Determination of 131I Uptake in Fucus Gardneri Using Gamma-Ray Spectroscopy

Determination de 1'Accumulation de I dans Fucus Gardneri par Spectroscopie Gamma

A thesis submitted to the Division of Graduate Studies of the Royal Military College of Canada

By

Kristine Margaret Mattson

In Partial Fulfillment of the Requirements for the Degree of Master of Applied Science in Nuclear Engineering

August 2011

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I wish to express my appreciation to Dr. David Kelly and Dr. Leslie Bennett, my thesis advisers, for their guidance, advice and support during the course of this research. I wish to thank Dr. Louis Druehl for his expert advice with respect to seaweeds and for sampling and shipping excellent specimens of Fucus gardneri from his kelp farm in Bamfield, BC to the Royal Military College of Canada. I would like to thank Ms. Kathy Nielsen, Director of the SLOWPOKE-2 Facility at RMC, for allowing me to use the High Purity Germanium Detectors in the Facility without interruption. I wish to thank Mr. David Ferguson for his help setting up my aquaria and for helping me with the construction of my lead casde and to the Nuclear Emergency Response members and the Navy divers for their assistance in collection of the seaweed samples in Shearwater, NS. Appreciation is extended to Dr. Christopher Lane, Dalhousie University, for his commitment to help me identify the seaweeds and other specimens collected in Shearwater. Thanks go to Kim Bylow and the staff in the Imaging Department, at the Kingston General Hospital, for their help acquiring 131I solutions, and to DGNS who kindly provided funding for this thesis. Finally, I especially wish to thank my family. Collin, you were very loving, supportive, patient and understanding. Your help and commitment to the rest of our daily life together was amazing and I cannot thank you enough. To Blake and Emma, my precious children, thank you for being absolutely wonderful and for letting me take over the computer without ever complaining. It is with my heartfelt gratitude and love that I dedicate my thesis work to my family.

11 Abstract

Low level releases of 131I and other fission products in the environment, such as seawater, may be difficult to detect by standard methods Seaweeds have a high iodine concentration and absorb 131I to levels measurable by gamma-ray spectroscopy. A gamma-ray detection system was designed and validated to use for the detection of low level activities The detection limit and minimum detectable activity of 131I for the system were determined to be 0 28 ± 0.07 Bq and 0 09 ± 0.02 Bq, respectively. Samples of seaweeds were collected on the East and West coasts of Canada. Ascophyllum Nodosum and the Sacchanna Latissima were sampled in Shearwater, NS (Eastern Passage) in December 2006 and had 131I average dry weight activity of 30 ± 2 Bq kg1 and 175 ± 7 Bq kg1, respectively Fucus gardnen samples were harvested from the western shoreline of Vancouver Island in Bamfield, Bntish Columbia, at low tide in January, March and November of 2008. The average concentration of iodine in Fucus gardnen determined using INAA was 290 ± 50 fig g' dry weight Assuming an average concentration of iodine in seawater at the sampling location in Bamfield, BC, in the range of 0.03—0.05 |4.g g1 and the average concentration of iodine in the Fucus gardnen, the equilibrium constant for iodine between Fucus gardnen and seawater in this study was 5800-9700 mL g1. The equilibrium of 131I between seawater and Fucus gardnen can be established within hours and can be modelled using first order equilibrium kinetics. The average equilibrium constant, measured experimentally using first order equilibrium kinetics, for Fucus gardnen is 78 ± 46 mL g1 based on wet weight and 480 ± 270 mL g based on dry weight. The average rate constants kf +kb, kf and kb are 0.57 ± 0.22 h1, 0 55 ± 0.21 h1 and 0.012 ± 0.011 h\ respectively. It was found that seaweed samples can be stored for up to one week in temperatures ranging from -17°C to 25°C without any loss of 131I, indicating that samples may be kept for later analysis, as necessary. Fucus gardnen exposed to reactor container water from the SLOWPOKE-2 Facility absorbs the low level fission products within 4 hours The fission products include radioisotopes of iodine, metals and noble gases.

in Resume

Les methodes de detection standard eprouvent des difficultes a detecter avec precision les faibles relachements de 131I et d'autres produits de fission dans l'environnement comme l'eau de mer. Les plantes marines sont capables d'accumuler de grandes concentrations d'iode et peuvent absorber 1'131I a des niveaux mesurables par spectroscopic gamma. On a concu et valide un systeme de detection par rayonnement gamma afin de l'utiliser pour la detection de faibles niveaux d'activite. On a determine la limite de detection et l'activite minimum detectable de P,MI pour ce systeme a 0.28 ± 0.07 Bq et 0.09 ± 0.02 Bq, respectivement. Des echantillons de plantes marines ont ere recueillis sur les cotes est et ouest du Canada. Ascophyllum Nodosum et Saccharina Latissima ont ete echantillones a Shearwater N.E. (Passage de l'Est) en decembre 2006 et avaient une activite specifique moyenne (a sec) pour F13,I de 30 ± 2 Bq kg1 et 175 ± 7 Bq kg1, respectivement. Des echantillons de Fucus gardneri ont ete recueillis sur la cote ouest de l'ile de Vancouver a Bamfield, Colombie-Britannique, a maree basse en Janvier, mars et novembre 2008. La concentration specifique moyenne d'iode dans Fucus gardneri tut determinee a l'aide de l'Analyse Instrumentale par Activation Neutronique (AIAN) comme etant egale a 290 ± 50 |Jg g1 (de masse a sec). En supposant que la concentration moyenne de l'iode dans l'eau de mer a l'emplacement de rechantillonage a Bamfield C.-B. se trouvait entre 0.03 |Jg g' et 0.05 [Jg g' et en supposant la valeur ci-dessus pour la concentration moyenne d'iode dans Fucus gardneri, on a pu determiner la constante d'equilibre pour l'iode entre Fucus gardneri et l'eau de mer comme etant de 5800-9700 mL g-1 pour cette etude. L'equilibre de 1'131I entre l'eau de mer et Fucus gardneri peut etre etablie en quelques heures et peut etre modelisee a partir d'un modele de cinetique a l'equilibre du premier ordre. La constante d'equilibre moyenne, mesuree experimentalement a l'aide du modele de cinetique du premier ordre pour l'equilibre et pour Fucus gardneri est de 78 ± 46 mL g' , valeur basee sur une masse mouillee, et de 480 ± 270 mL g' pour une masse a sec. Les constantes de taux moyennes 1%

