Development of Nitride Fuel and Pyrochemical Process for - - PowerPoint PPT Presentation

10-IEMPT Mito, Japan 1

The 10th OECD/NEA Information Exchange Meeting on Actinide and Fission Product Partitioning and Transmutation October 6-10, 2008 Mito, Japan

Development of Nitride Fuel and 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 Strata Transmutation Cycle

U, Pu MA, FP

Short-lived FP 1st Strata Commercial 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 1500 5 10 15 20 25 30 NpN PuN (Arai et al.) UO2 (Ronchi et al.) AmN Thermal conducticvity (Wm

• 1K
• 1)

Temperature (K) UN (Arai et al.)

500 1000 1500 2 4 6 AmN : on heating : on cooling : on heating : on cooling Thermal diffusivity (10

• 6m

2s

• 1)

Temperature (K) NpN

• Ref. T. Nishi, et al (2008)

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Thermal Conductivity of Burnup Simulated Nitrides

200 600 1000 1400 1800 10 20 30 120 150

UN [ Thi s wor k] UN+M o 7. 1 m ol % [ Thi s wor k] UN+M o 1. 6m ol % [ Thi s wor k] U 0.

973Nd0. 027N

[ Thi s wor k] U 0.

878Nd0. 122N

[ Thi s wor k] M o( Handbook) ( U, Nd) N+M o ( L) [ Thi s wor k] ( U, Nd) N+M o ( H) [ Thi s wor k]

Ther m al conduct i vi t y,

κ0

( W m

• 1

K

• 1)

Tem pr atur e, 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 1850

10 20 30 40 50 60 70 80

250 650 1050 1450 1850

10 20 30 40 50 60 70 80

UN+Ti N [ Thi s wor k] UN+Ti N [ Thi s wor k] UN+Ti N [ Schul z Eq. ] Therm al conduct i vi ty,

κ0

( W m

• 1

K

• 1)

UN [ Thi s w ork] U 0.

4Zr 0. 6N

[ Thi s w ork] Zr N ( 100 % T. D. ) [ Basi ni ] Zr N ( 70 % T. D . ) [ Basi ni ] Zr N ( 89. 2 % T. D. ) [ Hedge] Ti N [ l i terature] Tem pr at ur e, T ( K)

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Electrochemical measurement in LiCl-KCl-UCl3: CV and EMF Potential-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 cathode Mo 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

Current / mA

UN+Mo

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Molten Salt Electrolysis of Nitrides with Diluent Materials

Electrochemical measurement in LiCl-KCl-UCl3: CV and EMF Potential-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 0.8

Potential / V vs. Ag/AgCl Current / mA 120

• 40

40 80 (U0.4Zr0.6)N Before After

• Ref. T. Satoh, et al (2008)

100 50

• 50

(B) (A) UN (U0.4Zr0.6)N ZrN

• 1.2 -0.8 -0.4 0.0 0.4

Potential / V vs. Ag/AgCl Current / mA (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.) Intensity (arb. unit)

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 Al2O3 crucible 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-H2 atmosphere at 2023K Single phase of (U,Pu)N Density: ~84%TD O2 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

• ngoing 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