HAL Id: cea-02338475
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Fission products and nuclear fuel behaviour under
severe accident conditionsSpeciation of fission
productsin the Verdon 3 and -4 samples
F. Audubert, C. Le Gall, L. Fayette, P. Bienvenu, I. Zacharie-Aubrun, K. Hanifi, Yves Pontillon
To cite this version:
F. Audubert, C. Le Gall, L. Fayette, P. Bienvenu, I. Zacharie-Aubrun, et al.. Fission products and nuclear fuel behaviour under severe accident conditionsSpeciation of fission productsin the Verdon 3 and -4 samples. NUMAT 2018 - The Nuclear Materials Conference 2018, Oct 2018, Seattle, United States. �cea-02338475�
FISSION PRODUCTS AND NUCLEAR FUEL BEHAVIOUR
UNDER SEVERE ACCIDENT CONDITIONS
:
SPECIATION OF FISSION PRODUCTS
IN THE VERDON 3 AND -4 SAMPLES
NUMAT 2018|October 19th– 23th, 2018
CEA Cadarache|DEN |DEC |SA3E |LAMIR
F. Audubert, C. Le Gall, L. Fayette, P. Bienvenu, I. Zacharie-Aubrun, K. Hanifi, Y. Pontillon
CONTEXT
Phenomenology of a PWR severe accident
| PAGE 2
Normal operating conditions
Further heat-up
Of the rods Corium formation
Heat-up of Fuel rods Cladding oxidation Production of H2 (Reducing atmosphere) Zr + 2H2O → ZrO2+ 4H2 Production of steam (Oxidizing atmosphere)
Failure of the building
(Oxidizing atmosphere) Oxidation plateau (1100-1500°C) High temp. plateau (≥ 2300°C) Temperature ramp (400-1100°C) Temperature ramp (1500-2000°C) Initial state T0
MOX fuel irradiated t 56 GWd.tML-1 Neutral atmosphere Oxidizing atmosphere Reducing or oxidizing atmosphere O 2300 Thermal treatment up to 2300°C under oxidizing atm. R 2500 Thermal treatment up to 2500°C under reducing atmosphere
2 PWR MOX fuel pellets + M5 cladding
+
2 unirradiated half pellets (depleted UO2)
reirradiated in OSIRIS
THE VERDON-3 AND 4 SAMPLES
Characteristics
| PAGE 3 VERDON-3, 2300°C, H2O VERDON-4, 2530°C, H2 Father rod, 56 GWd.tHM-12 irradiated pellets, scarce visible pieces of cladding
+
2 unirradiated half pellets (depleted UO2)
2 irradiated pellets + molten Zr cladding
+
EPMA
POST-TEST CHARACTERIZATIONS
Method
| PAGE 4
Qualitative analyses
Quantitative analyses
Phases chemical composition Optical microscopy, SEM,
SIMS, X-ray maps
Microstructure evolution Fuel-cladding interaction
FP distribution and associations
Hotlab : LECA STAR
* Hanifi NT CEA (2009, 2010)
UO2 matrix (1.6 at% Pu) No more coating phase Pu agglomerates (4.5 at% Pu) Restructured area (0.4R) with
porous agglomerates
Densified agglomerates homogeneously distributed
Restructured area still visible, with densified agglomerates
Pu
U
U
Pu
Pu
U
| PAGE 5MICROSTRUCTURE EVOLUTION
Father rod, VERDON-3 and VERDON-4 samples
0R 0.5 R 0.75 R VERDON-3, 2300°C, H2O VERDON-4, 2530°C, H2 Father rod *, 56 GWd.tHM-1