1 1 1 +kb, kf et kb sont de 0.57 ± 0.22 h , 0.55 ± 0.21 h et 0.012 ± 0.011 h , respectivement. On a trouve que les echantillons de plantes marines peuvent etre entreposes pour une semaine a des temperatures entre -17°C et 25°C sans perte de 131I, indiquant que les echantillons peuvent etre gardes pour analyses ulterieures, au besoin. Fucus gardneri, lorsque espose a l'eau du vaisseau du reacteur SLOWPOKE-2, absorbe les produits de fission de faibles niveaux en 4 heures au plus. Ces produits de fission incluent l'iode, certains metaux et des gaz nobles. iv Contents

Acknowledgements ii

Abstract iii

Resume iv

Contents v

List of Figures ix

List of Tables xii

Nomenclature xiv

Acronyms xvi

Chapter 1 Introduction 1 1.1 Project Background 1 1.2 Thesis Objectives 2 1.3 Radiation in the Environment 3 1.3.1 General 3 1.3.2 Radiation from Fission 7 1.3.3 Activation Products 9 1.4 Environmental Radionuclide Monitoring Program 9 1.4.1 Visiting Nuclear Powered Vessel (NPV) Types and Estimated Nuclear Inventory 9 1.4.2 Nuclear Emergency Response and Environmental Radionuclide Monitoring Program 10 1.5 13,I 12 1.5.1 Production of 1311 12 1.5.2 Decay of1311 13 1.5.3 Sources of1 }11 in the Environment 14 1.5.4 Levels and Discharges of1}11 from Victoria General Hospital in Halifax 15 1.6 Seaweeds 16 1.6.1 Ion Uptake Pathways in Seaweeds 16 1.6.2 Iodine in the Environment and in Seaweeds 16 1.6.3 Bioaccumulation of Radionuclides in Seaweeds 17 1.6.4 Fucus Gardneri 18 1.7 Reaction Kinetics and Thermodynamic Equilibrium 19 1.8 Gamma-Ray Spectroscopy 24 1.9 Instrumental Neutron Activation Analysis 28

Chapter 2 Experimental 30 2.1 Experimental Introduction 30 2.2 Instrumentation 30 2.2.1 SLO WPOKE-2 Reactor at the Royal Military College (RMC), Kingston 30 2.2.2 Gamma-Ray Spectroscopy Systems 31 2.3 Radionuclide Preparation and Instrument Validation 32 2.3.1 Design and Construction of Detector Shielding for Low Level Counting 32 2.3.2 Validation and Detection Limit of "I on a 60% GEM60P4 HPGe 34 2.4 Field Sample Collection and Analysis 37 2.4.1 Collection of Seaweed Samples from Shearwater, NS and Preparation for Shipment 37 2.4.2 Shearwater, NS, Seaweed Sample Preparation and Counting 38 2.5 Fucus Gardneri Collection and Preservation at RMC 38 2.5.1 Collection of Fucus Gardneri and Shipment 38 2.5.2 Artificial Seawater and Aquarium 39 2.5.3 Receipt and Preparation for Introduction into Artificial Seawater Aquaria 40 2.6 Measurement of Stable Iodine in Fucus Gardneri 41 2.6.1 Instrumental Neutron Activation Analysis (INAA)for the Determination of Iodine in Fucus Gardneri 41 2.7 Determination of Surface Area of Fucus Gardneri 41 2.8 Fucus Gardneri1MI Exposure Experiments 42 2.8.1 Fucus Gardneri ' 'I Uptake Measurements with Varying Parameters 42 2.8.2 Measurement of Removal of ''}>I from Artificial Seawater by Fucus Gardneri 44 2.8.3 Retention of1>1I in Fucus Gardneri Under Different Storage Conditions 46 2.8.4 Fucus Gardneri Exposure to Reactor Container Water 47 vi Chapter 3 Results and Discussion 48 3.1 Validation of GEM60P4 Detector 48 3.1.1 Linearity 48 3.1.2 Background Reduction Due to Detector Shielding 49 3.1.3 Precision and Accuracy 54 3.2 Detection Limit of 131I 59 3.3 Shearwater Seaweeds Sample Results and Discussion 62 3.4 Sample Receipt and Preparation for Introduction into Artificial Seawater Aquaria 64 3.5 INAA for the Determination of Iodine in Fucus Gardnen 65 3.6 Determination of Surface Area of Fucus Gardnen 66 3.7 Exposure Experiments 72 3.7.1 Exploratory Expenments of Fucus Exposure to 'I in Artificial Seawater 72 3.7.1.1 Investigative Expenment Using Fucus Plant Number 20 74 3.7.1.2 Investigative Expenment Using Fucus Plant Number 29 andMeasunng ,3'I Activity Removal from Seawater 75 3.7.1.3 Time Required to Approach Equtlibnum 78 3.7.1.4 Uptake for Three Combined Plants, Fucus 38, 44 and 47 80 3.7.1.5 Uptake in Fucus gardnen with a Low Initial Concentration of 13'I in Seawater 82 3.7.1.6 Summary of Investigative Expenments 82 3.7.2 Equtlibnum Constant and Reaction Rates for 11 and Fucus Gardnen 83 3.7.2.1 13'I Uptake in Fucus Gardnen 83 3.7.2.2 131I Loss from Spiked Fucus Gardnen to Seawater 90 3.7.2.3 Mass Balance Calculation for the Concentration of ,3'l in Shearwater, NS 91 3.7.3 Retention of13'I in Fucus Gardnen under Different Storage Conditions 94 3.7.4 Fucus Exposure to Reactor Container Water 96

