Methodologies for determination of radionuclides in ...Methodologies for determination of...
Transcript of Methodologies for determination of radionuclides in ...Methodologies for determination of...
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Methodologies for determination of radionuclides in environmental
or waste samples
Phil Warwick & I W CroudaceGAU‐Radioanalytical
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GAU‐Radioanalytical
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Why is radioanalytical science important?
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Nuclear fission
Actinide / heavy element chemistry
Contaminated land clearance
Environmental monitoring
Nuclear forensics
Environmental process studies
Radiation metrology
Nuclear fusion
Medical radionuclides
Homeland security
Waste characterisation
Radioecology
Radioanalyticalsciences
Radiotracer studies
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The changing analytical landscapeOPERATIONAL‐ Radiological protection‐ Process control‐ Environmental
monitoring‐ Routine waste
sentencing
4
DECOMMISSIONING‐ Waste exemption ‐ Waste stream
fingerprinting‐ Waste characterisation of
unusual matrices‐ Land remediation
© DSRL / NDA © Magnoxsites
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More challenging matrices
‐ Heterogeneous soft wastes‐ Construction materials (metals / concretes)
‐ Ion exchange resins / desiccants
‐ ‘Sludges’ (highly variable composition)
‐ Oils
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Changes in analytical requirements
• Historically, analytical schedules have focussed on activation and fission products which dominate the fingerprint in terms of activity and pose the greatest radiological risk e.g....
60Co90Sr, 137Cs
239+240Pu, 241Am
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Changes in analytical requirements41Ca (1.03 x 105 y –
irradiation of bioshield concrete)
79Se (6 x 105 y – fission product)
93Zr (1.5 x 106 y – fission + activation product)
113mCd (14 y – irradiation of Cd metal)
151Sm (90 y – fission product)
7© NDA
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Factors impacting analytical quality
Highly trained & experienced
staff
Use of validated procedures
Robust QA / QC systems
Suitably calibrated
instrumentation
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Key stages in analysisSample collection / storage
Homogenisation / sub‐sampling
Solubilisation / liberation of analyte
Quantification of analyte
Separation / purification of analyte
Clear / accurate reporting of data
Experienced / trained staff
Validated procedures
Knowledge of analytedistribution &
association with matrix
Knowledge of potential interferences
Suitable calibration standards
Method validation
Knowledge of analytedistribution &
association with matrix
Suitable calibration standards
Method validation
Use of validated procedures
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Sample collection
0
50
100
150
200
250
300
0 50 100 150 200 250 300
Initial leach Bq/g
Tota
l H-3
Bq/
g
room temperature
refrigerated
Loss of 3H during sample collection / storage
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SamplingUse of
validated procedures
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Radionuclide association with matrix
Inner
0
20
40
60
80
100
0 120 240 360 480 600 720
3 H r
ecov
ery
(%)
Middle
0 120 240 360 480 600 720
Combustion time (min)
Outer
0 120 240 360 480 600 7200
200
400
600
800
1000
Temp. (ºC
)
Speciation of 3H in reactor bioshield concrete
Potentially impacts on sampling, storage and analysis procedures
Use of validated procedures
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Sample dissolution
0
500
1000
1500
2000
2500
Leach 1 Leach 2 Leach 3 Leach 4
Bq/g
Aqua regia Aqua regiaHF/HClO4
Leaching of 241Am from ‘debris’
Use of validated procedures
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Borate fusion
0.0001
0.0010
0.0100
0.1000
1.0000
10.0000
0 20 40 60 80 100 120 140
Extraction time (minutes)
I/I0
Diphonix resinActinide resin
Proportion of U extracted with time(0.1 g of Actinide resin in 100ml of 0.8M HNO3 with stirring)
Fusion of soils / marine sediments
D.A.R. – Double aqua regia digestF / Pyro – fluoride / pyrosulphate fusionFusion – borate fusion
Fusion of Actinide resin for actinide in water extraction
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Instrument calibration
• Traceable standard solutions do not exist for some of the radionuclides now being requested.
• For liquid scintillation analysis, proxy radionuclides are often used which is not ideal.
Suitably calibrated
instrumentation
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Use of proxy radionuclides
for LSC calibration
93Zr (- Emax 60.6 keV, 1st forbidden unique) VS 63Ni (- Emax 65.9 keV, allowed)
3H Efficiency (%)
10 20 30 40 50 60 70
Pred
icte
dEf
ficie
ncy
(%)
50
60
70
80
90
100
93Zr63Ni
Predicted 63Ni Efficiency (%)
50 60 70 80 90 100Pred
icte
d93
ZrEf
ficie
ncy
(%)
50
60
70
80
90
100
79Se (- Emax 151 keV, 1st forbidden unique) VS 14C (- Emax 157 keV, allowed)
3H Efficiency (%)
10 20 30 40 50 60 70
Pred
icte
dEf
ficie
ncy
(%)
80
90
100
79Se14C
Predicted 14C Efficiency (%)
80 90 100Pred
icte
d79
SeEf
ficie
ncy
(%)
80
90
100
151Sm (- Emax 76.3 keV, allowed) VS 63Ni (- Emax 65.9 keV, allowed)
3H Efficiency (%)
10 20 30 40 50 60 70
Pred
icte
dEf
ficie
ncy
(%)
50
60
70
80
90
151Sm63Ni
Predicted 63Ni Efficiency (%)
50 60 70 80 90 100Pred
icte
d15
1 SmEf
ficie
ncy
(%)
50
60
70
80
90
Suitably calibrated
instrumentation
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CN2003 calibration of 41Ca & 45Ca
0
10
20
30
40
50
60
0 20 40 60 80 100
distance (cm)
Bq/
g
LSC
AMS
Predicted
41Ca (EC )
SQPE680 700 720 740 760 780 800 820 840
Effic
ienc
y (%
)
0
10
20
30
40
MeasuredPredicted
45Ca (- Emax 257keV, allowed)
SQPE680 700 720 740 760 780 800 820 840
Effic
ienc
y (%
)
70
80
90
100
110
MeasuredPredicted
Suitably calibrated
instrumentation
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Suitably calibrated
instrumentation
y = 0.0709x2 - 0.6274x + 97.353R2 = 0.9999
96.0
96.2
96.4
96.6
96.8
97.0
97.2
97.4
97.6
97.8
98.0
0 1 2 3 4
4M HCl (ml)
113m
Cd
eff %
113mCd Gamma spec.
