ML22271A677
Text
C1 - Framatome Restricted
IDENTIFICATION REVISION
I FF/DC/00817 E0 11 4.0 I Framatome framat ome Fuel
TOTAL NUMBER OF PAGES : 37
SAFETY/CRITICALITY STUDY OF FCC3 and FCC4 CONTAINERS 15x15 and 17x17 ASSEMBLIES 17x17 XL, 17x17 EPR, 16x16 and 18x18 ASSEMBLIES
I NON-PROPRIETARY VERSION I
ADDITIONAL INFORMATION:
PROJECT DISTRIBUTION TO PURPOSE OF DISTRIBUTION
HANDLING Restri cted Fram atom e Fo r a ctio n Fo r a ctio n Fo r info rmatio n CATEGORY STR -Stud y Re po rt
STATUS BPE
ROLES NAMES DATES ORGANIZATIONS SIGNATURES AUTH OR REVIEWER AP PROVER
Classification Exg;ort Al: OE001 ECCN: N RELEASE DAT A : Les m archandises portan t la d8signation " AL in8Qal W sent sou mises a la rElglementa tion e u rop@enne ou allemande en mauere de contrOle des exportations au seln ou hors de l'UE. Les marehandlses portant la d8signatio n "ECCN in8ga l N" sont soumises a la r8 glemen ta tion am8ricaine. Les marchand ises p ortant les d8slgna tlons "AL: N" ou "ECCN: N" peuvent, selon la destination ou l'ulilisa tlon finales du p rodull, egale ment ~tre soumlses a autor1sat1on.
Exuort classificatio n AL: OE001 ECCN: N Goods labeled wi th *AL not equal to N" are su bject to European or German export authorization w h en being expo rted within or out of the E U. Goods labeled with *ECCN not equal to W are subje c t to US reex p ort authorization. Even withou t a label, o r with labe l *AL: W or *ECCN: W, authorization may be requ ired due to the final whereabouts and purpose for which the goods are to be used.
CHANGE CONTROL RECORDS: France: y Ex12ortkennzeichn u n g AL: O E 01 ECCN: N Die mlt "AL unglelch N" gekennzelchneten Gllter unterliegen bel der Ausfuhr aus der EU bzw.
This documen t, w he n revised, m us t be USA: N lnnergem elnschaftHchen Verb r1ngung der europa lschen bzw. deutschen Ausfuh rg enehm lgungspflicht. Die m lt "ECCN u nglelch W geken nzelchne ten GOter unter11egen der US-Reexportgenehmlgu ngspfllcht. Auch oh ne rev iew ed or app roved by follow ing regio ns : Germany : N Kennze ichen, bzw. bei Kennzeidle n " AL: N" oder "ECCN : W, kan n sich eine Genehmigu ngspflich t, unte r anderem durch den EndVerblelb und Verwendunaszw eck der GOter, eraeben.
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REVISIONS
REVISION DATE EXPLANATORY NOTES
A 28/ 05/2004 First issue
B 28/ 11 /2008 Document FFDC04751 taken into account (French - modification of the pellet and cladding characteristics ((13])
version) 26/ 06/2009 -17x17 EPRadded ([14])
(English - definition of packaging types added version) - update from Cristal v0.2 to v1.1
- in CAT delete the non-expanded configurations and full height expansion
- in CAT cancel of 820x527 shell case
3.0 03/ 11 / 2020 Removal of the TM in the title ("Trademark in the USA" is no longer of interest to date)
Editorial Corrections in § 1, §5.2.2 and §5.3.2
4.0 See 1st page Editorial Correction and additional information in §1 release date
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TABLE OF CONTENTS
- 1. INTRODUCTION................................................................................................................... 8
- 2. DEFINITIONS AND CONVENTIONS..................................................................................... 9
- 3. CODES AND QUALIFICATION........................................................................................... 12
- 4. COMPUTATION AND MODELLING HYPOTHESES.......................................................... 13 4.1. CHARACTERISTICS OF THE PACKAGE.................................................................................. 13 4.1.1. PACKAGE UNDER NORMAL TRANSPORT CONDITIONS (NTC).............................. 13 4.1.2. PACKAGE UNDER ACCIDENT TRANSPORT CONDITIONS (ATC)........................... 14 4.2. CHARACTERISTICS OF THE NEUTRON ABSORBING RESIN............................................... 14
- 4. 2. 1. RESIN UNDER NORMAL TRANSPORT CONDITIONS (NTC)..................................... 15
- 4. 2. 2. RESIN UNDER ACCIDENT TRANSPORT CONDITIONS (A TC).................................. 15 4.3. CHARACTERISTICS OF THE ASSEMBLIES............................................................................. 15 4.3. 1. ASSEMBLY UNDER NORMAL TRANSPORT CONDITIONS (NTC)............................ 16