Chapter 4 Conclusions & Recommendations 100 4.1 Conclusions 100 4.2 Recommendations 103

References 104

VU Appendices 112

Appendix A : Sampling Maps for ERMP Program 113

Appendix B : Derivation of First Order Equilibrium Equations 116

Appendix C : Lead Castle Design Parameters 119

Appendix D: Field Notes Pertaining to Sampling of Seaweed Samples in

Shearwater 121

Appendix E: Uncertainty in Background Calculation 123

Appendix F: ml Uptake Results 124

Appendix G: Fission and Activation Product Uptake in Fucus Gardner/ 129

Curriculum Vitae 131

Vlll List of Figures

Figure 1-1: Fission Product Yield from the Fission of 235U. 7 Figure 1-2: 131I Beta Decay Scheme Showing Gamma Rays Produced. 13 Figure 1-3: Fucus Gardneri Seaweed. 19 Figure 1-4: Shape of Zero and First Order Reactions with Respect to [A] as a Function of Time. 21 Figure 1-5: First Order Equilibrium Reactions. 23 Figure 1-6: Effect of Different Sample Geometries on Efficiency. 25 Figure 1 -7: 450mL Marinelli Beakers used for Increased Counting Efficiency of Samples on an HPGe Detector. 25 Figure 1-8: Interaction of Radiation with Detector Shielding. 28 Figure 2-1: Lead Brick from Canada Metal Showing the Unique Shape used to Prevent Radiation Streaming. 33 Figure 2-2: Detector Shielding Showing Lead, Copper and Lucite and the GEM60P4 HPGe Detector Inside the Shielding. 33 Figure 2-3: Smart GEM60P4 HPGe Detector in the Detector Stand while Connected to the X-Cooler II. 35 Figure 2-4: Smart GEM60P4 HPGe Detector in Liquid Nitrogen Dewar and Inside Lead Shielding. 36 Figure 2-5: Map Showing the Shearwater Jetty, the Location of ERMP Shearwater Sampling. 37 Figure 2-6: Fucus Gardneri in Seawater Aquaria Showing Plants Supported out of the Seawater. 40 Figure 3-1: linearity Plots for 60% GEM60P4 HPGe Detector. 49 Figure 3-2: Linearity Plots for 60% GEM60P4 HPGe Detector. 49 Figure 3-3: Spectra Collected for MDA Showing the Counts Obtained versus Energy for Three Configurations. 54 Figure 3-4: Dry weight 131I Activity for Shearwater Seaweeds Sampled Around the Shearwater Jetty. 63 Figure 3-5: Surface Area to Number of Pixels Calibration Plot. 68 Figure 3-6 a&b: Fucus Digital Image (top) and Fucus Bitmap Image (bottom). 69 Figure 3-7: Relationship of Surface Area to Mass for Fucus Gardnert. 71 Figure 3-8: Relationship of the Ratio of the Surface Area to Mass for Fucus Gardnert. 71 Figure 3-9: Uptake of 131I by Fucus 20 Showing an Exponential Shape 74 Figure 3 10 a & b: Uptake of 131I by Fucus 29 and Removal From Seawater. 77 Figure 3-11: Activity of 131I in Seawater Plot of Equation (28) with Time for Fucus 29 Suggesting First Order Equilibrium Kinetics. 78 Figure 3-12: Uptake and Consequent Removal of 131I from Seawater in Fucus 14 Suggesting First Order Equilibnum Kinetics. 79 Figure 3-13: Activity of 131I in Seawater Plot of Equation (28) with Time for Fucus 14 Illustrating First Order Equilibnum Kinetics. 80 Figure 3-14: Uptake of 131I by Fucus 38, 44 and 47 Illustrating Similar Uptake based on Mass of Plant. 81 Figure 3-15: Relationship of Equilibnum Constants Calculated using Mass of the Fucus and Surface Area of the Fucus. 87 Figure 3-16: The Dependence of the Equilibnum Constant on Mass. 88

Figure 3-17: The Dependence of Rate Constants kf + kbon Mass. 88

Figure 3-18: The Dependence of Rate Constant kfon Mass. 89

Figure 3-19: The Dependence of Rate Constant kbon Mass. 89 Figure 3-20: Map of Halifax Harbour Showing Sewage Outfalls. 93 Figure 3-21: Results of 131I Retention for all Samples, where Sample Identifiers Represent Combination of Uniquely Numbered Plants. 95 Figure 3-22: Average of Results for 131I Retention for Different Storage Conditions. 95 Figure 3-23: Fission and Activation Product Back-calculated Activity Measured in Bq in IL of SLOWPOKE-2 Reactor Container Water and in Fucus Gardnert. 98 Figure A-l: Base Line Study Sample Location Map - Esquimalt, BC. 113 Figure A-2: Base Line Study Sample Location Map - Halifax, NS. 114 Figure A-3: Base Line Sample Location Map - Nanoose, BC. 115 Figure A-4: Detector Shielding Design Parameters. 119 Figure A-5: Removal of 131I from Artificial Seawater by Fucus Gardnert. 124 Figure A-6: Removal of 131I from Artificial Seawater by Fucus Gardnert. 125 Figure A-7: Removal of 131I from Artificial Seawater by Fucus Gardneri. 126 Figure A-8: Removal of 131I from Artificial Seawater by Fucus Gardneri. 127 Figure A-9: Removal of 131I from Artificial Seawater by Fucus Gardneri. 128

