Effect of Burn-up and High Burn-up Structure on UO2 Spent Fuel Matrix Dissolution
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Transcript of Effect of Burn-up and High Burn-up Structure on UO2 Spent Fuel Matrix Dissolution
Effect of Burn-up and High
Burn-up Structure on UO2
Spent Fuel Matrix Dissolution D. Serrano-Purroy1, I. Casas2, E. González-Robles3,
J. P. Glatz1, D. Wegen1, F. Clarens3, J. Giménez2,
J. de Pablo2,3, A. Martínez-Esparza4
MRS’11, BUENOS AIRES, OCTOBER 2-6, 2011
1
2
3
4
This work is a part of a Collaboration
Agreement between ITU/JRC-ENRESA-
CTM/UPC to obtain the scientific data
needed to better understanding the
behaviour of High Burn-up Spent Fuels
SPENT FUEL DISSOLUTION
Rod14C
Gap14C; 129I;135Cs; 137Cs;79Se; 99Tc;90Sr
UO2-matrix
Actínides & FP
(~ 98 %)
Grain Boundary14C; 129I;135Cs; 137Cs;79Se; 99Tc; 90Sr
Cracks
Bubbles
-8
-7
-6
-5
-4
-3
-2
0 1 2 3 4 5 6 7
log
Frac
tio
nal
Re
leas
e R
ate
(d
-1)
log time (y)
matrix
grain boundaries
gap
L.H. Johnson, D.W. Shoesmith, “Radioactive Waste Forms
for the future“, W. Lutze and R.C. Ewing, Eds., 1988
PREVIOUS UO2-MATRIX DISSOLUTION RATES
• Dynamic experiments
• Air conditions
• Powder
• Fragment
• Segment (Fuel+Cladding)
-12.00
-11.50
-11.00
-10.50
-10.00
-9.50
-9.00
-6 -5 -4 -3 -2 -1
log
r (m
ol/
m2
·s)
log [HCO3-]
Gray_33 MW d/ kgU
Serrano_53 MW d/ kg U
Röllin_43 MW d/ kgU
Gray_28 MW d/ kgU (0.01 M HCl/DIW)
Gray_43 MW d/ kgU (0.01M HCl/DIW)
Serrano_53 MW d/ kgU_segment
Serrano_29 MW d/ kg U_segment
Jegou_60 MW d/kg U_segment
High Burn-up Structure (HBS)
Increasing burn-ups, neutron capture of U-238 produces Pu-239 generating
an external layer with a higher burn-up (BU), increased porosity and fuel
grain subdivision resulting on the formation of the so-called HBS. The width
of this layer, observed for BU’s higher than 40 MW d/kgU, increases with
the BU and depends on the irradiation history.
CORE particle
HBS particle
CORE particle
HBS particle
HBSIntermediate zone HBSIntermediate zone
RIM THICKNESS
20
30
40
50
60
70
80
90
100
110
20 30 40 50 60 70 80
Rim
BU
(M
W/
d k
gU)
Average BU (MW/d kgU)
Rt = 5.44BUR – 281
Johnson L., Ferry C., Poinssot C., Lovera P. Estimates of the Instant
Release Fraction for UO2 and MOX Fuel at t=0. NAGRA-TR-04-08, 2004
RN release from Spent Fuel
Cladding : C
Gap region : C, I, Cs, Se, Tc
Cracks
Pellet gap
20kV x 1.500 10 µ m 030996
Grains: (U,An,Ln)O 2
Grain boundaries: C, I, S, Cs, Se, Tc
RIM or HBS: enriched in Pu
Oxide precipitates: Rb, Cs, Ba, Zr, Nb, Mo, Tc
? - particles/ metallic precipitates Mo, Ru, Pd, Tc, Rh (Ag, Cd, In, Sn, Sb)
