ML22271A814
| ML22271A814 | |
| Person / Time | |
|---|---|
| Site: | Orano USA |
| Issue date: | 08/03/2022 |
| From: | Framatome |
| To: | Division of Fuel Management |
| Garcia-Santos N | |
| Shared Package | |
| ML22271A128 | List:
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| References | |
| A33010, L-2022-DOT-0007 | |
| Download: ML22271A814 (37) | |
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IDENTIFICATION REVISION FS1-0062270 DOS-18-016472-017 (EN) CD 0 Framatome Fuel framatome TOTAL NUMBER OF PAGES: 37 APPENDIX 2.2 BEHAVIOR OF A ROD MADE OF M5Framatome OR ZIRCALOY-4 ALLOY SUBJECTED TO THE IAEA THERMAL TEST IN FCC PACKAGING I NON-PROPRIETARY VERSION I
ADDITIONAL INFORMATION:
DRAFT DISTRIBUTION PURPOSE OF DISTRIBUTION I I For action CLASSIFICATION PUBLIC For information For information CATEGORY LRP - Licensing Report STATUS This document is electronically approved. Records regarding the signatures are stored in the fsanpexp EDRMS object Id. : 09012167813b551e Documentum docbase. Any attempt lo modify this file may subject employees to civil and criminal penalties. Released date (Western EU time) : 2022/06/03 08:57:36 Role Name - - - - - - - - - - - , Date (YYYY/MM/DD) Organization_ _ _ _ _ _ _ _ _ _ _--11 Writer Reviewer Approver OTHER DATA: Export classification AL: Eoo1 EccN N GoOds bearing the designation WAL not equal tow are subject to European or Gem1an regulations for export wllhln or o utside of the EU. Goods bearing the designation "ECCN not equal to N" are subject to US regulations. Goods bearing the designations -AL:N" or *ECCN:W may also be subject to authorisation. depending on the final destination and intended use of the product.
Export classification AL: 0E001 ECCN: N Goods labelled with "AL not equal lo W are subject to European or German export authorizaUon when being exported within or out of the EU. Goods labelled ~ecCN not equa l to N" are subject to US re-export authorisation.
Even without a label, or with label &AL: N" or *ECCN: N", authorisation may be required due to the final whereabouts and purpose for which the goods are to be used.
France: Y Exportkennzeichnung AL: 0E001 ECCN: N CHANGE CONTROL: Die mil "AL unglelch W gekennzeichneten GOter unterliegen bel der Ausfuhr aus der EU bzw.
This document must be checked and USA: N innergemeinschaftlichen Verbringung der europaischen bzw. deutschen Ausfuhrgenehmigungspflicht. Die mit "ECCN ungleich W gekennzelchneten GOter unterHegen der US-Reexportgenehmlgungspfllcht. Auch ohne approved by the following regions when it Germany: N Kennzelchen. bzw. bei Kennzelchen "AL: W oder"ECCN: W, kann slch elne Genehmlgungspfllcht, unter anderem is revised: durch den Endverb1eib und Verwendungszweck der GUier, ergeben.
CW01F Rev. 5.2 - 17110/2018
No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 framatome I
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NON-PROPRIETARY Page 2/37 VERSION SAFETY Appendix 2.2-3 ANALYSIS BEHAVIOR OF A ROD MADE OF M5FRAMATOME OR ZIRCALOY-4 ALLOY REPORT SUBJECTED TO THE IAEA THERMAL TEST IN FCC PACKAGING PreparationNerification Date S ignature Identification DOS-18-016472-017 FCC3-FCC4 See first page Rev. 1 Page 2 / 37 REVISIONS (Documents in French)
WRITER/CH REVISION DATE NOTES ECKER 12-00057682-203 S. GEROUT / F.
04/2012 First issue Revision 00 LANOY Rewriting of document taken from reference AREVA NP PEEL-F 2011 J.C.
12-00057682-203 DC 170 revision A 10/2016 SPINNATO/S.
Revision 01 GEROUT 12-00057682-203 Revision 02 Change from brand name M5,ramalome F. BOURLIER /
11/2020 (FS1-0052549 Incorporat ion of M5,,amatome rods coated with up to 30 µm of chrome C. VERDON rev. 1.0) 18-016472-017 Revision 1.0 F. BOURLIER /
05/2021 Update of thermal-mechanical analysis following update of thermal (FS1-0052549 R. CHOSSON studies in Appendix 2.2-1 rev. 2.0)
REVISIONS (Documents in English)
REVISION DATE NOTES WRITER/CH ECKER 18-016472-017 (EN) Revision 1.0 F. BOURLIER /
See first page Translation in English of 18-016472-017 Revision 1.0 (FS1-0062270 R. CHOSSON rev. 1.0)
BRAND NAMES AFA 3G, M5Framatome , MS, Q12, PROtect, MONOBLOC, TRAPPER, AGORA, HTP, HMP and ROBUST FUELGUARD are brands or registered brands of Framatome or its subsidiaries, in USA or in other countries. Pour les nouvelles revisions, deplacez le texte "Voir premiere page" comme "DATE" de la nouvelle revision, et entrez pour la revision precedente sa date de sortie effective.