- 4. 3. 2. ASSEMBLY UNDER ACCIDENT TRANSPORT CONDITIONS (ATC)......................... 16
- 5. METHODOLOGY AND RESULTS...................................................................................... 17
- 5. 1. PARTICULAR NON PENALISING CONDITIONS....................................................................... 17 5.2. PACKAGES CONSIDERED INDIVIDUALLY.............................................................................. 17
- 5. 2. 1. INDIVIDUAL PACKAGE UNDER NORMAL TRANSPORT CONDITIONS (NTC)......... 17
- 5. 2. 2. INDIVIDUAL PACKAGE UNDER ACCIDENT TRANSPORT CONDITIONS (ATC)...... 18 5.3. ARRAY OF PACKAGES.............................................................................................................. 19 5.3. 1. ARRAY OF PACKAGES UNDER NORMAL TRANSPORT CONDITIONS (NTC)......... 19
- 5. 3.2. ARRAY OF PACKAGES UNDER ACCIDENT TRANSPORT CONDITIONS (ATC)...... 19 5.4. ANALYSIS OF THE IMPACT OF THE PELLET OR PELLET DEBRIS EJECTION...................20 5.4.1. CASE OF THE PELLET SPHERE OR PELLET CHIPS................................................. 20 5.4.2. CASE OF ASSEMBLY REMODERATION..................................................................... 21 5.5. ANALYSIS OF THE IMPACT OF THE NEUTRON CAVITY BEING OFF-CENTRE RELATIVE TO THE SHELL........................................................................................................................... 21
- 6. CONCLUSION..................................................................................................................... 23
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REFERENCES
Note : titles translated for information only
[1] 229 K 0102 : Conteneur pour 2 assemblages de combustible UO2 Modele 12 pieds - 17x17 "12 pieds" Ensemble colis Caracteristiques liees a la surete
[Container for 2 U02 fuel assemblies 12-leg model - 17x17 "12 legs" Package assembly Safety-related characteristics J (2] 229 K 0202 : Conteneur pour 2 assemblages de combustible UO2 Modele 12 pieds - 15x15 Ensemble colis
[Container for 2 U02 fuel assemblies 12-leg model-15x15 Package assembly Safety-related characteristics]
[3] 229 K 0402 : Conteneur pour 2 assemblages de combustible UO2 Modele 14 pieds-17x17 (type XL et XLR)
Ensemble colis Caracteristiques liees a la sOrete
[Container for 2 U02 fuel assemblies 14-leg model - 17x17 (type XL and XLR)
Package assembly Safety-related characteristics]
[4] 229 K 0502: Conteneur pour 2 assemblages de combustible UO2 Modele 14 pieds - 16x16 et 18x18 Ensemble colis Caracteristiques liees a la sOrete
[Container for 2 U02 fuel assemblies 14-leg model - 16x16 and 18x18 Package assembly Safety-related characteristics]
[5] TRANSNUCLEAIRE 10373-B-1 rev 3: Note de synthese sur la caracterisation de la resine FS69
[Note summarising the characterisation of resin FS69]
[6] IPSN/DSMR/96-393 du 22/08/96 : Elements necessaires a !'expertise des etudes des etudes de criticite des emballages charges de matieres fissiles.
[Information required to assess the criticality studies of the packages loaded with fissile materials.]
[7] TS-R-1 (ST1, revisee) : Reglement de transport des matieres radioactives Edition de 1996 (revisee)
Prescriptions Collection Normes de sOrete de l'AIEA
[Rules for the transport of radioactive materials 1996 issue (revised)
Regulations IAEA collection of safety standards]
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(8] TS-G-1.1 (ST-2) : Advisory Material for the IAEA Regulations for the Safe Transport of Radioactive Material Safety Guide IAEA Safety Standards Series
[9] TFJN DC 1403: Conteneurs FCC3 et FCC4.
Syntheses des Etudes de criticite. Assemblages 15x15 et 17x17 Assemblages 17x17XL, 17x17XLR, 16x16 et 18x18.
[FCC3 and FCC4 containers. Summaries of the criticality studies. 15x15 and 17x17 assemblies 17x17XL, 17x17XLR, 16x16 and 18x18 assemblies.]
[1 OJ TFJN DC 1671 : Conteneurs FCC3 version 2.
Transport des assemblages 14x14 "8 pieds" et 14x14 "10 pieds" Etudes de criticite.
[FCC3 containers version 2.
Transport of the 14x14 "8 legs" and 14x14 "10 legs " assemblies Criticality studies.]
[11] D-FDE-07-03536 : CRISTAL V1.1 Mise en production [Production startup]
[12] FF DC 00561 rev. 4.0: Colis de transport de combustibles UO2 neufs Determination des incertitudes a appliquer aux etudes de criticite realisees avec CRISTAL.