XI List of Tables

Table 1-1: Average Annual Individual Radiation Doses to Humans from Natural and Man Made Sources. 4 Table 1-2: Environmental Radionuclides from Natural and Man Made Sources. 6 Table 1-3: The Dose Rate from Radionuclides that Cause the Greatest Harm to Humans if Released into the Environment in the Plume of a Severe NPV Reactor Release (mSv). 8 Table 1 -4: Administered Dose to Thyroid Patients and Estimate of Discharge to Sewer of 131I in Halifax. 15 Table 2-1: Ortec Gamma-ray Spectroscopy Detector Models, Relative Efficiency and MCAs Used for Gamma-ray Spectroscopy. 32 Table 2-2: Artificial Seawater Masses and Concentrations 39 Table 2-3: Experimental Parameters for Fucus Gardneri 131I Exposure Experiments with Varying Parameters. 43 Table 2-4: Experimental Parameters for 131I Removal by Fucus Gardneri. 45 Table 2-5: Division of Fucus GardneriPlants into Sub-groups with Different Storage Conditions. 46 Table 3-1: Calculated MDA in Bq for a Specific Radionuclide at a Given Energy for the GEM60P4 HPGe Detector System. 52 Table 3-2: Percent Relative Precision for a Radioactive 450mL Geometry Source for the GEM60P4 HPGe Detector System. 56 Table 3-3: Percent Uncertainty for a Radioactive 450mL Geometry Source for the GEM60P4 HPGe Detector System. 56 Table 3-4: Percent Relative Precision for a Radioactive Petri Geometry Source for the GEM60P4 HPGe Detector System. 57 Table 3-5: Percent Uncertainty for a Radioactive Petri Geometry Source for the GEM60P4 HPGe Detector System. 57 Table 3-6: Percent Relative Precision for a Radioactive Filter Paper Geometry Source 58 Table 3-7: Percent Uncertainty for a Radioactive Filter Paper Geometry Source 58

Xll Table 3-8: Determination of Activity of 131I Solution used for Detection Limit Determination for the GEM60P4 HPGe Detector System 60 Table 3-9: Results for detection limit of ,3,I in a 200 mL mannelli geometry 61 Table 3-10: Detection of 131I in Seaweeds from Shearwater NS 62 Table 3-11: Concentration of Iodine in Fucus Gardnen Determined using INAA. 66 Table 3 12: Calibration of the Surface area to number of pixels data. 68 Table 3 13: Measured Surface Area of Fucus Gardnen. 70 Table 3-14: Summary of Results for Fucus Exposure to 131I in Artificial Seawater. 73 Table 3-15: Activity of Plant 20 Uptake of ,3,I. 74 Table 3-16: Activity of Uptake of 13,I by Fucus 29 76 Table 3-17: Activity of Uptake of ,31I by Fucus 14 79 Table 3-18: Activity of Uptake of 13,I by Fucus 38, 44 and 47. 81 Table 3-19: Experimental Results for 131I removal by Fucus Gardnen Based on Wet Mass. 84 Table 3-20: Experimental Results for 131I removal by Fucus Gardnen Based on Dry Mass. 85

Table 3-21: Time Required to Reach Equilibrium Based on Reaction Rates kf and kb. 86 Table 3-22: Comparison of Experimental and Predicted Results for 131I Spiked Fucus Gardnen Placed in Clean Artificial Seawater. 91 Table 3-23: Percent Activity for Each Isotope Detected in Fucus Gardnen 99 Table A-1: Field Notes Pertaining to Sampling of Seaweed Samples in Shearwater NS. 121 Table A-2: Results of 131I Removal from Artificial Seawater By Fucus Gardnen. 124 Table A-3: Results of 131I Removal from Artificial Seawater By Fucus Gardnen. 125 Table A-4: Results of 131I Removal from Artificial Seawater By Fucus Gardnen. 126 Table A-5: Results of I31I Removal from Artificial Seawater By Fucus Gardnen. 127 Table A-6: Results of 131I Removal from Artificial Seawater By Fucus Gardnen. 128 Table A-7: Results of Fission Product Uptake By Fucus Gardnen. 130

Xlll Nomenclature

Symbol Name Units A Activity [Bq]or[s]]

B Sensitivity Constant, B = A °th - contributing [dimensionless]

parameters also defined

C Concentration Hgg'

1 Keq Equilibrium Constant mLg'.gg LT Live Time

/ Branching Ratio M Atomic Mass of Element [amu]

1 NA Avogadro's Number [mol ] SD Standard Deviation W Mass IgJ k, Rate constant in the Forward Direction h1 Rate constant in the Reverse (Backwards) h1 K Direction a Years d Days h Hours n Net Number of Counts n neutron

K Time of Count [*] t, Irradiation Time [s] h Decay Time [s] h/2 Half-life [s] X A number from a set of data

X Sample mean average

XIV a Alpha Particle P Beta Particle y Gamma Ray £ Geometric Detector Efficiency

s X Decay Constant, ln(2)/t1/2 I ] contributing parameters also defined a^ Thermal Neutron Cross Section barn [b] = lO^m2 ab Uncertainty in the background

