ML22271A809
| ML22271A809 | |
| Person / Time | |
|---|---|
| Site: | Orano USA |
| Issue date: | 09/01/2017 |
| From: | Boyle R, Shaw D TN International |
| To: | Division of Fuel Management |
| Garcia-Santos N | |
| Shared Package | |
| ML22271A128 | List:
|
| References | |
| A33010, L-2022-DOT-0007 | |
| Download: ML22271A809 (44) | |
Text
Non-proprietary version Form: PM04-4-MO-6 Rev. 00 AREVA TN AREVA UNRESTRICTED DISTRIBUTION NUCLEAR LOGISTICS OPERATIONS APPENDIX 2.1-13 COMPLEMENTARY ANALYSIS OF FCC PACKAGE BEHAVIOUR IN ACCIDENTAL DROP CONDITIONS SAFETY ANALYSIS REPORT FCC3-FCC4 Prepared by Identification DOS-13-00081778-113-NPV Rev.
02 Page 1 / 44 TN International TableofContents Revisionshistory 2
- 1. Purpose 3
- 2. Analysisofminorsafetyrelatedchanges 3
- 3. Analysisofsignificantsafetyrelatedchangesforthetransportationoffuelassemblieswithandwithoutcontrolclusters 4
- 4. Impactofthedifferencesinmassbetweentheprototypeandthepackagemodelforthedroponbar 42
- 5. Conclusion 44
- 6. References 44
A AREVA
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02 Page 2 of 44 Non-proprietary version Revisions history Rev.
Date Purpose and record of changes Prepared by / Checked by 0
04/12 First issue
- Revision of AREVA document FFDC 5071 revision C.
- Calculation details added for dynamic coefficient of wood
- Justification that balsa has not reached crushing limit modified to include drop test for normal transport conditions, crushing on flange side, shearing of wood
- Justification of acceptance of clamping system at bottom nozzle
- Impact of weight differences between prototype and package 1
09/12 Consideration of a mm reduction in the thickness of the shell absorber in balsa crushing calculations.
2 09/16 Update to minor changes for safety purposes:
- Absorber behaviour with and without clusters with consideration of the FCC4 package mass incremented to 5550 kg and the deferred impact of the content,
- Addition of the shear strength analysis for the bolted connection of FCC3 and FCC4 packaging shells under the effects of an axial drop.
- Addition of the impact of the presence of the dummy with smooth walls on package safety.
Consideration of the mass of the FCC4 package incremented to 5550 kg for the analysis of the impact of the difference of mass between the package and the drop prototype with a 1 m drop onto a bar.
- Movement of the paragraphs describing the modifications to the package model to the relevant chapters of the report.
- Movement of the paragraphs justifying significant safety-related modifications, excluding mechanical justification.
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02 Page 3 of 44 Non-proprietary version
- 1.
Purpose The purpose this document is to analyse the impact of modifications made to the FCC3 and FCC4 packagings on the safety of the packagings. Modifications of particular relevance to the transportation of EPRTM assemblies are also analysed.
- 2.
Analysis of minor safety-related changes 2.1. Support leg locking system Given its constituent materials, the system has no thermal or criticality impact. Given its position in relation to the internal equipment, it can only have an impact during a flat drop with whiplash action. In testing, the 9-metre flat drop onto the top shell did not produce any crushing of the shell as far as contact with the internal equipment. By analogy, in the case of a flat drop onto the stronger bottom shell, there will be no contact of the shell with the cradle and the internal equipment. The locking system cannot therefore cause any damage to the lower part of the frame. There is therefore no impact on the safety of the package.
2.2. Closure of lifting boxes Given the constituent materials, closure of the lifting boxes can only have an impact on safety from the mechanical standpoint (no thermal impact or criticality impact).
The components added to the lifting boxes may constitute structural reinforcement of the lifting boxes and therefore have an impact on their mechanical behaviour during flat drop tests with whiplash action.
In testing, the flat drop produced partial crushing of the box with a large tear in the shell at the level of the first stiffener.
During the 9-metre flat drop with whiplash on the upper shell, the blanking plates on the box ends cannot store the strain energy because they are held by 2 small welded metal lugs which do not withstand the drop and effectively act as a "fuse".
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02 Page 4 of 44 Non-proprietary version Given its folded V shape, the closure plate in the handling hole cannot constitute a significant zone of resistance and storage of strain energy. This is especially the case given that this zone in proximity to the handling hole was only slightly distorted during the flat drop, as the shell sustained severe tearing. The reinforcement does not therefore constitute a shock absorption zone any more than previously.
Consequently, closure of the lifting boxes does not in any way modify the results of the flat drop test, and therefore has no impact on the safety of the package.
- 3.
Analysis of significant safety-related changes for the transportation of fuel assemblies with and without control clusters The purpose of this paragraph is to analyse the impact of changes to the equipment described in chapter 1.4 on regulatory drops, as these changes are important for package safety.
Reminder: the main changes are as follows:
axial securing of the clusters; axial securing of the assemblies by the lower nozzle; securing of the EPRTM assembly grids; changes to equipment for the transport of a dummy assembly with smooth walls in a version 1 FCC4 packaging:
radial wedging of the dummy with smooth walls; axial wedging of the dummy with smooth walls or the assembly model; system securing the content, with or without a cluster system securing the support leg locknut.
3.1. Regulatory requirements and assumptions for the analysis of the behaviour of the absorbers described in § 3.2, 3.3 and 3.4 The study is carried out considering that the wood next to the bar has entirely disappeared up to the top or bottom plate. This is a highly conservative assumption and means that:
- the shell was perforated,
- the shell absorber casing was perforated,
- the shell absorber wood was entirely crushed and is no longer able to absorb some of the energy over a surface area with a diameter of 150 mm.
Furthermore, in order to simplify calculations, on a conservative basis, it is considered that the 1 m drop on bar test is performed before the drop in normal conditions of transport (the volume of wood enabling the drop energy to be absorbed in normal conditions of transport is therefore reduced, which means that the crush limit will be reached).
In addition, this analysis incorporates testing in normal conditions of transport (1.2 m axial drop for the FCC3 package and 0.9 m for the FCC4 model package) and in accident conditions of transport with consideration of the deferred impact of the internal fittings (9 m + 0.25 m axial drop for FCC3 and FCC4 model packages). The additional 250 mm gap corresponding to the deferred impact of the content is a bounding gap covering all potential configurations. To give an example, details of the maximum gap obtained using the nominal dimensions of the FCC4
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02 Page 5 of 44 Non-proprietary version configuration without clusters, with clamping at the upper nozzle are given below (the dimensions are taken from the drawings in appendix in chapter 1.4) :
Gap= Lshell-L(internal fit.)-Gap(bottom-abs)-Th.(abs. bottom)-Th.(bottom plate)-Th.(abs. top)-Th.(top plate)= mm Data used to calculate the gap:
L shell Overall length of the shell: 5610 mm, L int. fittings Overall length of the internal fittings: mm, Gap bottom-abs Gap between the bottom of the internal fittings and the bottom shell absorber:
mm, Th bottom abs. Thickness of the bottom shell absorber: mm, Th base pl. Thickness of the shell base plate: mm, Th top abs. Thickness of the top shell absorber: mm, Th base pl. Thickness of the top base plate: mm.
3.2. Determining the dynamic amplification factor for the shock-absorbing material in the top plate and shell absorbers During the 9 m vertical drop test for prototype 1, crushing was equal to mm for a contact surface of cm² with a suspended mass of kg (see § 2.3.1.2 of appendix 2.1-7).