Fission Gas bubbles: Xe, Kr, I
Cladding : C
Gap region : C, I, Cs, Se, Tc
Cracks
Pellet gap
20kV x 1.500 10 µ m 030996 20kV x 1.500 10 µ m 030996
Grains: (U,An,Ln)O 2
Grain boundaries: C, I, S, Cs, Se, Tc
RIM or HBS: enriched in Pu
Oxide precipitates: Rb, Cs, Ba, Zr, Nb, Mo, Tc
? - particles/ metallic precipitates Mo, Ru, Pd, Tc, Rh (Ag, Cd, In, Sn, Sb)
Fission Gas bubbles: Xe, Kr, I
Objective
Study the leaching behavior of High Burn-up
PWR fuels (48 and 60 Mw d/kgU) with
special emphasis on the HBS region related
to UO2-matrix dissolution
Burn-up
(MW d/kgU)
48
(MBU) PWR
60
(HBU) PWR
Irradiation cycles 3 5
End of radiation 2000 2001
RIM (µm)
calculated76 µm 155 µm
MBU
HBU
Spent fuel samples
Spent fuel sample preparation
Two different samples were prepared from a different radial position in order to study the
effect of HBS region
RIM width
OUT sample
4. Sieving (50-100 µm)
5. Removing fines
1. Cut pin into segments
2. Drill
3. Separation from cladding
Core sample
OUT sample
HBU: Core (left) and OUT (right) sample after drilling and detachment
Spent fuel sample preparation
SEM characterisation of core sample a) before cleaning b)
after cleaning at 1000 magnification (Scale: 30 µm)
Spent fuel sample preparation
Fuel Parameter Core OUT
60BU
Mean particle size (μm)
68 ± 15 82 ± 8
Specific surface area (m2/g)
0.027 ± 0.007 0.022 ± 0.002
48BU
Mean particle size (μm)
90 ± 40 A: 45 ± 15
B: 140 ± 50
Specific surface area (m2/g)
0.020 ± 0.009A: 0.04 ± 0.01
B: 0.013 ± 0.009
Spent fuel sample characterization
Spent fuel sample characterization
The percentage of the surface broke through trans-
granular process in the Core sample was 98 % for
48MBU fuel and 97% for 60HBU fuel. Therefore, only
about 3% of the particle surface was estimated to
contain open grain-boundaries in both fuels.
The percentage of HBS particles present in OUT
samples for 48MBU and 60HBU fuels determined by
direct counting from SEM images is 5 and 19
respectively, these values change to 19 and 40 if
geometry is taking into account.
Experimental Setup
Experimental Setup installed inside Hot Cell
Element 60BU-CORE 60BU-OUT 48BU-CORE 48BU-OUT
Rb 500 ± 10 600 ± 100 320 ± 20 490 ± 20
Sr 800 ± 40 800 ± 100 730 ± 100 700 ± 20
Y 650 ± 10 770 ± 30 540 ± 10 660 ± 30
Zr 6300 ± 200 7900 ± 700 3800 ± 300 4500 ± 200
Mo 5900 ± 300 8000 ± 400 3600 ± 200 4500 ± 200
Tc 1300 ± 100 1600 ± 50 840 ± 30 1090 ± 30
Ru 4400 ± 200 5300 ± 600 2400 ± 100 3200 ± 200
Rh 650 ± 20 800 ± 100 510 ± 20 700 ± 100
Cs 3800 ± 200 4800 ± 400 2600 ± 200 4200 ± 100
Ba 3300 ± 400 4300 ± 500 1800 ± 400 2000 ± 300
La 2000 ± 400 2300 ± 300 2700 ± 1000 2800 ± 500
