 m drop e) Drop onto a bar h) Immersion g) Thermal test Normal conditions of transport Accident conditions of transport After the mechanical tests, the package is required to undergo the regulatory thermal test and maintain subcriticality in the case of an isolated package and in the case of multiple packages, which means that the radioactive material must remain in its enclosure (zirconium alloy claddings), and that the geometrical deformation of the shell and the cavities must be measured together with the condition of the resin contained in the doors and frame of the packaging.
I I
~
~
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The water spray and immersion tests are not analysed below as no water tightness criterion is applicable to the FCC4 packaging given that the penetration of water into the packaging is taken into account in the criticality-safety studies (see Chapter 2.5 of this Report). Water tightness is provided by the enclosure formed by the fuel rod cladding and the welded end plugs. The pressure on the internal system could not in any case cause damage to the rods, compared with the effects of the two drops onto a bar.
The cumulative damage caused by the regulatory tests for normal conditions of transport and in accident conditions of transport is analysed below.
The regulatory mechanical tests representative of normal conditions of transport are justified by calculation.
The regulatory mechanical tests representative of accident conditions of transport were carried out on full-scale prototypes of FCC3 and FCC4 packagings loaded respectively with a dummy assembly and a ballast weight. The cumulative effect of the drops in normal and accident conditions of transport is analysed afterwards.
4.2.
Tests relating to normal conditions of transport 4.2.1. Stacking test Verification of the behaviour of the FCC4 packaging in stacking conditions is demonstrated below and in Appendix 2.1-5; the mass of 5,550 kg is used in Appendix 2.1-5.
Compressive force for a mass of 5,550 kg The package must be subjected for at least 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to a compressive force equal to the higher of the following two values:
The equivalent of 5 times the mass of the actual package, The equivalent of the product of 13 kPa by the vertical projection area of the package.
However, the number of stacking levels for the FCC4 container is limited by the requirements in Chapter 1.7, which limits this number to 2.
Therefore, the compressive force considered is F1 = 5,550 x 9.81 x 1.33 = 72,413 N, applied uniformly on the 4 bearing points of the packages stacked for storage (lifting lugs). The weighting factor of 1.33 is taken into account for the compressive force F1 in compliance with the CM66 Code <4>.
Mechanical strength Each lifting lug is therefore subjected to a vertical load of F = 18,103 N. The mechanical strength of the container must therefore be verified for:
strength of the lifting lug/upper enclosure connection, crushing strength of the enclosure.
Appendix 2.1-5 shows that in a stacking configuration of two containers the stresses generated on the bottom container do not exceed the yield strength of the steel. This conclusion is also valid for the plates, container walls and lifting boxes, as well as for the welds. The minimum margins are respectively 47% for the steel plate and 28% for the welds.
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Analysis of buckling risk of support lugs By design, only the vertical part of the plate of each support lug may be subjected to this risk. This part has a height of mm, a thickness of mm and a length of mm.
Assuming it to bear the full load to which the lug is subjected, the average load per unit length would represent or N/mm.
The connection system for this part of the plate at its upper end is midway between the fixed end and the free end. It is the stiffness of the system, comprising the horizontal and inclined parts of the plate that will make the difference. Using a highly conservative approach, we will assume that the end is free. The value of the critical buckling load is therefore:
4 Or, depending on the plate dimensions and considering the values per unit length:
12
4 There is also a welded connection between the vertical part of the lug and the circumferential stiffeners. The effect of this connection will be to prevent the risk of buckling.
This could be modelled by taking an equivalent height that would in any event be less than the actual height of the plate. In the first instance, while still maintaining a conservative approach, we shall disregard this connection.
Under these conditions E = 209,000 MPa, e = mm and h = mm.
/
In spite of the highly conservative assumptions (the whole of the force taken up by the vertical part, assumption of a free connection at the end, S9 welds not taken into account),
there remains a safety factor close to 7 relative to the critical load. This leaves an ample margin to accommodate small fluctuations in the load distribution associated with the presence of the lug holes.
Therefore, there is no risk of buckling of the support lugs.
In conclusion, the stresses that would be generated by the stacking test cannot in any case produce stresses in the package structures higher than the yield strength.
