Speciation of Long-Lived Radionuclides in the Environment

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Chemical Speciation of Long-Lived
Radionuclides in the Environment
Xiaolin Hou
Risø-R-1677(EN)
Risø National Laboratory for Sustainable Energy
Technical University of Denmark
Roskilde, Denmark
November 2008
Author: Xiaolin Hou Risø-R-1677(EN)
November 2008
Title: Chemical Speciation of Long-Lived Radionuclides in the
Environment
Division: Radiation Research Division

Abstract (max. 2000 char.): ISSN 0106-2840
ISBN 978-87-550-3730-4

This project started in November 2005 and ended in November
2008, the work and research approaches are summarized in this
report.

This project studied the speciation of radionuclides in environment.
A number of speciation analytical methods are developed for
129 99 237
determination of species of I, Tc, isotopes of Pu, and Np in Contract no.:
seawater, fresh water, soil, sediment, vegetations, and concrete. The

developed methods are used for the investigation of the chemical
speciation of these radionuclides as well as their environmental
Group's own reg. no.:
behaviours, especially in Danish environment. In addition the

speciation of Pu isotopes in waste samples from the
decommissioning of Danish nuclear facilities is also investigated.
The report summarizes these works completed in this project. Sponsorship:
Through this research project, a number of research papers have Supported by the Villum
been published in the scientific journals, the research results has Kann Rasmussen Foundation
also been presented in the Nordic and international
Cover :
conference/meeting and communicated to international colleagues.

Some publications are also enclosed to this report.

Participants of this project:
Xiaolin Hou (Risø-DTU, project leader))
Per Roos (Risø-DTU)
Sven P. Nielsen (Risø-DTU)
Jussi Jernstroem (Risø-DTU)
Svend Olsen (Risø-DTU)
Violeta Hansen (Risø-DTU)
Ala Aldahan (Uppsala University, Sweden)
Göran Possnert (Uppsala University, Sweden)
Susanne Persson (Uppsala University, Sweden)
Pages: 145
Edvard Englund (Uppsala University, Sweden)

Information Service Department
Acknowledgement:
Risø National Laboratory for
Sustainable Energy
We like to thank the Villum Kann Rasmussen Foundation for the
Technical University of Denmark
finical support to complete this project.
P.O.Box 49
DK-4000 Roskilde
We also like to thank all stuffs in Radioecology and Tracer
Denmark
Program, Radiation Research Division, Risø National laboratory for Telephone [phone]
Sustainable Energy, Technical University of Denmark for their
Contents:
1. Objectives of the project
2. Instrumentations
II
2.1 X Series ICP-MS and HPLC
2.2 Air sampler for iodine species collection from atmosphere
2.3 Combustion furnace
3. Development of analytical methods
127
3.1 Determination of I in environmental samples using ICP-MS
3.1.1 Separation of iodine from solid sample using combustion
3.1.2 Measurement of iodine using ICP-MS
129
3.2 Determiantion of I using accelerator mass spectrometry (AMS)
237
3.3 Determination of Pu isotopes and Np in environment
3.3.1 Separation of Pu and Np from environmental samples
238 239,240 237
3.3.2 Measurement of Pu, Pu and Np using alpha spectrometry
239 240 241 237
3.3.3 Measurement of Pu, Pu, Pu and Np using ICP_MS
241
3.3.4 Measurement of Pu using liquid scintillation counting
99
3.4 Determination of Tc and Pu/Am in environmental samples using HPLC
coupled with ICP-MS.
3.4. 1 Separation of Pu and Am using ion chromatography HPLC
3.4.1.1 Extraction chromatography for separating trivalent light lanthanides and
actinides
3.4.1.2 Cation exchange column for pre-concentrating trivalent actinides
3.4.1.3 Ion chromatography column for final separation of trivalent actinides
3.4.2 Separation of Tc using ion chromatography HPLC
3.4.2.1 Separation procedure
3.4.2.2 Elution of technetium from ion chromatography column
129 127
3.5 Method for the speciation of I and I in water samples
3.5.1 Speciation separation of iodine in water samples using ion exchange
chromatography.
129
3.5.2 Speciation of I in water using extraction and co-precipitation
129 127
3.5.2 Speciation/fractionation of I and I in soil/sediment samples
129 127
3.5.3. Speciation method for I and I in atmosphere
237 241
3.6 Speciation/fractionation of plutonium isotopes, Np and Am in soil,
sediment and concrete samples using dynamic sequential extraction
3.7 Analytical method for the determination of rhenium