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No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 LRP - Licensing Report framatome I
NON-PROPRIETARY Page 3/37 VERSION CONTENTS
- 1. INTRODUCTION ..................................................................................................................... 4
- 2. INPUT DATA ........................................................................................................................... 4 2.1. GENERAL BEHAVIOR OF RODS ............................................................................................... .4 2.2. WORST-CASE CONFIGURATION .............................................................................................. .4 2.3. THERMAL DISTRIBUTIONS STUDIED ....................................................................................... -4 2.4 . CREEP LAWS ...............................................................................................................................5 2.4.1. DESCRIPTION OF THE EDGAR SYSTEM AND THE PROTOCOL FOR CREEP TESTS AT HIGH TEMPERATURE ..................................................................................5 2.4.2. CHARACTERISTICS OF TUBES TESTED ......................................................................6 2.4.3. RESULTS OF CREEP TESTS AT HIGH TEMPERATURE: UNIFORM ELONGATION AND TOTAL ELONGATION FOR CLADDING TUBES MADE OF M5FRAMATOME AND ZIRCALOY-4 ......................................................... ............................................................6 2.4.4. CREEP LAWS - M5FRAMATOME AND ZIRCALOY-4 ...........................................................8 2.5. ADDITIONAL TESTS ......................................................... ............................................................9 2.5.1. ADDITIONAL CREEP TESTS AND RAMP TESTS .........................................................9 2.5.2. RAMP TESTS WITH AZIMUTHAL THERMAL GRADIENT ...........................................19 2.5.3. RODS MADE OF M5FRAMATOME COATED WITH CHROME ............................................23 2.6. STRESS-RELIEVING PROCESSES ON CLADDING POTENTIALLY STRAIN HARDENED AFTER A DROP ..........................................................................................................................25
- 3. COMPUTER SIMULATION METHOD FOR RODS .............................................................. 27
- 4. STUDY OF RISK OF ROD BURST ....................................................................................... 28 4.1. APPLICATION TO M5FRAMATOME (EDGAR LAW 2008) ................................................................ 28 4.2. APPLICATION TO ZIRCALOY-4 (EDGAR LAW 1999) .............................................................. 31
- 5. CONCLUSION ....................................................................................................................... 34
- 6. REFERENCES ...................................................................................................................... 35 LIST OF APPENDICES Appendix 1: Result of simulations of EDGAR tests with azimuthal thermal gradient... ... ....................... 36 Framatome
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- 1. INTRODUCTION The purpose of this document is to study the mechanical behavior of a fuel rod in FCC packaging subject to the thermal test as described in the IAEA regulations, 2018 edition. The study concerns the 17x17 rod because Appendix 2.2-1 established that the 17X17 array is the one that leads to the highest temperatures. Temperature evolution of rods are taken from Appendix 2.2-1 .
The risk identified and assessed here is the risk of a rod cladding burst due to creep under the cumulative effect of the temperature and internal pressure. This risk is assessed in the hottest zone of the rod . The azimuthal thermal gradient is considered. The study concerns the three rods reaching the maximum temperatures for the cladding materials made of M5Framatome (without coating or coated with a chromium layer) and Zircaloy-4.
- 2. INPUT DATA 2.1. GENERAL BEHAVIOR OF RODS Under the effect of the internal pressure (which is a function of the initial pressurization of the rods and the heating of the gas during the thermal test), a stress field is generated in the cladding of the rods. Due to the temperature increase, creep can occur in the cladding material. This creep under internal pressure first causes generalized uniform swelling of the cladding and second produces a local instability in the form of ballooning of the cladding.
2.2. WORST-CASE CONFIGURATION For a single given temperature distribution, the worst-case configuration is obtained with the following characteristics:
The highest initial pressurization (the worst-case scenario is that of the 17x17 rod pressurized to 32.7 bar absolute at ambient temperature),
Minimum cladding thickness: 0.52 mm, Maximum external radius of claddingllll mm 2.3. THERMAL DISTRIBUTIONS STUDIED Changes in mean and maximum temperatures of the three hottest rods for the cladding made of M5Framatome and Zircaloy-4 are taken from the thermal hydraulic calculations in Appendix 2.2-1 . This Appendix 2.2-1 also specifies that addition of a chromium coating improves thermal resistance of cladding in the fire test.
For Zircaloy-4 cladding, the maximum temperatures and mean temperatures at the same time for the three hottest rods are obtained in the plenum area (case 16: reference case - Zircaloy-4):
Cladding 1: T max. =- °C - T mean. =- °C; Cladding 2: T max. =- °C - T mean. =- °C; Cladding 3: T max. =- °C - T mean. =- °C.
For M5Framatome cladding, the maximum temperatures and mean temperatures at the same time for the three hottest rods are obtained in the plenum area (case 17: M5Framatome - Pre-ox):
Cladding 1: T max. =- °C - T mean. =- °C; Cladding 2: T max. =- °C - T mean. =_ , C; Cladding 3: T max. =- °C - T mean. =_ , C ;
- Fuel This document is sub'ect to the restrictions indicated on the first a e
No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 NON-PROPRIETARY LRP - Licensing Report framatome I VERSION I Page 5/37 It should be noted that the phenomenon of oxidation by air during accident conditions of transport (fire test) is taken into account in the thermal hydraulic calculations.
2.4. CREEP LAWS The creep tests at high temperature, used to establish the laws used in calculating the risk of bursting, were performed with the CEA EDGAR experimental system. These laws are developed below.