[Fresh UO2 fuel transport package Determination of uncertainties to be applied to the criticality studies using CRISTAL.]
[13] FFDC 04751 : Renewal of the FCC3 and FCC4 packages certificates - Assumptions for the fuel assemblies and single rods characteristics
[14] 229 K 0602: Container for 2 fuel U02 assemblies Model 14 legs - 17x17 (standard XL, XLR and EPR')
Package unit Characteristics related to safety
[Container for 2 U02 fuel assemblies 14-leg model-17x17 (standard XL, XLR and EPR')
Package unit Safety-related characteristics]
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LIST OF TABLES
Table 1: Characteristics of the packages........................................................................................ 25 Table 2: Characteristics of the assemblies..................................................................................... 26 Table 3: Composition of the resin................................................................................................... 27
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LIST OF FIGURES
Figure 1: Cross - section XYof package under NTC 15x15, 16x16, 17x17, 17x17 XL,17x17 EPR and 18x18........................................................................................................................ 28 Figure 2 : Cross-section XY of package Configuration of the shell under NTC and ATC................. 29 Figure 3: Cross - section XY of package under ATC 15x15, 16x16, 17x17, 17x17 XL, 17x17 EPR and 18x18........................................................................................................................ 30 Figure 4: Half cross-section XY at pad detail of the neutron cavity under NTC.............................. 31 Figure 5 : Cross - section XZ of the neutron cavity under NTC with Y=112 (15x15, 17x 17 & 17x 17 XL and EPR ) and Y=120 (16x16 & 18x18)....................................................................... 32 Figure 6 : Cross-section XZ of the package Shell / neutron ca v ity interface under NTC and ATC..... 33 Figure 7: Cross - section XZ of the package under ATC Position of fissile sections......................... 34 Figure 8: Block diagram showing the grouping of cavities.............................................................. 35 Figure 9 : FCC4v1 cavities off-cent re in an infinite array................................................................. 36 Figure 10: FCC4v2 cavities off-centre in a 3x4x1 array.................................................................... 37
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- 1. INTRODUCTION Revision B of this note takes into account the changed characteristics of the fuel assemblies as defined in note [13], including the addition of the 17x17 EPR assemblies, and the changed width of the pad recesses on FCC4v1 in order to allow the transport of 17x17 EPR assemblies.
New UO2 fuel assemblies are transported out in packages known as :
FCC3 v 1 for the 15x15 and 17x17 assemblies, FCC4 v 1.a for the 17x17 XL assemblies, FCC4 v 1.b for the 17x17 XL and EPR assemblies, FCC4 v 2 for the 16x16 and 18x18 assemblies.
These packages are classified as "Type II Fissile Industrial Packages" according to the recommendations of the IAEA [7] and, as such, their design must guarantee subcriticality for an individual package and for an array of packages under Normal Transport Conditions (NTC) and Accident Transport Conditions (ATC), in compliance with IAEA guidelines [7].
The design of FCC packages consists in confining the fuel in a volume having a known cross-section, as small as possible, and ensuring that this geometry is maintained subsequent to regulatory tests.
These tests are performed under Accident Transport Conditions (ATC), which determine dimensions, namely:
9 m drop, 1 m drop onto a 150 mm dia. spike,
- thermal test at 800 °C for 30 minutes.
At the design stage, criticality studies [9] were c~OLLO 1 - MORET Ill calculation codes, while observing a subcriticality margin of----for an array of packages.
Changing over to the CRISTAL calculation tool and taking IAEA recommendations [7] and [8], into account lead us to revise the initial studies for the regulatory configurat ions. The sensitivity studies carried out in study [9] have not been repeated; their conclusions remain applicable and are restated in §5.1.
For the revision B of this note, we only calculate in ATC those configurations when the hull is crushed in a realistic manner and expansion of the assemblies over one third of its height (bounding value resulting from the regulatory tests). Only the results of these calculation are given from version B onwards.
The purpose of this study is to verify that the safety-criticality criterion of Keff s; 0.95 is observed, including all uncertainties, for the transport of FCC containers under NTC and ATC in accordance with IAEA recommendations [7].
Document [12] defines the uncertainties to be applied with regard to the use of the CRISTAL form for the transport of fresh UO2 fuel.
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- 2. DEFINITIONS AND CONVENTIONS
To make this report clearer and easier to understand, a list of the definitions and conventions is provided below :
FCC3y1; package for fuel assemblies or non-assembled rods transported in a - nominal size cavity. Version 1 breaks down into the following variants:
FCC3v1.a : package for the 17x17 or 15x15 17x17 type fuel assemblies without cluster FCC3v1.b: package for the 17x17 or 15x15 17x17 type fuel assemblies with cluster FCC3v1.c: package for the non-assembled rods in FCC3 rod boxes
FCC3y2: package for fuel assemblies transported in a -nominal size cavity. That is to say for 8-leg 14x14 assemblies and 10-leg 14x14 assemblies.