Risø-R-167(EN) 3
3.8 Investigation on Re-absorption of Pu during the fractionation of Pu in soil and
sediment
4. Investigation of speciation of the radionuclides in environmental samples
129
4.1 Speciation of I in North Sea surface water
129
4.2 Speciation of I in precipitation collected in Roskilde, Denmark 2001-2006
137 129
4.3. Partition of Cs and I in the Nordic lake sediment, pore-water and lake
water
129 127
4.4 I and I and their speciation in lake sediment
127 129
4.5 Iodine isotopes ( I and I) in aerosols
4.6. Speciation of Pu in soil, sediment and concrete samples from decommissioning
of Danish nuclear reactor
99
4.7 Speciation of Tc and Re in seaweed samples
237
4.8 Speciation of Pu isotopes and Np in water samples collected from Framvaren
fjord
4.9 Speciation of 129I and 127I in atmosphere for investigation of geochemical
cycle of iodine using reprocessing 129I as tracer.
5. Conclusion and perspective
6. List of papers published and to be published
7. Papers presented in conferences and meetings

Appendix: Some published materials

Paper-1-EST-129I-NorthSea-2007.pdf
Paper-2-JER-Dynamic adsorption2008.pdf
Paper-3-129I-speciation-review-ACA2008.pdf
Paper-4-ACA-review-article-2008.pdf
Paper-5-Handbook of Iodine-CH015-iodine speciation-2009.pdf
Paper-6-EST-modeling129I-2008.pdf
Paper-7- Jussi-PuAm.pdf

4 Risø-R-1677(EN)
1. Objectives of the project:

The aim of the project is to study the chemical speciation of the radionuclides
129 238,239,240,241
iodine-129 ( I), plutonium-238, -239, -240, -241 ( Pu), technetium-99
237
and neptunium-237 ( Np) in order to obtain information on their behaviour in the
environment. Once released to the environment these radionuclides and their
radioactive decay products remain for a long time due to their very long halflives.
The results of the project will provide understanding and data for the quantification
of the environmental processes governing the dispersion and biological transfer of
these radionuclides and thus enable reliable assessments to be made of the associated
risks to man and environment.
Specific aims of the project include:
1) To examine the chemical speciation of the radionuclides in environmental
samples with emphasis on the radioactive contamination and nuclear waste
repositories covering
− Speciation analysis of Pu isotopes in contaminated environmental
samples from Thule, Greenland,
129 99
− Speciation analysis of Pu isotopes, I and Tc in samples related to
nuclear waste from the operation and decommissioning of nuclear
facilities in Denmark
129 99
− Environmental behaviour study of Pu isotopes, I and Tc related to
their transfer in the environment and to humans with an emphasis on the
Danish environment.
129
2) To develop analytical methods for the chemical speciation of I, isotopes
99 237
of Pu, Tc and Np in relation to risk assessment involving
99 129
− Development of ultra-trace analysis methods for Tc, I, isotopes of Pu
237
and Np with inductively-coupled plasma mass spectrometry,
accelerator mass spectrometry, alpha spectrometry and liquid
scintillation counting techniques.
129
− Development of separation methods for the chemical speciation of I,
99 237
isotopes of Pu, Tc, and Np in environmental samples using
chromatographic techniques as well as extraction, and sequential
extraction.
The project focuses on a quantitative understanding of the chemical speciation of
radionuclides in the environment that can be used for risk assessment of the
plutonium contamination in Thule, Greenland, issues related to a Danish repository
for nuclear waste and radionuclides in Danish waters from European reprocessing
facilities.
Risø-R-167(EN) 5
2. Instrumentations