2.4.1. DESCRIPTION OF THE EDGAR SYSTEM AND THE PROTOCOL FOR CREEP TESTS AT HIGH TEMPERATURE The EDGAR system is used to study the thermal-mechanical behavior of cladding made of Zirconium alloys under internal pressure in isothermal or anisothermal conditions (in an external steam environment). The creep of the cladding is studied up to burst if necessary.
The purpose of the EDGAR tests is to provide thermal-mechanical behavior models and data for the cladding tubes (including diametral deformation and the failure criteria), in the three metallurgical domains of interest for zirconium alloys: a, a/13 and 13 with a specific attention to the temperature range where there takes place the transformation of allotropic phases a- (a/13)- 13 which significantly influences the thermal-mechanical macroscopic behavior of the cladding.
Among other things, two types of tests are performed in the EDGAR equipment (see photographs below): isothermal creep tests and creep tests with a heating rate imposed.
The creep law parameters associated with the failure criteria (by instability) were identified for M5Framatome and Zircaloy-4 by means of various EDGAR test series.
PROPRIETARY PICTURE Overview of EDGAR device 1 Cladding tube portions of length - - mm are heated by the Joule effect at constant temperature (creep tests) or at heating rate imposed (ramp tests), under an imposed internal pressure, in an external steam environment.
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NON-PROPRIETARY Page 6/37 VERSION The temperature is monitored by two single-color and two-color pyrometers and by an internal thermocouple. The diametral deformation is monitored by laser beam. The temperature data (thermocouple, pyrometers), diametral deformation data and pressure change data are acquired continuously during the test and stored for later analysis.
After the test, two circumferential deformations are measured: At= total elongation at rupture and Ar= uniform elongation at mm from the edges of the burst opening.
PROPRIETARY PICTURE 2.4.2. CHARACTERISTICS OF TUBES TESTED The M5Framatome and stress-relieved Zircaloy-4 tubes with 17x17 geometry, used for the EDGAR creep tests and temperature ramp tests, were taken as samples from two batches from CEZUS industrial production. They are representative of those manufactured and used for Framatome fuel.
These two batches were subjected to the usual acceptance checks and tests, in particular 100% of the tubes were checked in relation to:
- the US dimensional inspection [external diameter - mm), internal diameter mm), thickness ( - mm), ovality and off-centering],
- structural soundness by US and Eddy Current (EC),
- visual appearance.
All tubes comply with these requirements.
For each batch, the tensile mechanical characteristics in ambient conditions are measured on two samples taken from two tubes of the batch of material. The results (yield strength at 0.2%, ultimate tensile strength and total elongation) comply with the criteria of Chapter 1.3 and are presented in the reference [2].
2.4.3. RESULTS OF CREEP TESTS AT HIGH TEMPERATURE: UNIFORM ELONGATION AND TOTAL ELONGATION FOR CLADDING TUBES MADE OF M5FRAMATOME AND ZIRCALOY-4 The figures below respectively supply values for uniform elongations (Ar = circumferential deformation measured atmm from the area of instability) and total elongations at rupture (At = circumferential deformation measured in the area of instability) for the cladding tubes made of M5Framatome and stress-relieved low-tin Zircaloy-4 in relation to the temperature in the range from 600°C to 1000°C.
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No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 NON-PROPRIETARY LRP - Licensing Report framatome I VERSION I Page 7/37 PROPRIETARY DRAWING Creep tests on M5Framatome and Zircaloy-4 (Afa-2G) - Changes in uniform elongation (Ar) in relation to temperature PROPRIETARY DRAWING Creep tests on M5Framatome and Zircaloy-4 (AFA2G) - Changes in total elongation at break (At) in relation to temperature NB: Zircaloy-4 is noted as AFA-2G or Afa-2G (low tin) in the caption above Framatome
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No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 LRP - Licensing Report framatome I NON-PROPRIETARY VERSION I Page 8/37 According to the figures below, for a temperature lower than _C, the minimum uniform elongation (Ar) measured is:
for cladding tubes made of M5Framatome, for cladding tubes made of Zircaloy-4.
2.4.4. CREEP LAWS - M5FRAMATOME AND ZIRCALOY-4 The creep law parameters were determined using EDGAR tests.
The laws used are those obtained for the a domain (the maximum temperatures of the transients remaining lower than 700°C). These laws take the form of Norton type secondary creep laws.
The creep deformation rate f. 00 depends on temperature T (Kelvin) and stress Clee (MPa):
f.00 = ACl00 n exp( -i)
M5Framatome Zircaloy-4 Where: Q= Where: Q =
n = n =
A= A=
In parallel with development of creep laws, the tests described in paragraph 2.4.1 made it possible to identify an instability criterion linking circumferential stress with temperature. It is used to calculate the time where rupture occurs due to elasto-visco-plastic instability and the corresponding uniform elongation. It is obtained by linear regression on the pairs of experimental values (rupture temperature, stress at rupture).
The instability stress depends on temperature T (Kelvin):
Cl; ? t = Cexp(-D X T)
Zircaloy-4
=-K-M5Framatome Where: C =-MPa Where: C = - M Pa D = - K *1 D 1
The EDGAR creep model for stress-relieved Zircaloy-4 presented above was established by the CEA in 2008, and mainly based on ramp tests.
An earlier EDGAR creep model for Zircaloy-4 was established by the CEA in 1999 giving greater weight to creep tests. The creep tests and ramp tests shown in §2.5.1, show a comparison of two EDGAR laws for Zircaloy-4 (1999 and 2008) applied in the simulation model. This highlights better predictability and a more conservative nature for behavior of simulated Zircaloy-4 cladding according to the 1999 EDGAR creep law. This 1999 creep law is therefore applied in the rest of this document, particularly for adjustment of gradient creep tests incorporating the azimuthal thermal gradient (see §2.5.2 below).
