Development of analytical techniques for studies on dispersion of actinides in the environment and

74 Pages·2006·1.72 MB·English

by  Jussi Jernström

University of Helsinki
Faculty of Science
Department of Chemistry
Laboratory of Radiochemistry
Finland

DEVELOPMENT OF ANALYTICAL TECHNIQUES FOR
STUDIES ON DISPERSION OF ACTINIDES IN THE
ENVIRONMENT AND CHARACTERIZATION OF
ENVIRONMENTAL RADIOACTIVE PARTICLES

Jussi Jernström

Academic Dissertation

To be presented with the permission of the Faculty of Science of the University of
Helsinki for public criticism in the lecture hall A129 of the Kumpula Department of
Chemistry on November 10th, 2006, at 13 o'clock.

Helsinki 2006
Custos

Professor Jukka Lehto
Laboratory of Radiochemistry
Department of Chemistry
University of Helsinki
Finland

Opponent

Professor Sue B. Clark
Department of Chemistry
Washington State University
USA

Reviewers

Professor Brit Salbu
Isotope Laboratory
Section Environmental Chemistry
Department of Plant and Environmental Sciences
Norwegian University of Life Sciences
Norway

Dr. Tarja K. Ikäheimonen
Research and Environmental Surveillance
STUK
Finland

ISSN 0358-7746
ISBN 952-10-3458-0 (nid.)
ISBN 952-10-3459-9 (PDF)
http://ethesis.helsinki.fi

Helsinki 2006
Yliopistopaino
ABSTRACT

Radioactive particles from three locations were investigated for elemental composition,
oxidation states of matrix elements, and origin. Instrumental techniques applied to the
task were scanning electron microscopy, X-ray and gamma-ray spectrometry, secondary
ion mass spectrometry, and synchrotron radiation based microanalytical techniques
comprising X-ray fluorescence spectrometry, X-ray fluorescence tomography, and X-
ray absorption near-edge structure spectroscopy.
Uranium-containing low activity particles collected from Irish Sea sediments
were characterized in terms of composition and distribution of matrix elements and the
oxidation states of uranium. Indications of the origin were obtained from the intensity
ratios and the presence of thorium, uranium, and plutonium. Uranium in the particles
was found to exist mostly as U(IV). Studies on plutonium particles from Runit Island
(Marshall Islands) soil indicated that the samples were weapon fuel fragments
originating from two separate detonations: a safety test and a low-yield test. The
plutonium in the particles was found to be of similar age. The distribution and oxidation
states of uranium and plutonium in the matrix of weapon fuel particles from Thule
(Greenland) sediments were investigated. The variations in intensity ratios observed
with different techniques indicated more than one origin. Uranium in particle matrixes
was mostly U(IV), but plutonium existed in some particles mainly as Pu(IV), and in
others mainly as oxidized Pu(VI).
The results demonstrated that the various techniques were effectively applied in
the characterization of environmental radioactive particles.
An on-line method was developed for separating americium from environmental
samples. The procedure utilizes extraction chromatography to separate americium from
light lanthanides, and cation exchange to concentrate americium before the final
separation in an ion chromatography column. The separated radiochemically pure
americium fraction is measured by alpha spectrometry. The method was tested with
certified sediment and soil samples and found to be applicable for the analysis of
environmental samples containing a wide range of 241Am activity.
Proceeding from the on-line method developed for americium, a method was
also developed for separating plutonium and americium. Plutonium is reduced to
Pu(III), and separated together with Am(III) throughout the procedure. Pu(III) and
Am(III) are eluted from the ion chromatography column as anionic dipicolinate and
oxalate complexes, respectively, and measured by alpha spectrometry.
PREFACE

