9th IEM on Actinide and Fission Product Partitioning and Transmutation
26-28 September 2006
Hotel Novotel Atria , Nîmes, France

JAEA’s Activities on Nitride Fuel
Research for MA Transmutation
Yasuo ARAI, Mitsuo AKABORI, Kazuo MINATO
Division of Fuels and Materials Engineering
Nuclear Science and Engineering Directorate
Japan Atomic Energy Agency (JAEA)
1

Nitride Fuel Development in Japan¾ Dedicated fuel for transmutation of long-lived MA
R&D on Accelerator-Driven System (ADS) for MA transmutation
is in progress in JAEA. The first candidate of the fuel material is
U-free nitride fuel, such as (MA,Pu)N-ZrN.

¾ Advanced fuel for Gen.-IV type fast reactors (FRs)
In the “Feasibility Study on Commercialized Fast Reactor CycleSystems” (FS) in Japan, (U,Pu,MA)N is considered as acandidate fuel for GFR and LFR.

R&D on nitride fuel has been shifted from FRs to ADS.
2

Study on MA Transmutation Fuel Cycle in JAEA
Contents of Presentation R&D
on
9 Fabrication of MA bearing
nitrides by carbothermic
reduction
9 Property measurements onMAbearing nitrides and burnup
simulated nitrides
9 Pyrochemical process fortreatment of spent nitridefuel
9 Nitride formation behaviorof actinides in liquid Cd
cathodeHLLW from Commercial Fuel CyclePartitioning

N-15MA(+Pu) NitrideADS
Spent Fuel
Molten Salt Electrorefining

N-15MA(+Pu) Electrodeposits
Nitride Formation in liq. Cd
Flowsheet for MA transmutationfuel cycle based on double-strata
concept3

Preparation of MA Nitride Fuel
- Preparation of MA nitrides by carbothermic reduction 9 Reduce loss of Am by evaporation
Lowering temperature of reduction
9 Reduce O and C impurities in nitride
Controlling C/MO2 mixing ratio
9 Confirm formation of solid solution
Single phase of (Np,Pu,Am,Cm)N

X-ray diffraction pattern of (Np,Pu,Am,Cm)N
4

Preparation of MA Nitride Fuel with ZrN- Effects of ZrN added as a diluent material in (MA,Zr)NFormation of two phases(Depending on composition)
Improvement of chemical stability

Weight gain, %

30

20AmN
Am(OH)3

100-10(Am0.1Zr0.9)N0.7C0.3

0100
200
Exposure time, h300

Weight gain of AmN and (Am,Zr)N
exposed in air at room temperature

XRD pattern of (Pu,Am,Cm)N and(Pu,Am,Cm,Zr)N5Preparation of Nitride Pellets without MA(1) Preparation of (Dy,Zr)N pellets for screening test of sintering aid
9Sintering temperature of MA nitride pellets should be lower than
1873K for preventing the loss of Am by evaporation.

9Pd, Ni, YH2, AlN, Si3Ni4, and Y2O3 powders were tested forsintering aid.

9(Dy0.4Zr0.6)N pellets with ~90%TD were prepared by sintering at
1823K in N2 gas stream by use of AlN as sintering aid.

(2) Preparation of UN-based burnup simulated pellets in which Nd, Mo orPd were added and UN pellets containing ZrN as a diluent material(U,Nd)N, UN+Mo, UN+Pd and (U,Zr)N pellets were prepared forthermal, mechanical and electrochemical property measurements.
(3) Preparation of PuN pellets containing ZrN or TiN as a diluent material(Pu,Zr)N and PuN+TiN pellets were prepared for irradiation tests
and electrochemical property measurements.
6Property Measurements of MA Nitride (1)- Determination of thermal conductivity of AmN 9 AmN disk with 78%TD was preparedby sintering at 1823K in N2-H2 stream.
9 Thermal diffusivity of AmN wasmeasured by laser flash method from373 to 1473K for the first time.
9 Thermal conductivity was determinedfrom thermal diffusivity of AmN
together with heat capacity of PuN.
9 Thermal conductivity of actinide
mononitrides decreases with atomic
number of actinides and gradually
increases with temperature in thetemperature range investigated.
Thermal conductivity of actinide
mononitrides corrected to 100%TD

7

Property Measurements of MA Nitride (2)- Determination of thermal expansion of NpN and AmN 9 Thermal expansion of NpN andAmN was measured by hightemperature X-ray diffractometry.
9 Thermal expansion of NpN
almost agreed with UN, whereasthat of AmN was larger than UNand comparable to PuN.
9 Measurements on thermal
expansion of (Np,Am)N and(Pu,Am)N are underway.
9 Besides thermal diffusivity andthermal expansion, heat capacity
measurements of MA nitrides
have been started recently.

Thermal expansion of NpN and AmN in
comparison with UN and PuN
8Pyrochemical Process of Spent Nitride Fuel• Electrodissolution at Anode

Anode basket+AnN = An3+ + 3e- + 0.5N2

Liquid Cd cathode-15N gas2• Electrodeposition at CathodeAn3+ + 3e- + xCd = AnCdx
Pu, MA• Nitride Formation fromElectrodeposits

FPAnCdx + 0.5N2 = AnN +xCd An = (MA, Pu)

Nitride fuelLiCl-KClmolten salt

Schematic of Pyroprocess for Spent Nitride
Fuel
9Electrochemical Behavior of Actinide Mononitrides=• Equilibrium of LiCl-KCl-AnCl3 system (An: actinides)
An = An3+ + 3eLa3+/La Pu3+/PuNp3+/Np
Ce3+/CeU4+/U3+U3+/U-1.5-0.5-1.0～～-2.0at 773K

0E(V) vs. Ag/AgCl=REN PuN NpN UN• Potential shift owing to the formation of actinide nitride(~0.7V)An = An3+ + 3eAnN = An + 0.5 N2 … ΔG˚f (Free energy of formation forAnN)

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Electrochemical Behavior of (U,Zr)N and (Pu,Zr)N¾ Since UN and PuN were stabilized by the formation of (U,Zr)N and(Pu,Zr)N solid solutions, higher anode potential than applied to UNand PuN was necessary for the dissolution. However, U, Pu and Zrcould be recovered in liquid Cd cathode by the potential controlled
electrolysis.