Given the brevity of the indentation force during a drop, the balsa wood is considered to behave as if it were harder. This dynamic crush stress producing such an indentation corresponds to the product of the stress and a dynamic amplification factor. This dynamic amplification factor is calculated as follows:
Given that: E drop = E crushing This gives M x g x h= S x x d And: = (M x g x h)/(S x d) = MPa S = cm2, the crushed section, d = mm is the indentation distance, M = kg is the mass of the internal equipment, h = 9 m is the drop height.
To maintain a conservative approach and to maximise the crushing values in the justification below, the static value is not taken to be equal to the measurement values for the prototype, but to the maximum stress value, i.e. MPa.
Which gives f = dynamic / static = / =.
The wood type is always the same between the mock-up and the packaging model and the impact velocity of the internal fittings on the balsa absorbers is of the same order of magnitude irrespective of the packaging configuration analysed. Therefore the dynamic amplification factor defined in the safety analysis report is consistent with all loading configurations.
To take a conservative approach, the crushing of the series-manufactured packagings is justified based on the minimum stress value, i.e. MPa, a value which maximises crushing.
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02 Page 6 of 44 Non-proprietary version 3.3. Behaviour of shell absorbers for the transport of assemblies without control clusters 3.3.1. Top side crushing calculation for the FCC3 packaging loaded with assemblies without control clusters For the FCC3 packaging, the top and bottom shell absorbers have a balsa thickness of mm. It is assumed, on a worst-case basis, that all of the drop energy generated by the internal equipment is dampened by the absorber (with the suspension system inactive).
Drop energy The drop energy to be absorbed, assuming a combined drop of 1.2 m and 9.25 m, is equal to:
kJ 297,3 h
g 2
m 2
1 chute E
Where:
m: mass of the internal fittings in the FCC3 packaging configuration without clusters, m = kg (see § 2.3.1.2 of appendix 2.17);
h: drop height, h = 1.2 + 9.25 = 10.45 m; g: acceleration due to gravity; g = 9.81 m s-2 The shell absorber is crushed in two phases:
Phase 1: the lifting ring leaves a mm imprint in the absorber (see § 2.3.1.2 of appendix 2.17);
Phase 2: the top plate will then come into contact with the shell absorber.
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02 Page 7 of 44 Non-proprietary version Outline diagram of shell absorber crushing by the lifting ring and the top plate The bar is considered to perforate the shell over a surface area not crushed by the ring in order to maximise the crushing rate at the ring.
Phase 1:
The energy absorbed by the absorber when the ling crushes the shell absorber is calculated:
Elug S d kJ Where:
- minimum static crush stress for the balsa supplied, multiplied by the dynamic amplification factor, = MPa x = MPa (see details in § 3.2) ;
S: crushed surface opposite the ring: S = = cm²;
d: indentation height for the lifting ring: mm; 4.1 kJ in energy is absorbed during this phase. 293.2 kJ in energy will remain to be dissipated after this phase.
Phase 2:
The top plate hits the entire surface of the shell absorber (less the surface area damaged by the bar (Ø 150 mm)).
The energy absorbed per mm of crushing of the shell absorber by the top plate is calculated. Unit energy for this phase is as follows:
kJ.
Where:
- minimum static crush stress for the balsa supplied, multiplied by the dynamic amplification factor, = MPa x = MPa (see details in § 3.2);
S:
crushed surface area opposite the top plate, S = S top plate - S bar = () = cm², where:
S top plate = cm² (as per § 2.3.1.2 of appendix 2.1-7);
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02 Page 8 of 44 Non-proprietary version S bar:
The crushed length of the shell absorber used to absorb residual drop energy after phase 1 is then determined:
Eunit E
rop E
h lug
d
= mm Crushed length of the top shell absorber: mm.
Calculation of the crush rate At the ring, this crushed length is equal to h crushed = h + d = = mm.
The crush rate for the shell absorber opposite the ring is equal to:
Tlug
55,9 %
Note: the mm of the flange imprint are not taken into consideration as the flange is not opposite the lifting ring.
The crush rate for the shell absorber opposite the flange is equal to:
43,4 %
3.3.2. Bottom side crushing calculation for the FCC3 packaging loaded with assemblies without control clusters The evaluation of crushing on the FCC3 packaging bottom side when loaded with fuel assemblies without clusters is covered by the evaluation of crushing on the bottom side of the FCC3 packaging loaded with fuel assemblies with clusters, described in detail in § 3.4.2.
3.3.3. Top side crushing calculation for the FCC4 packaging loaded with assemblies without clusters For the FCC4 packaging, the top and bottom shell absorbers have a balsa thickness of mm. It is assumed, on a worst-case basis, that all of the drop energy generated by the internal equipment is dampened by the absorber (with the suspension system inactive).
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02 Page 9 of 44 Non-proprietary version Drop energy The drop energy to be absorbed, assuming a combined drop of 0.9 m and 9.25 m, is equal to:
kJ 343,5 h
g 2
m 2
1 E drop
Where:
m: mass of the internal fittings in an FCC4 configuration without clusters, m = kg (see § 2.3.1.2 of appendix 2.17);
h: drop height, h = 0.9 + 9.25 = 10.15 m; g: acceleration due to gravity; g = 9.81 m s-2 The shell absorber is crushed in two phases:
Phase 1: the lifting ring leaves a mm imprint in the absorber (see § 2.3.1.2 of appendix 2.1-7);
Phase 2: the top plate will then come into contact with the shell absorber.
Crushing of the shell absorber due to the lifting ring and the top plate
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02 Page 10 of 44 Non-proprietary version The bar is considered to perforate the shell over a surface area not crushed by the ring in order to maximise the crushing rate at the ring.
Phase 1:
The energy absorbed by the absorber when the ring crushes the shell absorber is calculated:
Where:
- minimum static crush stress for the balsa supplied multiplied, by the dynamic amplification factor, = MPa x = MPa (see details in § 3.2);
S: crushed surface opposite the ring: S = = cm²;
d: indentation height for the lifting ring: mm; kJ in energy is absorbed during this phase. kJ in energy will remain to be dissipated after this phase.
Phase 2:
The top plate hits the entire surface of the shell absorber (less the surface area damaged by the bar (Ø mm)).
The energy absorbed per mm of crushing of the shell absorber by the top plate is calculated. Unit energy for this phase is as follows:
Where:
- minimum static crush stress for the balsa supplied, multiplied by the dynamic amplification factor, = MPa x = MPa (see details in § 3.2);
S:
crushed surface area opposite the top plate, S = S top plate - S bar = () = cm², where:
S top plate = cm² (as per § 2.3.1.2 of appendix 2.17);
S bar:
The crushed length of the shell absorber used to absorb residual drop energy after phase 1 is then determined:
unit lug drop E
E E
h
= mm Crushed length of the top shell absorber: mm.
Calculation of the crush rate At the ring, this crushed length is equal to h crushed = h + d = = mm.
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02 Page 11 of 44 Non-proprietary version The crush rate for the shell absorber opposite the ring is equal to:
66,8 %
Note: the mm of the flange imprint are not taken into consideration as the flange is not opposite the lifting ring.
The crush rate for the shell absorber opposite the flange is equal to:
57,7 %
3.3.4. Bottom side crushing calculation for the FCC4 packaging loaded with assemblies without control clusters The evaluation of crushing on the FCC4 packaging bottom side when loaded with fuel assemblies without clusters is covered by the evaluation of crushing for the bottom of the FCC4 packaging loaded with fuel assemblies with clusters, described in detail in § 3.4.4.
3.4. Behaviour of top side absorbers for the transport of the FCC3 or FCC4 packaging loaded with assemblies with control clusters The presence of the protrusion and the shock absorber on the top plate modifies the behaviour of the shell absorber. The purpose of the top plate shock absorber is to compensate the impact of the top plate protrusion by storing part of the drop energy.
