UCF

Metallic Nuclear Fuel Study at University of Central Florida (UCF)

Ke Huang 09/27/2011

UCF

2

Outline

Ø Introduction

Ø Objective

Ø Experimental Details

Ø Results and Discussion

Ø Future Plan

Ø Sponsor, Partner and Group Members

UCF

3

Introduction: Metallic Fuel

Nuclear energy is very important: Advantages: •  Safest •  Cheapest •  Clean •  High Efficiency

Major nuclear fuel types: •  Oxide •  Metallic •  Ceramics (carbide, nitride)

Metallic fuels[1]: Advantages: •  high thermal conductivity •  passive safety •  ease of fabrication •  ease of recycling

Alloy elements are required, such as: Zr, Mo, Ti, Cr.

Use of nuclear power: •  20% in USA •  30% in EU •  80% in France •  30% in Japan

[1] G.L. Hofman, et al, Prog Nucl Energ, 31 (1997) 83-110.

UCF

4

Introduction: U-Zr fuel

U-Zr fuel: •  developed for sodium fast reactor (SFR) •  encapsulated in stainless steel cladding

SFR[1]: •  generation IV nuclear reactor designs •  employs liquid sodium as coolant •  employs fast neutrons as source •  high efficiency of using nuclear fuels •  minimizes long-lived actinide waste production

FCI (Fuel Cladding Interaction)

U-23at.%Zr vs. Fe diffusion couple annealed at 923K [2].

[2] K. Nakamura, et al, J Nucl Mater, 275 (1999) 246-254.

UCF

5

Introduction: U-Mo fuel

U-Mo fuel: •  developed for the program of Reduced Enrichment for Research and Test Reactor (RERTR)

•  dispersed or laminated in aluminum or Al alloy RERTR [3]:

•  to avoid nuclear proliferation •  convert research and test reactor from using HEU fuels to LEU fuels •  increase density of U isotopes in the fuel

Al

UMo

U-10wt.%Mo vs Al at 550°C for 1 hour[4] U-10wt.%Mo vs Al after irradiation [5]

[3] D. Keiser, et al, JOM 55 (2003) 55-58. [4] F. Mazaudier, et al, J Nucl Mater, 377 (2008) 476-485. [5] D. Wachs, et al, High Density Fuel Development for Research Reactors,(2007).

UCF

6

Introduction: FCI and Objective

FCI (Fuel Cladding Interaction) •  induced by interdiffusion. •  involves multiple-phases and multiple-components. Deleterious effects: •  thins the cladding layer. •  produces phases with relative low melting point.

Objective: to help understand the complex FCI . to provide the experimental diffusion data to verify and improve FCI modeling. to explore potential barrier layer materials to impede FCI. Experiments: Solid-to-solid isothermal diffusion studies were carried out. Scanning Electron Microscopy (SEM) and Electron Probe Microanalysis (EPMA ) and Transmission electron microscopy (TEM) were applied to analyze the microstructure, phase constituents and concentration profiles.

UCF

7

Experimental Details

UCF

8

Diffusion Matrix

U related diffusion Cladding related diffusion

U  vs.  Fe   Fe  vs.  Mo  U  vs.  Fe-­‐15Cr   Fe  vs.  Zr  U  vs.  Fe-­‐15Cr-­‐15Ni   Mo  vs.  Zr  U-­‐Zr  vs.  Fe   Mo  vs.  Fe-­‐15Cr  U-­‐Zr  vs.  Fe-­‐15Cr   Zr  vs.  Fe-­‐15Cr  U-­‐Zr  vs.  Fe-­‐15Cr-­‐15Ni   Mo  vs.  Fe-­‐15Cr-­‐15Ni  U  vs.  Mo   Zr  vs.  Fe-­‐15Cr-­‐15Ni  U-­‐Mo  vs.  Al  U-­‐Mo  vs.  Al-­‐Si  

UCF

9

U vs. Fe Diffusion Couples

UCF

10

U vs. Fe: SEM and EPMA

U U6Fe UFe2 Fe

00.10.20.30.40.50.60.70.80.91

0 50 100 150

Concen

tration  (atom  fractio

n)

Distance  (µm)

FeU

SEM and EPMA concentration profiles of U vs. Fe at 923K for 4 days.

Thickness of U6Fe and UFe2.

UCF

11

U vs. Fe: Growth Constant

1E-­‐18

1E-­‐17

1E-­‐16

1E-­‐15

1E-­‐14

1E-­‐13

1 1.05 1.1 1.15 1.2

1000/T(K)

K2  U6Fe  in  A  phaseK2  U6Fe  in  B  phasesK2  UFe2  in  A  phaseK2  UFe2  in  B  phaseK1  U6Fe  in  A  phaseK1  U6Fe  in  B  phaseK1  UFe2  in  A  phaseK1  Ufe  2  in  B  phase

KII U6Fe  α-­‐UKII U6Fe  β-­‐UKII UFe2 α-­‐UKII UFe2 β-­‐UKI U6Fe  α-­‐UKI U6Fe  β-­‐UKI UFe2 α-­‐UKI  UFe2 β-­‐U

Grow

th  Con

stan

t,  K(

ν)   (m

2 /s)

• First kind (extrinsic) growth constant KI and second kind (intrinsic) growth constant KII were calculated according to Wagner [6] description. • KII is a characteristic constant value for a phase, and the values of KI may be affected by other phases existing in the diffusion zone. • The thick U6Fe impeded the growth of UFe2 because KI, UFe2 was smaller than KII, UFe2. However, UFe2 layer had a small influence on the growth of U6Fe, since UFe2 is very thin compared to U6Fe.

