Wir schaffen Wissen – heute für morgen

Paul Scherrer InstitutEberhard H. Lehmann , Pierre Boillat, A. Kaestner, P. Vontobel

P. Oberholzer

Neutron Imaging Methods for the Investigation of

Energy Related Materials

Fuel Cells, Battery, Hydrogen Storage and Nuclear Fuel24. September 2012PSI,

NEUTRONS for ENERGY

• 10 years ago: a conference about nuclear energy

would be expected

• today: most talks related to alternative (renewable)

energy research

• however: there is a potential in neutron research for

nuclear materials too …

Outline

24. September 2012PSI,

1. Introduction

2. THE METOD OF NEUTRON IMAGING

3. FACILITIES AT PSI

4. APPLICATIONS IN THE ENERGY FIELD• Electric Fuel Cell Research• Li-Ion Batteries• Hydrogen Storage• Nuclear Fuel Inspection

5. Discussion

6. Conclusion & outlook

Introduction: the problems to be solved

24. September 2012PSI,

•To provide non-destructive and non-invasive tools for material tests and performance optimization

•Neutrons have properties in this respect which can be used alternatively and complementarily to the more established X-ray methods

•As a guide line for neutron studies: heavy elements are transparent, light elements deliver relatively high contrast

Comparison N �������� X (example: hard-disk drive)

Neutron Image

X-ray Image

Principle of neutron imaging

deII ⋅Σ−⋅= 0

I0 = initial beam intensityI = beam intensity behind the sampled = sample thickness in beam directionΣ = attenuation coefficient of the material

���� quantification of the involved materials

Neutron Imaging - Setup

Spallation neutron source SINQ @ PSI

•In operation since 1997

•Driven by 590 MeVprotons on a Pb target

•Intensity about 1.2 mA,corresponding to 1MWthermal power

•Installations for researchwith thermal and coldneutrons

Still the world‘s strongeststationary spallation source

Still the world‘s strongeststationary spallation source

SINQ – Layout, Imaging Beam Lines

ICON

BOA

ICON-beam line @ SINQ

Micro-Tomography-Position

Position for large objects

variableapertures

1 … 80 mm,Be filter

Space for Selectoror Chopper

Beam limiters

Performance of the Imaging Beam Lines

Detector options with CCDs

0

0.1

0.2

0.3

0.4

0 50 100 150 200 250 300 350 400 450

Field-of-View [mm]

pixe

l siz

e [m

m] MAXI

MICROMIDI

FOV and pixel size for the detector systemsat PSI‘s neutron imaging facilities

Micro-Tomographie-Setup an ICON

Specifications•FOV: 2.7cm * 2.7cm•Pixel size: 13µm•CCD with 2048*2048 pixels•Scintillator 10 µm thick•L/D>1000

Example for neutron micro-tomography

5 mm

APPLICATIONS IN THE ENERGY FIELD

• Polymer-Electrolyte-Membrane (PEM) fuel cell ,

• Lithium -Ion batteries

• Hydrogen storage in several metallic structures

• Study of nuclear fuel and its cladding

� Results for these topics �

� appoaches and offer to partners �

PEM Fuel Cell - Principle

H2 O2

H2O

+

+

+

+

+

+

+

+

H+

e-

Fuel Cell Research @ PSI

Anode :H2 2 H+ + 2 e-

1/2 O2 + 2 H+ + 2 e-Cathode :

H2O

H2 O2

H2O

+

+

+

+

H+

e- Condensed water can disturb the access of gaseous reactants

Source: P. Boillat, Electrochemistry, PSI

The membrane needs humidification to provide proton conductivity

Through-plane option

Beam

Cell

Detector Radiogram

•High frame rate possible (~30 Hz), depending on beam intensity•Spatial resolution ~0.2 mm only•Behavior at cathode or anode not distinguished

In-Plane measurements: water inside the membrane

Beam

Detector

Cell

RadiogramBeam

Detector

Cell

Radiogramdobj = ddet

•High detector resolution required•Thickness of the cell in beam direction limited byneutron transmission

•High beam collimation needed•Less neutron flux � lower frame rate

Differential Fuel Cell – for high resolution imaging

I = 1 A/cm 2, p = 2 bar abs., T = 70 ° C

(MEA)

Differential Fuel Cell – in reality

beam direction

In-Plane measurements; Detector improvement - Tilting

Beam

Detector

Cell

Radiogram

Beam

Cell

Detector, tilted

Beam

Detector

Cell

Radiogram

Beam

Cell

Radiogram

dobj = ddet

dobj

ddet

Resolution improvement - Results

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

-50 0 50 100 150 200

Spatial position [ µµµµm]

Tra

nsm

issi

on p

rofil

e [a

.u.]