In the configuration with a cluster, the crush rate of the wood is assessed by considering the worst-case scenario where the bar removes the maximum volume of wood, taking into account the presence of the protrusion in the top plate absorber.
On this basis, the scenario adopted must incorporate a perforation in the shell absorber and the top plate absorber next to the protrusion for the entire height of the absorbers (shell absorber +
top plate).
Several configurations have been studied to determine the configuration maximising the surface hit by the bar (particularly considering the fact that the bar is able to hit two top plate absorbers simultaneously).
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02 Page 12 of 44 Non-proprietary version Configuration 2 has been adopted as it removes the most balsa from both the shell and top plate absorbers.
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02 Page 13 of 44 Non-proprietary version 3.4.1. Top side crushing calculation for the FCC3 packaging loaded with assemblies with control clusters For an FCC3 packaging, the top plate absorber has a mm thickness of balsa wood for a width and length of mm. At its centre it features a protrusion hole with an mm diameter, i.e. a surface area of balsa wood of cm² for each top plate absorber.
The shell absorber has a balsa thickness of mm and is much larger than the impact zone of the 2 top plate absorbers side by side. This surface area is 2 times mm x mm spaced out every mm. By subtracting the hole with a diameter of mm due to the protrusion tube, the impacted surface area is cm². It is assumed, conservatively, that the entirety of the drop energy generated by the internal equipment is damped by the absorber (suspension system inactive).
The calculations presented below also take into account crushing of the shell absorber on the flange side by mm (value taken from the report in Appendix 2.1-9) over the whole surface of the absorber. It is therefore assumed that the balsa thickness of the shell absorbers is mm for the FCC3 packaging. This is a conservative assumption because the indentation of the flange is localised and the absorption capacity of the balsa wood is only locally reduced.
The maximum mass of the internal fittings of an FCC3 packaging is kg (including clusters, a new plate and a new absorber). Drops representative of normal conditions of
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02 Page 14 of 44 Non-proprietary version transport taken cumulatively with the drops representing accident conditions of transport, taking into account the deferred impact of the internal fittings (i.e. considering the maximum gap between the top plate absorber and the shell absorber of mm - see details on the conservative gap of mm in § 3.1) give rise to a drop energy to be absorbed of 9 + 1.2 + 0.25 = 10.45 m for the FCC3 packaging, which represents the following drop energy:
Edrop FCC3 = 2950 x 9.81 x 10.45 = 302.4 kJ.
3 cases are analysed below:
1st case: The shell absorber and the top plate absorbers have the same crush stresses
( MPa) 2nd case : The shell absorber has a crush stress lower than that of the top plate absorbers 3rd case: The shell absorber has a crush stress higher than that of the top plate absorbers
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02 Page 15 of 44 Non-proprietary version 1st case:
The shell absorber and the top plate absorbers have the same crush stresses
( MPa)
Modelling is divided into two phases:
Phase 1: Crushing until the protrusion comes into contact with the shell absorber.
Phase 1: Mutual crushing of the 2 absorbers.
Phase 1: Mutual crushing of the 2 absorbers.
The distance between the balsa wood of the top plate absorber and the protrusion is mm. Contact between the protrusion and the shell absorber occurs at the moment where the shell absorber has come closer by mm (with the zone facing the protrusion not crushed). Given that the 2 absorbers have the same crushing stresses, that the same pressures produce the same crush values, and that the surfaces are facing each other, the crushing of each of the absorbers is identical and thus amounts to mm.
The 2 top plate absorbers and the shell absorber are deformed and crushed simultaneously while storing energy.
Consideration of piercing leads to the modification of the surface of the top plate absorbers
= cm2 to - = cm2 ( cm² = the plate absorber surface affected by the bar). Assuming a dynamic stress of x = MPa for the balsa wood of the top plate absorber (see details in § 3.2) and allowing for a total crush surface of cm², the energy dissipated for an indentation of 1 mm is kJ for the 2 top plate absorbers.
The energy dissipated for mm of crushing is 50.7 kJ.
Consideration of piercing leads to the modification of the surface of the top shell absorber cm2 to - = cm2 ( cm² = the shell absorber surface affected by the bar). Assuming a dynamic stress of MPa for the balsa wood of the shell absorber (see details in § 3.2) and allowing for a crush surface of cm², the energy dissipated for an indentation of 1 mm is kJ for the shell absorber.
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02 Page 16 of 44 Non-proprietary version The energy dissipated for mm of crushing is 56.6 kJ.
Phase 2: Dissipation of the remainder of the potential energy in crushing each of the absorbers Phase 2 : Additional crushing at the protrusion.
In this phase, in addition to the above crushing effects, the area of the shell absorber facing the 2 protrusions is crushed. It is crushed twice as fast as that of the plate absorbers as the latter are crushed simultaneously.
Assuming a dynamic stress of MPa for the balsa wood of the shell absorber (see details in § 3.2) and allowing for a crush surface of twice cm², the energy dissipated at the protrusions in a shell absorber for an indentation of 1 mm is kJ.
The residual energy after mm of crushing of each of the absorbers is:
Eres = 302.4 - 50.7 - 56.6 = 195.1 kJ.
The unit energy per 1 mm of indentation of the top plate absorber is:
Euni = + + 2 x = kJ Crushing of the top plate absorber and shell absorber in the zone facing the top plate absorbers is:
Lc = Eres / Euni = 195.1 / = mm The total crushing of the top plate absorbers is:
Lapt = + = mm The total crushing of the shell absorber facing the top plate absorbers is:
Lacc = + = mm Crushing of the shell absorber in the zone facing the 2 protrusions is:
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02 Page 17 of 44 Non-proprietary version Le = Lc x 2 = mm The crush rate in the top plate absorber is:
Tapt = / = 30.8%
The crush rate for the shell absorber in the zone facing the top plate absorbers is:
Tacc = / (-) = 41.9%
The crush rate for the shell absorber in the zone facing the 2 protrusions is:
Tacc = / () = 40.5 %
Note: the 35 mm of the flange imprint are not taken into consideration as the flange is not opposite the protrusion.
Given that these values are each below 75%, there is no risk of reaching the crush limit of the balsa wood of the top plate absorbers and the shell absorber in the case of identical crushing stresses (simultaneous crushing). In addition, the calculations do not integrate the potential contribution of the top plate to the dampening of the lifting ring, which helps to reduce the crushing of the absorbers.
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02 Page 18 of 44 Non-proprietary version 2nd case: The shell absorber has a crush stress lower than that of the top plate absorbers Modelling is divided into three phases:
Phase 1: Crushing of the shell absorber alone until the protrusion makes contact with the shell absorber.
As a conservative approach, the crush stress for the balsa wood of the shell absorber is taken at its minimum value of MPa.
Consideration of piercing leads to the modification of the surface of the top shell absorber cm2 to - = cm2 ( cm² = the shell absorber surface affected by the bar). Assuming a dynamic stress of MPa for the balsa wood of the shell absorber (see details in § 3.2) and allowing for a crush surface of cm², the energy dissipated for an indentation of 1 mm is kJ for the shell absorber.
The energy dissipated for mm of crushing is 113.1 kJ.
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02 Page 19 of 44 Non-proprietary version Phase 2: Crushing of the shell absorber alone, until the crush limit is reached In this phase, in addition to the above crushing effects, the area of the shell absorber facing the 2 protrusions is crushed.
Assuming a dynamic stress of MPa for the balsa wood of the shell absorber (see details in § 3.2) and allowing for a crush surface of twice cm², the energy dissipated at the protrusions in a shell absorber for an indentation of 1 mm is kJ.
The shell absorber is assumed to reach the crush limit at a 75% crush of the balsa wood, i.e. for a top plate absorber height of (-) mm, a crush limit for a crush value of 0,75x(-)= mm.