XV Acronyms

AN Ascophylium Nodosum ASG Analytical Sciences Group BC British Columbia CFB Canadian Forces Base CFMETR Canadian Forces Maritime Experimental and Test Ranges CMS Chief of Maritime Staff CNSC Canadian Nuclear Safety Commission COGMA Compagnie Generate des Matieres Nucleaires CVN Multipurpose Aircraft Carrier Nuclear Propulsion DND Department of National Defence DRDC Defence Research and Development Canada EFADS Emergency Filtered Air Discharge System ERMP Environmental Radionuclide Monitoring Program HEPA High Efficiency Particulate Air HPGe High Purity Germanium IAEA International Atomic Energy Agency INAA Instrumental Neutron Activation Analysis MCA Multichannel Analyser MDA Minimum Detectable Activity MSRMS-4 Maritime Staff Risk Management Services Nuclear Safety 4 NA Not Avalaible NER Nuclear Emergency Response NCV Nuclear Capable Vessel NERT Nuclear Emergency Response Team NIST National Institute of Standards and Technology NPV Nuclear Powered Vessel NS Nova Scotia

XVI NUREG United States Nuclear Regulatory Commission Regulation OFHC Oxygen Free High Conducting PWR Pressurized Water Reactor RMC Royal Military College of Canada SIRCIS SLOWPOKE Integrated Reactor Control and Instrumentation System SL Sacchanna Latisstma SLOWPOKE Safe LOW POwer K(c)atical Experiment SSN Submarine Nuclear Propulsion TSA Technical Safety Assessment UPS Un interruptible Power Supply

xvu Chapter 1 Introduction

1.1 Project Background

Authorization was given in 1991 by a Government of Canada Order-in-Council to allow nuclear powered vessels (NPVs) and nuclear capable vessels (NCVs) from the Governments of the United States of America and the United Kingdom of Great Britain and Northern Ireland to visit ports on both the East and West coasts of Canada [1, 2]. These visits occur throughout the year. Perception of radiation in society is often accompanied by fear and misunderstanding. To ease public fears and to perform appropriate due diligence with respect to environmental radioactivity, programs relating to radioactive material have been implemented by the Canadian government to regulate, monitor and respond to radioactivity issues [3-6]. It is the responsibility of the Department of National Defence (DND) to manage the safety of NPV and NCV visits to Canadian ports and anchorages. Visits of NPVs and NCVs to three locations in Canada, namely, Canadian Forces Base (CFB) Halifax (on the Shearwater side) in Nova Scotia, and CFB Esquimalt and Canadian Forces Maritime Experimental and Test Ranges (CFMETR) Nanoose in British Columbia, give cause for radionuclide monitoring to ensure that no radioactivity is released into the environment [7]. Currently, environmental samples are taken by Nuclear Emergency Response Teams (NERTs) on both coasts through a program called the Environmental Radionuclide Monitoring Program (ERMP) [8]. The samples are analysed for fission product and activation product radionuclides, by gamma-ray spectrometry, to establish a baseline of expected levels of radioactivity and to detect the release of radioactivity during an NPV and NCV visit. It is well documented that radionuclides, such as 137Cs, from weapons testing and nuclear reactor accidents such as Chernobyl can be detected in environmental samples around the world [8-12]. Medical radionuclides are detected in municipal sewage systems from patient effluent after receiving a radionuclide treatment [13-15]. Of particular interest in this body of literature is the discharge of 1311 and its subsequent uptake into seaweed. In December 2005, elevated levels (above the baseline) of 13II were found in seaweed samples taken near Shearwater, Nova Scotia (NS). It was postulated that the source of the 131I came from a local hospital which uses 131I for the treatment and diagnosis

1 of thyroid diseases [16]. Whilst this postulation was logical, it was determined that more research was needed to investigate the significance of trace 131I and its uptake by aquatic plants including, A.scophyllum nodosum, Saccharina latissima, and Fucus gardneri.

1.2 Thesis Objectives

The objective of this thesis was to determine the source of the 1MI found in Hahfax Harbour, specifically whether the 131I observed is due to a medical release or to the release of nuclear material from an NPV nuclear reactor. It is desirable to determine the uptake and removal rate and the equilibrium that is reached between 1MI in seawater and in Fucus gardneri. The mechanisms required to reach these goals were to:

• Design lead shielding for an intrinsic, High Purity Germanium (HPGe) detector to reduce background noise originating from surrounding building materials;

• Validate a 60% GEM60P4 HPGe detector for accuracy, precision, linearity, detection limit and minimum detectable activity; • Confirm the presence of 131I in seaweeds sampled from Shearwater, NS;

• Determine the iodine concentration in Fucus gardneri using instrumental neutron activation analysis (INAA);

• Determine the equilibrium constant (Keq) and the forward and backward rates of reaction (kf and k,,) for the uptake of 131I by Fucus gardneri in artificial seawater;

• Investigate sample storage requirements for seaweeds during shipment to the Royal Military College to determine if there is a loss of 131I based on sample storage conditions; and to

• Investigate the uptake of other fission and activation products produced and available in low levels in the SLOWPOKE-2 reactor at RMC. Using validated detection equipment and the technique of gamma-ray spectroscopy, the detection of the continued presence of 131I in seaweeds from Shearwater in the absence of other fission or activation products, would give increased confidence that the source of 131I found in Hahfax harbour is a medical radioisotope. The time required for 131I to reach equilibrium between seawater and seaweeds is useful information that can be used to help determine sampling strategies for the NERT.