Framatome - Fuel This document is sub'ect to the restrictions indicated on the first a e
No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 LRP - Licensing Report framatome I I NON-PROPRIETARY Page 9/37 VERSION For this model, the laws used are those obtained for the metallurgical structure in the a domain. This model is described by the following equations and coefficients:
fee = Aa00 n exp( -i)
Zircaloy-4 1999 Where:
a00r upt
= Cexp( -D x T )
Where: C = IIIIMPa D = - K-1 2.5. ADDITIONAL TESTS Two additional types of tests were performed on the two cladding alloy grades, M5F,ama1ome and Zircaloy-4:
Creep tests and ramp tests intended respectively to check:
- The validity of the EDGAR creep laws for temperature ranges corresponding to the accident conditions of transport of the rod cladding (i.e. a temperature range of . °C to . °C and pressures ofto
- bar),
- The validity of the deformation laws for temperature increase rates similar to those obtained under the regulatory fire condition.
- The ramp tests with an azimuthal thermal gradient imposed intended to confirm application of the EDGAR creep laws in these conditions.
Tests were also carried out on samples of MSF,ama1ome coated with a -external layer of chromium, for comparison with the results obtained on samples made of MSF,amatome without coating, with the same test conditions.
2.5.1. ADDITIONAL CREEP TESTS AND RAMP TESTS The test system is identical to that presented in §2.4.1 .
The creep test matrix is as follows :
Creep tests Internal pressure (bar)
Temperature (°C)
- - X X X
- X X X X
- X X X -
- X X X -
X X - - -
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No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 LRP - Licensing Report framatome I I NON-PROPRIETARY Page 10/37 VERSION The ramp test matrix is as follows:
Ramp tests Heating rate (°C/s)
X X X dT/d t - = - X X X Results:
Each of the ramp tests was then simulated by calculation based on the EDGAR creep laws defined in § 2.4.4 (M5Framatome, Zircaloy-4 1999 and 2008).
The results of the tests are compared with the values obtained by computer simulation. To achieve this the EDGAR creep laws and their rupture criterion are implemented in a 1D model constructed in the MATLAB interface.
The simulation diagram is as follows:
Creation of the thermal-mechanical loading file. Each simulated test uses a real thermal-mechanical loading using measured pressure and measure temperature at the recorded time steps. The circumferential stress is calculated based on the measured internal pressure and the measured circumferential deformation; Importation of the thermal-mechanic loading of the test to be simulated in MATLAB; Calculation using EDGAR model based on thermal-mechanical loading of:
- Changes in the fraction of phase a in the cladding;
- Changes in the circumferential deformation, until the failure criterion is reached.
The comparison of simulations and tests is provided below.
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NON-PROPRIETARY VERSION I Page 11 /37 MSFramatome alloy:
PROPRIETARY DRAWING MSFramatome: comparison of test with calculation of creep rupture time PROPRIETARY DRAWING SFramatome: comparison O test Wit ca cu at,on O um orm e ongat,on Framatome
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No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 NON-PROPRIETARY LRP - Licensing Report framatome I VERSION I Page 12/37 PROPRIETARY DRAWING M5Framatome: comparison of test with calculation of rupture temperature in ramp test PROPRIETARY DRAWING MSFramatome : comparison of test with calculation of uniform elongation (Ar) in ramp test Framatome
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No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 NON-PROPRIETARY LRP - Licensing Report framatome I VERSION I Page 13/37 The EDGAR creep law of 2008 for the M5Framatome alloy:
- correctly predicts the gradient creep tests, is penalizing with regard to the creep rupture time.
As specified in § 2.4.4, identification of the creep law parameters associated with the rupture criteria favors ramp tests.
The ramp tests performed on the M5Framatome alloy confirm the validity of the EDGAR 2008 creep law in the pressure and temperature domain under regulatory fire conditions.
Zircaloy-4:
The results of the tests performed with Zircaloy-4 are compared with the values obtained by simulation using the EDGAR creep models of 1999 and 2008. This comparison is presented below.
PROPRIETARY DRAWING Zircaloy-4: comparison of test with calculation of the creep rupture time Framatome
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No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 LRP - Licensing Report framatome I I NON-PROPRIETARY Page 14/37 VERSION PROPRIETARY DRAWING Zircaloy-4: comparison of test with calculation of uniform elongation (Ar) in creep tests PROPRIETARY DRAWING Zircaloy-4: comparison of test with calculation of the rupture temperature in ramp test Framatome
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No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 NON-PROPRIETARY LRP - Licensing Report framatome I VERSION I Page 15/37 PROPRIETARY DRAWING Zircaloy-4: comparison of test with calculation of uniform elongation (Ar) in ramp test These figures show that the EDGAR creep model of 1999:
provides a satisfactory prediction of uniform elongation (Ar) in creep and conservatively underestimates uniform elongation (Ar) in ramp test,
- conservatively underestimates creep rupture time, provides a satisfactory prediction or even slight underestimation for conservative purposes of rupture temperatures with ramp test The stress-relieved Zircaloy-4 model of 1999, compared with the model of 2008, leads to a correct, or even conservative, prediction for creep and ramp tests.