Note: the mm correspond to the presence of the flange and are applied to the entire surface of the absorber. This is a highly conservative assumption because the damage to the flange is only local and the absorption capacity of the balsa wood is only locally reduced.
Given that mm has already been crushed in the first phase, the amount of crush to reach the crushing limit is mm in the second phase.
In this phase, the unit energy per 1 mm of indentation of the shell absorber is:
E unit = + = kJ The energy dissipated during this crushing phase is :
Etal = x = 170.2 kJ.
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02 Page 20 of 44 Non-proprietary version Phase 3: Dissipation of the remainder of the potential energy In this phase, the shell absorber in the area facing the plate absorber is not crushed any further, the area of the shell absorber facing the 2 protrusions and the 2 top plate absorbers is crushed.
As a conservative approach, the crush stress for the balsa wood of the top plate absorber is taken at its minimum value of MPa.
Assuming a dynamic stress of MPa for the balsa wood of the shell absorber (see details in § 3.2) and allowing for a crush surface of twice cm², the energy dissipated at the protrusions in a shell absorber for an indentation of 1 mm is kJ.
Consideration of piercing leads to the modification of the surface of the top plate absorbers 2x = cm2 to - = cm2 ( cm² = the plate absorber surface affected by the bar). Assuming a dynamic stress of MPa for the balsa wood of the top plate absorber (see details in § 3.2) and allowing for a total crush surface of cm²,
the energy dissipated for an indentation of 1 mm is kJ for the 2 top plate absorbers.
The residual energy after the preceding 2 phases is:
Eres = 302.4 - 113.1 - 170.2 = 19.1 kJ Euni = + = kJ Crushing of the top plate absorber is:
Lapt = 19.1/ = mm The total crushing of the shell absorber in the zone facing the top plate absorbers is:
Lacc = + = mm Crushing of the shell absorber in the zone facing the 2 protrusions is:
Le = + = mm The crush rate in the top plate absorber is:
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02 Page 21 of 44 Non-proprietary version Tapt = / = 4.0 %
The crush rate for the shell absorber in the zone facing the top plate absorbers is:
Tacc = / (-) = 75.0 %
The crush rate for the shell absorber in the zone facing the 2 protrusions is:
Tacc = / = 37.9%
Note: the mm of the flange imprint are not taken into consideration as the flange is not opposite the two protrusions.
The shell absorber reaches a crush of 75% and the crush limit is assumed to be reached beyond this value. The opposite absorber is well below 75% crushing and the shell absorber facing the protrusions does not reach the crush limit. This absorber does therefore reach the crush limit, but there is no hard impact and all of the energy is absorbed in the case of a crushing stress of the shell absorber lower than that of top plate absorbers.
3rd case: The shell absorber has a crush stress higher than that of the top plate absorbers Modelling is divided into two phases:
Phase 1: Crushing of the top plate absorber alone until the protrusion makes contact with the shell absorber.
Phase 1 : Crushing of the top plate absorber.
As a conservative approach, the crush stress for the balsa wood of the top plate absorber is taken at its minimum value of MPa.
Consideration of piercing leads to the modification of the surface of the top plate absorbers 2x = cm2 to - = cm2 ( cm² = the plate absorber surface affected by the bar). Assuming a dynamic stress of MPa for the balsa wood of the top plate absorber (see details in § 3.2) and allowing for a total crush surface of cm²,
the energy dissipated for an indentation of 1 mm is kJ for the 2 top plate absorbers.
The energy dissipated for mm of crushing is 101.4 kJ.
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02 Page 22 of 44 Non-proprietary version Phase 2: Dissipation of the remainder of the potential energy In this phase, in addition to the above crushing effects, the area of the shell absorber facing the 2 protrusions is crushed.
As a conservative approach, the crush stress on the balsa wood of the shell absorber is assumed equal to its minimum value of MPa, even though in the relevant reasoning it is assumed to be higher than that of the top plate absorber.
Assuming a dynamic stress of MPa for the balsa wood of the shell absorber (see details in § 3.2) and allowing for a crush surface of twice cm², the energy dissipated at the protrusions in a shell absorber for an indentation of 1 mm is kJ.
The residual energy after mm of crushing of the shell absorber is:
Eres = 302.4 - 101.4 = 201 kJ.
The unit energy per 1 mm of indentation of the top plate absorber and indentation of the shell absorber facing the protrusions is:
Euni = + = kJ Crushing of the shell absorber in the zone facing the protrusions is:
Lc = 201 / = mm The total crushing of the top plate absorber is Lacc = + = mm The crush rate of the top plate absorbers is:
Tapt = / = 64.9%
The crush rate for the shell absorber in the zone facing the 2 protrusions is:
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02 Page 23 of 44 Non-proprietary version Tacc = / = 43.9%
Given that these values are each below 75%, there is no risk that the balsa wood will reach the crush limit in the case of a crush stress on the shell absorber lower than that of the top plate absorbers.
3.4.2. Bottom side crushing calculation for the FCC3 packaging loaded with assemblies with control clusters Drop energy The drop energy to be absorbed, assuming a combined drop of 1.2 m and 9.25 m, is equal to:
kJ 302,4 h
g 2
m 2
1 E drop
Where:
m: mass of the internal fittings in an FCC4 without a cluster, m = kg; h: drop height, h = 1.2 + 9.25 = 10.45 m; g: acceleration due to gravity; g = 9.81 m s-2 The energy absorbed per mm of crushing of the shell absorber by the bottom plate is calculated. Unit energy is as follows:
Where:
- minimum static crush stress for the balsa supplied, multiplied by the dynamic amplification factor, = MPa x = 33.8 MPa (see details in § 3.2);
S:
crushed surface area opposite the bottom plate, S = S bottom plate - S bar = cm², where:
S bottom plate = x = cm²;
S bar:
The crushed length able to absorb all of the drop energy is then determined:
h
Calculation of the crush rate The crush rate for the shell absorber opposite the flange is equal to:
41.0 %
Given that this value is less than 75%, there is no risk that the crush limit of the balsa will be reached in the configuration with a cluster with the combined axial drops on the bottom.
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02 Page 24 of 44 Non-proprietary version 3.4.3. Top side crushing calculation for the FCC4 packaging loaded with assemblies with control clusters For an FCC4 packaging, the top plate absorber has a mm thickness of balsa wood for a width and length of mm. At its centre it features a protrusion hole with an mm diameter, i.e. a surface area of balsa wood of cm² for each top plate absorber.
The shell absorber has a balsa thickness of mm and is much larger than the impact zone of the 2 top plate absorbers side by side. This surface area is 2 times mm x mm spaced out every mm. By subtracting the hole with a diameter of mm due to the protrusion tube, the impacted surface area is cm². It is assumed, conservatively, that the entirety of the drop energy generated by the internal equipment is damped by the absorber (suspension system inactive).
The calculations shown below also allow for flange side crushing of mm over the whole surface of the absorber (value taken from the report in Appendix 2.1-9) for determining the maximum crush rate. It is therefore assumed that the balsa thickness of the shell absorbers is mm for the FCC4 packaging. This is a conservative assumption because the indentation of the flange is localised and the absorption capacity of the balsa wood is only locally reduced.
The maximum mass of the internal fittings of an FCC4 packaging is kg (including clusters, a new plate and a new absorber). The consideration of a drop representative of normal conditions of transport taken cumulatively with the drops representing accident conditions of transport, taking into account the deferred impact of the internal fittings (i.e.
considering the maximum gap between the top plate absorber and the shell absorber of mm - see details on the conservative gap of mm in § 3.1) correspond to a drop energy to be absorbed of 9 + 0.9 + 0.25 = 10.15 m for the FCC4 packaging, which represents the following drop energy:
Edrop FCC4 = 3700 x 9.81 x 10.15 = 368.4 kJ.