FCC4v1: package for the assemblies or non-assembled rods transported in a nom inal size cavity. Version 1 breaks down into the following variants:
FCC4v1.a : package for the 17x17 type fuel assemblies without cluster apart from the EPR type 17x17 assemblies FCC4v1.b: package for the 17x17 type fuel assemblies with cluster apart from the EPR type 17x17 assemblies FCC4v1.c: package for rods not assembled in FCC4 rod boxes
FCC4v2: package for fuel assemblies transported in a - nominal size cavity. That is to say assemblies of the 16x16 or 18x18 types.
Frame:
Fabricated structure with an inverted T-shaped cross-section used to support the assemblies during transport, this sheet-metal structure consists of a vertical core and a lower box section filled with neutron absorbing resin.
Doors:
Fabricated assembly with an L-shaped cross-section hinged on the frame. This sheet-metal structure is filled with neutron absorbing resin. On the inner faces of these doors and facing the assembly grids, there are recesses in which the metal pads used to hold the assemblies during transport, by clamping onto the grids, are located.
Neutron cav;tv;
Overall volume delimited by the metal sheets on the inside of the doors, the frame and the head and foot plates.
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co-ordjnate system;
The OX Y Z three-dimensioned reference system is used (Figure 4 and Figure 5), where:
origin 0: is a point at the intersection of the plane of vertical symmetry of the neutron cavity (middle of the core), of the plane of longitudinal symmetry and of the plane that passes along the lower face of the metal sheet of the frame.
axis OX : transverse axis, merging with the lower horizontal face of the metal sheet of the frame,
- axis OY : vertical axis passing along the plane of vertical symmetry of the neutron cavity,
- axis OZ: longitudinal axis.
fissile sectjoff
Square cross-section (plane XY) representing the fuel assembly with a chemical medium resulting from a calculation using APOLLO 2 in which the non-fissile components, other than the fuel rod cladding, are equated with water.
Nominal assembly:
Assembly of which the fissile section is as manufactured.
Expanded assembly;
Assembly, the fissile section of which is calculated on the basis of the cross-section of the neutron cavity.
fuel stage;
Portion of an assembly between 2 grids.
Moderator radius;
Radius of the moderator portion of an APOLLO 2 fissile cell, represent ing the fissile medium. The moderator radius is calculated as follows:
Qiffereotial floodjna;
Accident configuration in which only the neutron cavity is immersed in water (density= 1 ).
Total reflectjon;
Conditions at the limits (boundary conditions) applied to a computational 3D geometric configuration and which prevents any neutron leakage.
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Voitocro roist;
The water density is varying and remains the same in the fissile section, the neutron cavity and inside the package.
Heterogeneous mjst;
The water density is equal to 1 g/cm3 in the fissile section and the neutron cavity, all the other free volumes have a variable water density.
Three-dimensional arrangement of several packages. The array is surrounded by a 20-cm water reflector (articles 681 and 682 of [7]). The array is referred to as "array Xx Y x Z" where:
- X: is the number of packages in direction X,
- Y: is the number of packages in direction Y,
- Z : is the number of packages in direction Z.
Infinite array:
X Y Z array where X, Y and Z are infinite. This array is modelled by applying the conditions for total reflection to each of the faces of the package instead of the 20-cm reflector applied to the periphery of an array of finite dimensions.
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- 3. CODES AND QUALIFICATION Computations in version B of the present note are carried out using:
- CIGALES version v3.1
- APOLLO 2 version 2.5 MORET 4 version 4.8.3
These three codes are part of CRISTAL V1.1 calculation tools and their use is validated [11].
A brief description of these codes is restated in report [12].
Use of the CRISTAL calculation tools is qualified for the present study by applying an uncertainty of
- to the Keff calculated according to report [12]. In the present report, all the reactivity values given take this uncertainty into account.
The results obtained with version v1. 1, based on the same input data (ATC package array), are consistent with those obtained with version v0.2 used for the computations in version A of the note.
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- 4. COMPUTATION AND MODELLING HYPOTHESES
4.1. Characteristics of the package The package consists of a cylindrical steel shell with a horizontal ax is, housing internal equipment comprising the following main components:
an inverted T-shaped frame for receiving the assemblies, said "T" being filled with neutron-absorbing resin, 2 L-shaped doors filled with neutron-absorbing resin, said doors pivoting on axes linked to the frame and enclosing the assemblies, 2 steel end plates: a two-part head plate and a foot plate, which serve to close the cavities.
