ML22271A798

E-61283 Enclosure 4, 013b1 Appendix 2.5-2, Document No. FFDC01046E E0, Non-Proprietary, Safety/Criticality Study of Fcc3 and Fcc4 Containers Transport of Fuel Rods in Boxes (Public)

ML22271A798
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Site:	Orano USA
Issue date:	08/03/2022
From:	Boyle R, Shaw D Framatome
To:	Division of Fuel Management
Garcia-Santos N
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A33010, EPID L-2022-DOT-0007
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Text

IDENTIFICATION REVISION

I FF/DC/01046 E0 11 3.0 I Framatome framat ome Fuel

TOTAL NUMBER OF PAGES : 32

SAFETY/CRITICALITY STUDY OF FCC3 AND FCC4 CONTAINERS TRANSPORT OF FUEL RODS IN BOXES

I NON-PROPRIETARY VERSION I

ADDITIONAL INFORMATION:

PROJECT DISTRIBUTION TO PURPOSE OF DISTRIBUTION

HANDLING Restri cted Framatome For act io n For act io n Fo r info rmatio n CATEGORY STR -Study Re po rt

STATUS BPE

ROLES NAMES DATES ORGANIZATIONS SIGNATURES AUTH OR RE VIEWER APPROVER

Class i fica tion Ex12ort AL: 0 E001 ECCN : N RELEASE DATA : Les marchandises portant la designa tion "AL tneQal W sont soumlses a la reglemen taUon europeenne ou allemande en matiere de contrOle des exportatio ns au sein ou hors de l 'UE. Les marchandises portant la d8slgnatlon HECCN 1nega1 N" sont soumlses a 1a reg1ementat1on amer~ lne. Les marchandlses portant 1es d8signations "AL:W ou "ECCN:N" peuvent, salon la destination ou !'utilisation fina les du produit, 8galemen t Atre soumlses a autorlsatlon.

Ex12ort classification A L : 0 E001 ECCN : N Goods labeled with *AL not equal to W are subject to European or Gennan export authorizat ion when being exported within or out of the EU. Goods labeled with *ECCN not equal to N" are subject to US reexport authortzatlon. Even without a label. orwlth label "AL: N" or "ECCN : W. authorization may be required due to the final whereabo uts and purpose for which the goods are to be used.

France: y Ex12ortkennzeichnung A L : 0E001 ECCN:N CHANGE CONTROL RECORDS: Die mil "AL unglelch N" gekennzelchne ten GUier unterllegen bel der Ausfuhr aus der EU bzw.

This d oc ument, w he n re vi sed, mu st be U SA: N innergemeinschaftlichen Verbringung der europ.3ischen bzw. deutschen Ausfuhrgenehmigungspflicht. Die mit reviewed o r approve d by following regions: Ge rman y : N "ECCN unglelch W gekennzelchneten Guter unterllegen der US-Reexportgenehmlgungspfllcht. Auch ohne Kennzelchen. bzw. bei Kennzelchen "AL: W oder"ECCN : W, kann slch elne Genehmlgungspfllcht, unteranderem durch den Endvert::i1eib und Verwendunqszweck der GUier, erqeben.

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REVISIONS

REVISION DATE EXPLANATORY NOTES

A 28/ 05/2004 First Issue

B 28/ 11 /2008 Note FFDC04751 taken into account (French - modification of cladding characteristics ([12])

version) - 17x17 EPR added ([12])

26/ 06/2009 - change from Cristal v0.2 to v1.1 (English version)

3.0 See 1st page Removal of the §5.6 (Transport of a small quantity of rods without wedging) -

release date Modification of the §6 Editorial Corrections

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TABLE OF CONTENTS

1. INTRODUCTION................................................................................................................... 8

2. DEFINITIONS AND CONVENTIONS..................................................................................... 9

3. CODES AND QUALIFICATION........................................................................................... 11

4. COMPUTATIONAND MODELLING HYPOTHESES........................................................... 12 4. 1. CHARACTERISTICS OF THE PACKAGE.................................................................................. 12 4.1.1. PACKAGE UNDER NORMAL TRANSPORT CONDITIONS (NTC).............................. 12

4. 1.2. PACKAGE UNDER ACCIDENT TRANSPORT CONDITIONS (ATC)........................... 12 4.2. CHARACTERISTICS OF THE NEUTRON ABSORBING RESIN............................................... 13