2 1.3 Radiation in the Environment

1.3.1 General

In considering radiation, not derived from human activities, cosmic radiation and terrestrial radiation are the two sources of radiation in the environment. Cosmic radiation is a highly energetic mixture of protons, alpha particles, heavy nuclei and electrons from outer space. Terrestrial radiation can be divided into two forms; radiation resulting from the decay of radionuclides which are themselves formed from the interaction of matter with cosmic radiation, and radionuclides which represent the parent or daughter radionuclides of radioactive species which are sufficiendy long-lived to have survived the nuclear processes from which the Earth's elements are formed [17]. There are approximately 70 naturally occurring radionuclides found on Earth Table 1-1 contains information about the average annual individual doses from natural and man-made sources [18, 19]

3 Table 1-1: Average Annual Individual Radiation Doses to Humans from Natural and Man Made Sources. Source Dose /mSv a'1 (additional information in brackets)

Natural Radiation

External Sources

Cosmic rays 0.028 (Whole Body)

Terrestrial gamma-rays 0.026 (Whole Body)

Internal Sources

"°K 0.019 (Gonads), 0.015 (Bone marrow)

Heavy Elements 0.08 (Gonads), 0.085 (Bone marrow)

14C 0.007 (Gonads), 0.007 (Bone marrow)

87Rb 0.003 (Gonads), 0.006 (Bone marrow)

222Rn 2 (Lungs), 0.006 (Bone marrow)

Man-made radiation

1.03 (Bone marrow of patients), Medical X-rays 3-3.5 (Whole body of medical personnel)

0.03 (Bone marrow of patients), Dental X-rays 0.5-1.25 (Whole body of dental personnel)

3 (Bone marrow of patients), Radiopharmaceuticals 2.6-3.5 (Whole body of medical personnel)

Nuclear weapons Fallout 0.04-0.05 (Whole Body)

<<0.1 (Population < 10 miles away) Nuclear power plants 4 (Whole body of Workers)

0.07 (Whole body of persons living in brick or masonry Building materials buildings)

0.03 (Whole Body Passengers) Air Travel 1.6 (Whole Body Crew)

Television 0.002-0.015 (Gonads of viewers)

Tobacco 80 (Bronchial epithelium of smokers)

4 Radiation can be divided into two classes: ionizing and non-ionizing radiation [20]. The distinction is based on the respective ability or inability to ionize atoms or molecules. Some examples of non­ ionizing radiation include radio waves, microwaves, infrared light, and visible light. Examples of ionizing radiation include alpha and beta particles and gamma-rays.

Common alpha emitters found in the environment naturally or due to human causes include parts of the decay series of 235U, 238U, 232Th, and artificially produced ^^u and 241Am. Common beta emitters include 3H, 14C, 32Si, 32P, *K, ^Sr, 241Pu and parts of the uranium and thorium decay series. Many alpha and beta decays have associated gamma-rays and some common isotopes detected by the emission of gamma-rays include 7Be, ^K, 54Mn, ^Co, 137Cs, and 210Pb (These isotopes may also decay by alpha or beta emission or by electron capture). Neutron emitters include Cf, Am-Be and Pu-Be sources. The average amount of natural background radiation received per person each year in Canada is 2.62 mSv [21]. Half-lives and principal modes of decay for common environmental radionuclides are provided in Table 1 -2.

5 Table 1-2: Environmental Radionuclides from Natural and Man Made Sources.

Element Radioisotope Radiation Type Half-life Source

Ra ^Ra a,y 1 60 x 10' a Natural

9 U 2381J a.Y 4 47x 10 a Natural U 235U a,y 71 x 10» a Natural

10 Rb 87Rb P,Y 4 8 x io a Natural Th 232X1, a,y 1 40 x 1010 a Natural

4 Pu 239pu a,y 2 41 x 10 a Neutron Activation Product Pu 241pu PY 144a Neutron Activation Product

2 Am 241 Am a,y 4 32 x IO a Neutron Activation Product H m P 12 23 a Neutron Activation Product C 14C P 5 73 x 103 a Natural Si «Si P 1 72 x IO2 a Natural P 32p P 143d Neutron Activation Product Sr 90Sr P 28 79 a Fission Product Be TBe a,y 53 3 d Natural

K 40K P,Y 1 3 x 10» a Natural Mn 54Mn P,Y 312 d Fission Product, Neutron Activation product Co ^Co P,Y 5 27 a Neutron Activation product Cs 137Cs P.Y 30 07 a Fission Product Pb 2ioPb P,Y 22 3 a Natural Values for the half-lives are provided in units of years (a), days (d) and hours (h).

6 1.3.2 Radiation from Fission

Uranium is the most widely used element for the purpose of fission in nuclear reactors [22].

238 a5 23 Abundances of uranium isotopes in nature are 99.284% UJ 0.711% U and 0.0058% V by mass. Although both 238U and ^U undergo spontaneous fission, their rate is quite small [23], but the rate for 235U is dramatically increased in the presence of thermalized neutrons. Each fission of 235U results normally in two fission fragments. The fission products created fall into two groups, one group with high mass numbers and the other of low mass number as illustrated in Figure 1-1. The fission products undergo successive decays, leading to production of decay products forming a fission decay chain.

10 - i—r i r f*\ >** f 14MeV */ \ o^ / \ •o a> '5> t c 0.1 o 5> /thermal ( a) 4 001 - ; \y a) u

235 0.001 =-! U fission • thermal neutrons o 14-MeV neutrons I 0.0001 4 J L J L JL 70 80 90 100 1 10 120 130 140 150 160 mass number Figure 1-1: Fission Product Yield from the Fission of 23iU [24].

There are over 400 fission product radionuclides that are produced in the fission of 235U [17]. The 18 radionuclides listed in Table 1-3 by decreasing whole body dose are those that cause the greatest harm to humans since they are the most likely to be distributed in a plume after a severe NPV reactor release of radioactivity and therefore inhaled by any exposed population.

7 Table 1-3: The Dose Rate from Radionuclides that Cause the Greatest Harm to Humans if Released into the Environment in the Plume of a Severe NPV Reactor Release (mSv) [25-27].