When assembled, the above components form two identical neutron cavities, in which the assemblies to be transported are placed. The neutron absorbing resin located inside the doors and the frame lim its the interactions between the assemblies, whether they are from the same package or from different packages, furthermore, the resin provides thermal protection for the assemblies during the thermal test.
The main characteristics of the package, taken from drawings [1], [2], [3], [4] and [14], are restated in Table 1.
- 4. 1. 1. Package under Normal Transport Conditions (NTC)
Under normal conditions, the package is cylindrical (see Figure 1) and is modelled as follows :
- a cylindrical shell, the internal length of which is determined on the basis of the length of the neutron cavity, the thickness of the end plates and the longitudinal clearances between the shell and the neutron cavity taken to be identical at each end and determined on the basis of the minimum clearance between the end late and the shell the dam er is re laced with water or empty space) as indicated in Figure 6.
a neutron cavity closed at each end by an end plate (head or foot plate) ; the internal length of the cavity is determined on the basis of the length of the fissile column and the minimum inert height of one end of the assembly (see Table 2) as follows :
- for 15x15, 17x17, 17x17 XL, 17x17 EPR, 16x16 and 18x18 desi ads for retainin the rids are located
- attachment of the pads in the resin of the doors is modelled by
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- the axial position of the pad recesses is modelled symmetrically at the average spacing of the grids, as indicated in Figure 5 (15x15, 17x17, 17x17 XL, 17x17 EPR, 16x16 and 18x18). The pad on the upper grid has not been modelled, since it does not face the fissile column.
The d imensions take into account for modelling purposes are given in Figure 1, Figure 3, Figure 4, Figure 5 and Figure 6.
- 4. 1.2. Package under Accident Transport Conditions (A TC)
The modelling adopted integrates the results of expert appraisal subsequent to the mechanical tests and the thermal study, i.e.:
Therefore, under accident conditions, the package is modelled (see Figure 3) with a box-shaped steel shell, the dimensions of which are calculated so that it is located symmetrically about the neutron cavity so as to have identical neutronic interactions between the packages, irrespective of the faces considered. The longitudinal clearance between the shell and the neutron cavity is determined on the basis of the minimum thickness of the damper after the 9 m vertical drop, as indicated in Fi ure 6.
In revIsIon B, we only studied the rectangu~ee Figure 2) which corresponds to a relatively realistic crushing of in width and -- in height. Th is leads to shell /cavity clearances of:
o a-lateral sided and-vertical sided for the FCC3v1 (15x15 and 17x17 design) and FCC4v1 (17x17 XL and EPR design) packages,
o a - lateral sided and a -vertical sided for the FCC4v2 (16x16 and 18x18 design). The shell/neutronic cavity distances are modelled symmetrical ly,
- the neutron cavity remains dimensionally unchanged relative to the normal conditions, but the composition of the resin is modified as indicated in §4.2.2.
4.2. Characteristics of the neutron absorbing resin It is a polyester resin with a loading
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4.2.1. Resin under Normal Transport Conditions (NTC)
The characteristics of the resin originate from [5]; the values taken into account in the modelling are restated in Table 3.
4.2.2. Resin under Accident Transport Conditions (A TC)
After the thermal test (800°C for 30 mn), the characteristics of the resin are modified.
Report [5] gives envelope values to be taken into account in the criticality studies; the modelling adopted is as follows :
4.3. Characteristics of the assemblies The characteristics of the assemblies are restated in Table 2. Only the fissile height of the rods is taken into account in the modelling. The nozzles, the grids, the guide tubes and the rod ends (plugs, plenum, shim for the 17x17 EPR, 16x16 and the 18x18) are replaced by water.
The assemblies are modelled complete with all rods identical, possible specific rods (rods treated with gadolinium, depleted uranium rods, stainless steel rods, zirconium alloy rods) are replaced by UO2 rods.
For the computation of moderation, the rods are assumed to be arranged uniformly over the entire fissile section.
The density of the pellets is taken to be equal to 100 % of the theoretical density, i.e. 10.96 g /cm 3
- The addition into the pellets of capturing compounds (chromium oxide for instance) in quanti ties close to those of the impurities is ignored in the criticality study as their presence reduces the reactivity of the assemblies.
. This modelling is conservative, as demonstrated in report [9], and complies with the guidelines [6].
The material taken into account for the cladding is Zirconium, a material that is "neutronically transparent" and is therefore conservative, from the safety point of view, relative to the various cladding materia ls containing capturing materials.
Enrichment equal to :
5% 235 U for 15x15 and 17x17 assemblies,
- 4.5% 235U for 16x16 and 18x18 assemblies.
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4.3.1. Assembly under Normal Transport Conditions (NTC)
The assembly is modelled as follows:
- the cross-section of the assembly is maintained, the fissile section is the nominal cross-section of the assembly,
- the assembly is in contact with the frame, which leaves a - clearance relative to the doors,
- the fissile portion of the assembly is axially centred in the neutron cavity.