Imaging plate: 100 µmHigh res. CCD: 50 µmTilted CCD: 20 µm

Source: P. Boillat, Electrochemistry, PSI

Investigation ofa 150µm wideabsorber stripe

Investigation ofa 150µm wideabsorber stripe

Cell performance and water management

current topics of Fuel Cell Research using Neutrons

• Simultaneous neutron imaging of 6 cells

• Start-up behavior of PEM-FC and operation under sub-zero conditions

History

2002 – 2008 : Through-plane

100 µm pixel200 µm FWHM

History

2.35 µm pixel< 10 µm FWHM

2008 – 2012 : High resolution In-plane

History

2012 : In-plane, but with 6 cells !

6 µm pixel25 µm FWHM

Motivation

2012 : In-plane, with 6 cells … but why ?

� Efficient use of beam time

�Improved repeatability

�Identical conditions for all cells

�Study of design parameters

Motivation

�Testing different designs

Motivation

�Testing different compression rates

Motivation

�Testing different materials

MPL = Micro Porous Layer

Motivation

�Imaging

�Impedance spectroscopy

Motivation

�Imaging

�Helox pulse (cf. P.Boillat et al., J. Electrochem Soc. 2012)

How ?

Set-up

How ?

Set-up

Results

�Influence of the MPL : voltage

T = 70° C, RH = 100%/100%

Results

�Influence of the MPL : water distribution

T = 70° C

RH = 100%/100%

i = 0.5 A/cm 2

Results

Mass transportlosses…

… may originate fromwater accumulation in MEA region

Neutron imaging of

Isothermal Sub-Zero Degree Celsius Cold-Starts

of a Polymer Electrolyte Fuel Cell (PEFC)

H2

O2

H2O

+

+

+

+

Voltage

TimeCurrent

Motivation

∆twork

Procedure

RH

T 25°

30%

U

0,1 A/cm2

10min

i

20min 2 to 117min 15min

0,9 V

35min 20s

-10°

Isothermal Sub Zero Startup

Anode Cathode

Startup at -10 oC, 0.2 A/cm2

Total time: 20 minutes

Results: Isothermal Sub Zero Startup

0%

1%

2%

3%

4%

5%

6%

7%

8%

9%

10%

0 5 10 15 20

Time [min]

Wat

er c

onte

nt [%

vol t

ot]

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Vol

atge

[V] /

Cur

rent

den

sity

[A

/cm

2]

Water in GDL Water in Membrane/CLCurrent density Voltage

GDLMembrane& Catalyst

Anode Cathode

Startup at -10 oC, 0.2 A/cm2

Fuel Cell Research using Neutron Imaging

•Established as powerful non-invasive method

•direct water quantification

•through plane and in-plane observation possible

•coupled with in-situ electrical scanning (voltage, current density)

•high flexibility in spatial and time resolution

Li-Ion battery research

• Li- Ion migration during charging/discharging processes visible with neutron imaging methods ? (�ongoing)

• Gas production during operation and its influence onto the cell performance

work done:

D. Goers, M. Holzapfel, W. Scheifele, E.Lehmann, P. Vontobel, P. Noak, J. Power Sources Vol. 130, Issue 1-2, May 2005, pp. 191-199

The migration process within Li-Ion batteries

might it be possible to visualizethe transfer with neutrons ?

Specitific approach:

Li-6: tot. CS=944 barnLi-7: tot. CS=1.1 barn

� Doping of the agents

Li-Ion battery development and performance improvement

1. Teflon bolts2. Polypropylene sealing ring3. Aluminum cell covers4. Current collector plates5. Electrodes6. Gel-type electrolyte7. Gas space

TEST DEVICE

Data from:D. Goers et al., J. Power SourcesVol. 130, Issue 1-2, May 2005, pp. 191-199

Gas production in relation to the charging process

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.03.0

3.2

3.4

3.6

3.8

4.0

4.2

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

Stopd

cbaCurrent

Volta

ge [V

]

Time [h]

Cur

rent

[mA]

Voltage

•lateral distribution of gas bubbles visible •formation of growing gas channels •PC (propylene carbonate) electrolytes show the evolution of large amounts of gas, resulting in an unfavorable distribution of the local current density and reduction of the cell charge capacity. •GBL-based gel-type electrolytes show a usable electrochemical behavior and the evolution of only very small amounts of gas.

a b c d

Hydrogen storage in metal hydrides

•Processes are reversibly•For gas release high temperature required•Efficiency still topic for investigations

Attenuation coefficients with neutrons [cm??]