Ce 4100 ± 500 4500 ± 800 3000 ± 700 3000 ± 400
Pr 1800 ± 200 2100 ± 300 1300 ± 200 1100 ± 200
Nd 7000 ± 1000 8000 ± 900 4900 ± 1300 4000 ± 600
Sm 1270 ± 100 1500 ± 100 1000 ± 200 800 ± 100
Eu 190 ± 10 200 ± 20 130 ± 10 130 ± 10
Gd 620 ± 20 800 ± 200 340 ± 40 300 ± 30
U 780000 ± 10000 770000 ± 60000 790000 ± 10000 780000 ± 10000
Np 810 ± 80 760 ± 80 900 ± 100 750 ± 20
Pu 8000 ± 540 11000 ± 1600 10400 ± 600 15200 ± 400
Am 840 ± 100 1200 ± 100 500 ± 30 800 ± 30
Cm 290 ± 40 460 ± 50 70 ± 10 110 ± 10
Inventory for CORE, OUT (μg of element/g of SNF)
Inventory of each fraction
experimentally
determined by dissolution
in acidic media and
further HR-ICP-MS and
γ-spectroscopy analysis
•NaHCO3 10-3 mol·dm-3
•NaCl 1.9·10-2 mol·dm-3
•In air PO2 21%•Temperature 25 ± 5 ºC•pHi 8.0 ± 0.2 •pHo 7.2 ± 0.5•Flow rate 0.025-0.1 L/min•Weight of solid 1 g
Experimental conditions
Radionuclide rates normalized to uranium:
Dissolution Rates:
ACQ
rate ii
U
i
i
Uii M
Mmassmass
raterate normalized
CORE
1,E-17
1,E-16
1,E-15
1,E-14
1,E-13
1,E-12
1,E-11
1,E-10
1,E-09
1,E-08
1,E-07
0 50 100 150 200 250 300 350 400 450 500
time (d)
rate
s (
mo
l/m
2. s
)
U Np Pu Am Cm
CORE
1,E-13
1,E-12
1,E-11
1,E-10
1,E-09
1,E-08
0 50 100 150 200 250 300 350 400 450 500
time (d)
no
rm.
rate
s (
mo
l/m
2. s
)
U Np Pu Am Cm
OUT
1,E-16
1,E-15
1,E-14
1,E-13
1,E-12
1,E-11
1,E-10
1,E-09
1,E-08
0 100 200 300 400 500
time (d)
rate
s (m
ol/m
2. s)
U Np Pu Am Cm
OUT
1,E-13
1,E-12
1,E-11
1,E-10
1,E-09
1,E-08
1,E-07
0 100 200 300 400 500
time (d)
norm
. rat
es (m
ol/m
2.s)
U Np Pu Am Cm
60HBU Dissolution & normalized rates for Actinides
48 MBU Dissolution & normalized rates for Actinides
CORE
1.E-15
1.E-14
1.E-13
1.E-12
1.E-11
1.E-10
1.E-09
1.E-08
0 50 100 150 200 250 300 350
time (d)
rate
s (
mo
l m
-2 s
-1)
U Np Pu Am Cm
OUT
1.E-12
1.E-11
1.E-10
1.E-09
1.E-08
1.E-07
1.E-06
0 50 100 150 200 250 300 350
Time (days)
norm
alis
ed r
ate
s (
mol m-2
s-1)
U Np Pu Am Cm
OUT
1.E-15
1.E-14
1.E-13
1.E-12
1.E-11
1.E-10
1.E-09
1.E-08
1.E-07
1.E-06
0 50 100 150 200 250 300 350
time (d)
rate
s (
mol m
-2 s-1
)
U Np Pu Am Cm
CORE60HBU
OUT60HBU
CORE48MBU
OUT48MBU
NORMALIZEDRATE
(mol/m2 s)
U 5.1 10-12 2.1 10-12 8.0 10-11 4.0 10-11
Np 1.6 10-10 5.2 10-11 1.0 10-10 8.0 10-11
Pu 1.0 10-11 5.7 10-12 3.0 10-11 1.4 10-11
Am 3.5 10-12 2.5 10-12 5.0 10-11 2.0 10-11
RATIO
Np/U 11.3 15.2 1.4 2.2
Pu/U 1.2 1.7 0.4 0.4
Am/U 0.4 0.6 0.7 0.7
Results
Some remarks
Uranium and Actinide dissolution rates are twice
faster in the CORE region than in the Periphery
Except for Np in 60HBU fuel, actinides dissolve
congruently with uranium