4.2.2. Perforation test The most fragile part of the package is the enclosure whose thickness is mm. Dropping, from a height of 1 m, a bar of 3.2 cm in diameter with a hemispherical end and a mass of 6 kg can leave only a shallow imprint. Under no circumstances can it perforate the enclosure, as shown by the following calculation:
The drop height is 1 m. As the bar weighs 6 daN, an energy of 6 daN.m must be absorbed at the moment of impact. The aim therefore is to evaluate the rupture energy of this wall.
The steel breaks on a circular line of length bounding the bar of diameter.
To cut a plate of thickness, the force exerted on the cut edges of area must move its point of application by a distance.
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Therefore, if is the shear rupture stress of the steel, the rupture energy is given by:
With the following values:
6 1 : drop height 32 : bar diameter
- minimum enclosure thickness 0.8
- minimum value for steel grade ()
This gives a rupture energy :
daN. mm daN. m The energy to be absorbed at the moment of impact is only 6 daN.m. There is therefore no perforation of the enclosure.
4.2.3. Free fall from 0.9 m The packaging loaded with an assembly and a ballast weight (of the same mass) was subjected to a 9-metre free drop, which is a more severe test than the 0.9-metre free drop test, following which there was no dispersal of the radioactive content. The relative positions of the assemblies did not change and deformation of the packaging remained localised. The condition of the packaging at the end of this free drop test shows no significant damage.
4.2.4. Conclusion The state of the package after the regulatory tests relating to normal conditions of transport (spraying, free fall, stacking and penetration) is as follows: the enclosure of the package sustains only localised deformations with no impact on the spacing between packages; the state and the distribution of the contents within the enclosure remain unchanged.
This condition is taken into account in the criticality studies in Chapter 2.5.
There is no dispersal of the radioactive contents on completion of the regulatory tests for normal conditions of transport.
4.3.
Regulatory compliance of the FCC4 packaging in accident conditions of transport Compliance of the FCC4 package with IAEA requirements <1> is demonstrated by subjecting full-scale prototypes to the regulatory mechanical tests. Thus, a prototype referred to as "prototype 2", corresponding to the FCC4 packaging, was used for the lateral drop configuration and a prototype referred to as "prototype 1", corresponding to the FCC3 packaging, was used for the vertical drop configuration. The mechanical properties of the component parts of the two drop test prototypes are detailed in the fax Erreur ! Source du renvoi introuvable.. The cumulative effect of the drops in normal and accident conditions of transport is also analysed.
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4.3.1. Representativity of prototype 2 The significant differences between the prototype used and the packaging model are described in Table 2.1-1. The analysis of differences between the packaging model and the drop test prototype is also supplemented by the analyses described in Paragraph 4.3.7 and Appendix 2.1-13. The analysis shows that the differences between the package model and the drop test prototype do not call into question its representativity. The mass of the package model, 5,550 kg, has increased the drop energy by 3.8% (
,.1.038) over that used for prototype 2, which is insignificant. Moreover, Appendix 2.1-13 shows the absence of the shock absorber crush limit phenomenon, taking into account the mass of the package model of 5,550 kg.
4.3.2. Evaluation of the strain rate of the fuel claddings Proof of the mechanical strength of the fuel claddings under accident conditions of transport over the temperature range corresponding to the conditions of normal conditions of transport (from -40°C to +°C) is demonstrated in Appendix 2.1-6. This proof includes a strain rate for the claddings representative of accident conditions of transport.
To determine this strain rate in the cladding, one must:
evaluate the elastic and plastic strain of the cladding, determine the natural frequency of the cladding between two grids, obtain the dynamic response of the cladding versus its own natural frequency, calculate the associated maximum strain rate.
4.3.2.1. Determining the strain rate of cladding during a 9m drop test The calculation of plastic strain of the outer fibre of a beam undergoing bending, using the natural frequency of the cladding, gives a strain rate relating to the flat drop from 9m. In fact, as indicated in Appendix 2.1-6 of the safety analysis report, this drop is considered to be the severest in terms of the loading on the rods.
Elastic and plastic strain of the cladding:
In Appendix 2.1-10, the test report for Drop No. 3 using prototype 2 (flat drop with slap-down) mentions that a maximum residual strain of mm was measured from one of the fuel rods; this strain should be added to the elastic strain, which can be estimated in the following manner:
Where = MPa from Appendix 2.1-6 and = GPa from <6>.
