Hot particle measuring techniques and applications Mats

Slide 1Mats Eriksson IAEA-MEL
International Atomic Energy Agency Dept. of Nuclear Sciences and Applications
Log-normal Particle size distribution • Material dispersed after an explosion • Mineral resources in the earth crust • Pollutants in the air
• Log normal distribution - Size relation to Mass/Activity; Few large sized particles carry the majority of the mass released.
Two ways of characterizing lognormal distributions, in terms of the original data (a) and after log-transformation (b).
http://www.inf.ethz.ch/personal/gut/lognormal/brochure.html
1.3 % of the particles carry 1.3 % of the particles carry 80% of the activity80% of the activity
• Why Study Hot Particles? • Formed in events involving explosions (e.g. the Chernobyl and the
Thule accidents) and at nuclear installations (power and reprocessing plants)
• They “carry” the main fraction of the mass released, however they are very rare, leading to heterogeneous activity distribution
• Mostly a close-in fallout problem • “Contain” some geochemical “memory”! • However, a “needle in a haystack” problem
1 Bq Pu particle ≈ diameter of 20µm
Hot Particles
Focus on Hot Particles
• Finding and Identification of them • Image techniques (e.g. image plates, beta camera,
SEM,…) • Analytical techniques
• µ-XRF µ-XRF tomography and µ-XANES
• Gamma and alpha spectrometry • SIMS and ICP-MS
Mats Eriksson Risø, Nov-2009
Marine Environment Laboratories Monaco
The Thule accident
• B-52 bomber, HOBO 28 • 21 January, 1968 • Particles spread to the marine and terrest enviroment
The last flight path of HOBO 28
Arctic food web
Hot Particles
• Effects of ingestion is not well described and the dosimetry is complex and not well understood
• One study (B. Salbu, conf. proc., year 2002) on cheep have shown that 2 of 7 particles where incorporated in the GI tack of 2 animals. Also Dahlgaard et al, 2001, seen a similar effect in benthic biota.
• Surface chemistry unknown, related do dissolution rates of the particles
• Focus on particles consisting of alpha emitting radionuclides (e.g. Pu, U particles)
Pu Hot Particle Hot particle separation technique
20 h acquisition time 1 h acquisition time
Sampling splitting
Measurements for identification IDE Bioscope Beta camera
241Pu T½=14.4y
241Am T½=432y
α
β-
α
β-
SEM EDX WDX
0.00E+00
2.00E+02
4.00E+02
6.00E+02
8.00E+02
1.00E+03
1.20E+03
1.40E+03
10 10.5
2 11.0
4 11.5
6 12.0
What is Synchrotron Light
• Synchrotron light is the electromagnetic radiation emitted when electrons, moving at velocities close to the speed of light, are forced to change direction under the action of a magnetic field.
• The electromagnetic radiation is emitted in a narrow cone in the forward direction, at a tangent to the electron's orbit.
• Synchrotron light is unique in its intensity and brilliance and it can be generated across the range of the electromagnetic spectrum: from infrared to x-rays.
Properties of synchrotron light Synchrotron light has a number of unique properties. These include:
• High brightness: synchrotron light is extremely intense (hundreds to thousands of times more intense than that from conventional x-ray tubes) and highly collimated.
• Wide energy spectrum: synchrotron light is emitted with energies ranging from infrared light to hard x-rays.
• Tunable: it is possible to obtain an intense beam of any selected energy.
• Highly polarised: the synchrotron emits highly polarised radiation, which can be linear, circular or elliptical.
• Emitted in very short pulses: pulses emitted are typically less than a nano-second (a billionth of a second), enabling time-resolved studies.
SR-Fluorescence and Absorption Spectroscopy
* elemental mapping (microfocused beam size mode)
* high sensitivity to low concentrations (primary “white light” beam with its high flux mode)
• Absorption spectroscopy, elements between Al and Am: * information about the local atomic geometry (EXAFS) * chemical state of the absorbing atom (XANES). * investigations on ordered (crystalline) and disordered (amorphous, liquid) materials.
• Advantages * Nondestructive, surface / volume sensitive, * Multiple X-ray techniques with microfocus without sample remounting * Spectroscopy from light elements (Al) to Am at a single beamline
Why and how can these synchrotron techniques be used for radioecology studies
• Preferential leaching was observed in a time-series on totally dissolved U/Pu particles
• Mixed U/Pu particles, ICP-MS destructive, SR not! • Uranium cross contamination not a problem in SR • Homogenity of the particles ? • Preferential leaching (surface effects) • Oxidation state determination, geochemical
behaviour
Beam Line L in HASYLAB, and the micro confocal XRF setup
X-ray Fluorescent computer tomography (XFCT)
Synchrotron 3D XRF setup at ANKA
The IAEA set-up at the synchrotron beamline
µ-XRF, X-ray attenuation I=I0 exp(-µen/ρ x)
Experiment set-up
Detector
Scan
I
I0
10 0.429 50 0.014
100 0.0002