3 cases are analysed below:
1st case: The shell absorber and the top plate absorbers have the same crush stresses
( MPa) 2rd case: The shell absorber has a crush stress lower than that of the top plate absorbers 3rd case: The shell absorber has a crush stress higher than that of the top plate absorbers 1st case:
The shell absorber and the top plate absorbers have the same crush stresses
( MPa)
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02 Page 25 of 44 Non-proprietary version Modelling is divided into two phases:
Phase 1: Crushing until the protrusion comes into contact with the shell absorber.
The distance between the balsa wood of the top plate absorber and the protrusion is mm. Contact between the protrusion and the shell absorber takes place at the moment where the shell absorber has come closer by mm (zone facing the protrusion not being crushed). Given that the 2 absorbers have the same crushing stresses, that the same pressures produce the same crush values, and that the surfaces are facing each other, the crushing of each of the absorbers is identical and thus amounts to mm.
The 2 top plate absorbers and the shell absorber are deformed and crushed simultaneously while storing energy.
Consideration of piercing leads to the modification of the surface of the top plate absorbers 2x = cm2 to - = cm2 ( cm² = the plate absorber surface affected by the bar). Assuming a dynamic stress of MPa for the balsa wood of the top plate absorber (see details in § 3.2) and allowing for a total crush surface of cm²,
the energy dissipated for an indentation of 1 mm is kJ for the 2 top plate absorbers.
For mm of crushing, which brings the mm protrusion into contact with the shell absorber, 39.0 kJ is dissipated in energy.
Consideration of piercing leads to the modification of the surface of the top shell absorber cm2 to - = cm2 ( cm² = the shell absorber surface affected by the bar). Assuming a dynamic stress of MPa for the balsa wood of the shell absorber (see details in § 3.2) and allowing for a crush surface of cm², the energy dissipated for an indentation of 1 mm is kJ for the shell absorber.
For mm of crushing, which brings the mm protrusion into contact with the shell absorber, 43.5 kJ is dissipated in energy.
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02 Page 26 of 44 Non-proprietary version Phase 2: Dissipation of the remainder of the potential energy in crushing each of the absorbers Phase 2: Additional crushing at the protrusion In this phase, in addition to the above crushing effects, the area of the shell absorber facing the 2 protrusions is crushed. It is crushed twice as fast as that of the plate absorbers as the latter are crushed simultaneously.
Assuming a dynamic stress of MPa for the balsa wood of the shell absorber (see details in § 3.2) and allowing for a crush surface of twice cm², the energy dissipated at the protrusions in a shell absorber for an indentation of 1 mm is kJ.
The residual energy after mm of crushing of each of the absorbers is:
Eres = 368.4 - 39.0 - 43.5 = 285.9 kJ.
The unit energy per 1 mm of indentation of the top plate absorber is:
Euni = + + 2 x = kJ The crushing able to absorb the residual drop energy during phase 2 of the top plate absorber and the shell absorber in the zone facing the top plate absorbers is equal to:
Lc = Eres / Euni = 285.9 / = mm The total crushing of the top plate absorbers is:
Lapt = + = mm The total crushing of the shell absorber in the zone facing the top plate absorbers is:
Lacc = + = mm Crushing of the shell absorber in the zone facing the 2 protrusions is:
Le = Lc x 2 = mm
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02 Page 27 of 44 Non-proprietary version The crush rate in the top plate absorber is:
Tapt = / = 60.1 %
The crush rate for the shell absorber in the zone facing the top plate absorbers, considering the presence of the flange, is:
Tacc = / (-) = 48.4 %
The crush rate for the shell absorber in the zone facing the 2 protrusions is:
Tacc = / = 57.6 %
Note: the mm of the flange imprint are not taken into consideration as the flange is not opposite the protrusion.
Given that these values are each below 75%, there is no risk that the balsa wood of the top plate absorbers and the shell absorber will reach the crush limit in the case of identical crushing stresses (simultaneous crushing). In addition, the calculations do not integrate the potential contribution of the top plate to the dampening of the lifting ring, which helps to reduce the crushing of the absorbers.
2nd case: The shell absorber has a crush stress lower than that of the top plate absorbers
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02 Page 28 of 44 Non-proprietary version Modelling is divided into three phases:
Phase 1: Crushing of the shell absorber alone until the protrusion makes contact with the shell absorber.
As a conservative approach, the crush stress for the balsa wood of the shell absorber is taken at its minimum value of MPa.
Consideration of piercing leads to the modification of the surface of the top shell absorber cm2 to - = cm2 ( cm² = the shell absorber surface affected by the bar). Assuming a dynamic stress of MPa for the balsa wood of the shell absorber (see details in § 3.2) and allowing for a crush surface of cm², the energy dissipated for an indentation of 1 mm is kJ for the shell absorber.
The energy dissipated for mm of crushing is 87.0 kJ.
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02 Page 29 of 44 Non-proprietary version Phase 2: Crushing of the shell absorber alone, until the crush limit is reached In this phase, in addition to the above crushing effects, the area of the shell absorber facing the 2 protrusions is crushed.
Assuming a dynamic stress of MPa for the balsa wood of the shell absorber (see details in § 3.2) and allowing for a crush surface of twice cm², the energy dissipated at the protrusions in a shell absorber for an indentation of 1 mm is kJ.
The shell absorber is assumed to reach the crush limit at a 75% crush of the balsa wood, i.e. for a top plate absorber height of (-) mm, a crush limit for a crush value of 0,75x(-)= mm.
Note: the mm correspond to the presence of the flange and are applied to the entire surface of the absorber. This is a highly conservative assumption because the damage to the flange is only local and the absorption capacity of the balsa wood is only locally reduced.
Given that mm has already been crushed in the first phase, the amount of crush to reach the crush limit is mm in the second phase.
In this phase, the unit energy per 1 mm of indentation of the shell absorber is:
E unit = + = kJ The energy dissipated during this crushing phase is :
Etal = x = 210.9 kJ.
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02 Page 30 of 44 Non-proprietary version Phase 3: Dissipation of the remainder of the potential energy In this phase, the shell absorber in the area facing the plate absorber is not crushed any further, the area of the shell absorber facing the 2 protrusions and the 2 top plate absorbers is crushed.
As a conservative approach, the crush stress on the balsa wood of the top plate absorber is assumed equal to its minimum value of MPa, even though in the relevant reasoning it is assumed to be higher than that of the shell absorber.
Assuming a dynamic stress of MPa for the balsa wood of the shell absorber (see details in § 3.2) and allowing for a crush surface of twice cm², the energy dissipated at the protrusions in a shell absorber for an indentation of 1 mm is kJ.
Consideration of piercing leads to the modification of the surface of the top plate absorbers 2x = cm2 to - = cm2 ( cm² = the plate absorber surface affected by the bar). Assuming a dynamic stress of 33.8 MPa for the balsa wood of the top plate absorber (see details in § 3.2) and allowing for a total crush surface of cm²,
the energy dissipated for an indentation of 1 mm is kJ for the 2 top plate absorbers.
The residual energy after the preceding 2 phases is:
Eres = 368.4 - 87.0 - 210.9 = 70.5 kJ Euni = + = kJ Crushing of the top plate absorber is:
Lapt = / = mm The total crushing of the shell absorber in the zone facing the top plate absorbers is:
Lacc = + = mm Crushing of the shell absorber in the zone facing the 2 protrusions is:
Le = + = mm
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02 Page 31 of 44 Non-proprietary version The crush rate in the top plate absorber is:
Tapt = / = 23.6 %
The crush rate for the shell absorber in the zone facing the top plate absorbers is:
Tacc = / (-) = 75 %
The crush rate for the shell absorber in the zone facing the 2 protrusions is:
Tacc = / = 55.4 %
Note: the mm of the flange imprint are not taken into consideration as the flange is not opposite the two protrusions.