C u rre n t / m A

1 20Beforeelectrolysis

80

電解前電解後Afterelectrolysis

400-40Appearance of (Pu,Zr)N anode used
for the cyclic voltammetry and thepotential controlled electrolysis-1 .2-0 .8 -0 .4
0 .0
0.4
0 .8
P o te n ti a l / V (vs . A g / A g C l)

Cyclic voltammograms of (U,Zr)N in LiClKCl melt before and after the electrolysis 11

Electrode Reaction of Am in LiCl-KCl-AmCl3 Melt
¾ Electrode reaction of Am in LiCl-KCl-AmCl3 melt was investigated byuse of solid Mo and liquid Cd electrodes. Redox reactions ofAm(III)/Am(II) and Am(II)/Am were observed at solid Mo electrode,
while only redox reaction of Am(III)/Am was observed at liquid Cdelectrode.
0.005

0.01

IIa

Cd2+/Cd

Ia/Am2+
Am3+I(A)
I(A)

IIIa

I(A)

0Ic

0IIc

Am2+/Am-0.005

Am 3+/Am(in Cd)

100mV/s
50mV/s
10mV/s-0.01
Li+/Li(in Cd)

IIIc
Li+/Li-0.01-2.5-2-1.5-1

E(V) vs Ag/AgCl-0.5

0-2-1.5-1-0.5

E(V) vsvs Ag/AgClAg/AgCl
E(V)Cyclic voltammograms of LiCl-KCl-AmCl3 with solid Mo (left)
and liquid Cd (right) electrodes at 723K

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Nitridation-Distillation Reaction for Pu-Cd- Heating Pu-Cd alloy (Pu; 12wt.%) at 973 K in flowing N2 gas -Appearance of Pu-Cd alloy(lower) and PuN powder
recovered (upper)

Change of XRD pattern during reaction
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Nitridation-Distillation Reaction for Pu-U-Cd- Heating Pu-U-Cd alloy with small amount of RE at 973 K in flowing N2 gas
Pu/(U+Pu)=0.71

Appearance of(U,Pu,RE)-Cd alloy
Concentrationin Cd (wt.%)
UPuLaCePr
Nd

2.88
6.93
0.016
0.101
0.105
0.251

Change of XRD pattern duringreaction

14Pellet Preparation from Nitride Powder Recovered- Nitride fuel fabrication in pyrochemical process PuN

PowderPu/(U+Pu)=0.53

U2N3XRD pattern of powder obtained by thenitridation-distillation combined method

Sintered pellet(U,Pu)N(U,Pu)O2XRD pattern of pellet sintered at 1973K
in Ar-H2 mixed gas stream15Irradiation Test of U-Free Nitride Fuel in JMTR
(Pu,Zr)N pellets(Pu,Zr)N

PuN+TiN

Irradiation period May 2002 ~ Nov. 2004 (246PuN+TiN pellets
Upper endplug(SUS316)

EFPD)
Av. linear power
408 W/cm
355 W/cm
Burnup14.7 at%-Pu
17.0 at%-Pu
Max. fuel Temp.
1273 K1083 K(Estimation)
tube
SUS316,mm∅,-Cladding
PIEs havebeen completed
in 9.40
JAEA’shot0.51
cells.mmt
Plenum spring(Inconel X)

UNpellet(Pu,Zr)Npellet

PuN+TiNpellet36UNpellet

Lower endplug(SUS316)

3696230
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Results of PIEs for U-Free Nitride Fuel (1)Diameter (mm)- Cross sections, profilometry, X-ray radiography and gamma scanning-(Pu,Zr)N

径

9.60

9.6

9.55

9.55

9.50

9.5

9.45

9.45

9.40

9.4(Pu,Zr)N

9.35

PuN+TiN

9.3
0

20

40

60

80

100

120

140

160

180

200

測定位置（ｍｍ）

UN

PuN+TiN

UN

UN

Cs134

17

Results of PIEs for U-Free Nitride Fuel (2)- Results of swelling and fission gas release of pellets -(Pu,Zr)N

PuN+TiN

Density before irradiation 7.22 g/cm3
90.4 %TD

5.14 g/cm3
86.6 %TD

Density after irradiation

6.91 g/cm3
86.4 %TD

4.92 g/cm3
83.7 %TD

Volume increase rate ΔV/V

3.6 %

2.6 %

FP gas release rate
1.6%((Xe+Kr) released/(Xe+Kr) produced)

18

Conclusion
9 R&D on nitride fuel cycle for transmutation of MA in
JAEA has been progressed by experiments on fuelfabrication, property measurements, pyrochemical
process and irradiation test.
9 Thermal and electrochemical properties of MA bearing
nitrides have been investigated, mainly focusing on AmN
and nitrides containing ZrN as a diluent material.
Property measurements of UN-based burnup simulated
nitrides are also in progress.
9 PIEs of U-free nitride fuel, (Pu,Zr)N and PuN+TiN,
irradiated in JMTR have been completed. For the moment,
no detrimental effect on irradiation behavior has been
observed by the addition of such diluent materials.
9 Domestic and international collaboration is essential for
19further development of nitride fuel cycle for MA

Acknowledgement

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.

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