The present study was carried out within the Nuclear Chemistry unit of the Institute for
Transuranium Elements (ITU), European Commission, Karlsruhe, Germany, during
2001-2005 with a grant and a contract from the European Commission. The work was
also financed by the Helsingin Sanomain 100-vuotissäätiö and The Finnish Society of
Sciences and Letters. All grants are gratefully acknowledged.
I am deeply grateful to Professor Maria Betti for giving me the opportunity to
work in her group at the ITU, and advicing and encouraging me throughout the whole
project. I am also sincerely grateful to Professor Jukka Lehto for supporting and guiding
me, and giving me the possibility to finalize my work.
I wish to express my sincere gratitude to Professor Emeritus Timo Jaakkola who
gave me a warm welcome into the world of radiochemistry, and guided me through my
studies and earlier works. I very warmly thank Dr. Sinikka Pinnioja who connected me
with the TL analysis – which are still part of the picture – and channeled me through the
final stages of my masters' degree. I give my sincere thanks to Professor Olof Solin who
gave me support during his years as the head of the Laboratory in Helsinki.
I sincerely thank my friend Mats who has such a big role in the preparation of
this book. The arrival of you with the particles to the research group spirited the work of
myself and the whole group up. I am also grateful to my friend Lorenzo who had made
a great work on separation methodology ready to be further applied.
I am obliged to Professor Brit Salbu and Dr. Tarja K. Ikäheimonen for critically
reviewing the dissertation and offering constructive comments.
I thank Dr. Roland Schenkel and Dr. Gerard Lander, former directors of the
ITU, for the opportunity to work at the Institute.
It is my pleasure to acknowledge the co-authors that have taken part in the
publications. It has been a pleasure to work with all of you, and I hope to have the
opportunity to work with you also in the future.
Very special thanks go to Dr. Erich Hrnecek who helped me so very much in the
beginning of the project. Martti Hakanen and Esa Puukko are gratefully acknowledged
for giving help in numerous chemistry-related problems. My family owes many thanks
to Maikki and Pirkko who babysat little Laura with excellent skills.
All my friends, colleagues and the whole Nuclear Chemistry unit are warmly
thanked and remembered for all the happy moments, good laughs, tricky discussions,
and successful manoeuvres and co-operation. Many friends as Anki, Anne and Marko,
Arto and Leena, Aurélien, Cinta, Dina and Vellu, Franco, Fred and Catharina, Jean,
Jean-Yves and Maria, Jouni and Donata, Make, Marcus, Mare, Maria and Olivier,
Marika and Ari, Mikael, Monia and Paolo, Nadine, Nick and Sarah, Olivier, Peter and
Natalie, Peter, Petra, Reijo, Reko, Ripa, Sheelagh, Tuomo and Leena, and Ylva have
been giving me the spirit needed for the work. Trim-tracking on Saturdays with Ian and
Liam in german forests was a healthy start for a weekend; beers with Juliette was
always a pleasant way to cut loose from the workday; cosy lunches and dinners with
Helle and Michael introduced me to Danish delicacies; husmanskost at Mats' and Pia's
brought together friends of multiple origins; visits to sunny Strassbourg with Leena
made the charming older part of the town familiar; office and coffee machine
conversation with Paula was very often a great way to release pressure.
I am deeply grateful to my father and my siblings and their families who have
been present and showed understanding during the process. I warmly think back to my
late mother who would have been filled with joy in sharing this all with me. My dear
thanks are due to Taimi Takalo for her precious help and support during the years.
Finally, my warmest thoughts and thanks go to my fiancée Tarja and daughter
Laura. You have made this all possible. You have had the faith.

Kallio, Helsinki, October 2006
LIST OF PUBLICATIONS

The doctoral thesis is based on the following publications and manuscripts, hereafter
referred to in the text by their Roman numerals [I-V].