Gastro­ Whole Body Thyroid Lung Dose Red Bone intestinal Nuclide Half Life Effective Dose Marrow Dose Tract Dose Dose /mSv /mSv /mSv /mSv /mSv «°Sr 28.8 years 0.127 9E-5 1.052 0.011 0.007

1MCs 2.1 years 0.030 0.027 0.030 0.030 0.035

I37Cs 30.2 years 0.019 0.018 0.020 0.019 0.021

89Sr 50.5 days 0.017 1E-5 0.117 2E-4 0.020

132Te 78 hours 0.012 0.230 0.008 0.002 0.038 131J 8.0 days 0.012 0.241 6E-4 5E-5 2E-5 133J 20.9 hours 0.004 0.084 0.002 5E-5 4E-5

itofia 12.8 days 0.003 7E-4 0.004 3E-3 0.011 "Mo 66.0 hours 0.002 2E-5 0.006 8E-5 0.008

,36Cs 13.1 days 0.002 0.002 0.002 0.002 0.002

131mXe 30.0 hours 0.001 0.012 0.002 1E-4 0.002

9'Si 9.5 hours 7E-4 2E-5 0.003 3E-5 0.002

•<»Ru 39.4 days 5E-4 5E-5 0.003 6E-5 6E4

129m'Te 33.5 days 4E-4 1E-5 0.003 2E-4 7E-4 13SJ 6.6 hours 1E-4 2E-3 1E-4 7E-6 6E-6

86Rb 18.8 days 4E-5 3E-5 8E-5 6E-5 3E-5 132 J 2.3 hours 6E-7 7E-7 1E6 6E-8 5E-8 134 J 0.9 hours 9E-10 5E-9 3E-9 1E-10 1E-10

Note that, of the eighteen radionuclides in Table 1-3, five are radioisotopes of iodine. Radioisotopes of iodine have been released into the environment as a result of nuclear testing, from nuclear reactors and from use as a medical radioisotope. Iodine as a trace nutritional element is concentrated by the thyroid. Exposure to radioisotopes of iodine therefore may result in significant localized activity within the thyroid. The risk, particularly to children, is demonstrated by the high levels of thyroid cancer exhibited by children who were allowed to consume milk containing elevated levels of iodine following the Chernobyl accident. By 2002, more than 4000 thyroid cancer cases had been diagnosed in this group and it is most likely that a large fraction of these thyroid cancers is

8 attributable to radioiodine intake [28]. Clearly, early detection of radioactive iodine is crucial in response to a leak of nuclear material from a nuclear reactor.

1.3.3 Activation Products

In a nuclear reactor, other radioisotopes are created due to neutron activation of elements. Neutron activation occurs when the nucleus of an atom is absorbed by a neutron (usually a thermal neutron) and is excited to a higher energy state. If atomic nuclei that capture a neutron are unstable, they will generally decay by emission of beta and/or gamma radiation; however, it is also possible that they may decay producing alphas, protons, neutrons and tritium [17]. The activation products produced in an NPV or NCV nuclear reactor that are of interest for the ERMP program include ^Co, 58Co, 54Mn, 59Fe, 65Zn and 51Cr [29], The precursors of the radionuclides are all common components in stainless steel; for example, 60Co is produced from the interaction of a neutron with a 59Co atom. 59Co is the sole isotope present in naturally occurring cobalt [30]. fflCo is of particular interest since it has a relatively long half-life (5.27 years) and is easily detected using gamma-ray spectroscopy due to its high energy gamma-rays at 1173.23 keV and 1332.50 keV [30].

1.4 Environmental Radionuclide Monitoring Program

1.4.1 Visiting Nuclear Powered Vessel (NP V) types and Estimated Nuclear Inventory

Visiting NPVs from allied nations are usually a submarine of the Type SSN where SS denotes a submarine and N denotes nuclear propulsion, or an aircraft carrier of the class CVN (CVN denotes Multi-purpose Aircraft Carrier Nuclear-Propulsion) [31]. The frequency of visits on both the East and West coasts at Canadian Force Bases (CFB) and The Canadian Forces Maritime Experimental and Test Ranges (CFMETR) has decreased to just a few per year from between 17 to 44 visits since their commencement in the early 1990's. The type of nuclear reactor utilized in most NPVs is a pressurized water reactor (PWR) type [25]. The specific design information of nuclear reactors in use on these vessels is not disclosed due to national security concerns and therefore assumptions must

9 be made to determine the nuclear inventory. In the Technical Safety Assessment (TSA) Sub-surface Vessel: TSA Generic Reference Design Core Inventory [32], an estimate of the fission products in the core is made based on a series of assumptions. The details of the reactor core are not known and therefore an engineering estimate of 380 kg of ^"U is used for the core mass, since it assumed that the fuel is highly enriched. The fission product yield is dependent on the operating history. To determine the fission product yield, the core burn-up, based on the hours of operation of the reactor, must be estimated. For the inventory of short-lived radionuclides, the operating flux has the largest effect on the inventory. The short-lived radionuclide inventories are proportional to the last flux experienced. The long-lived radionuclide inventories are estimated based on the core burn-up [32]. For 1MI, the range of activity that may be found in the core ranges from 4.44 x 1016 to 6.36 x 1016 Bq (1.12 x 106 to 1.72 x 106 Ci) for the best estimate and conservative cases, respectively. As a comparison, an estimate of the Chernobyl reactor 131I loading at the time of its incident on 26 April 1986 is 0.67 kg, which equates to 3.1 x 1018 Bq [33]. Unlike commercial land base nuclear reactors, which have High Efficiency Particulate Air (HEPA) filter banks and an Emergency Filtered Air Discharge System (EFADS), NPV reactors do not have a safety system responsible for filtering particulates and radioiodine from the gases, which may escape during a nuclear event. A nuclear accident on an NPV could thus possibly result in a significant amount of radiation released to the environment even though the 131I loading is approximately 2% of that of Chernobyl. Nuclear- powered submarine reactor accidents of the former Soviet Union from 1961 to 1989 have resulted in radioactive releases causing radiation sickness, land contamination and death of crew members due to acute radiation sickness [25].

