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?

3

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

19

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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