II
2.1 X Series ICP-MS and HPLC
II
An X Series ICP-MS and HPLC equipments
were purchased from Thermo Electron
Corporation, the instruments have been installed
and tested in July 2006 (Figure 1). The
performance of the instruments have been tested
and optimized for the determination of the target
radionuclides and speciation separation-
determination. Satisfied results (sensitivity,
detection limit, stability, etc.) have beenobtained
127 99
for the determination of I, Tc, isotopes of Pu, Figure 1 Thermo X SeriesII ICP-MS coupled with HPLC
237
and Np. The HPLC has been coupled to ICP- for speciation analysis of nuclides
MS for the automated separation and speciation of

127 99
analytes including I, Tc, and isotopes of Pu
237
and Np.
2.2 Air sampler for iodine species collection from atmosphere
Two sets of air sampler was designed and manufactured by a commercial
company (Staplex, USA), which has been used to collect different chemical
speciation of iodine from atmosphere, such as particle, inorganic gaseous iodine,
and organic gaseous iodine. The equipments have been installed and tested (Figure
2). A satisfied performance has been obtained, except the problems of vacuum
pump, in which carbon brush has to be replaced every 150 hours operation. The
equipment has been successfully applied to collect atmospheric samples from
different location in Denmark, Sweden and Lithuania.

Figure 2 Air sampler setup for collecting particulates
associated, in organic gaseous and organic gaseous iodine

6 Risø-R-1677(EN)
2.3 Combustion furnace
A specific combustion furnace was designed and manufactured by a commercial
company (Carbolite, UK), which is used to separate iodine from various solid
samples such as soil, sediment, vegetation, tissues, air particles, filters, and active
charcoal. The furnace has been installed and tested (Figure 3), a good separation
efficiency (>80%) was obtained. The equipment has been successfully used for
129 127
the analysed the samples for I and I in solid samples.

Figure 3 Schematic diagram and picture of
combustion facility (Carbolite, UK) for the
separation of iodine from solid sample. 1)
Gas bubbler (filling with NaOH solution for
trapping iodine); 2) Oxygen supply; 3)
Exhaust gas manifold; 4) Temperature
controller of combustion furnace; 5) Second
furnace (for complete combustion of residue

from first furnace); 6) sample boat in the first

furnace; 7) Quartz working tube; 8) gas inlet

adaptor; 9) Three ways valve; 10) main

oxygen supply; 11) Compressed air supply

(In the beginning of combustion, air is

supplied to avoid a violet combustion under

pure oxygen condition)

3. Development of analytical method for the speciation
analysis of radionuclides

127
3.1 Determination of I in environmental samples using ICP-MS
An analytical method was developed for the determination of stable iodine in
various environmental samples. For the solid samples such as soil, sediment, plants,
tissues and filters, the samples were first decomposed using combustion method
using the furnace established (Figure 3), the separated iodine in NaOH solution is
measured by ICP-MS. For seawater samples, the samples is first diluted with 0.15
-1
mol mL NH4OH solution and then iodine is measured using ICP-MS. For fresh
-1
water samples (rain, lake, river, and ground water), 6 mol mL NH4OH is first added
to the samples to a concentration of NH4OH of 0.15 mol mL-1, iodine in the samples
is then measured by ICP-MC.
Risø-R-167(EN) 7
3.1.1 Separation of iodine from solid sample using combustion
The dried solid sample is weighted to the samples boat, a maximum of 50 grams
of soil and sediment, 10 grams of grass, lichens, leaves, wood, seaweed, or tissues,
and 20 g of active charcoal can used, the filter paper of size less than 50cm × 50 cm
125
can be used. I tracer is then added to the samples for monitoring the recovery of
iodine during the separation procedure including combustion. The boat with sample
is then put in to the furnace.
In the combustion facility, there are two furnaces; the sample is put in the middle
of the first furnace. The second furnace is used for completely burn out the particles
and organics, which is turn on and increasing the temperature to 850 °C in 30
minutes. Oxygen gas is supply in this furnace from the beginning to assist the
complete combustion of materials in this furnace. The compressed air is passed
through the combustion tube until the temperature is increased to 800 °C. This is
necessary to avoid a violet combustion of the samples, articulately for organic
samples. The oxygen gas may cause a explosion due to fast combustion and fast
production of gases. The temperature in the first furnace is gradually increased, first
to 100 °C and keep for 15 minutes to remove the water content in the samples, then
slowly increased the temperature to 400 °C in the speed of 3-5°C per minute, this
step is important, especially for organic samples such as grass, lichens, leaves, wood,
seaweed, and tissue, active charcoal impregnated with TEHA also require a slowly
increasing of temperature. The temperature is kept at 400 °C for 30 minutes to
complete the carbonation of the organic in the samples. Afterwards the temperature
is increased to 850-900 °C in 30 minutes, the supplied gas is then switch to oxygen,
and finally the temperature is kept for 1 hour at this temperature. Iodine released as
elemental iodine (I2) from the sample during the combustion is trapped in the
bubbler which is filled with 0.4 mol mL-1 NaOH with 0.02 mol mL-1 NaHSO3. The
125
trapping efficiency is checked using measuring I in the trapping solution.
125
Recovery of iodine monitored using I in the soil and sediment samples is 95-99%
with an average of 98%, the recovery of iodine in filter, and active charcoal is also
higher (90-98%), while the recovery of iodine in organic samples (grass, lichens
seaweeds, tissues etc.) is normally lower (50-70%).

