development of nitride fuel and pyrochemical process for ... · content of presentation (1)...
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10-IEMPT Mito, Japan 1
The 10th OECD/NEA Information Exchange Meeting on Actinide and Fission Product Partitioning and Transmutation
October 6-10, 2008Mito, Japan
Development of Nitride Fueland Pyrochemical Process for
Transmutation of Minor Actinides
Y. Arai1), M. Akabori1), K. Minato1) and M. Uno2)
1) Japan Atomic Energy Agency (JAEA)2) Osaka University
10-IEMPT Mito, Japan 2
Content of Presentation
(1) Introduction of nitride fuel cycle development for transmutation of minor actinides (MA)
(2) Progress of thermal property measurements on nitride fuel• Thermal expansion, thermal conductivity, and so on • MA nitrides and their solid solutions• Burnup simulated nitrides• ZrN or TiN-containing nitrides
(3) Progress of pyrochemical process for treatment of spent nitride fuel• Electrochemical behavior of nitrides in LiCl-KCl melt• Formation of nitrides from electrodeposits in cathode
(4) Summary
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Double-Strata Cycle Concept and Nitride Fuel
Fuel Fabrication
Reprocessing
Repository
LWR/FBR
U, Pu
U, Pu
2nd StrataTransmutation
Cycle
U, PuMA, FP
Short-lived FP
1st StrataCommercial Cycle
MA, FP
• Each fuel cycle pursues safety and economy of the fuel cycle independently.
• Performance of the commercial power-generation fuel cycle is not disturbed by MA.
• Hazardous MA are confined in the dedicated transmutation fuel cycle with a small throughput.
Double-strata fuel cycle concept
Nitride fuel for MA transmutation• High thermal conductivity,
high melting point and high heavy metal density
• Mutual solubility among actinide mononitrides
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R&D Activities on Nitride Fuel and Pyrochemical Process
Flowsheet for MA transmutation fuel cycle
N-15
HLLW from Commercial Fuel Cycle
Partitioning
MA(+Pu) Nitride
Transmuter (ADS)
Spent Fuel
Molten Salt Electrorefining
MA(+Pu) Electrodeposits
Nitride Formation in liq. Cd
N-15
Preparation of MA bearing nitrides by carbothermic reduction
Measurement of thermal properties on MA nitrides and burnup simulated nitrides
Molten salt electrolysis for treatment of spent nitride fuel
Formation of nitrides from electrodeposits in cathode
Irradiation behavior of U-free nitride fuel
N-15 related issues
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Preparation of Nitride Fuel for ADS
Nitride fuel for ADS is a so-called U-free fuel. In this case, MA are contained as a principal component and a diluent material such as ZrN is added in place of U. A composition of nitride fuel proposed by JAEA is (MA0.24Pu0.16Zr0.6)N. There are two routes for preparation of nitride fuel for ADS.
One is the carbothermic reduction of MA oxides partitioned from HLLW, and the other is the nitride formation of MA and Pu recovered in liquid Cd cathode by pyrochemical reprocessing.
1) MA partitioned from HLLW
(MA oxide + carbon) sphere
MA nitride sphere
2) (MA + Pu) in liquid Cd cathode
(MA + Pu) nitride powder
(MA,Pu,Zr)N fuel for ADS ZrN
Sol-gel method
Carbothermic reduction
Nitridation/distillation combined reduction
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Thermal Expansion of MA Nitrides and Their Solid Solutions
• Thermal expansions of MA nitrides and their solid solutions were measured from room temperature to 1478K by high temperature X-ray diffractometry.
• Average thermal expansion coefficients of the solid solutions could be approximated by the linear mixture rule of respective mononitrides.
Ref. M. Takano, et al (2008)
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Heat Capacity of NpN and AmN
• Heat capacities of NpN and AmN were measured from 374 to 1071K by drop calorimetry and compared with literature values for UN and PuN.
• Heat capacities of actinide mononitrides had similar temperature dependence, although that of AmN was slightly smaller than those of UN, NpN and PuN.
Ref. T. Nishi, et al (2008)
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Thermal Conductivity of NpN and AmN
• Thermal diffusivities of NpN and AmN were measured from 473 to 1473K by laser flash method, from which thermal conductivities were derived.
• Thermal conductivities of actinide mononitrides decreased with the atomic number of actinides, although they had similar temperature dependence.
500 1000 15000
5
10
15
20
25
30
NpN
PuN (Arai et al.)
UO2 (Ronchi et al.)
AmN
Ther
mal
con
duct
icvi
ty (W
m-1K
-1)
Temperature (K)
UN (Arai et al.)
500 1000 15000
2
4
6
AmN : on heating : on cooling
: on heating : on cooling
Ther
mal
diff
usiv
ity (1
0-6m
2 s-1)
Temperature (K)
NpN
Ref. T. Nishi, et al (2008)
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Thermal Conductivity of Burnup Simulated Nitrides
200 600 1000 1400 18000
10
20
30
120
150
UN [This work] UN+M o 7.1 m ol% [This work] UN+M o 1.6m ol% [This work] U
0.973N d
0.027N [This work]
U0.878
N d0.122
N [This work]
M o(Handbook) (U,Nd)N+M o (L) [This work] (U,Nd)N+M o (H) [This work]
Therm
al condu
ctivity,
κ 0 (W m
-1 K
-1)
Tem prature, T (K)
• Thermal conductivity of UN+Mo : Almost independent of Mo content• Thermal conductivity of (U,Nd)N : Decrease with Nd content• Thermal conductivity of (U,Nd)N+Mo : Decrease with Nd content but
independent of Mo content
Ref. M. Uno, et al (2007)
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Thermal Conductivity of Nitrides with Diluent Materials
• Thermal conductivity of (U0.4Zr0.6)N : ≅ UN
• Thermal conductivity of 0.4UN+0.6TiN: >UN
Ref. M. Uno, et al (2007)
250 650 1050 1450 18500
10
20
30
40
50
60
70
80
250 650 1050 1450 18500
10
20
30
40
50
60
70
80
UN+TiN [This work] UN+TiN [This work] UN+TiN [Schulz Eq.]