Uranium dissolution rate is lower in 60HBU fuel than
in 48MBU fuel
60HBU Normalized Rates for Fission Products
CORE
1,E-14
1,E-13
1,E-12
1,E-11
1,E-10
1,E-09
1,E-08
1,E-07
0 100 200 300 400 500
time (d)
no
rma
lize
d r
ate
s (
mo
l/m
2. s
)
Rb Sr Y Zr Mo Tc Ru Rh Cs Nd U
OUT
1,E-14
1,E-13
1,E-12
1,E-11
1,E-10
1,E-09
1,E-08
1,E-07
0 100 200 300 400 500
time (d)n
orm
alize
d r
ate
s (
mo
l/m
2.s
)
Rb Sr Y Zr Mo Tc Ru Rh Cs Nd U
48MBU Normalized Rates for Fission Products
CORE
1.E-13
1.E-12
1.E-11
1.E-10
1.E-09
1.E-08
1.E-07
0 50 100 150 200 250 300 350
time (d)
norm
alised r
ate
s (
mol m
-2 s
-1)
Rb Sr Y Zr Mo Tc Ru Rh Cs La Nd U
OUT
1.E-13
1.E-12
1.E-11
1.E-10
1.E-09
1.E-08
1.E-07
1.E-06
0 50 100 150 200 250 300 350
times (t)
norm
alised r
ate
s (
mol m
-2 s
-1)
Rb Sr Y Zr Mo Tc Ru Rh Cs La Nd U
Ratio CORE60HBU
OUT60HBU
CORE48MBU
OUT48MBU
Rb/U 25.4 113.7 11.0 4.0
Sr/U 7.7 16.2 3.5 1.4
Y/U 1.8 1.7 2.3 3.0
Zr/U 0.02 0.04 0.2 0.1
Mo/U 4.1 29.7 4.2 2.0
Tc/U 0.5 0.5 1.3 1.1
Ru/U 0.3 0.8 0.3 0.7
Rh/U 0.2 0.5 0.3 0.8
Cs/U 2.0 40.2 10.0 3.1
Results
0,00
20,00
40,00
60,00
80,00
100,00
120,00
Rb/U Sr/U Y/U Zr/U Mo/U Tc/U Ru/U Rh/U Cs/U
dis
solu
tio
n r
ate
rat
io
60core
60out
48core
48out
Results: FP rates/ U rate
Some remarks
Fission products normalized dissolution rates are
similar in 48MBU for both core and out samples
Fission products normalized dissolution rates are
higher in out than in core samples in 60HBU
Rb, Sr, Mo, Cs are more segregated from UO2-grains
in 60HBU than in 48MBU
-12.00
-11.50
-11.00
-10.50
-10.00
-9.50
-9.00
-4.50 -4.00 -3.50 -3.00 -2.50 -2.00 -1.50 -1.00
log
rate
log [HCO3-]
Gray_33 MW d/kgU Röllin_43 MW d/kg U this_work_6OHBU_out this_work_60HBU_core
Serrano_53 MW d/kg U this_work_48MBU_core this_work_48MBU_out
Matrix dissolution rate comparison
Conclusions
Rim
Grains
Gap
Grains Boundaries
IRF 2 options:
IRF or matrix
2 options IRF or matrix
This work indicates that High BU Structure (RIM) can not be considered IRF. OUT Dissolution rate (including a percentage of RIM) lower than CORE rate for both HBU and MBU
Congruent dissolution with UO2-matrix: Np, Pu, Am, Cm, except for Np in 60HBU. Rb, Sr, Cs, Mo are more segregated from UO2-grains in 60HBU than in 48MBU
-phase Dissolution lower than UO2-matrix similar in both HBU and MBU fuels
Not studied in detail in
this work, only 3% of
grain boundary present
Not studied in this
work, no gap was
present
UO2-matrix dissolution ratehigher in MBU than in HBU
THANK YOU FOR YOUR ATTENTION
GRACIAS POR SU ATENCIÓN
And thanks to Argentina for sendingthis guy to Barcelona
Que bueno que viniste