These strains are obtained for cladding in the prototype 2, at a temperature of approximately 20°C.
Using the residual strain value, we can determine the radius of curvature and therefore the plastic strain of the associated cladding.
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The external plastic strain of the cladding is obtained in the following manner:
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The strain rate for the cladding is therefore in the order of.
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4.3.3. Representativity of the prototype 2 contents The test was performed with a dummy fuel assembly and a ballast weight representing the mass of a second assembly. The dummy assembly is filled with depleted uranium pellets and is representative of enriched uranium pellets in terms of lateral stiffness and in terms of shear behaviour. The skeleton and cladding material of this assembly is a Zr4 zirconium alloy. Other grades of zirconium alloy may be used. Appendix 2.1-6 specifies the conditions in which the results obtained during the mechanical tests can be extended to any other zirconium alloy. This means that any skeleton material may be used, and that the characteristics of the cladding materials must conform to one of the following three criteria, only considering the maximum acceleration as a static load at 20°C:
1 2
3 4
5 Rp0.2% (MPa) and Rm (MPa) and At (% over 50 mm)
Appendix 2.1-6 also proves the strength of the Zy-4 and M5Framatome cladding alloys under the accident conditions of drops, over the temperature range for normal conditions of transport (from -40°C to +°C) at the strain rate calculated in the previous paragraph, representative of the dynamic loadings during the drops.
As described in Chapter 1.3 of this Report, the cladding may receive a surface treatment consisting of pre-oxidation of the cladding tubes. This pre-oxidation does not modify the mechanical characteristics or the structure of the fuel assemblies. Thus, any pre-oxidation of the claddings has no impact on the mechanical behaviour of the assembly in normal and accident conditions of transport. The claddings may also be chromed with a maximum thickness of 30 m.
The conservative drop test configurations for prototype 2 in terms of the stresses applied to the packaging and the assemblies are justified in Appendix 2.1-7. In conclusion, the details presented in the relevant sections of Appendix 2.1-7 show that for the regulatory drop test configurations, the use of a 17x17 XL assembly loaded with 24 rods in the guide tubes, covers all of the assembly types to be transported as defined in Chapter 1.3.
The 17x17 XL assembly (AFA XL design for use in EDF reactors) is adopted for the prototype configuration tested during the regulatory tests supplemented by a ballast weight simulating the second assembly.
The presence of a rod box in place of a fuel assembly makes no visible change to the behaviour for two reasons:
The weight of the loaded rods box is at most equal to that of an assembly, The rigidity of a door is greater than that of the rods box.
The second point is demonstrated by comparing the rigidity of one of the cavity components with that of the rods box.
The rods box is composed of a mm U-plate reinforced with two square tubes.
The bending inertia of the rods box is less than mm4.
For comparison purposes, the bending inertia of the frame alone is. This calculation takes into account neither the resin inside the frame nor the presence of other components such as the doors which provide some structural rigidity and displace the neutral fibre towards to the neutral fibre of the rods box. The replacement of a fuel assembly by a rod box does not therefore modify the behaviour of the neutron cavity.
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4.3.4. Regulatory drop test programmes for prototype 2 The drop configurations adopted (see Appendix 2.1-7) for the tests are as follows:
drop with a longitudinal incidence of 0° and orientation ° relative to the joint plane, drop onto a bar with a longitudinal incidence of °, an azimuth angle of ° and at mm from the lower end of the internal system, flat drop of metres with a longitudinal incidence of ° and azimuth angle of
°.
The bar drop tests are carried out first.
The regulatory drop test programme for prototype 2 is described in Appendix 2.1-8.
4.3.5. Drop test results for prototype 2 The results of these tests are given in Appendix 2.1-10.
The analysis attached in Table 7.1 of Appendix 2.1-10 shows that all of the following safety components:
continue to perform their functions on completion of the three successive drops (two bar drops and one 9-metre flat drop).
Expert assessment of the packaging after the drop gave the following results:
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The frame-door assembly suffered some damage during the mechanical tests. The constriction of the cavity is a favourable parameter in terms of the criticality study, and the tearing of the doors may be attributed to the cumulative result of the two drops onto a bar which targeted the same point of impact on the door containing the assembly.