LSC
Sample A 8.7 1.6 12.0 0.8
Sample B 8.6 1.4 11.2 0.8
Gamma spec.
LSC
Sample A 11 2 12.0 0.8
Sample B 11 2 11.2 0.8
Gamma emission probabilities(collaboration with PTB)Published 0.023 Revised 0.01839
Warwick & Croudace (2009) Radiocarbon, LSC2008, p429 ‐ 434Kossert et al (2011) Appl. Radiat. Isot., 69, 500 ‐ 505
113mCd
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Beta nuclide identification
...89\Q052101N.001 11
...89\Q020601N.001 11
...89\Q041601N.001 11
...89\Q073101N.001 11
...90\Q031101N.001 11
Sample Spectrum
1,000950900850800750700650600550500450400350300250200150100500
240
230
220
210
200
190
180
170
160
150
140
130
120
110
100
90
80
70
60
50
40
30
20
10
0
63 keV
156 keV
224 keV
294 keV
710 keV
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Suitably calibrated
instrumentation
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Beta nuclide identification
20
Suitably calibrated
instrumentation
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Mass spectrometry – U isotopics
2sd error 2sd error
-117-112-107-102-97-92-87-82-77-72-67-62-57-52
125 130 135 140
238U/235U
dept
h (m
)
Alpine Ice Core
1945
1950
1955
1960
1965
1970
1975
1980
1985
1990
137 137.5 138 138.5
238U/235U
year
RothamstedGrass (UK)
Warneke et al. (2002). EPSL, 203, 1047 ‐ 1057
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Thermo Element XR sensitivity for 133Cs
0
50000
100000
150000
200000
250000
0 2 4 6 8 10 12
CPS
Concentration (ng/L)
Aridus II + X‐skimmer cone + JET interface (turbo pump and sample cone)
700 ± 102 500 ±20
5 000 ± 30
21 000 ± 80
Counts per ng/L
0.03
LOD (ng/L)
0.080.150.62
Aridus II
Standard
Aridus II + X‐skimmer cone
Instrumental setup
Mass spectrometry – 135Cs
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05000
100001500020000250003000035000400004500050000
0.0 1.0 2.0 3.0
Coun
ts per se
cond
Concentration (ng/L)
Nov‐12
Feb‐13
Cs‐133standard
Repeat measurement of 135Cs Comparing gamma spec and ICP‐MS measurement of 137Cs
• Final Ba concentration determines accuracy and LOD
• Applications for 135Cs/137Cs include:
• Arctic Ocean water samples
• Salt marsh sediment core
Preliminary 137Cs results (Bq/m3)
0
0.5
1
1.5
2
2.5
3
0 1 2 3
ICP‐MS (ng/L)
Gamma spec (ng/L)
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Other applications
Comparison of iron uptake in surface waters in the hypothesised iron depleted “South” and iron replete (because of the Crozet Isles) “Central” sites
South a
Incubation time, h
0 5 10
55Fe
upt
ake,
DP
M p
er s
ampl
e
0
2x103
4x103
6x103
Fe u
ptak
e, %
0
20
40
Ads.Upt.Regr.
Central b
Incubation time, h
0 5 10 15 20
55Fe
upt
ake,
DP
M p
er s
ampl
e0
2x103
4x103
Fe u
ptak
e, %
0
20
40
60
55Mn (p,n) 55Fe
Zubkov et al (2007)Deep Sea Res. II, 54, 2126 ‐ 2137
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Reference materials• Reference materials are required for method validation and
ongoing quality control purposes.
• Reference standards are required that more closely reflect the matrices and contaminant form encountered in decommissioning samples.
Range of matrices Analyte present in form comparable with real samples Range of certified analytes to reflect nuclides encountered Presence of contaminants comparable to those found
operationally.
Robust QA / QC systems
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Method validation
Test sample
Sample type Exposure history Interfering radionuclides
Accuracy Precision Decon. Factors
Robustness Matrix interferences
Use of validated procedures
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Summary• Decommissioning analysis has resulted in new challenges
for the radiochemical laboratory.
• High quality analysis relies on a good understanding of the distribution and association of the analyte with the matrix.
• Careful consideration must be given to instrument calibration, particularly for less common radionuclides.
• There is a clear requirement for more representative matrix‐matched standards for method validation and quality control. However, alternative approaches to method validation are also required.
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Acknowledgements
• Daeji Kim (3H studies)• Thorsten Warneke (U isotopic studies)• Ben Russell (135Cs studies)• Nicola Holland (CN2003 studies)• Mike Zubkov (55Fe tracer studies)
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