nitride fuel and pyrochemical process developments for transmutation of minor actinides in jaeri...

Nitride Fuel and Pyrochemical Process Nitride Fuel and Pyrochemical Process Developments for Developments for

Transmutation of Minor ActinidesTransmutation of Minor Actinidesin JAERIin JAERI

Masahide Takano, Mitsuo Akabori, Kazuo Minato, Yasuo Arai

Japan Atomic Energy Research Institute

OECD/NEA 8th Information Exchange Meeting on Actinide and Fission Product Partitioning & Transmutation, Las Vegas, USA, 9-11 Nov. 2004


>Background

>PROMINENT program

>Fabrication of MA nitrides Carbothermic synthesis of (Pu,Am,Cm)N & (Pu,Am,Cm,Zr)N

>Property Measurements of MA nitrides Hydrolysis & Evaporation behavior of AmN & (Am,Zr)N

>Pyrochemical process Pu nitridation in Pu-Cd alloy

>Irradiation test (Pu,Zr)N & PuN+TiN

>Conclusion

Content


Nitride fuel cycle - background

> JAERI has proposed double strata fuel cycle for MA transmutation, based on U-free nitride fuel, ADS, and pyrochemical reprocessing.

> Expected on nitride fuel: Good thermal properties, Mutual solubility among MA nitrides, High heavy metal density

> Experiments on MA nitride: Limitation in facility, apparatus, handling, material amount, High purity inert atmosphere required

> We have studied on: Fuel fabrication technology Property measurements Irradiation behavior Pyrochemical process


PROMINENT program

Pyrochemical ProcessTechnology

Fuel IrradiationExperiment

Nitride Fuel Cycle

Fuel Fabrication

Reprocessing Pu/MA burning

Fuel FabricationTechnology

Fuel PropertyMeasurement

Research areas in PROMINENT program

> JAERI, Osaka Univ, MMC, NDC, JAPC

> Started Nov. 2002, five year program

> Development and demonstration of elemental technology

for nitride fuel cycle in laboratory scale

PROMINENT:

Property Measurements,

Pyrochemical Process and

Irradiation Experiments Needed

for Nitride Fuel Cycle Technology.


Fabrication of MA nitrides (1)

243Am2O3, (240Pu,244Cm)O2, ZrO2

amorphous carbon

> Starting materials

> Fabrication method

Carbothermic reduction of oxides mixture

MOx + xC + 1/2N2 MN + xCO

Nitridation: N2 1300 ºC

Decarburization: N2+4%H2 1500 ºC> Analyses

X-ray diffraction

N,O,C analyses

(Pu,Am,Cm)N

(Pu,Am,Cm,Zr)N

Process temperature and CO gas release

> Pu+Am+Cm+(Zr) nitrides

30~40 mg scale



Expected product

Pu/Am/Cm/Zr molar ratio

C/O molar ratio

Mixture weight (mg)

(Pu,Am,Cm)N (Pu,Am,Cm,Zr)N

31.40 37.58

0.45 /0.34 /0.21 /0 0.14 /0.10 /0.06 /0.70

1.32.0

Composition of the oxides and carbon mixtures



(Pu,Am,Cm)N

(Pu,Am,Cm,Zr)N

XRD profiles of products

> (Pu,Am,Cm)N

Single phase solid solution

0.4956nm (0.4960 nm by Vegard’s law)

No oxide phase

Low carbon content (<0.05 wt%)

> (Pu,Am,Cm,Zr)N

Double phases with NaCl structure

different (Pu,Am,Cm)/Zr ratio

Low oxygen content (0.15 wt%)

High carbon content (1.3 wt%)

remained as carbonitride


AmN Am(OH)3 Am2O3

Property measurements (1) Hydrolytic behavior

> MA nitrides are reactive with moisture

> Hydrolysis of AmN and (Am,Zr)N

observed in ambient air

> AmN reacted with moisture

to form Am(OH)3

> (Am0.1Zr0.9)N retained the phase

over 1000h

Weight gain of AmN, (Am,Zr)Nand (Dy,Zr)N in air and moist N2


Property measurements (2) Evaporation behavior

> Am has high vapor pressure

> Evaporation behavior of AmN &

(Am,Zr)N in He gas flowAmN = Am(g) + 1/2N2

> Evaporation rate constant, k (s-1)

v = -(dN/dt) = kN

> AmN retained the phase while heating,

no metallic phase

> Selective evaporation of AmN on (Am,Zr)N

change in composition

> k of AmN in (Am,Zr)N depressedArrhenius’ plots of k


Property measurements (3) New apparatus

> Apparatus for thermal property measurements installed

> Thermal diffusivity ~ laser flash method sample diameter 3~5 mm installed in Ar atmosphere

> Specific heat capacity ~ drop calorimeter sample sealed in Pt capsule

> Designed for nitrides and small sized samples

> Thermal expansion ~ high temp. XRD installed in Ar atmosphere


Pyrochemical process of nitride fuel

> Anodic dissolution of PuN

in LiCl-KCl eutectic salt examined

> Recovery of Pu into liquid Cd cathode

demonstrated with high current efficiency

Schematic diagram of pyrochemicalprocess for nitride fuel

> Pu in Pu-Cd alloy converted to PuN

> Experiments on Am-containing nitride

will start soon at “TRU-HITEC”


Nitridation of Pu in Pu-Cd alloy

(a) N2 bubbling process

Cd

N2 gas

Pu-Cd

PuN

Furnace

(b) Nitridation-distillation combined process

> N2 bubbling process

U in U-Cd: 100% recovery

Pu in Pu-Cd: only 10% recovery

decrease in Pu activity in Pu-Cd

> Nitridation-distillation combined process

Pu: 99% recovery

PuN with high purity obtained

Pu-Cd (12wt% Pu) Recovered PuN

Crucible

N2 gas

Pu-Cd melt

PuN

LiCl-KCl

723K

973K


Irradiation test ongoing

(Pu,Zr)N

PuN+TiN

> (Pu,Zr)N & PuN+TiN pellets

Pu: 20wt%, He-bond

> Irradiation ongoing at JMTR

Linear power: ~40kW/m

Target burnup: 20 at% of Pu

> Basic irradiation behavior of

U-free nitride fuel

Irradiation: May 2002 ~ Nov. 2004

PIE: Apr. 2005 ~

Irradiation test schedule> Irradiation of (Pu,Np,Zr)N pellet

scheduled at JOYO with JNC


Concluding remarks

> (Pu,Am,Cm)N and (Pu,Am,Cm,Zr)N synthesized

by carbothermic reduction of the oxides

Mutual solubility among PuN-AmN-CmN was demonstrated.

> Hydrolysis and evaporation behavior of AmN and (Am,Zr)N studied

> Pu nitridation in Pu-Cd alloy investigated

AmN was chemically and thermodynamically stabilized

by formation of solid solution with ZrN.

Simultaneous nitridation-distillation process yielded high purity PuN.

nitride fuel and pyrochemical process developments for transmutation of minor actinides in jaeri...

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