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,