4. 2.1. RESIN UNDER NORMAL TRANSPORT CONDITIONS (NTC)..................................... 13

4. 2. 2. RESIN UNDER ACCIDENT TRANSPORT CONDITIONS (A TC).................................. 13 4.3. CHARACTERISTICS OF THE BOXES....................................................................................... 13 4.4. CHARACTERISTICS OF THE FISSILE MEDIA.......................................................................... 14

5. METHODOLOGY AND RESULTS...................................................................................... 15 5. 1. PARTICULAR NON PENALISING CONDITIONS....................................................................... 15 5.2. OPTIMUM MODERATION RATIO.............................................................................................. 15 5.3. PACKAGES CONSIDERED INDIVIDUALLY.............................................................................. 16 5.3. 1. INDIVIDUAL PACKAGE UNDER NORMAL TRANSPORT CONDITIONS (NTC)......... 16

5. 3. 2. INDIVIDUAL PACKAGE UNDER ACCIDENT TRANSPORT CONDITIONS (ATC)...... 16 5.4. AN ARRAY OF PACKAGES........................................................................................................ 17 5.4.1. ARRAY OF PACKAGES UNDER NORMAL TRANSPORT CONDITIONS (NTC)........ 17 5.4.2. ARRAY OF PACKAGES UNDER ACCIDENT TRANSPORT CONDITIONS (ATC)...... 18 5.4.3. IMPACT OF ROD SLIPPAGE........................................................................................ 19 5.4.4. IMPACT OF THE EJECTION OF PELLETS.................................................................. 19 5.5. TRANSPORT OF UO 2-GD 2O3 RODS......................................................................................... 19

6. CONCLUSION..................................................................................................................... 20

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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

[229 K 0102 :Container for 2 UO2 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

[229 K 0202 :Container for 2 UO2 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

[229 K 0402 :Container for 2 UO2 fuel assemblies 14-leg model - 17x17 (type XL and XLR)

Package assembly Safety-related characteristics]

[4] FF DC 04934 Description des boites a crayons de conteneur FCC

[FF DC 04934 : Description of FCC container rod boxes]

[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 surete de l'AIEA

[Rules for the transport of radioactive materials 1996 issue (revised)

Regulations IAEA collection of safety standards]

[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] FF DC 00817 : Etude de sarete-Criticite Conteneurs FCC3 et FCC4.

Assemblages 15x15 et 17x17 Assemblages 17x17XL, 17x17EPR, 16x16 et 18x18.

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{FF DC 00817 : Safety-criticality study FCC3 and FCC4 containers.

15x15 and 17x17 assemblies 17x17XL, 17x17EPR, 16x16 and 18x18 assemblies.]

[10] D-FDE-07-03536: CRISTAL V1.1 Mise en production [Production start-up}

[11] 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.

[FF DC 00561 rev. 4.0 : Fresh UO2 fuel transport package Determination of uncertainties to be applied to the criticality studies using CRISTAL.]

[12] FFDC 04751 : Renewal of the FCC3 and FCC4 packages certificates -Assumptions for the fuel assemblies and single rods characteristics

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LIST OF TABLES

Table 1: Characteristics of the packages........................................................................................ 21 Table 2 : Characteristics of the rods................................................................................................ 22 Table 3 : Composition of the resin................................................................................................... 23

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LIST OF FIGURES

Figure 1: Cross-section XY of package under NTC FCC3v1 and FCC4v1...................................... 24 Figure 2: Cross-section XY of the package under ATC FCC3v1 and FCC4v1................................ 25 Figure 3: Half cross-section XY at pad, detail of the neutron cavity under NTC.............................. 26 Figure 4: Cross-section XZ of the neutron cavity under NTC with Y=112 FCC3v1 and FCC4v1..... 27 Figure 5: With Laplacien operator................................................................................................... 28 Figure 6: Individual package under NTC......................................................................................... 29 Figure 7: Individual package under ATC......................................................................................... 30 Figure 8: Infinite array under NTC................................................................................................. 31 Figure 9: Infinite array under ATC................................................................................................... 32

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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 (12], including the addition of the 17x17 EPR assemblies. In the initial study, we showed (§5.4.3) that 2-D modelling gave results equivalent to the 3-D modelling. As a result, revision B of the calculation note is carried out in 2-D.

Fresh UO2 fuel assemblies are transported in packages referred to as FCC3 version 1 (for 15x15 and 17x17 design assemblies), FCC4 version 1 (for 17x17 XL and 17x17 EPR design assemblies) and FCC4 version 2 (for 16x16 and 18x18 design assemblies).

For particular cases, it is necessary to transport rods in variable quantities. The rods are then transported in boxes [4], which are inserted instead of the assemblies inside the neutron cavity.