Consequently, the 1999 EDGAR creep model is more suitable for the study of thermal-mechanical behavior of rod cladding under fire accidental conditions defined by the regulations.
Consistency of strain rates of cladding tests/simulation:
In order to judge consistency of strain rates in relation to time between tests and EDGAR models used, we have chosen for some cases at the boundary of the test matrices, to plot diametral strain as a function of time (measured and predicted) on a single graph.
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No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 LRP - Licensing Report framatome I NON-PROPRIETARY VERSION I Page 16/37 M5Framatome alloy:
PROPRIETARY PROPRIETARY DRAWING DRAWING M5Framatome : creep a t -°C, - bars M5Framatome : creep at-C, -bars PROPRIETARY PROPRIETARY DRAWING DRAWING M5Framatome: ramp test at .°C/s-bars M5Framatome: ramp test at .°C/s, - bars Framatome
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NON-PROPRIETARY Page 17/37 VERSION PROPRIETARY PROPRIETARY DRAWING DRAWING MSFramatome: ramp test at -C/s,.,ars MSFramatome: ramp test atac,s, - bars Zircaloy-4:
PROPRIETARY DRAWING Zircaloy-4: creep Note: the EDGAR modelling of Zircaloy-4 in 1999 was implemented favoring gradient tests, which explains the differences observed in creep at low temperature in relation to measurements. The prediction for creep is also penalizing in relation to measurements.
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No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 NON-PROPRIETARY LRP - Licensing Report framatome I VERSION I Page 18/37 PROPRIETARY DRAWING PROPRIETARY DRAWING Zircaloy-4: ramp test at* °C/s,. bars Zircaloy-4: ramp test at *°C/s, - bars PROPRIETARY PROPRIETARY DRAWING DRAWING Zircaloy-4: ramp test at-°C/s,.bars Zircaloy-4: ramp test at-°C/s, - bars The M5Framatome and Zircaloy-4 1999 EDGAR models performance are confirmed by these comparisons that show, for analyzed cases, that:
- the experimental kinetics of the diametral deformation with creep and with ramp test creep is correctly predicted in pre-transition conditions and accelerated,
- the rupture times are very correctly predicted especially in ramp tests.
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No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 NON-PROPRIETARY LRP - Licensing Report framatome I VERSION I Page 19/37 2.5.2. RAMP TESTS WITH AZIMUTHAL THERMAL GRADIENT To take account of the azimuthal thermal gradient in the cladding tested, the EDGAR system test device presented in § 2.4.1 is adapted for a single-rod configuration and a multi-rod configuration.
These modifications consist of placing a shield, close to the cladding tested (this concerns cladding made of the same material as the cladding tested, creating a thermal shield locally),
near the test sample made of Zircaloy-4 or M5Framatome- The shield is not pressurized. The cladding is heated by Joule effect, by means of a coil simultaneously heating the cladding tested and the shield.
PROPRIETARY PICTURE Diagram of EDGAR system with shield (the shield is represented in yellow and the pressurized cladding in red; the pyrometer is used to control the temperature)
The ramp tests are preferred for validating the applicability of the EDGAR laws in the presence of an azimuthal gradient imposed because they are representative of the kinetics of the fire accident conditions defined by the regulations.
The ramp tests matrix is as follows:
Creep tests Internal pressure (bar)
Heating rate (°C/s)
X dT/dt(-)=- X Framatome
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No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 NON-PROPRIETARY LRP - Licensing Report framatome I VERSION I Page 20/37 The tests are performed for the 2 alloy grades Zircaloy-4 or M5Framatome and are duplicated for each case selected.
The heating rates o f -°C/s anc9lll°C/s applied are representative of the increase in temperature of the hottest claddi~lements made of M5Framatome and Zircaloy-4 over the temperature range from-°C t o -°C which corresponds to about 95% of the 30 minutes of the fire test (according to the temperature profiles provided below taken from Appendix 2.2-1 ).
PROPRIETARY DRAWING Temperature profiles of the 3 hottest cladding elements (Zircaloy-4 and MS) during the fire test Pressurization of cladding elements at 100 bar is not applied for these tests. It is likely to generate too short a failure time, preventing a satisfactory comparison between the test results and the simulations.
Results:
Each of the tests were then been simulated by calculation using the creep laws based on the EDGAR models for M5Framatome of 2008 and Zircaloy-4 of 1999 defined previously.
The simulation tool is described in §3. However, the specific input data for the creep test with azimuthal thermal gradient as well as the basic data corresponding to the test conditions are integrated into the simulation tool.
The input data used is as follows :
Mean temperatures recorded for each time step in the test (depending on the heating rate imposed,. °C/s o r -°C/s);
Constant azimuthal thermal gradient throughout the test ofac; Constant pressurellllllor-ar) imposed throughout the test; The basic data relative to the test conditions integrated into the simulation tool is as follows:
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No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 NON-PROPRIETARY LRP - Licensing Report framatome I VERSION I Page 21 /37 Geometry of rods tested;
- The rods tested are empty of any contents.
The comparison of the calculation with the tests is carried out on the basis of the following respective parameters: rupture time and mean rod temperature at rupture.
As a reminder, and in accordance with the EDGAR laws, rupture by bursting occurs at the point in time where circumferential stress is equal to the criterion of instability.
The results of simulations for each sample tested with azimuthal gradient are described in detail in Appendix 1.