4.3.2. Assembly under Accident Transport Conditions (A TC)
The modelling adopted integrates the results of expert appraisal subsequent to the mechanical tests and the thermal study, i.e.:
- the cross-section of the neutron cavity remains unchanged,
- the assembly has a compacted cross-section,
- there may be a slight increase in the cross-section of the assembly on the end fuel stage, at most, in the event of an axial drop.
On account of the above observations, the modelling adopted for verifying the safety /criticality criteria is as follows:
- the cross-section of the assembly is expanded to the cross-section of the neutron cavity over a third of its height and remains intact over the remaining two-thirds,
- the fissile portion of the assembly is axially centred in the neutron cavity.
The compacting of the cross-section is not taken into account since it tends to reduce the reactivity of the assembly.
The configuration in which a certain number of rods slip axially has not been considered as a penalising situation, since it does not have any influence on the subcriticality of the packages, as demonstrated in study [9].
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- 5. METHODOLOGY AND RESULTS Computation is performed, for each design, for an individual package and a plurality of packages in normal transport configurations (NTC) and accident transport configurations (ATC). In accident configurations, two variants are studied:
differential drainage,
- water-filled package.
5.1. Particular non penalising conditions During the criticality studies performed at the design stage [9], we studied the impact of different parameters and particular configurations. We demonstrated the absence of any impact and the non-penalising nature of the following particular configurations:
mist conditions: no reactivity peak occurs,
pellets of minimum diameter : this case is covered by pellets of maximum diameter,
impact of the reinforcing ribs on doors: no significant impact on the reactivity in comparison to the calculations performed without ribs; therefore, the ribs are not modelled,
impact of tolerances and geometric shapes : the tolerances of the sheet metal, rounded edges and possible shrinkage during the pouring of the resin do not have a significant impact and therefore shall not be taken into account,
partial differential flooding: the case of partially immersed assemblies is covered by the case of fully immersed assemblies,
partial slipping of the rods: this configuration does not have a significant impact on the reactivity of the packages.
Since the above configurations are not penalising, they are not studied further in this report.
5.2. Packages considered individually The individual package, whether damaged or not, must be subcritical with total reflection by a 20 cm layer of water around the containment envelope (articles 677 and 678 of [7]).
The subcriticality margin to be observed for the individual package is 5000 pcm. The safety /criticality criterion to satisfy is: Keff s; 0.95 (appendix Vll.38 of [81), including all uncertainties.
5.2.1. Individual package under Normal Transport Conditions (NTC)
The configuration studied is: the undamaged package (cylindrical modelling) filled wit h water and surrounded by a reflector consisting of 20 cm of water; modelling of the package is described in §4, Figure 1,
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Figure 4 and Figure 5.
The results of the calculations, provided in the table below, show that the undamaged individual package amply complies with the safety /criticality criterion of Kett s; 0.95.
PROPRIETARY TABLE
5.2.2. Individual package under Accident Transport Conditions (A TC)
The configuration studied is : the damaged package (rectangular modelling) surrounded by a reflector consisting of 20 cm of water ; modelling of the package is described in §4.
The space between the cavity and the shell is:
- either filled with water: package in water-filled configuration,
- or empty : package in differential drainage configuration.
The assembly is studied in the configuration described in §4.3.2.
The results of the calculations, provided in the table below, show that the individual damaged package amply complies with the safety/criticality criterion of Kett s; 0.95, whether in the differential flooding or water-filled package configuration, even when penalizing hypotheses on the expansion of the rod array over a third of the height of the fissile column and on the dimensions of the shell are adopted.
PROPRIETARY TABLE
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5.3. Array of packages An array of packages must remain subcritical, with the array of packages surrounded on all sides by a 20-cm layer of water (articles 681 and 682 of [7]).
The subcriticality margin to be observed for an array of packages is 5000 pcm. The safety/criticality criterion to satisfy is: Keff :5 0.95 (appendix Vll.38 of [8]), including all uncertainties.
5.3.1. Array of packages under Norma/Transport Conditions (NTC)
If N is the number of packages to be transported, 5N undamaged packages must be subcritical without there being anything between the packages (article 681 of [7]).
The configuration studied is an infinite array of undamaged packages (cylindrical modelling), the modelling of the package is described in §4. Conditions of total reflection are applied to all the faces of the package. The space between the cavity and the shell is:
either full of water: package in water-filled configuration,
or empty : package in differential flooding configuration.
The results of the calculations, provided in the table below, show that an infinite array of undamaged packages amply complies with the safety/ criticality criterion of Keff :5 0.95, even in the differential flooding configuration, which adds a penalty of between depending on the type of assemblies.
The number N is therefore infinite under normal transport conditions.