Thus, on completion of the drop tests representative of accident conditions of transport, the package model sustained changes of geometry and position of contents inside the cavity.
These changes are taken into account in the criticality safety studies in Chapter 2.5 of this Report. The cladding tubes remain intact and leaktight and there is no dispersal of contents on completion of the tests representative of accident drop conditions.
4.3.6. Strength of rod boxes Details of the strength of the rod boxes are given in Appendix 2.1-12. The calculation is performed for a static radial loading of g (maximum value observed during the drop tests for prototype 2).
Appendix 2.1-12 assumes the bounding case of a radial loading on conventional rod boxes (excl. EPR) and for EPR rod boxes (as detailed in Appendix 1.3-1 of Chapter 1.3 of this report). The proof for the chosen case is in Paragraph 2.3.1 of Appendix 2.1-12.
Appendix 2.1-12 also justifies the preservation of wedging during an axial drop on the top end from m, with deferred impact of the internal fittings and ignoring the balsa shock absorber. In fact, the axial drop onto the top end with deferred impact covers that of the bottom end drop with deferred impact, as:
the bottom spacer, when fitted, is identical to the top spacer (See Appendix 1.3-1 of this report) and, the additional height ( m) bounds the gaps between the shock absorber and the internal fittings at the top and bottom ends for the various versions of FCC3 and FCC4 packagings (see Appendix 2.1-13).
The calculations in Appendix 2.1-12 are completed for the conventional rod boxes (excl.
EPR) and for the EPR rod boxes, given the specific natures of the load configurations. The proof for the chosen case is in Paragraph 2.3.2 of Appendix 2.1-12.
In conclusion, the components designed to support the rod bundle retain their geometry under accidental drop conditions. The volume of the fuel rod bundle cannot therefore expand.
Furthermore, even in the event of detachment of the lengthwise restraint system for the fuel rods, the criticality safety studies in Chapter 2.5 take into account possible differential slippage of the rods over a given length insofar as the calculations are performed for an infinite length and with a given moderation ratio on the fissile cross-section.
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4.3.7. Analysis of modifications made to the packaging An analysis of the safety impact of modifications to the packaging is given in Appendix 2.1-13. In particular, the following analyses are made:
Analysis of minor safety changes to the packaging, Analysis of safety changes made for the transportation of fuel assemblies with control
- clusters, Impact of differences in mass between the prototype and the package model during the bar drop test.
These modifications notably call for an evaluation of crushing of the balsa shock absorbers which remain below the crushing limits. This evaluation considers the cumulative effect of drops representative of normal conditions of transport and accident conditions of transport as well as the minimum crushing stress of the balsa wood as defined in Chapter 1.4 of this Report.
The conclusions reached at the end of the mechanical tests are not called into question.
4.3.8. Vertical drop with prototype 1 A vertical drop with no adverse effects has already been carried out on prototype 1 (FCC3 packaging). The test results are presented in Appendix 2.1-9 and the effects of this drop on the FCC4 packaging are analysed in Appendix 2.1-7 supplemented by the information given in Appendix 2.1-13.
The results of the vertical drop test notably demonstrate the satisfactory behaviour of the balsa wood shock absorbers (Appendix 2.1-7 supplemented by the analysis given in Appendix 2.1-13) and demonstrate the strength of the bolted connections of the shells given in Appendix 2.1-11, which assures that the two half-shells do not come apart. This verification is carried out for the packaging with the most load in half-shell hold-down screws in CNT as well as in ACT, that is to say the FCC3 packaging, which covers therefore the FCC4 packaging.
Appendix 2.1-13 shows the absence of the shock absorber crush limit phenomenon, taking into account the mass of the package model of 5,550 kg.
4.3.9. Analysis of the impact of damage on the door for the internal fittings in FCC3 and FCC4 packagings, after a 1m drop onto a bar at the maximum temperature reached during normal conditions of transport During the drop onto a bar, the bar perforates the outer shell to impact on the door of the packaging. During the drop tests carried out on prototype No. 2, a maximum strain of the door was noted ( mm maximum on the outer surface, see Appendix 2.1-10) for a maximum residual strain of the assembly of mm. The assembly therefore is subjected to a strain during a drop onto a bar, triggered by the strain of the door. This is dependent on the behaviour of its stainless steel plates and the neutron-absorbing resin.