The shell absorber reaches a crush of 75% and the crushing limit is assumed to be reached beyond this value but the absorber facing it is well below 75% and the shell absorber facing the protrusions does not reach the crush limit. This absorber does therefore reach the crush limit, but there is no hard impact and all of the energy is absorbed in the case of a crushing stress of the shell absorber lower than that of top plate absorbers.
3rd case: The shell absorber has a crush stress higher than that of the top plate absorbers Modelling is divided into three phases:
Phase 1: Crushing of the top plate absorber alone until the protrusion makes contact with the shell absorber.
As a conservative approach, the crush stress for the balsa wood of the top plate absorber is taken at its minimum value of MPa.
Consideration of piercing leads to the modification of the surface of the top plate absorbers 2x = cm2 to - = cm2 ( cm² = the plate absorber surface affected by the bar). Assuming a dynamic stress of MPa for the balsa wood of the top plate absorber (see details in § 3.2) and allowing for a total crush surface of cm²,
the energy dissipated for an indentation of 1 mm is kJ for the 2 top plate absorbers.
The energy dissipated for mm of crushing is 78.0 kJ.
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02 Page 32 of 44 Non-proprietary version Phase 2: Crushing of the top plate absorber up to the crush limit In this phase, in addition to the above crushing effects, the area of the shell absorber facing the 2 protrusions is crushed.
As a conservative approach, the crush stress on the balsa wood of the shell absorber is assumed equal to its minimum value of MPa, even though in the relevant reasoning it is assumed to be higher than that of the top plate absorber.
Assuming a dynamic stress of MPa for the balsa wood of the shell absorber (see details in § 3.2) and allowing for a crush surface of twice cm², the energy dissipated at the protrusions in a shell absorber for an indentation of 1 mm is kJ.
The top plate absorber is assumed to reach the crush limit at 75% of the crush of the balsa wood, i.e. for a top plate absorber height of mm, a reaching of the crush limit for a crushing value of mm.
Given that mm has already been crushed in the first phase, the amount of crush to reach the crush limit is mm.
In this phase, the unit energy per 1 mm indentation of the top plate absorber and indentation of the shell absorber facing the protrusions is:
Euni = + = kJ The energy dissipated during this crushing phase is :
Etal = x = 137.2 kJ.
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02 Page 33 of 44 Non-proprietary version Phase 3: Dissipation of the remainder of the potential energy In this phase, the top plate absorbers are no longer crushed, the zone of the shell absorber facing the 2 top plate absorbers is crushed.
Consideration of piercing leads to the modification of the surface of the top shell absorber cm2 to - = cm2 ( cm² = the shell absorber surface affected by the bar). Assuming a dynamic stress of MPa for the balsa wood of the shell absorber (see details in § 3.2) and allowing for a crush surface of cm², taking into account shear, the energy dissipated for an indentation of 1 mm is kJ for the shell absorber.
The residual energy after the preceding 2 phases is:
Eres = 368.4 - 78.0 - 137.2 = 153.2 kJ.
The unit energy per 1 mm of indentation of the facing shell absorber is:
Euni = + = kJ The total crushing of the shell absorber facing the top plate absorbers is:
Lc = / = mm Crushing of the shell absorber in the zone facing the 2 protrusions is:
Le = + = mm The total crushing of the top plate absorber is Lapt = + = mm The crush rate in the top plate absorber is:
Tapt = / = 75.0 %
The crush rate of the shell absorber facing the top plate absorbers is:
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02 Page 34 of 44 Non-proprietary version Tacc = / (-) = 37.5 %
The crush rate for the shell absorber in the zone facing the 2 protrusions is:
Tacc = / = 58.4 %
Note: the mm of the flange imprint are not taken into consideration as the flange is not opposite the two protrusions.
The top plate absorber reaches a crush of 75 % and the crush limit is assumed to be reached beyond this value but the shell absorber is well below 75 % and the crush limit is not reached. This absorber does therefore reach the crush limit, but there is no hard impact and all of the energy is absorbed in the case of a crushing stress of the shell absorber lower than that of top plate absorbers.
3.4.4. Bottom side crushing calculation for the FCC4 packaging loaded with assemblies with control clusters Drop energy The drop energy to be absorbed, assuming a combined drop of 0.9 m and 9.25 m, is equal to:
kJ 368,4 h
g 2
m 2
1 E drop
Where:
m: mass of the internal fittings in an FCC4 with a cluster, m = kg; h: drop height, h = 0.9 + 9.25 = 10.15 m; g: acceleration due to gravity; g = 9.81 m s-2 Crushing of the absorber The energy absorbed per mm of crushing of the shell absorber by the bottom plate is calculated. Unit energy is as follows:
Where:
- minimum static crush stress for the balsa supplied, multiplied by the dynamic amplification factor, = MPa x = MPa (see details in § 3.2);
S:
crushed surface area opposite the bottom plate S = S bottom plate - S bar = cm², where:
S bottom plate = x = cm²;
S bar:
The crushed length able to absorb all of the drop energy is then determined:
h
61.4
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02 Page 35 of 44 Non-proprietary version Calculation of the crush rate The crush rate for the shell absorber opposite the flange is equal to:
48,0 %
Given that this value is less than 75%, there is no risk that the crush limit of the balsa will be reached in the configuration with a cluster with the combined axial drops on the bottom.
3.4.5. Impact of possible shearing of the shell absorber The above calculations consider several possible modes of behaviour of the top plate and shell shock absorbers.
One of the cases likely to lead to rips due to shear phenomena is phase 3 of case no. 3 in section 3.4.2, i.e. top side crushing for the FCC4 packaging loaded with fuel assemblies with clusters when the shell absorber sustains a crush stress which is greater than that of the top plate absorbers from the point in time when the shell absorber must dissipate the residual potential energy (see diagram below).
This case presents the possibility that the shell absorber sustains a piercing which could then produce tearing. Taking a conservative approach, and so as to take into account possible tearing of the wood fibres around the edge of the well created by the protrusion in the shell absorber, it is assumed that 25% around the surface of the protrusion does not contribute to the absorption of energy by the shell absorber.
Thus the residual impact energy at the start of phase 3 of case 3 described in section 3.4.2 is 153.2 kJ.
At the start of phase n° 3 the balsa wood of the top plate has reached the crush limit and plays no further shock absorbing role.
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02 Page 36 of 44 Non-proprietary version The crushed section of the shell absorber facing the top plate absorber helping to absorb residual energy (previously cm²) is then modified and equal to:
S
(104.29 cm² = the surface area removed by the bar from the shell absorber).
Assuming a dynamic stress of MPa for the balsa wood of the shell absorber (see details in § 3.2) the unit energy for 1 mm of crushing corresponding to the section of the top shell absorber is kJ in this phase (compared with kJ mm-1 previously).
The unit energy per 1 mm of indentation in the top shell absorber at the plate absorber is therefore equal to:
E uni = + = kJ mm-1 The total crushing of the top shell absorber facing the top plate absorbers, with consideration of shear, is:then:
Lc = / = mm The crush rate for the top shell absorber in the zone facing the 2 protrusions is:
Tacc =(+) / = 60.4% (compared with 58.4% without shear).
Given the crush rate of the shell absorber facing the protrusions, the consideration of shear due to potential rips in the balsa following the vertical drop has no significant impact on the overall crush rate for the absorber wood.