I Jernström, J., Eriksson, M., Osán, J., Tamborini, G., Török, S., Simon, R.,
Falkenberg, G., Alsecz, A. and Betti, M. (2004). Non-destructive
characterization of low radioactive particles from Irish Sea sediment by micro
X-ray synchrotron radiation techniques: micro X-ray fluorescence (μ-XRF) and
micro X-ray absorption near edge spectroscopy (μ-XANES). Journal of
Analytical Atomic Spectrometry 19, pp. 1428-1433.

II Jernström, J., Eriksson, M., Simon, R., Tamborini, G., Bildstein, O., Carlos
Marquez, R., Kehl, S. R., Hamilton, T. F., Ranebo, Y. and Betti, M.
Characterization and source term assessments of radioactive particles from
Marshall Islands using non-destructive analytical techniques. Spectrochimica
Acta Part B, in press.

III Eriksson, M., Osán, J., Jernström, J., Wegrzynek, D., Simon, R., Chinea-Cano,
E., Markowicz, A., Bamford, S., Tamborini, G., Török, S., Falkenberg, G.,
Alsecz, A., Dahlgaard, H., Wobrauschek, P., Streli, C., Zoeger, N. and Betti, M.
(2005). Source term identification of environmental radioactive Pu/U particles
by their characterization with non-destructive analytical techniques.
Spectrochimica Acta Part B 60, pp. 455-469.

IV Perna, L., Jernström, J., Aldave de las Heras, L., de Pablo, J. and Betti, M.
(2003). Sample cleanup by on-line chromatography of Am in sediments and
soils by α-spectrometry. Analytical Chemistry 75, pp. 2292-2298.

V Jernström, J., Lehto, J. and Betti, M. On-line separation of Pu(III) and Am(III)
using extraction and ion chromatography. Submitted to Journal of
Radioanalytical and Nuclear Chemistry.
ABBREVIATIONS

AMS accelerator mass spectrometry
BNFL The British Nuclear Fuel plc
CRL compound refractive lens
DU depleted uranium
EDX energy dispersive X-ray
EXAFS X-ray absorption fine structure
HPGe high purity germanium
HPLC high performance liquid chromatography
IC ion chromatography
ICP-MS inductively coupled plasma mass spectrometry
LSC liquid scintillation counting
MCA multichannel analyzer
NEXAFS near-edge X-ray absorption fine structure
OM organic matter
PDCA 2,6-pyridinedicarboxylic acid, dipicolinid acid
PET pentaerythritol
PIN positive-intrinsic-negative
ROI region of interest
SDD silicon drift detector
SEM scanning electron microscopy
SIMS secondary ion mass spectrometry
SR synchrotron radiation
SSNTD solid state nuclear track detection
TOF time-of-flight
WDX wavelength dispersive X-ray
µ-XANES micro X-ray absorption near-edge structure
XAS X-ray absorption spectroscopy
XFCT X-ray fluorescence computed tomography
XPS X-ray photoelectron spectroscopy
XRD X-ray diffraction
µ-XRF micro X-ray fluorescence
µ-XRFT X-ray fluorescence microtomography
TABLE OF CONTENTS