The test results are compared with the values obtained by simulation and are presented in the figures below:
PROPRIETARY DRAWING MSF,amatome: comparison of test with calculation of mean temperature at rupture in ramp test with azimuthal gradient Framatome
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No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 LRP - Licensing Report framatome I I NON-PROPRIETARY Page 22/37 VERSION PROPRIETARY DRAWING M5Framatome: comparison of test with calculation of rupture time in ramp test with azimuthal gradient PROPRIETARY DRAWING Zircaloy-4: comparison of test with calculation of mean rupture temperature in ramp test with azimuthal gradient Framatome
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No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 LRP - Licensing Report framatome l I NON-PROPRIETARY Page 23/37 VERSION PROPRIETARY DRAWING Zircaloy-4: comparison of test with calculation of rupture time in ramp test with azimuthal gradient These figures show that the EDGAR creep models of MSF,amatome of 2008 and of Zircaloy-4 of 1999 produce conservative underestimations of the rupture temperature and rupture time in ramp test with azimuthal thermal gradient.
Application of the EDGAR creep laws of MSF,amatome of 2008 and of Zircaloy-4 of 1999 is validated in the presence of an azimuthal gradient under temperature and pressure conditions representative of fire accident conditions of the FCC packaging.
2.5.3. RODS MADE OF M5FRAMATOME COATED WITH CHROME Samples of Zy-4 or of MSF,amatome, with the same initial geometry of 17x17 as those used in the EDGAR tests described in the paragraphs above, but covered with a metal chromium coating, with thickness of about to µm, were tested in the CEA EDGAR system.
The creep conditions or ramp test conditions were chosen in order to allow direct comparison with tests already performed on samples without coating.
The figure below represents the rupture temperatures for ramp tests in conditions comparable with samples made of MSF,amatome with or without coating. Setting aside two tests with heating rates ( and . C/s) that are not representative of the accident conditions of transport for rod cladding, the tests with samples coated with chromium have rupture temperatures equal to or higher than those of comparable tests on samples without coatings.
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No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 NON-PROPRIETARY LRP - Licensing Report framatome I VERSION I Page 24/37 PROPRIETARY DRAWING Comparison of rupture temperatures between cladding with and without coating for
--°C .
ramp tests with heating rates from °C/s to ll°Cls The figures below compare two creep tests on samples of Zy-4 coated with 15 µm chromium relative to earlier tests on Zy-4 without coating. Addition of a chromium layer slows down the strain rate in creep for the temperature range PROPRIETARY DRAWING Changes in the deformation measured by laser, in the middle of the cladding, over time, during creep tests. Comparison between Zy-4 cladding coated with *1-1m chromium and Zy-4 cladding without coating.
The comparisons of EDGAR tests (creep and ramp test) under the same conditions for specimens with or without coating show that, for thicknesses of
- t o * µm, the behavior in creep of the coated specimens is at least equivalent, but sometimes more resistant, than for specimens without coating.
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No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 NON-PROPRIETARY LRP - Licensing Report framatome I VERSION I Page 25/37 The tensile mechanical tests performed on specimens made of M5Framatome coated with chromium for thicknesses up to* µm, described in Appendix 2.1-6, show similarity in the behavior of specimens coated with chromium for the different thicknesses studied. This similarity in behavior is extended to the creep tests .
Thus, all analyses performed in the following chapters concerning the M5Framatome alloy also apply to the M5Framatome alloy coated with chromium up to a thickness of* µm.
2.6. STRESS-RELIEVING PROCESSES ON CLADDING POTENTIALLY STRAIN HARDENED AFTER A DROP In the case of dropping of the assembly onto a stamp prior to the fire test, the cladding may be deformed locally and strain hardened at the start of the thermal mechanical analysis specific to the fire test.
As described in §2.4, the creep laws used are taken from tests performed on straight tubes in the final metallurgical state * * * *
- 1 o r M5Frama1ome and stress-relieved for Zircaloy-4).
The rod deformations after the drop onto a stamp were used to identify the envelope arrays for the deflection recorded after the drop, which were then characterized by a thermal study in Appendix 2 .2-1. These deformations do not lead to thermal penalties compared with the non-deformed assemblies.
Regarding partial strain hardening after the drop, the figures below show the changes in yield strength and total elongation respectively, measured during tensile tests at ambient temperature on strain hardened cladding, as a function of annealing time for temperatures representative of the regulatory fire test (* * * * * *°C).
PROPRIETARY DRAWING Changes in yield strength at*% under tension in ambient conditions as a function of time and temperature Framatome
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No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 LRP - Licensing Report framatome I I NON-PROPRIETARY Page 26/37 VERSION PROPRIETARY DRAWING Changes in total elongation under tension in ambient conditions as a function of time and temperature The tensile tests were performed on a standard tensile machine, at ambient temperature in accordance with the standard ASTM E8. The cladding has previously undergone strain hardening and heat treatment. The samples used are cladding of the 17x17 type made of M5Framatome alloy, with total length of cladding usually used in testing o f . mm, given that the effective zone (between extensometers) is fixed at* mm. The heat treatment on strain hardened cladding is usually carried out in small laboratory furnaces.
- a t -°C after* minutes held at this temperature
- at-C and-°C after the first minutes of annealing.
Appendix 2.2-1 indicates that the cladding of the three hottest fuel rods is subject to the following temperature transients:
- Rod 1: T >
- c for 29 minutes, T >
- c for 23 minutes, T > -°C for 11 minutes and 0
a maximum of 671 °c.