3.1.2 Measurement of iodine using ICP-MS.
For the trapping solution from the combustion, since the high salt content (18 g
-1
L ), the sample is diluted 10 time with 0.15 mol L-1 NH4OH. Cs as CsCl is added to
-1
a concentration about 2 ng mL , Cs is used as internal standard for monitoring and
harmonizing the sampling introduction efficiency. The standard of iodine was
-1 -1
prepared using KIO3 and KI in 0.15 mol L NH4OH and 0.04 mol L NaOH
solution. The results (Figure 4) show a good linearity of iodine prepared and the
-1 -1
measured in a concentration range from 0.1 ng mL to 50 ng mL . In addition, no
different of the single intensity for iodide and iodate was observed (Fig. 4).

8 Risø-R-1677(EN)
It means that in routine analysis, one standard is enough for the determination of the
total iodine the samples. Due to high stability, iodate is normally used as the routine
standard of iodine for ICP-MS analysis.
In the ICP-MS analysis of iodine, hot plasma is always used due to high
ionization potential of iodine. The Xt skimmer cone is used due to its good stability
for “dirty” samples with high salt content to avoid the block of the small Xs cones,
although the analytical sensitivity is lower by using Xt cone comparing with Xs
cone. Various parameters is tuned to the optimal value to get the best sensitivity, the
normal parameter tuned are shown in Table 1. The sensitivity of 15100 ± 450 cps for
-1
1 ng mL iodine was obtained, and the blank (0.15 mol mL-1 NH4OH) counts of
1750±110 cps was measured. It is there a detection limit of 0.02 ng mL-1 is
calculated.

25
KI standard

KIO3 standard
20
Figure 4 Standard curves
water-standard addition
y = 0.9944x - 0.0551
of iodine measured using
R2 = 0.9984
ICP-MS (Thermo, X
15
y = 1.
2062x + 3.2187 SeriesII). KI and KIO3 are
R = 0.9998
y = 0.9795x + 0.1035 prepared in 0.15 mol mL-1

10 2
R = 0.9992 NH
4OH solution, standard
addition of iodate to rain
5 water and NH4OH was

added to a concentration
-1
of 0.15 mol mL .
0
0 5 10 15 20 25

-1
Added iodide, ng mL

Table 1 Setup of ICP-MS for the measurement of iodine.
Parameter Value Parameter Value
127
Skimer cone Xt Dwel time ( I) 25 ms
133
RF forward power 1400 W Dwel time ( Cs) 10 ms
Plasma gas flow rate 14.0 L min-1 Sweeps 1200
Nebilizer gas flow rate 1.00 L min-1 Channel space 0.02
Auxiliary gass flow rate 1.10 L min-1 Acquistion duration 64000 ms
-8
Vacuum pressure 5.3× 10 mbar Integration time 5 min.
Pole Bias -6.0 Evaluation software PlasmaLab
Scan mode Peak hopping

Risø-R-167(EN) 9
-1
Measured iodine, ng mL