The packages used for transporting the rods are those intended for the transport of assemblies, i.e.:

- the FCC3 version 1 package for the transport of 14x14 "8 foot", 14x14 "10 foot", 15x15 and 17x17 design rods,

- the FCC4 version 1 package for the transport of 16x16, 17x1 ?XL and 18x 18 design rods, but also 14x14 "8 foot", 14x14 "10 foot", 15x15 and 17x17, 17x17 EPR design rods.

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 diameter spike,

- thermal test at 800 °C for 30 minutes.

The purpose of this study is to verify that the safety-criticality criterion of Kett s 0.95 is observed, incl uding all uncertainties, for the transport of FCC3 v1 and FFC4 v1 containers under NTC and ATC in accordance with IAEA recommendations [7].

Document (11] 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 :

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.

P00 rs;

Fabricated assembly with an L-shaped cross-section hinged on the frame. This sheet-metal structu re 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 cavity:

Overall volume delimited by the metal sheets on the inside of the doors, the frame and the head and foot plates.

co-ordjnate system;

The O X Y Z three-dimensioned reference system is used (Figure 3 and Figure 4 ), 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 sectjon;

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.

In the case of rod boxes, the section concerned is that of the neutron cavity reduced in its upper section by the volume the longitudinal wedge occupies.

Moderator radjus;

Radius of the moderator portion of an APOLLO 2 fissile cell, represent ing the fissile medium. The moderator radius is calculated as follows:

Rmo de rator =

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Qiffereotial flooding;

Accident configuration in which only the neutron cavity is immersed in water (density= 1 ).

Total reffectjon;

Conditions at the limits (boundary conditions) applied to a computational 3D geometric configurat ion and which prevents any neutron leakage.

Three-dimensional arrangement of several packages. The array is surrounded by a 20-cm water reflector (articles 681 and 682 of [71). 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.

loUoite 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

Computation is 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 [10].

A brief description of these codes is restated in report [11].

Use of the CRISTAL calculation tools is qualified for the present study by applying an uncertainty of I to the Keff calculated according to report [11 ]. In the present report, all the reactivity values given take this uncertainty into account.

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4. COMPUTATIONAND MODELLING HYPOTHESES

4.1. Characteristics of the package

The characteristics of the package are restated below, and are the same as for transporting the assemblies to which report [9] refers.

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 closing on the assemblies or the rod boxes,

- 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 rod boxes to be transported are placed.

The neutron absorbing resin located inside the doors and the frame limits 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] are restated in Table 1.

4. 1.1. Package under Normal Transport Conditions (NTC)

Under normal conditions, the package is cylindrical (see Figure 1 ), it is mode lled in 2D as follows:

- a cylindrical shell with external dia. of- *

- a neutron cavity (see Figure 4)

ads for retaining the grids are located are modelled by (see detail Figure 4),

- attachment of the pads in the resin of the doors is modelled by alongside each pad,

is shown in Figure 4,

The d imensions taken into account for modelling purposes are given in Figure 1, Figure 2, Figure 3 and Figure 4.

4. 1.2. Package under Accident Transport Conditions (A TC)

The modelling adopted integrates the results of expert appraisal subsequent to the mec hanical tests and the thermal study, i.e.:

- the neutron cavity is entirely detached from the cradle subsequent to one of the drops or the thermal test,

- the shell is radially crushed 9m drop onto a flat surface, with localised crushing reaching a maximum

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- the shock absorbers are crushed to the maximum of their capacity subsequent to the axial drop,

i.e. 80 mm.

Therefore, under accident conditions, the package is modelled (see Figure 2) 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 acka ective of the faces considered.

- 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 of approximately

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 boxes

There are two versions of the boxes :

- version FCC3 for transporting all types of the 12 feet, 10 feet and 8 feet rods,

- version FCC4 for transporting all types of 14 feet, 12 feet, 10 feet and 8 feet rods.

The box consists of a stamped U-shaped metal sheet, closed at both ends and reinforced wit h two beams welded in the upper portion of the metal sheet [4].

The rods are located ax ially in the centre of the box and the space at the ends is taken up by wedges of a length suited to that of the rods.

The box is loaded with full rows of rods and, if necessary, the last row is completed with inert rods.

The space in the cavity above the rods is filled over its entire length with a system of radial wedges.

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The wedging system ensures the position of the rods in the box and the box in the cavity, under both normal and accident transport conditions.

4.4. Characteristics of the fissile media

The characteristics of the rods are restated in Table 2.

. 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 materials containing isotopes in the Zirconium alloys.

Enrichment is taken to be equal to 5 % 235 U for all types of rods.