Within the range of temperature variations for normal conditions of transport, determined in Appendix 2.2-6, the mechanical characteristics of the resin remain unchanged. There is no need to specifically study the representative nature of the resin for the temperatures (mean temperature of just °C).
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A maximum shell temperature of °C has little impact on the mechanical characteristics of the steel. In fact, the steel used for the doors is a type stainless steel, for which, the temperature of °C will have little impact on the mechanical characteristics when compared with ambient temperature (Std <5> gives, for a temperature of 100°C, a reduction in the minimal Re of approximately 15%, and a decrease in the minimal Rm of approximately 10%). Assuming a linear evolution of the mechanical characteristics between 20°C and 100°C, for a maximum temperature of °C, the drop in mechanical characteristics is 9% for Re and 6% for Rm less than that of 20°C.
Moreover, the increase in the drop energy for a 1m drop onto a bar, for a mass of 5,550 kg for the package model, is 5.5% (
,1.055) over the drop energy for the test of prototype No. 2.
As a consequence, the combination of the difference in package model mass against the mass of prototype No 2 and the effect of the maximum temperature under normal conditions of transport (°C) is equivalent to a reduction in the mechanical characteristics of the steel in the doors of prototype No. 2 of 15% of Re and 12% of Rm.
This difference leads to a slight increase in the indentations of the door on the package model during the 1m drop onto a bar against the prototype No. 2, and which has no impact on the behaviour of the fuel assembly claddings keeping in mind the safety margins given in the analysis in Appendix 2.1-6.
In fact, the distortion in the assembly, triggered by the drop onto a bar, takes the form of bending of the rods similar to that noted during the lateral drop from 9m. Appendix 2.1-6 shows that, taking into account the conservative cladding mechanical properties, during the drop from 9m, including whiplash, the strength of the M5Framatome cladding under bending is assured, with a minimum margin of 1.6 over the chosen criteria for mechanical strength, even taking into account the dynamic mechanical properties (at s-1) for the cladding.
4.3.10. Analysis of the impact of the mechanical properties variations over the temperature range of the package Appendix 2.1-14 deals with the influence of the mechanical properties variation of the steels used for the shells and screws over the temperature range from -40°C to +78°C. The conclusions are as follows:
for shells and angle bars, the decrease in the energy absorption capacity is less than for screws, the decrease in the energy absorption capacity is less than %.
This result is used in the Appendix 2.1-11 analysis and demonstrates that the half-shells do not come apart, over the whole temperature range of NCT, considering the cumulative effect of the vertical NCT and ACT drop tests.
Similarly, according to Appendix 2.1-10, all hammer head screws remain also in place during the lateral drop. The removal of the bolts is happened without difficulty and they did not exhibit any sign of shearing start-up. A maximum variation of % in the energy absorption capacities of the components (shells and screws) does not call into question these conclusions.
Thus, temperature variation between -40°C and +78°C of the mechanical properties of the steels used for the shells and screws has a very slight effect on the energy absorption capacities of the materials (shells and screws) and therefore does not significantly impact the drop behaviour of the packaging.
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Concerning the claddings behaviour over the temperature range corresponding to the normal conditions of transport, Appendix 2.1-6, which deals with the strength of the claddings during a lateral drop including whiplash, demonstrates the existence of the following significant margins over the temperature range from -40°C to +78°C:
margin of minimum % on the failure of the M5Framatome cladding for FCC3 and FCC4
- packages, margin of minimum % on the failure of the Zircaloy-4 cladding for FCC3 and FCC4 packages.
In the case of transport of rods into rod boxes, the mechanical analysis in Appendix 2.1-12 demonstrates a minimum margin of the stresses in the wedges of %, compared to the yield strength at the maximum NCT temperature.
Moreover, the protection of the assemblies is mainly provided by the internal fittings, made up of the T-shaped frame, two doors and top and bottom plates. Following the analyses of the cumulative effect of the drops in NCT and ACT in Paragraphs 4.2 and 4.3 of this Chapter, it is demonstrated that the deformations of the assembly are limited by the cavity of the internal fittings and that the containment of fissile materials remains provided by the rods claddings.