-µen/ρ = 73.9 cm2 g-1 (22 keV) ρ ≈ 11 g cm-3 (80%UO2+20%PuO2)
SR µ-XRF study
From 2D to 3D with Confocal µ-XRF (add. Information)
µ- XRF Tomography
Absorption Spectroscopy
• information about the local atomic geometry (EXAFS) • chemical state of the absorbing atom (XANES) • investigations on ordered (crystalline) and disordered (amorphous,
liquid) materials.
More XANES problems
• No standard technique to analyse the XANES spectra's • White line energy • Fitting oxidation standard spectra's • Fitting white line, first multiple scattering peak
and the edge • Polynomial fit, inflection point from df2/dE2=0 • Edge energy matrix dependent
Even more XANES problems (Radiolysis chemical changes)
XANES spectra's of some Thule HP
Pu in the particles in the +4 state. i.e. in the less mobile state
µ-XRF Confocal vs. bulk analysis
Particle ID Pu/U ratio μ-PIXE (summed spectra) ( 1 SD)
Pu/U ratio μ-XRF (summed spectra ) (1 SD)
Thu 68-1 0.222 ± 0.005 0.172 ± 0.005
Thu 97-1 0.17 ± 0.01 0.20 ± 0.01
Thu 975371-4 0.117 ± 0.007 0.113 ± 0.008
Thu 2003-7524 0.268 ± 0.006 0.235 ± 0.002
Particle ID Pu/U ratio (voxel derived) ( 1 SD)
Relative uncertainty
Thu 68-1 0.20 ± 0.02 ( n= 67 ) 10 0.172 ± 0.005
Thu 97-1 N.A. N.A 0.20 ± 0.01
Thu 975371-4 0.12 ± 0.03 ( n= 622 ) 25 0.113 ± 0.008
Thu 2003-7524 0.38 ± 0.33 ( n= 414 ) 87 0.235 ± 0.002
T2003-7524, Pu/U Lalfa ratio mean=0.43 +/- 0.38 (1 sd)
mean=0.28 +/- 0.07 (ex ratio >0.5)
Pu/U Lalfa ratio
0 20
40 60
80 10
5
0
2 0 12
Characteristic L-x-ray, 241Am(241Pu) to Pu
• Two spectra groups:
Relatively High 241Am/ 238+239+240Pu ≈ 0.17
10 11 12 13 14 15 16 17 18 19 20 21 22 Energy [keV]
102
103
104
105
2
102
103
104
Alpha spectrometry and fitting program AASI Alpha fit
Alpha spectrometry
• 241Am/239,240Pu ratio ??
ICP-MS on bulk samples 24
0 P u/
23 9 P
SIMS (next talk by Ylva) Isotopic fingerprint
SIMS Results-Isotopic Ratio
1,42 3,7110-2
1,46 3,6410-2
1,46 3,6310-2
1,45 3,6310-2
1,36 5,7710-2
1,39 5,7810-2
1,38 5,7410-2
1,38 5,7510-2
1,31 5,9210-2
1,32 5,9010-2
1,32 5,9010-2
1,32 5,9010-2
Thu 79-6 235U/238U
Combined techniques: SR and SIMS
A new source in Thule
All U voxels
log((U[log(U) > -2]))
50 0
10 00
15 00
20 00
25 00
Fr eq
ue nc
0 50
0 10
00 15
20 40
60 80
10 0
High 235U enriched particles 235U /238U = 8.2 ± 0.1
Fig. 3. This figure shows the U (red-yellow pixel image) and the Pu (the superimposed iso-intensity lines) distribution in one cross- section of the particle shown in Fig 2. A line profile of the Pu/U ratio is also shown (blue line in the figure). The Pu/U ratio is multiplied by a factor of 100.
B
A
C
C
B
A
Area
µ-XANES
0.3
0.4
0.5
0.6
0.7
0.8
5.4
5.5
5.6
5.7
5.8
1.4
1.6
1.8
2.0
Conclusions
PARTICLES are important to consider in radiological studies! Particles are Site specific and difficult to extrapolate results to other sites! The use of advanced analytical techniques for hot particle characterisation Image techniques (e.g. image plates, beta camera, SEM,…) An obligation • Analytical techniques
• Gamma and alpha spectrometry An obligation • SEM-EDX-WDX Almost an obligation • Synchrotron radiation techniques and PIXE
• µ-XRF Very useful, need improvement • µ-XRF tomography Very useful, need improvement • µ-XANES Needs seriously improvement before applied
• SIMS Very useful, need improvement • ICP-MS Very useful
Leaching experiments should be conducted to support the theoretical conclusions.
Hot particles a hot topic
• Ph.D thesis • R.Pöllänen. Ph.D thesis, Nuclear fuel particles in the environment - characteristics, atmospheric
transport and skin doses. STUK-A188. Helsinki 2002. 63p. • J. Jernström, Ph.D thesis, Development of analytical techniques for studies on dispersion of actinides
in the environment and characterization of environmental radioactive particles, University of Helsinki, 2006
• O. C. Lind, Ph.D thesis Characterisation of radioactive particles in the environment using advanced techniques, Norwegian University of Life Sciences, 2006
• M. Eriksson, On weapons plutonium in the arctic environment (Thule, Greenland), Riso-R-1321, Riso National Laboratory, Roskilde, Denmark, 2002.
• NEXT year Maria-Carmen Jimenez Ramos, Seville, Spain (Palomares particles)
Institute for Transuranium Elements Ylva Ranebo
Nedialka Niagolova Olivier Bildstein
G. Tamborini Maria Betti
Per Roos
R. Simon (ANKA) G. Falkenberg (HASYLAB)
IAEA’s XRF group : D. Wegrzymek
STUK R. Pöllänen
Log-normal Particle size distribution
What is Synchrotron Light
Properties of synchrotron light
SR-Fluorescence and Absorption Spectroscopy
Why and how can these synchrotron techniques be used for radioecology studies
Beam Line L in HASYLAB, and the micro confocal XRF setup
X-ray Fluorescent computer tomography (XFCT)
Synchrotron 3D XRF setup at ANKA
µ-XRF, X-ray attenuation
SR µ-XRF study
µ- XRF Tomography
XANES spectra's of some Thule HP
µ-XRF Confocal vs. bulk analysis
Characteristic L-x-ray, 241Am(241Pu) to Pu
Alpha spectrometry andfitting program
Alpha spectrometry
Conclusions

Documents

Hot particle measuring techniques and applications Mats