PROPRIETARY TABLE
5.3.2. Array of packages under Accident Transport Conditions (A TC)
If N is the number of packages to be transported, 2N damaged packages must be subcritical, with moderation between the packages (article 681 of [71).
The configuration studied is: an array of damaged packages (rectangular modelling) with no space between the packages and a reflector consisting of 20 cm of water on the periphery of the array; modelling of the package is described in §4; In this configuration, two variants are studied :
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- the inside of the shell is empty and the fuel is moderated: this is the case of differential drainage,
- the inside of the shell is filled with water and the fuel is moderated.
The results of the calculations, provided in the table below, show that an array of damaged packages complies with the safety/criticality criterion of Keff ::;; 0.95 with a shell crushed to a realistic extent
The number N depends on the type of assembly transported under accident transport conditions.
The differential drainage configuration is a highly penalising configuration that generates an increase in reactivity relative to the water-filled package. This increase in reactivity varies from -*
depending on the type of assembly.
PROPRIETARY TABLE
5.4. Analysis of the impact of the pellet or pellet debris ejection One eventual consequence of the accidental transport conditions (drop, fire, etc.) for the package could be the embrittlement of the rod cladding. This could lead to its rupture and consequently ejection of the pellets or remains of pellets.
This section demonstrates that safety and criticality are not jeopardised even in implausible cases of this type.
Two approaches are used to determine the maximum number of rods that may rupture with its pellets or remains of pellets all escaping from the rods:
- The pellets or remains of pellets gather in a free space within the cavity,
- There is remoderation of the assembly due to its loss of fissile material.
5.4.1. Case of the pellet sphere or pellet chips The criticality standards give for any medium (pellet chips, pellet bounding medium) in water a minimal mass of 25 kg of U02 with 5% maximum enrichment in 235 U.
According to the design of the assembly this value corresponds to a rupture of
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5.4.2. Case of assembly remoderation PWR U02 assemblies are undermoderated by design. Any increase in the moderation by the removal of rods will lead to an increase in the reactivity of this assembly up to an optimum moderation value.
Analyses have been performed on several assembly designs (15x15, 16x16, 17x17 and 17x17 XL) in order to determine the maximum number of rods that could rupture while still complying with the safety-criticality criterion.
In order to identify the trend of increasing reactivity, a small standard deviation (20 pcm) was applied in the Monte Carlo computations.
The figure below shows the results obtained:
PROPRIETARY FIGURE
Therefore, it can be said that remoderation of the assembly is bounding with respect to the cavity sphere although it is the safe mass of the debris that is taken into account in the latter case.
The rupture of 7 rods with complete loss of fissile material satisfies the safety-cr iticality criterion for the 17x17 XL and 17x17 EPR design. For the other designs, a bounding value of 10 ruptured rods still complies with the safety-criticality criterion.
5.5. Analysis of the impact of the neutron cavity being off-centre relative to the shell Although this analysis was not repeated for version B, the conclusions are still valid.
In order to assess the impact of the cavity being off-centre relative to the she ll, due to the neutron cavity becoming detached subsequent to the regulatory tests (see §4.1.2), we compared the following three configurations (see Figure 8):
Case 1: cavities centred in the shell, i.e. the normal configuration,
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Case 2 : cavities laterally centred in the shell, but vertically off-centre, therefore forming groups of two, Case 3: cavities laterally and vertically off-centre in the shell, therefore forming groups of four.
For each case, we studied several sizes of shell so as to vary the clearances and, on account of the two possible array sizes, we selected two types of array:
infinite array of FCC4v1 packages under ATC, in differential floodin 17x17 XL assemblies enriched to 5 % with 235 U and expanded
3x4x1 array of FCC4v2 packages under ATC, in differential flooding configurat ion, loaded with 16x16 assemblies enriched to 4.5 % with 235 U and expanded
The results of the calculations (see Figure 9 and Figure 10) show that the cavity being off-centre relative to the shell does not have a significant impact on the reactivity of the array of packages, whether array size is small or infinite.
The aim of these configurations is to assess sensitivity to cavities being off-centre; the Keff ~ 0.95 safety / criticality criterion is exceeded due to:
either a number N of permissible packages greater than that determined for transport authorisation,
or more penalising crushing of the shell than obtained after the regulatory tests.