- Rod 2: T > -°C for 27 minutes, T > -°C for 19 minutes and a maximum of~C.
- Rod 3: T > -°C for 9 minutes, T > -°C for 2 minutes and a maximum of - °C.
It can therefore be concluded that the temperature and duration conditions of the regulatory fire test lead to the full relief of the stresses induced by local deformations prior to this test.
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No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 Classification:
LRP - Licensing Report framatome Page 27/37 Restricted Framatome
- 3. COMPUTER SIMULATION METHOD FOR RODS An initially pressurized rod is subjected to the variations in temperature calculated in Appendix 2.2-1.
The rod characteristics taken from [1] are the following:
Initial pressurization: 32.7 bar (absolute) at ambient temperature, Minimum cladding tube thickness: 0.52 mm, Maximum external radius of cladding tube: - mm, Empty rod volume:- mm3 ,
Gas volume-mm3 .
The cladding circumference is divided into 16 arcs of the same length in order to take account of the thermal gradient throughout the circumference. The modelling of the azimuthal gradient is carried out with the assumption that the circumferential distribution of temperature follows a sinusoidal form at each time step, passing through the maximum temperature and maintaining the mean temperature taken from the supporting calculations in Appendix 2.2-1 .
With each time step, the strain rate is calculated for each arc (of each zone or portion) with the creep law in §2.4.4. This is based on temperature and circumferential stress.
Generally, circumferential stress is written as:
( Dext-e)
- MP CJ99 = Pint 2O.e In a Where :
Pint : internal pressure in bar.
Dext : external diameter.
e : thickness.
Circumferential stress can also be written as:
(J = a000 . (1 + E00 ) 2 with a00 0 =p. ((Dext )o-eo) en MPa 00 mt ZO.eo The index O represents the initial values.
Pressure (in cladding) changes with the temperature and the volume that can be occupied by the gas.
Pressure is therefore updated again according to the following procedure:
Initially, the volume that can be occupied by the gas representsllll% of the total internal volume of the cladding (presence of pellets, springs, etc.); this value is taken from reference [1] which provides in the first approach a ratio of - % (Free volume/Internal cladding volume) for different configurations processed.
The value of this free space is updated again, taking account of:
- The circumferential deformation of the cladding,
- The variation in length of the cladding. Measurements of elongation made after rupture on cladding elements made of M5F,amatome show that the cladding is shortened at maximum b .%.
The assumption is made that the shortening is proportional to its circumferential deformation. It is considered that this maximum shortening is reached when circumferential deformation is equal to the minimum uniform deformation measured for M5F,amatome alloy, i.e .* % according to the figure in §2.4.2. These values are used for the two M5F,amatome and Zircaloy-4 alloys.
The free volume is therefore given by the following formula:
Vgaz = VJot ( 1 - . : Egg ) X (1 + E99)2 - (VJot - {'ogaz )
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No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 LRP - Licensing Report framatome I I NON-PROPRIETARY Page 28/37 VERSION Where:
Index O for the initial values.
v9 az gas volume.
t:88 circumferential deformation.
At a constant volume, pressure is proportional to absolute temperature (Kelvin) in accordance with the ideal gas law. The gas temperature is assumed to be identical to that of the cladding.
This gives the following formula for changes in internal pressure:
_ V g az T/az 0
Pi - Po ~ gaz TJ az Where:
Index O for the initial values.
Index i for the values at the time of calculation i.
P internal pressure of the cladding.
v g az gas volume.
T temperature in Kelvin.
At each time step, the strain rate is calculated for each arc as follows:
Calculation of the internal pressure (updated again with mean temperature and mean deformation of cladding),
Calculation of the circumferential stress (depends on internal pressure and updating of geometry again),
Calculation of the strain rate of each arc using the creep law (depends on circumferential stress and temperature of each arc).
Integration of the strain rate on the time interval considered provides the deformation for each of the 16 arcs that form the circumference of the cladding at each time step. The average of the deformations of the 16 arcs of the cladding is then calculated for each of the time steps. This mean deformation of cladding allows to evaluate the variation in length of the cladding (therefore the variation in free volume) with the next time step as well as the overall circumferential stress on the 16 arcs at the next time step.
At each point in time , the circumferential stress obtained is compared to the criterion of instability calculated at the maximum temperature of the cladding.
- 4. STUDY OF RISK OF ROD BURST In the tables presented below, the calculation time points representative of the kinetics are selected.
4.1. APPLICATION TO M5FRAMATOME (EDGAR LAW 2008)
The results of the calculation of the overall circumferential deformation and the circumferential stress in the three hottest cladding elements made of M5F,amatome during the thermal fire test are given in the three tables below. The criterion of instability, calculated at the maximum cladding temperature, is also given, as well as the stress/criterion ratio). The maximum local circumferential deformation is also provided.
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No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 LRP - Licensing Report framatome I I NON-PROPRIETARY Page 29/37 VERSION PROPRIETARY TABLE MSF,amatome (EDGAR law 2008) - Cladding 1 For transient of cladding 1, the minimum Criterion of instability/Minimum stress ratio equals 4.2.
The overall circumferential deformation reachesllll% whereas the maximum circumferential deformation reaches.%.
This is an acceptable level of deformation, because for a temperature lower than 700°C, the minimum uniform deformation measured equals-% (see figures in §2.4.2).