Therm
al conductivity, κ
0 (W m
-1 K
-1)
U N [This w ork]
U0.4Zr
0.6N [This w ork]
ZrN (100 % T.D.) [Basini] ZrN (70 % T.D .) [Basini] ZrN (89.2 % T.D.) [Hedge]
TiN [literature]
Tem prature, T (K)
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Electrochemical measurement in LiCl-KCl-UCl3: CV and EMFPotential-controlled electrolysis using liquid Cd cathode
UN in UN+Mo and (U,Nd)N: Dissolution in LiCl-KCl at the similar potential as pure UN and recovery of U in liquid Cd cathodeMo in UN+Mo: Remain in anode undissoved NdN in (U,Nd)N: Dissolution but Nd almost stay in the salt phase
Comparison of CV before and after the electrolysis for UN+Mo and (U,Nd)N
Ref. T. Satoh, et al (2007)
Molten Salt Electrolysis of Burnup Simulated Nitrides
(U,Nd)N
Cur
rent
/ m
A UN+Mo
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Molten Salt Electrolysis of Nitrides with Diluent Materials
Electrochemical measurement in LiCl-KCl-UCl3: CV and EMFPotential-controlled electrolysis using liquid Cd cathode
UN in (U,Zr)N: Dissolution in LiCl-KCl at more positive potential (~by 1V) than pure UN and recovery of U in liquid Cd cathode UN in UN+TiN: Dissolution in LiCl-KCl at the similar potential as pure UN and recovery of U in liquid Cd cathode
Comparison of CV before and after the electrolysis for (U0.4Zr0.6)N
-1.2 -0.8 -0.4 0.0 0.4 0.8Potential / V vs. Ag/AgCl
Cur
rent
/ m
A
120
0
-40
40
80(U0.4Zr0.6)N
BeforeAfter
Ref. T. Satoh, et al (2008)
100
50
0
-50
(B)
(A)
UN
(U0.4Zr0.6)NZrN
-1.2 -0.8 -0.4 0.0 0.4 Potential / V vs. Ag/AgCl
Cur
rent
/ m
A
(U0.4Zr0.6)N
Comparison of CV between UN, (U0.4Zr0.6)N and ZrN
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AmN Formation Behavior in Molten Cd
10 20 30(deg.)
Inte
nsity
(arb
. uni
t)
Reference AmN(by carbothermic reduction)
Products of reaction
**
××
××
Am-Cd alloy(Cd+AmCd6)
▼
▼
▼ ▼▼
▼▼▼
▼:Cd□:Am2O3
□ □▼ □ □ ▼
▼
*:Pt holder×:W holder
2θ
Appearance of AmN powder after heating the product in vacuum at 723K
(1) Electrolysis of AmN in LiCl-KCl-AmCl3 melt with liquid Cd cathode(2) Nitridation/distillation combined reaction of the electrodeposits
in N2 stream at 973K(3) Vacuum heating at 723K for removal of residual Cd
Prepared by carbothermic reduction of AmO2 Prepared by solid-solid reaction of AmN and CdCl2
Constituted by Cd and AmCd6
Ref. H. Hayashi, et al (2008)
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Nitride Pellet Preparation from Pyrochemical Process
(U,Pu)N pellet in Mo crucible before electrolysis
Liquid Cd cathode in Al2O3crucible after electrolysis
U-Pu-Cd in Y2O3 crucible before nitridation/distillation combined reaction
(U,Pu)N powder obtained by nitridation/distillation combined reaction
(U,Pu)N pellet prepared by sintering in flowing Ar-H2atmosphere at 2023K
Single phase of (U,Pu)NDensity: ~84%TDO2 impurity: 0.1~0.2wt%
Ref. Y. Arai, et al (2008)
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For demonstrating technical feasibility of nitride fuel cycle for transmutation of MA, fundamental study has been carried out continuously by use of MA, Pu and burnup simulated nitrides.
Thermal properties, such as thermal expansion, heat capacity and thermal conductivity, of MA nitrides and burnup simulated nitrides have been almost clarified. Measurements on MA nitrides with a diluent material such as ZrN or TiN are ongoing.
As for pyrochemical process for the treatment of spent nitride fuel, molten salt electrolysis and actinide-renitridation process have been investigated. Material balance of actinides throughout the process is to be clarified in a laboratory scale.
Further study shall include the preparation of thermal and thermodynamic database on MA nitride fuel cycle in addition to ongoing experimental study, which will contribute to the progress of design study and evaluation of fuel behavior.
Summary
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Part of this study was carried out within the task “Technological development of a nuclear fuel cycle based on nitride fuel and pyrochemical reprocessing” entrusted from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan.
Acknowledgement