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- 6. CONCLUSION In this study, we have verified that the safety/criticality criteria of FCC3 version 1, FCC4 version 1 and FCC4 version 2 packages are met for the transport of fresh UO2 fuel assemblies :
15x15 assemblies enriched to 5% with 235U transported in FCC3v1,
17x17 assemblies enriched to 5% with 235U transported in FCC3v1,
17x17 XL assemblies enriched to 5% with 235U transported in FCC4v1.a and FCC4v1.b,
17x17 EPR assemblies enriched to 5% with 235U transported in FCC4v1.b,
16x16 assemblies enriched to 4.5% with 235U transported in FCC4v2,
18x18 assemblies enriched to 4.5% with 235U transported in FCC4v2
the main characteristics of which are as follows:
- density 10.96 g/cm3 (100% of the theoretical density),
- full assembly: the missing UO2 rods must be replaced with rods treated with gadolinium, rods containing depleted uranium or a metal material, or solid rods made of a metal material (materials such as graphite and beryllium are strictly prohibited) so as not to increase moderation of the assemblies,
- the uranium can originate from reprocessing, since the 234 U and the 236U present in RRU are neutron poisons that reduce the reactivity of the assemblies,
- the pellets may contain capturing compounds (chromium oxide for instance) in a quantity that is close to those of the impurities, and their positive influence in term of margins are ignored.
The packages can only contain one or two assemblies of the same design and maximum enrichment:
5% with 235U for 15x15, 17x17, 17x17 XL and 17x17 EPR assemblies,
- 4.5% with 235U for 16x16 and 18x 18 assemblies.
The number N of packages, as defined in articles 681 and 682 of [7], that can be transported from the point of view of safety /criticality, serves to determine the SAFETY / CRITICALITY INDEX (SCI), as defined in article 528 of [7], i.e. :
ISC = 50/ (min. (NNrc; NArc))
The results are restated in the table below for the various assembly designs :
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Number of fuel Cross-section 1ber N of packages in array Assembly - % 235U rods per Package of the cavity ISC assembly (mm xmm) NTC ATC
15x15 - 5% 235 U 204 infinite 80 0.63 FCC3 v1 17x17 - 5% 235 U 264 infinite 80 0.63
17x17 XL - 5% 235 U 264 FCC4 v1.a infinite 80 0.63 FCC4 v1.b
17x17 EPR - 5% 235 U 265 FCC4 v1.b infinite 80 0.63
16x16 - 4.5% 235 U 236 infinite 6 8.33 FCC4 v2 18x18. 4.5% 235 U 300 infinite 6 8.33
The above table takes the possibility of the ejection of pellets and the re-moderat ion of the assemblies into consideration. From the point of view of criticality, the number of fuel rods per assembly that can eject all their pellets is:
10 for 16x16 and 18x18 assemblies transported in FCC4v2 packages,
10 for 15x15 and 17x17 assemblies transported in FCC3v1 packages,
7 for 17x17 XL assemblies transported in FCC4v1.a and v1.b packages,
7 for 17x17 EPR assemblies transported in FCC4v1.b packages.
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Table 1: Characteristics of the packages
PROPRIETARY TABLE
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-~,,,
- 0
~
E Cl)
,,, z
,,, 0 ca Cl) en
.c w 0:::
.._...J LU
-0 ! >
.:; 0 0:::
,,, I-<(
- .:::: Cl) !Li LU i
-0 o!: o2 ca a.
... a.. 0
.c 0::: ca ~
u a.. a. z I 0
z N
G)
- 0 (IJ I-
NOIS~3A A~'vl31~dO~d-NON Framatome - Fuel This document is subject to the restrictions set forth on the first or ti tle page No FF/ DC/00817 E0 Rev. 4.0 NON-PROPRIETARY VERSION I STR - Study Report framatome Han dling : Restric ted Fra matom e Pag e 27/37
Table 3: Composition of the resin
PROPRIETARY TABLE
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Figure 1: Cross-section XV of package under NTC 15x15, 16x16, 17x17, 17x17 XL,17x17 EPR and 18x18
PROPRIETARY FIGURE
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Figure 2: Cross-section XY of package Configuration of the shell under NTC and ATC
PROPRIETARY FIGURE
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Figure 3: Cross-section XV of package under ATC 15x15, 16x16, 17x17, 17x17 XL,17x17 EPR and 18x18
PROPRIETARY FIGURE
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Figure 4: Half cross-section XY at pad detail of the neutron cavity under NTC
PROPRIETARY FIGURE
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Figure 5: Cross-section XZ of the neutron cavity under NTC with Y=112 (15x15, 17x17 & 17x17 XL and EPR) and Y=120 (16x16 & 18x18)
PROPRIETARY FIGURE
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Figure 6: Cross-section XZ of the package Shell/neutron cavity interface under NTC and ATC
PROPRIETARY FIGURE
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Figure 7: Cross-section XZ of the package under ATC Position of fissile sections
PROPRIETARY FIGURE
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Figure 8: Block diagram showing the grouping of cavities
PROPRIETARY FIGURE
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Figure 9: FCC4v1 cavities off-centre in an infinite array
PROPRIETARY FIGURE
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Figure 10: FCC4v2 cavities off-centre in a 3x4x1 array
PROPRIETARY FIGURE
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