U U6Fe UFe2 Fe

[6] C. Wagner, Acta Metallurgica, 17 (1969) 99-107.

UCF

12

Intrinsic and Extrinsic Growth Constant

First Kind of Diffusion couples (N-∞=0 ; N+∞=1) “Extrinsic”

1,0

2)()(

2)(

== ∞+∞−

⎥⎦

⎤⎢⎣

⎡ Δ=

ii NN

vvI t

xK

1,0

)()(

)(

)()(

)()()()()(,

)(

)(

)(

)(

)1(

)1(

2)1(~~

==

∞+

∞−

∞+∞−

+

−

+

−

⎥⎥⎥⎥⎥⎥

⎦

⎤

⎢⎢⎢⎢⎢⎢

⎣

⎡

−×+

×−

Δ+−×==

∫

∫∫

ii

v

v

vi

vi

NN

x

vi

m

vmv

i

x

i

m

vmv

iv

vI

vi

vi

N

N ivInt

i

dxNV

VN

dxNV

VN

t

xKNNdNDD

Integrated Interdiffusion Coefficient:

Second Kind of Diffusion couples (N-∞= N(v-1) ; N+∞= N(v+1)) “Intrinsic”

[ ] )1()1( ,)(

)1()1(

)()1()1()()(,

)())((~

+∞+−∞− ==+−−+

−++−

×−

−−= v

iivii NNNN

vIIv

ivi

vi

vi

vi

vivInt

i KNN

NNNND

UCF

13

U-Zr vs. Fe Diffusion Couples

UCF

14

U-Zr vs. Fe: SEM

SEM of U10wt.%Zr vs. Fe at 650 C for 4 days.

•  Layer-A including reaction layers adjacent to Fe. •  Layer-B including layers with ε-phase and χ-phase. •  Layer-C including layer with λ-phase.

UCF

15

1.00E-17

1.00E-16

1.00E-15

1.00E-14

1.00E-13

1.00E-12

1.04 1.05 1.06 1.07 1.08 1.09 1.1 1.11 1.12

Gro

wth

con

stan

t (m

2 /s)

1000/T (K)

LayerA LayerB LayerC SUM

U-Zr vs. Fe: Growth Constant

Activation Energy Layer A : 393 kJ/mol Layer B : 363 kJ/mol Layer C : 224 kJ/mol Sum : 304 kJ/mol

UCF

16

U vs. Mo Diffusion Couples

UCF

17

U vs. Mo: SEM and EPMA

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

-­‐800 -­‐700 -­‐600 -­‐500 -­‐400 -­‐300 -­‐200 -­‐100 0 100

Fitted

Measurement  1  EPMA

Measurement  2  EPMA

XK=-­‐70

Distance  to  Matano  Plane,  x  (µm)

Concen

tration  of  M

o,  N

Mo(atom  fractio

n)

SEM image and concentration profiles of U vs. Mo at 1273K for 24 hours.

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

-­‐70 -­‐60 -­‐50 -­‐40 -­‐30 -­‐20 -­‐10 0 10 20

Fitted

Measurement  1  EPMA

Measurement  2  EPMA

XK=-­‐26

Distance  to  Matano  Plane,  x  (µm)

XK=-­‐26

Concen

tration  of  M

o,  N

Mo(atom  fractio

n)

 

SEM image and concentration profiles of U vs. Mo at 973K for 360 hours.

•  Phase Boundary •  Marker Plane •  U diffused faster than Mo

U XK MoXIXβγ

UCF

18

U vs. Mo: Interdiffusion

Interdiffusion coefficients of U-Mo alloy.

1.0E-­‐17

1.0E-­‐16

1.0E-­‐15

1.0E-­‐14

1.0E-­‐13

1.0E-­‐12

0.7 0.8 0.9 1 1.1 1.2

Interdiffusion  Co

efficient

(m2 /s)

1000/T  (K)

0.12  at.frac.  Mo

0.18  at.frac.  Mo

0.24  at.frac.  Mo

Temperature dependence of interdiffusion coefficients at NMo=0.12, 0.18, 0.24.

Composition dependence of activation energy of interdiffusion.

1E-­‐17

1E-­‐16

1E-­‐15

1E-­‐14

1E-­‐13

1E-­‐12

1E-­‐11

0 0.05 0.1 0.15 0.2 0.25 0.3

Interdiffusion  Co

efficient

(m2 /s)

1273K  this  study1173K  this  study1073K  this  study973K  this  study923K  this  study

NMo (atom  fraction)