UO2matrix (0.5 at% Pu) Coating phase (3 at% Pu) Pu agglomerates (5 at% Pu)
UO2 matrix (1.3 at% Pu) No more coating phase Pu agglomerates (1.8 at% Pu)
| PAGE 6
FUEL-CLADDING INTERACTION
Father rod, VERDON-3 and VERDON-4 samples
1/2
90Zr
238U
16O
U
Zr
1R 1R 0.5 RZr
U
VERDON-3, 2300°C, H2O VERDON-4, 2530°C, H2 Father rod *, 56 GWd.tHM-1 FCI on 5 µm at the periphery of the fuelFCI: melting of UyPuzZr1-y-zO2±x 0,5R: U0.48Pu0.03Zr0.49O1.58
1R: U0.42Pu0.03Zr0.55O1.50 FCI on 70 µm at the
periphery of the fuel (UyZr1-yO2±x 0 ≤ y ≤ 1)
1R
| PAGE 7
2/2
U
Zr
FUEL-CLADDING INTERACTION
VERDON-1 and VERDON-4 samples
* Geiger et al. JNM (2017) VERDON-1 *, UO2, 72 GWd.tHM-1 2600°C, H2O/H2= 0.9 VERDON-4, MOX, 56 GWd.tHM-1 2530°C, H2
FCI: melting of UyPuzZr1-y-zO2±x 0,5R: U0.48Pu0.03Zr0.49O1.58
1R: U0.42Pu0.03Zr0.55O1.50
FCI: melting of UyZr1-yO2±x Similar compositions in
both cases
Same phenomena in the case of UO2and MOX fuels
Zr
U
0.5 R 1R 0.75 R U0.77Zr0.23O1.85 U0.48Zr0.52O1.70* Hanifi NT CEA (2009, 2010)
| PAGE 8
FISSION PRODUCTS EVOLUTION
Metallic precipitates
1/2
Pu
U
Ru
Mo
Pu
U
Mo
Ru
| PAGE 8Pu
U
Ru
Mo
0R 0.5 R 0.75 R VERDON-3, 2300°C, H2O VERDON-4, 2530°C, H2 Father rod *, 56 GWd.tHM-1 1RMo
Ru
Zr
U
Metallic precipitates Ru-Mo-Rh-Pd-Tc Mainly located in the Puagglomerates
Metallic precipitates Ru-Rh-Tc
Migration of the precipitates from the agglomerates to the matrix
Metallic precipitates Ru-Mo-Rh-Tc Mainly located in the Pu
agglomerates
Melting/coalescence in molten UyPuzZr1-y-zO2±x
* Hanifi NT CEA (2009, 2010)
Zr
Ce
Ba
Cs
| PAGE 9
FISSION PRODUCTS EVOLUTION
Dissolved FP
2/2
90Zr
140Ce
16O
137Cs
138Ba
16O
138Ba
90Zr
240Pu
16O
238U
16O
0R 0.5 R 0.75 R VERDON-3, 2300°C, H2O VERDON-4, 2530°C, H2 Father rod, 56 GWd.tHM-1Dissolved FP mainly in the Pu agglomerates
Cs mainly in the UO2matrix
Dissolved FP mainly in the Pu agglomerates
Scarce precipitates or bubbles with Ba, Cs, Ce and Zr
Dissolved FP mainly in the Pu agglomerates
Oxidizing atmosphere:
FCI but no fuel melting (T effect)
Enhanced diffusion (Pu, FP...)
Mo and Cs total release *
| PAGE 10
CONCLUSIONS
Behavior of MOX fuel and
FP in SA conditions?
Post-test qualitative and
quantitative analyses
VERDON-3, 2300°C, H2O VERDON-4, 2530°C, H2 Father rod, MOX, 56 GWd.tHM-1Reducing atmosphere:
Melting of U
yPu
zZr
1-y-zO
2±x(dissolution of (U, Pu)O
2by ZrO
2)
Melting and coalescence of
metallic precipitates
CEA / DEN / DEC / SA3E / LCPC:
S. Reboul, I. Roure, T. Blay, I. Félines, J. Noirot, V. Basini
DEN / DEC SA3E / LAMIR Commissariat à l’énergie atomique et aux énergies alternatives
Centre de Cadarache| 13108 Saint Paul lez Durance T. +33 (0)4 42 25 70 00