Finally, as specified in Paragraph 4.3.9 and supplemented with the drop analyses of prototypes 1 and 2 in Appendix 2.1-9 and 2.1-10 respectively, shell properties of FCC3 and FCC4 packagings have no impact on drops onto a bar.
Thus, the mechanical properties variation of the materials over the range from -40°C to
+78°C does not call into question the package integrity in NCT and in ACT.
4.3.11. Conclusion The condition of the package on completion of the regulatory tests, under accident conditions of transport as mentioned above, was as follows: the package enclosure suffered localised, permanent deformation, which had no effect on the safety of the package. This condition is taken into account in the criticality studies in Chapter 2.5 and in the thermal studies in Chapter 2.2.
There is no dispersal of the radioactive contents on completion of the regulatory tests for accident conditions of transport.
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- 5.
References
<1> Regulations for the Safe Transport of Radioactive Materials - at the revision indicated in Chapter 1.2.
<2> Code RCCMR, May 1993 edition - Design and construction rules for mechanical components of FBR nuclear islands
<3> KTA 3905 Safety Standards (2020-12) - Safety Standards of the Nuclear Safety Standards Commission (KTA) - Load Attachment Points on Loads in Nuclear Power Plants
<4> CM66 Code - Methods of calculation for the design of steel structures
<5> Std. NF EN 10088 December 2014 Stainless steels - Section 3
<6> Mechanical characteristics of fuel rod claddings in transport conditions conference Packaging, Transport - Storage & Security of Radioactive Material 2009 vol. 20 No. 2.
<7> Reminder - Material resistance notes - DUNOD publications - 1996 edition
<8> Harris shock and vibration handbook - chap 8.25 - Fifth Edition.
<9>
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- 6.
List of tables Appendix Title Number of pages 2.1-1 Impact on representativity of the principal differences of prototype 2 1
TOTAL 1
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- 7.
List of Appendices Appendix Title Number of pages 2.1-1 AREVA NP document FFDC 05091 rev. B "FCC4 Containers - Tie-down diagrams" 2 + 8 2.1-2 AREVA NP document - NEEL-F 2008 DC 118 rev. B "FCC4 containers for fresh fuel assemblies - Data for fatigue strength analysis of lifting boxes and upper shell" 2 + 57 2.1-3 TN International document - NTC-08-00135891 rev. 01 "Analysis of the fatigue strength of FCC3/FCC4 containers, TN International document" 2 + 18 2.1-4 Framatome document - D02-ARV-01-186-617 rev A FCC4 - Container for 14-foot assemblies - Sizing verification of lifting points" 2 + 51 2.1-5 Framatome document - D02-ARV-01-186-618 rev A "FCC4 - Containers for 14-foot fresh fuel assemblies - Stacking stability" 2 + 39 2.1-6 AREVA NP document - FFDC 04223 rev. 6.0 "Transportation in FCC containers - Mechanical aspects related to changes in assembly constituent materials" 2 + 61 2.1-7 AREVA NP document - TFXEDC 2104 rev. E "Modification of RCC containers - Selection of drop configurations for prototype 2 in the context of regulatory tests" 2 + 46 2.1-8 AREVA NP document - TFX DC 2108 rev. B "Modified RCC container - Prototype 2 - Regulatory test programme" 2 + 14 2.1-9 AREVA NP document - TFX DC 2087 rev. A "Container prototype n°1 - Drop test report" 2 + 44 2.1-10 AREVA NP document - TFXE DC 2132 rev. B "Container prototype n°2 - Drop test report" 2 + 65 2.1-11 Appendix 2.1-11 DOS-19-021165-011 v. 1.0 "Justification of the performance of the FCC3 shell fasteners during a 9m vertical drop" 60 2.1-12 Appendix 2.1-12 DOS-13-00081778-112 rev 01 "Fuel rod boxes for FCC containers - Proof of mechanical strength of box equipment" 44 2.1-13 Appendix 2.1-13 DOS-13-00081778-113 rev 02 "Additional analysis of package behaviour in accidental drop conditions" 44 2.1-14 Appendix 2.1-14 DOS-19-021165-012 v. 1.0 Variation in the mechanical properties of shell and screw steels between
-40°C and +78°C 13 TOTAL 584
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Table 2.1-1 Impact on the representative natures of the principal differences of prototype 2