3.5. Mechanical strength of top plate The uninterrupted thickness of the top plate is mm. A central counterbore of mm Ø and depth of mm locally reduces its thickness to mm. By considering a static crush stress on the balsa wood in the shell absorber maximised at MPa and a dynamic amplification factor of, i.e. a dynamic crush stress equivalent to MPa, the stress in the circular ligament at the counterbore under a uniformly distributed pressure on the mm Ø disk is very much lower than the ultimate tensile strength of steel (77 MPa < 490 MPa). Details of the calculation:
MPa 77 e
D
4 D
2 dyn.
balsa plate top
Where:
- : maximum static crush stress for the balsa supplied, multiplied by the dynamic amplification factor, = MPa x = MPa (see details in § 3.2);
D: diameter of the top plate central counterbore, mm; e: thickness of the circular ligament at the central counterbore of mm.
With reference to the top plate protrusion due to the axial securing system for the clusters (see geometric details in chapter 1.4) and taking into account the mm thickness of the cylinder and a pressure on the end disk of the protrusion (Ø mm) equal to the static crush stress of the balsa wood of the shell absorber maximised to MPa multiplied by a dynamic amplification factor of, the crush pressure on the balsa wood produces a compressive stress in the thickness of the cylinder 185 MPa less than the minimum yield strength of the stainless steel.
The protrusion will not therefore be deformed by a drop. Details of the calculation:
I
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02 Page 37 of 44 Non-proprietary version MPa 185
)
4 2e)
(D 4
(D
4 D
2 2
2 dyn.
balsa protusion
Where:
- : maximum static crush stress for the balsa supplied, multiplied by the dynamic amplification factor, = MPa x = MPa (see details in § 3.2);
D: diameter of the top plate protrusion, mm; e: thickness of the top plate protrusion cylinder, mm.
3.6. Axial restraint of the assemblies via the bottom nozzle As described in detail in chapter 1.4, given the presence of the cluster and its securing system at the centre of the top plate, an assembly with a cluster is secured using the bottom plate.
The bottom plate is mm thicker than the standard bottom plate to facilitate machining of the slides. The thickness at the 2 central dishes is the same as the thickness of a standard plate
( mm). It is therefore at least as strong as the standard plate.
The indexing fingers project from the bottom plate by mm. This projection is less than the projection of the top side lifting lug ( mm), which is conservative when justifying the packaging. However, these fingers do not extend beyond the plane of the connecting plate of the bearing. This modification therefore has no additional negative mechanical impact on the packagings compared to a standard plate.
The clamping system described in chapter 1.4 is different for the drops carried out. During the drops carried out on prototype 1, the dummy assembly was axially clamped by the top nozzle and the axial clamp broke (see report in appendix 2.1-9 of this report). The system used to clamp the assembly by the bottom nozzle similarly failed and absorbed energy during the drop. The energy absorbed by the 2 systems was subsequently estimated and compared to the total drop energy of the assembly.
I I
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02 Page 38 of 44 Non-proprietary version Clamping screw at the top end During the vertical drop the clamping screw was subjected to forces giving rise to buckling stresses. During tests on prototype 1, the free part of the screw broke. Buckling strain energy is difficult to quantify as it is generated by a so-called critical instability force. During the drop the maximum radial movement of the screw before rupture is not known. Taking a conservative approach, this displacement is assumed to be half the length of the screw, i.e. mm, which maximises the energy absorbed by this system.
The clamping screw has a diameter of. We assume a diameter value d = -0.9283p =
mm corresponding to the diameter of the tensile stress area of the screw.
The energy absorbed in buckling is estimated by the following formula (per reference <2>):
l = free height of the screw = mm
= maximum transverse displacement = mm E = Young's modulus = 210 000 MPa I
E l
64
U 3
4 2
Buckling
Where:
I
210 2823 Retaining claws at the bottom end During vertical drops the retaining claws are subjected to forces giing rise to tensile stresses.
The screws each have a diameter of and the minimum characteristics of this screw are Re:
= (MPa), Rm = (MPa) and A% = %. We assume a diameter value of corresponding to the diameter of the tensile stress area of the screw. The energy absorbed in tension is calculated as follows:
l S
A%
2 Rm Re utraction
Where l = hauteur libre de la vis = mm S
- Hence, J
124 Utraction and the rupture energy for the 8 screws is 994 J.
Conclusion The energy absorbed by the retaining claws is lower than that of the clamping screw system at the top of the assembly (by a factor of 2.8). However, the energy orders of magnitude used are low compared with the total drop energy for the assembly, of around 77,430 J. The energy values involved represent 3.6% of the total drop energy and are not likely to call into question the conclusions as to the damage sustained by the packaging and the assemblies transported.
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02 Page 39 of 44 Non-proprietary version 3.7. Securing EPR' assembly grids The adaptation of the doors for the securing system of EPR' assembly grids as described in section 1Erreur ! Source du renvoi introuvable. has no impact on the mechanical justification of the doors since the ribs have the same dimensions, apart from the addition of 2 shoulders to some of them. In addition the pad restraint system at the level of the grids is identical to that for the FCC4 packaging not used to transport EPR' fuel assemblies'.
3.8. Insertion of control clusters into the fuel assemblies This purpose of this section is to justify the absence of impact on the justification of the condition of the assemblies following the regulatory tests due to the addition of control clusters inserted into the assemblies during transportation in FCC3 and FCC4 packagings. The situations liable call into question the safety of the package are a 9-metre vertical drop and a 9-metre lateral drop test during accident conditions of transport.
3.8.1. Impact on mass The addition of a cluster in the fuel assembly does not contribute any additional mass to be considered in the demonstrations of compliance for the safety analysis report, which use the maximum mass of the assembly, as the presence of this additional weight is already included in the definition of the maximum mass value for the assembly (757 kg for the 17x17 12-foot assembly in FCC3 packagings, 865 kg for the 17x17 14-foot assembly in FCC4 packagings). The differences in mass between the prototype and the package model are specifically addressed in section 3.9.
3.8.1.1.
Vertical drop on bottom end During the 9-metre vertical drop onto the bottom end, the constituent components of the cavity behave as follows:
The cluster securing system is an integral part of the top plate, and the weight of the wedging system is less than 1 kg, for an assumed axial acceleration of g (see Appendix 2.1-12);the section of the pad retaining pin, which is the most fragile part of the system, is subjected to a stress of less than 25 MPa. Thus it will not rupture.
The rods will slide in the grids and rest on the bottom nozzle. It will then be deformed in a similar way as for the top nozzle of prototype 1 during an axial drop (see photo enclosed).
The cluster hub bears on the upper face of the upper nozzle of the assembly after total compression of the hub spring. Thereafter, a deformation due to the bearing force of the cluster (in the order of 60 kg) at the centre of the upper nozzle with an axial acceleration of g has less effect than the bearing force of the rod bundle of prototype 1 (in the order of 640 kg) during the axial drop on the top end.
On EPR' assemblies, the total gap between the fuel rods and the nozzles is mm. On 12 ft. assemblies the total gap is about mm. A gap of 40 mm is sufficient to avoid any interaction between the slightly deformed upper nozzle and the fuel rod bundle; such interaction could impair the integrity of the fuel rods
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02 Page 40 of 44 Non-proprietary version Thus the insertion of clusters into the fuel assemblies for transportation in FCC3 and FCC4 packagings has no impact on the safety of the packages during a 9-metre vertical drop on the bottom end.