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 quantities close to those of the impurities is ignored in the study of criticality as their presence reduces the reactivity of the assemblies.

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, ie.

- the radial wedging maintains a minimum thickness of --

For the purposes of calculating the moderation, the rods are assumed to be distributed uniformly over the entire available cross-section of the boxes, i.e.. The number of rods will be variable so as to cover all transport configurations, i.e. from a few rods to a maximum fill determined according to the weight limits.

On account of the above observations, the modelling adopted for verifying the safety / criticality criteria is as follows:

- the fissile portion of the rods is in the neutron cavity,

- the rods can be brought together to form 2 groups :

o rods with a diameter of== 10.7 mm : 14x 14, 15x15 and 16x16,

o rods with a diameter of== 9.5 mm: 17x17, 17x17 XL, 17x 17 EPR and 18x18.

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5. METHODOLOGY AND RESULTS

The methodology used in this study consists of searching the optimum value (in terms of reactivity) of the moderation ratio (VmNf) for the fissile medium, with a neutron cavity in section, for both rod diameters.

The reactivity is then calculated, for both rod diameters and moderat ion ratios varying either side of the optimum, for an individual package and an array of packages in normal transport configurations (NTC) and accident transport configurations (ATC). In accident configurations, two variants are studied :

differential flooding (VD),

- water-filled package.

Radial wedging is studied in water and vacuum.

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 reactivi ty 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. As regards boxes, this case is covered by the calculations at opt imum moderation and with rods of maximum length. A two-dimensional calculation for the most reactive configuration shows (see 5.4.3 ) that it remains largely subcritical.

The accident configuration in which the neutron cavity is off-centre, thereby coming closer to the neighbouring packages, is dealt with in report [9], which demonstrates that it has no significant impact.

Since the above configurations are not penalising, they are not studied further in this report.

5.2. Optimum moderation ratio

In order to determine the optimum moderation ratio, material buckling (8 2 m} is calculated according to the moderation ratios (VmNf) using APOLLO 2 code.

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The resulting graphs are shown in Figure 6 according to the moderation ratio (VmNf) and the number of rods distributed in a section -(mm x mm). The VmNf value that gives maximum B2m corresponds to the moderation ratio that would give the maximum reactivity value.

The maximum material buckling values are obtained respectively for:

- :::::: 110 rods (VmNf:::::: -) -in diameter,

- :::::: 85 rods (VmNf:::::: -) -mm in diameter.

5.3. 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 [8]), including all uncertainties.

5.3.1. Individual package under Normal Transport Conditions (NTC)

The configuration studied is: the undamaged package (cylindrical modelling) filled with water and surrounded by a reflector consisting of 20 cm of water ; modelling of the package is described in §4, Figure 1, Figure 3 and Figure 4. The radial wedging system is modelled as water, the wedge then playing the role of reflector. It is not penalising to model the wedge as empty space, as is shown by the calculations under A TC. The rods are spread uniformly over in the 219 mm x 134 mm section and the number of rods varies either side of optimum moderation.

The results of the calculations, are provided in Figure 6 and the maximum Keff values restated in the table below show that the individual damaged package amply complies with the subcriticality criterion of Keff s 0.95, regardless of the number of rods and their type.

PROPRIETARY TABLE

5.3. 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 flooding configuration.

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The results of the calculations are provided in Figure 7 and the maximum Keff restated in the table below.

They show that the undamaged individual package amply complies with the subcriticality criterion of Keff s 0.95, whether in the differential drainage or the water-filled package configuration and regardless of the number of rods transported. The most penalising configuration is the one in which the wedge is in water, and acts as reflector.

PROPRJIETARY TABLE

5.4. An 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 a plurality of packages is 5000 pcm. The safety /criticality criterion to satisfy is: Keff s 0.95 (appendix Vll.38 of (8)), including all uncertainties.

5.4.1. Array of packages under Normal Transport Conditions (NTC)

If N is the number of packages to be transported, SN 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 app lied 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 are provided in Figure 8 and the maximum Keff restated in the table below.

They show that an infinite array of undamaged packages amply complies with the subcriticality criterion of Keff s 0.95 even in the case of the differential flooding configuration, and regardless of the number of rods transported. The configuration in which the wedge is modelled as water is the most penalising, as the wedge plays the role of reflector. The number N is therefore infinite, regardless of the number of rods transported under accidental transport conditions.

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PROPRIETARY TABLE

5.4.2. 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 ([7]).

The configuration studied is: an array of damaged packages (rectangular modelling); modelling of the package is described in §4; In this configuration, two variants are studied:

- the inside of the shell is empty and the fuel is moderated: this is the case of d ifferential flooding,

- the inside of the shell is filled with water and the fuel is moderated.