1a 2a 3b 4b 5b 6b 7b 8 1b 2b 3a 4a 5a 6a 7a 0 H He

3.44 0.02 Li Be B C N O F Ne

3.30 0.79 101.60 0.56 0.43 0.17 0.20 0.10 Na Mg Al Si P S Cl Ar

0.09 0.15 0.10 0.11 0.12 0.06 1.33 0.03 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr

0.06 0.08 2.00 0.60 0.72 0.54 1.21 1.19 3.92 2.05 1.07 0.35 0.49 0.47 0.67 0.73 0.24 0.61 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe

0.08 0.14 0.27 0.29 0.40 0.52 1.76 0.58 10.88 0.78 4.04 115.11 7.58 0.21 0.30 0.25 0.23 0.43 Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn

0.29 0.07 0.52 4.99 1.49 1.47 6.85 2.24 30.46 1.46 6.23 16.21 0.47 0.38 0.27 Fr Ra Ac Rf Ha 0.34

Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

*Lanthanides 0.14 0.41 1.87 5.72 171.47 94.58 1479.04 0.93 32.42 2.25 5.48 3.53 1.40 2.75 Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr

**Actinides 0.59 8.46 0.82 9.80 50.20 2.86 neut. Legend

σ-total * sp.gr. * 0.6023

Attenuation coefficient [cm??] = at.wt. σ-total: JEF Report 14, TABLE OF SIMPLE INTEGRAL NEUTRON CROSS SECTION DATA FROM JEF-2.2, ENDF/B-VI, JENDL-3.2, BROND-2 AND CENDL-2,

AEN NEA, 1994. and Special Feature: Neutron scattering lengths and cross sections, Varley F. Sears, AECL Research, Chalk River Laboratories Chalk River, Ontario, Canada KOJ

1JO, Neutron News, Vol. 3, 1992, http://www.ncnr.nist.gov/resources/n-lengths/list.html. sp.gr.: Handbook of Chemistry and Physics, 56th Edition 1975-1976. at.wt.: Handbook of Chemistry and Physics, 56th Edition 1975-1976.

Attenuation coefficient Neutrons (25meV) [cm-1]

Thermal neutron data

Verification of the hydrogen accumulation

Simplified setup for non-invasive hydrogen determination

neutron beam

attenuated beamhydrogen storage

device transmission image =hydrogen distribution

�in-situ determination of loading/reloading processes�direct quantification of the hydrogen amount�high spatial and time resolution�2D and also 3D investigations possible

Investigation of nuclear fuel

U-235 and U-238 can be distinguished easily:

tot. CS (U-235) = 700 barntot. CS (U238) = 12.17 barn

�non-invasive determination of the enrichment�observation of the pellet integrity�status of the fuel burnup

Investigation of nuclear fuel cladding

•In the long-term operation of NPPs a hydrogen accumulationin the Zr based cladding can happen

•A final consequence of this hydrate clustering might be cladding failure and fission product release

•Neutron imaging is a useful tool for the visualization andquantification of the amount of locally fixed hydrogen

Investigation of nuclear fuel and its cladding

broken fuel rod (caused by H load?)

neutron beam

sample

transportcontainer

shieldingblock

support

special setup (NEURAP)required

ppm(H) (Masse)

-2000

0

2000

4000

6000

8000

10000

12000

14000

0 50 100 150 200 250

Position x [mm]

ppm

(H)

(Mas

se)

2916 mm

Hydrogen Quantification in the cladding

Conclusions

24. September 2012PSI,

•It has been shown that neutron imaging can contributeto analyze energy relevant samples and to optimize related processes

•High resolution in time and space is provided togetherwith the specific contrast in the neutron transmission

•The quantitative data obtained from the images can becompared to model considerations

•Further progress will be obtained by energy-selectiveimaging, phases contrast imaging and the use of polarized neutrons

The facilities at PSI are prepared to host further such studies on demand

24. September 2012PSI,