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No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 LRP - Licensing Report framatome I I NON-PROPRIETARY Page 30/37 VERSION PROPRIETARY TABLE M5Framatome (EDGAR law 2008) - Cladding 2
-lo.
For transient of cladding 2, the minimum Criterion of instability/Minimum stress ratio equals 4.5.
The overall circumferential deformation reaches - % whereas the maximum circumferential deformation reaches This is an acceptable level of deformation, because for a temperature lower than 700°C, the minimum uniform deformation measured equals-% (see figures in §2.4.2).
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No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 LRP - Licensing Report framatome I I NON-PROPRIETARY Page 31 /37 VERSION PROPRIETARY TABLE MSF,amatome (EDGAR law 2008) - Cladding 3 For transient of cladding 3, the minimum Criterion of instability/Minimum stress ratio equals 4.5.
The overall circumf~ial deformation reaches.% whereas the maximum circumferential deformation reache5-'%.
This is an acceptable level of deformation, because for a temperature lower than 700°C, the minimum uniform deformation measured equals-% (see figures in §2.4.2).
4.2. APPLICATION TO ZIRCALOY-4 (EDGAR LAW 1999)
The results of the calculation of the overall circumferential deformation and the circumferential stress in the three hottest cladding elements made of Zircaloy-4 during the thermal fire test are given in the tables below. The criterion of instability, calculated at the maximum cladding temperature, is also given, as well as Criterion of instability/Stress ratio. The maximum local circumferential deformation is also provided.
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No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 NON-PROPRIETARY LRP - Licensing Report framatome I VERSION I Page 32/37 PROPRIETARY TABLE ZIRCALOY-4 (EDGAR law 1999)- Cladding 1 For transient of cladding 1, the minimum Criterion of instability/Minimum stress ratio equals 3.3.
The overall circumferential deformation reaches whereas the maximum circumferential deformation reaches - %.
This is an acceptable level of deformation, because for a temperature lower than 700°C, the minimum uniform deformation measured equals about % (see figures in §2.4.2).
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No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 LRP - Licensing Report framatome l I NON-PROPRIETARY Page 33/37 VERSION PROPRIETARY TABLE ZIRCALOY-4 (EDGAR law 1999)- Cladding 2 For transient of cladding 2, the minimum Criterion of instability/Minimum stress ratio equals 3.4.
The overall circumferential deformation reaches. % whereas the maximum circumferential deformation reaches-%.
This is an acceptable level of deformation, because for a temperature lower than 700°C, the minimum uniform deformation measured equals about% (see figures in §2.4.2).
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No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 LRP - Licensing Report framatome l I NON-PROPRIETARY Page 34/37 VERSION PROPRIETARY TABLE ZIRCALOY-4 (EDGAR law 1999)- Cladding 3
-lo.
For transient of cladding 3, the minimum Criterion of instability/Minimum stress ratio equals 3.4.
The overall circumferential deformation reaches - % whereas the maximum circumferential deformation reaches This is an acceptable level of deformation, because for a temperature lower than 700°C, the minimum uniform deformation measured equals about % (see figures in §2.4.2).
- 5. CONCLUSION The study of thermal-mechanical behavior of the rods during the thermal fire test is carried out considering the maximum temperatures of the hottest rods for the cladding made of M5Framatome and Zircaloy-4 in accordance with Appendix 2.2-2, the azimuthal thermal gradient and the presence of pellets inside the rods. It shows that the risk of the cladding ballooning and bursting under the effect of creep may be eliminated for the two alloys.
For M5Framatome (according to the EDGAR law 2008), minimum Instability stress/stress ratio equals 4.2.
The average circumferential deformation reaches-% whereas the maximum circumferential deformation reaches.%. This is an acceptable level of deformation because the minimum uniform deformation measured (CEA EDGAR tests) equals-% for a temperature lower than 700 °C. These conclusions also apply to the rods made of M5Framatome coated with chromium, up to a thickness of µm, Framatome
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No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 LRP - Licensing Report framatome I I NON-PROPRIETARY Page 35/37 VERSION due to their behaviour in creep, under accident conditions of transport of the rod cladding, at least equivalent to that of rods made of M5Framatome without coating.
For Zircaloy-4 (according to the EDGAR law 1999), minimum Instability stress/stress ratio equals 3.3.
The average circumferential deformation reaches - % whereas the maximum circumferential deformation reaches- %. This is an acceptable level of deformation because the minimum uniform deformation measured (CEA EDGAR tests) equals about % for a temperature lower than 700°C.
- 6. REFERENCES
[1] Note AREVA-NP FS1-0004231 Rev. 1.0: Calculations of volumes for different designs of fuel rod -
Transport issue - In French
[2] AREVA-NP internal note FD-16-00285 EN Rev. 1.0: Answers to French Safety Authority (ASN) questions on EDGAR tests and the associated Zircaloy-4 model.
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No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 LRP - Licensing Report framatome I I NON-PROPRIETARY Page 36/37 VERSION Appendix 1: Result of simulations of EDGAR tests with azimuthal thermal gradient (1/2)
PROPRIETARY DRAWINGS Framatome
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No. FS 1-0062270 Rev. 1.0 DOS-18-016472-017 (EN) 1.0 LRP - Licensing Report framatome I I NON-PROPRIETARY Page 37/37 VERSION Appendix 1: Result of simulations of EDGAR tests with azimuthal thermal gradient (2/2)
PROPRIETARY DRAWINGS Framatome
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