The results of the calculations, are provided in Figure 9 and the maximum Keff values restated in the table below show that the individual damaged packag~ the subcriticality criterion of Keff s 0.95, with a shell crushed to a realistic extent (----)-

The number N is therefore infinite, regardless of the number of rods transported under accidental transport conditions.

The differential flooding configuration is a highly penalising configuration that generates an increase in reactivity relative to the water-filled package.

PROPRI ETARY TABLE

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5.4.3. Impact of rod slippage

This analysis has not been reworked for revision B, but the conclusions reached remain valid. The calculations for revision B have been excluded in 2-D. This case is therefore covered.

In order to check that slippage of the rods does not have a significant impact, a two-dimensional calculation was carried out (modelling of a - portion of package with a set of pads and reflection conditions at the ends) for the most reactive configuration of each type of rods, i.e. an infinite array of packages under ATC and differential flooding configuration with the radial wedge modelled as water.

The results obtained for the two-dimensional calculation are statistically equivalent to those of the three-dimensional calculation, as shown in revision A.

The calculations are carried out varying the moderation ratio either side of the optimum, slippage of the rods does not therefore have a significant impact on reactivity.

5.4.4. Impact of the eiection of pellets

The above calculations are carried out with different moderation ratios either side of the optimum. The ejection of pellets would not have a significant effect, since it is the effect of the optimum moderation of the rods that contributes to the maximum r eactivity of the infinite network of pac kages, with margins greater than 10000 pcm.

In the case where rods treated with gadolinium are transported, the pac kage is not studied, only the reactivity of the rods in an infinite medium, calculated using APOLLO 2 code.

The fissile material is a UO 2-Gd 2O3 mixture with the following characteristics :

UO2 enriched at a maximum of 5 % 235U,

minimum Gd 2O 3: 2% by weight.

The maximum reactivity in an infinite medium is less than 0.8, regardless of the moderation and the type of rods (10.7 mm or 9.5 mm diameter).

From the criticality concerns, the gadolinium-treated rods can therefore be transported in any package and in any number.

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6. CONCLUSION

In this study, we have verified that the safety /criticality criteria of FCC3 version 1 and FCC4 version 1 packages are met for the transport of fresh UO2 fuel rods, the main characteristics of which are:

maximum enrichment: 5% with 235 U,

density 10.96 g/ cm 3 ( 100% of the theoretical density),

nominal diameter 9.5 mm or 10.7 mm,

any length, slippage therefore possible,

any number.

Possible particular rods (gadolinium treated rods, depleted uranium rods, stainless steel rods, zirconium alloy rods) are covered by UO2 rods.

The pellets may contain capturing compounds (chromium oxide for instance) in a quantity that is close to those of the impurities. Their positive influence in terms of margins are ignored.

The maximum section, per cavity, for the rods, must be, whether under normal or accident conditions.

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 number N for the transport of rods, in a section, is infinite under NTC and ATC,

therefore ISC = 0.

Rods with a minimum gadolinium content of 2 % on a support enriched to a maximum of 5 % can be transported, regardless of their number and the type of package used.

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Table 1: Characteristics of the packages

PROAftlliTARY TAll..!i

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Table 2: Characteristics of the rods

PROPRfETARY TABLE

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Table 3: Composition of the resin

PROPRIETARY TABLE

The minimum density of the resin under Normal Transport Conditions (NTC) is taken to be -*

value derived from the mean measurement of the product, -* reduced by 3 standard deviations.

The composition of the resin under Accident Transport Conditions (ATC) is obtained by removing

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Figure 1: Cross-section XY of package under NTC FCC3v1 and FCC4v1

PROPRIETARY FIGURE

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Figure 2: Cross-section XY of the package under ATC FCC3v1 and FCC4v1

PROPRIETARY FIGURE

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Figure 3: Half cross-section XY at pad, detail of the neutron cavity under NTC

PROPRIETARY FIGURE

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Figure 4: Cross-section XZ of the neutron cavity under NTC with Y=112 FCC3v1 and FCC4v1

PROPRIETARY FIGURE

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Figure 5: With Laplacien operator

PROPRIETARY FIGURE

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Figure 6: Individual package under NTC

PROPRIETARY FIGURE

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Figure 7: Individual package under ATC

PROPRIETARY FIGURE

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Figure 8: Infinite array under NTC

PROPRIETARY FIGURE

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Figure 9: Infinite array under ATC

PROPRIETARY FIGURE

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