3.8.2. Vertical drop on top end The wedging system described in sections 1 and 1 prevents any hard contact between the assembly and the hub during a 9-metre vertical drop on the top end. The clearance between the upper nozzle and the wedging system ( mm) is such that the cluster spring is not fully compressed. During the drop of prototype 1, the assembly directly impacted the top plate at the upper nozzle; the axial clamping system failed (see above photograph). The nozzle did not sustain any deformation detrimental to the fuel rod bundle. The wedging system and the assemblys top nozzle have the same minimum mechanical characteristics due to the fact that they are composed of the same stainless steel. Knowing that, and that the cross section of the wedges of the wedging system is greater than those for the assemblys top nozzle, the wedging system is stronger than the top nozzle, which implies that the nozzle will be deformed in the same way as during the drop tests, whereas the wedging system will resist.
Thus, insertion of the clusters into the fuel assemblies for transportation in FCC3 and FCC4 packages has no impact on the safety of the packages during a 9-metre vertical drop on the top end.
3.8.3. Lateral drop The purpose of this section is to analyse lateral deformation of the guide-tubes during lateral drops of the packagings with whiplash action. These deformations are calculated for bareguide-tubes and guide-tubes containing cluster rods.
The worst case geometry is that of the bottom span of the AFA3GL assembly, with a height of mm. For this length the strain energy corresponding to the drop is equal to 10.768 J (see § 4.2.3.5.3 of Appendix 2.16 of this Report).
The strain energy of the guide-tube will be equal to the above value multiplied by the ratio of the guide-tube/rod linear masses. The linear mass of the rod in the fuel zone is equal to 0.644 kg/m, which corresponds to the linear mass of the pellets (0.540 kg/m) added to the linear mass of the cladding (0.105 kg/m).
For a fixed/fixed beam (very similar to the guide-tube configuration) with uniformly distributed loading, we obtain an expression of the deformation shape, with small displacements, from the following resistance-of-materials formulae:
The strain energy is given by the integral of the strains along the neutral line.
It is expressed by:
14 2
,l 4
2 3
= q *
-(~ ~
+ ~
=16 *y
- (E__ - 2 *~
+ ~ )
y 24 *E *I z2 l 3
/4 ma..x l 2 l 3 l
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02 Page 41 of 44 Non-proprietary version We finally obtain the expression of the maximum deflection in mid-span as a function of the energy.
Numerical application:
The numerical application is presented in the table below for the case of guide-tubes alone (thin or dashpots) and for guide-tubes with cluster rods.
During lateral drops the presence of cluster rods in the uninterrupted section of the guide-tube tends to increase the deformation shapes of the guide-tubes by about 50%.
However, the deflection of the guide-tube containing a cluster rod (in the order of 9 mm) remains in all cases lower than the specific deflection induced in the fuel rods by a flat drop test with whiplash (in the order of 27 to 40 mm depending on the material concerned).
In addition, the guide-tubes have a tendency in all cases to limit the deformation of the rods adjacent to them.
During lateral drops, the presence of the hub is accommodated radially by the adapter plate of the upper nozzle, which tends to increase the deformation shapes of the guide-tubes by about 50%.
Given that the axial components of the lateral drops are less than those generated by the vertical drop, their effects are covered by the analysis of vertical drops (see sections 3.8.1 and 3.8.2)
The presence of cluster rods in the guide-tubes therefore has no impact on the safety of the FCC3 and FCC4 packages during a lateral drop of 9 metres with whiplash action.
3.8.4. Elongation of the shell in FCC3 packagings The 2 x mm elongation of the shell only has an impact on the mechanical justification in terms of the addition of mass to the packaging. The mass of this elongation on the mm thick shell and the flanges is 7.5 kg. This increase in mass of the packaging is negligible in relation to its maximum mass (4385 kg).
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02 Page 42 of 44 Non-proprietary version 3.9. Shear strength analysis for the bolted connection of FCC3 and FCC4 packaging shells during an axial drop.
The purpose of this section is to justify the shear strength of the bolted connection for the FCC3 and FCC4 packaging shells in an axial drop from a height combining the regulatory drop height in normal conditions of transport with the regulatory drop height in accident conditions of transport at the maximum temperature reached in normal conditions of transport.
The bolted connection of the shells of FCC3 and FCC4 packagings comprises and,
screws in class minimum. As explained in appendix 2.1-11, the FCC3 packaging is more conservative than the FCC4 packaging in terms of screw strength during an axial drop. Only the FCC3 packaging is studied hereafter.
Appendix B of standard ISO 898-1 on screws stipulates that "up to typical service temperatures of 150°C, no change that is prejudicial to the mechanical characteristics is observed". The maximum temperature in normal conditions of transport determined on a conservative basis for the files is equal to °C (see chapter 2.2-2), so the conclusions for drops at ambient temperature apply at the maximum temperature reached in normal conditions of transport.
In addition, the drop report for prototype 1, which was subjected to an axial drop (chapters 2.1-9 of this safety report) indicates that, after the drops, all of the screws connecting the 2 half-shells are in position. The screws in the impact zone for the axial drop are slightly twisted (see figure below). The report also indicates that the screws connecting the 2 half-shells were easily removed. These drop results clearly demonstrate that the screws are little affected by the axial drop due to uniform crushing of the shell (no differential acceleration between the upper shell and the lower shell).
On this basis, the results of the axial drop combining the regulatory heights in normal conditions of transport and in accident conditions of transport demonstrate that no significant stresses, which would break all screws, are expected.
3.10. Impact of the presence of the dummy with smooth walls The maximum mass authorized for the dummy assembly with smooth walls with its spacers is identical to the maximum mass authorized for an assembly, i.e. 877 kg.
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02 Page 43 of 44 Non-proprietary version The wedging system for the dummy with smooth walls is identical to the system for the EPRTM assembly with cluster. The second cavity of the FCC4 packaging comprises an EPRTM assembly with a cluster.
On this basis, the mechanical behaviour of the package remains covered by the justifications in this Safety Analysis Report.
- 4.
Impact of the differences in mass between the prototype and the package model for the drop on bar Prototype 2 which underwent 2 drops onto a bar had a mass of 5262 kg for a maximum mass of the loaded packaging of 5,550 kg (maximum mass of the FCC4 package model covering the FCC3 package case). During the drop on bar test the outer shell was perforated and the bar impacted the internal equipment at the corner of the doors without causing them to open. The drop on bar caused a local indentation in the door and the door plates were subjected to bending stresses. The increase in mass produced an increase in the energy to be dissipated by deformation of the door. Given that door plates are subjected to bending forces, the increase in mass will have the effect of increasing the bending of the door with no impact on the other components which did not break during the test (see photographs in Appendix 2.1-10 of this Report). The strain energy of these plates is proportional to the square of the deformation shape and it is therefore possible to estimate the additional deformation created by this increase in mass.
The maximum mass of an FCC4 packaging and the prototype subjected to the drop test are respectively 5550 kg and 5262 kg. The increase in energy attributable to the difference is mass is 5.47 The deformation shape measured on the door of the prototype after a 1-metre drop onto a bar was mm (per Appendix 2.110 of this Report).
Taking into account the energy ratio we obtain the following deformation shape:
1.0547.
Thus the increase of mm in the deformation shape of the door for an increase in mass of 5.47 %
does not adversely affect the behaviour of the screws, ball-locking pins, etc., which did not break during the test. The frame-door assembly remains intact and this minimal increase in deformation will have the effect of increasing the compaction of the rod array or the cross-section of the assembly which will tend to reduce the reactivity of the assembly (as indicated in the criticality safety analysis in Chapter 2.5 of this Report).
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02 Page 44 of 44 Non-proprietary version
- 5.
Conclusion All of the modifications made to the FCC3 and FCC4 package models are without impact on the safety of the packagings.
- 6.
References
<1> Regulations for the Safe Transport of Radioactive Materials - Requirements N° TS-R at the revision indicated in Chapter 1.2.
<2> Materials Resistance - Volumes 1 and 2, "S.P. Timoshenko" - Published by Dunod