ABSTRACT

PREFACE

LIST OF PUBLICATIONS

ABBREVIATIONS

1 INTRODUCTION...................................................................................................1
1.1 Environmentally contaminated areas...........................................................1
1.1.1 Irish Sea...........................................................................................2
1.1.2 Runit Island (Marshall Islands).........................................................3
1.1.3 Thule (Greenland)............................................................................5
1.1.4 Uranium and plutonium in sediments...............................................6
1.2 Characterization of environmental radioactive particles...............................7
1.2.1 Separation and localization of particles............................................7
1.2.2 X-ray and gamma-ray spectrometry...............................................10
1.2.3 Scanning electron microscopy.......................................................10
1.2.4 Synchrotron radiation induced analytical techniques.....................12
1.2.5 Secondary ion mass spectrometry.................................................16
1.3 Determination of actinides in environmental samples................................17
1.3.1 Extraction chromatography............................................................18
1.3.2 Ion chromatography.......................................................................20
1.4 Scope of the study.....................................................................................22
2 EXPERIMENTAL.................................................................................................23
2.1 Characterization of environmental radioactive particles.............................23
2.1.1 Separation and localization of particles..........................................23
2.1.2 X-ray and gamma-ray spectrometry...............................................25
2.1.3 Scanning electron microscopy.......................................................25
2.1.4 Synchrotron radiation induced analytical techniques.....................25
2.1.5 Secondary ion mass spectrometry.................................................27
2.2 Analysis of bulk matrix...............................................................................28
2.2.1 Leaching.........................................................................................28
2.2.2 Separation methods.......................................................................28
2.2.3 Radiometric measuring techniques................................................32
3 RESULTS AND DISCUSSION............................................................................33
3.1 Characterization of environmental radioactive particles.............................33
3.1.1 Elemental composition and particle matrix structure......................33
3.1.2 Oxidation states of uranium and plutonium....................................38
3.1.3 Assessment of origin......................................................................39
3.2 On-line separation of americium and of plutonium and americium............43
3.2.1 Separation in TEVA extraction chromatography resin...................43
3.2.2 Pre-concentration in TCC-II cation exchange column....................44
3.2.3 Separation in CS5A ion chromatography column..........................44
3.2.4 Testing of the separation method for americium............................47
4 SUMMARY AND CONCLUSIONS......................................................................49
REFERENCES.............................................................................................................53
1 INTRODUCTION

Ever since humans began to exploit nuclear technology weapons tests, nuclear fuel cycles,
accidents and other sources have released radioactive elements into the environment. These
anthropogenic radionuclides, together with cosmic, cosmogenic and terrestrial radionuclides,
make up the background radiation in the world today. Determining the dose directed to a
particular population requires understanding of the long-term behavior of radionuclides in the
environment.
A large fraction of the radionuclides released from nuclear events is associated with
particles. The most realistic size distribution of radioactive particles in the environment is log-
normal [Eriksson 2002, Shevchenko 2004], i.e., most of the released activity is carried by
relatively few, large-sized particles. Although the release of radioactive particles from past
nuclear incidents and their presence in the environment today are widely documented, the role
of particles in estimating the significance of radioactive releases is not clear, nor do we fully
understand the environmental processes related to particles [Pöllänen 2004]. The importance
of analyzing radioactive particles along with bulk matter is nevertheless beyond question.
Development of analytical methods and the increased availability and performance of
synchrotron radiation sources have vastly expanded our capability for studying environmental
radioactive particles. These methods are mostly non-destructive, which means that the
particles remain intact after analysis, and further investigations such as leaching experiments
can be performed.
Separation of elements is a fundamental link in the chain of environmental analysis.
Traditional methods for separation tend to be time-consuming, require large volumes of
organic solvents or mineral acids, and embody the risk of cross-contamination. Development
of separation resins for chromatography has made it possible to construct on-line separation
procedures, which markedly reduce the weaknesses associated with traditional methods.

1.1 Environmentally contaminated areas

Anthropogenic radionuclides have entered the environment from various sources, including
the use and testing of nuclear weapons, nuclear power production, nuclear accidents, disposal
of radioactive waste, and the use of radionuclides as tracers of environmental processes
[MacKenzie 2000, IAEA 2001]. The main contributor to both marine and terrestrial
radioactivity is global fallout from nuclear weapons tests performed in the atmosphere,
especially in the 1950s and 1960s [Livingston and Povinec 2000]. Nuclear fuel cycles
contribute to the releases mainly at the stages of uranium mining and milling and nuclear fuel
reprocessing [MacKenzie 2000]. Sanderson et al. (1997) have identified altogether 150
accidents that have released radionuclides to the environment between 1945 and 1996. These
accidents involve reactors and other nuclear facilities, satellites, nuclear weapons and large
radiation sources. Waste disposal from various military and civilian operations has resulted in
1