1.4.2 Nuclear Emergency Response and Environmental Radionuclide Monitoring Program

The Nuclear Emergency Response program (NER) form part of the structured response to NCV/NPV visits developed by the Canadian Navy. It is the mandate of the Department of National Defence (DND) and the Canadian Forces that the visits of NPVs are monitored by the NER Team (NERT). When visits are not occurring, the NERT is responsible for taking environmental samples as part of the ERMP. Seawater is sampled monthly, sediment is sampled quarterly, and seaweeds (described in documentation as aquatic plants) and fauna are sampled biannually. A series of sampling locations are prescribed [8J. NERT members collect water samples 10 from the dock-side or from a boat. Sediment and seaweeds are collected with the assistance of scuba divers, and fauna is either caught using fishing gear (fishing pole) or is collected by the naval divers in the case of mollusks, crab or the like. Maps showing the general location of sample collection were produced as part of an original baseline study, which was conducted at the inception of the ERMP [34]. These maps are presented in Appendix A. Samples are transmitted as rapidly as possible by courier or using Canadian Forces personnel for laboratory analysis. Samples of seawater from Halifax/Shearwater are sent to Defence Research and Development Canada (DRDC Atlantic) in the CFB Halifax Dockyard. Seawater samples taken in Esquimalt and Nanoose are sent to the University of Victoria in British Columbia. Duplicate seawater samples and samples of other matrices are sent to the Analytical Sciences Group (ASG) and the SLOWPOKE-2 Facility at the Royal Military College in Ontario. Upon receipt at ASG and the SLOWPOKE-2 Facility, the samples are logged in and labelled. Preliminary gamma-ray surveys are taken. The samples are then prepared according to ISO 17025 [16] accredited methods and counted over high purity germanium detectors (HPGe) for the detection of radioactivity and more specifically fission and activation products that are expected in the event of a nuclear release from a reactor. Reports from all laboratories are issued to the Chief of Maritime staff (CMS) Maritime Staff Risk Management Services Nuclear Safety-4 (MSRMS-4). In general, the only fission product radionuclides found in any of the environmental samples described are 137Cs in sediment and ,3!I in seaweeds [8]. 137Cs is ubiquitous due to events such as the Chernobyl explosion, atomic bombs dropped on Hiroshima and Nagasaki and atomic weapons tests conducted in the 1950s and 1960s. Cs is occasionally detected in sediment samples, mainly from samples obtained in Halifax, but with a lesser frequency also from West Coast samples. 131I found in seaweed samples collected on the East Coast may be due to releases to the sewer systems from patients receiving I therapies, although no direct evidence is available to support this theory [16]. The average level of 13,I found in most of the seaweed samples has been in the range of 2-10 Bq kg 'dry weight. In December 2005, samples of seaweeds (Ascophyllum Nodosom and Saccarania Latissimd) had 131I levels of 1000 Bq kg' dry weight, 100 times the normal range. [16]. The Victoria General Hospital in Halifax may be the source of 131I found in seaweeds in Halifax and Shearwater, NS. The Capital Health authority in Halifax does keep track of estimated discharges of 131I to the sewer system from patients receiving treatment for thyroid diseases. The yearly activity of 131I to the sewer system in Halifax, NS from 2002-2006 are in the range of 77-133 GBq [35].

11 1.5 ml

1.5.1 Production of1}11

131I is produced commercially for medical and industrial uses and is produced through nuclear fission of 235U or by the neutron irradiation of 130Te. In 2003, there were 278 research reactors in operation, of which 73 were used for regular isotope production [36]. For the production of 1MI from tellurium, a medium thermal flux reactor (1013—1014 n cm-2 s-1) is the minimum requirement so that the length of irradiation can be kept to a reasonable amount of time. For example, in the wet distillation method, which uses a tellurium metal powder target, the irradiation time for a thermal flux of 1014 n cm2 s ' is 3 weeks [37,38]. It is not necessary to irradiate to saturation since the benefit of irradiating longer does not significandy increase the amount of 131I produced. In the process of neutron irradiation such as that carried out at MDS Nordian, 130Te in the form of a metal powder or tellurium oxide (TeO^ is exposed to a flux of neutrons creating 131Te by neutron capture [38]. 131Te decays by beta emission (P ) to 131I as shown in (1).

nn , . lalm (30/l)/T ,_. (8.04d)/?~ ..,, „. 13 131 13 x 5°2Te(n,Y) -» gTe » sll • \\Xe (*)

Since the 131I produced is a different element than the target 130Te, the 131I can be chemically separated from the target thus attaining a high specific activity or carrier-free radioisotope. The 131I is further refined to a medical grade radioisotope by either a wet or dry distillation method. Activities greater than 37 GBq mL1 (1 Ci mL1) are considered to be high concentrations while low concentrations are in the range of 7.4-37 GBq mL1 (0.200-1.0 Ci mL1). The radioisotope purity is greater than 99.9% with small impurities of 130I <0.1% and Te <1 ppm. 131I is also a by-product of the nuclear fission of 235U. Irradiating 235U in a reactor results in the production of fission product radionuclides. 235U has a thermal fission product yield for 131I of 2.878 ± 0.032 % per fission [39]. 131I can be extracted in the form of sodium iodide (Nal), for use as a medical radioisotope.

12 1.5.2 Decay of1'1!

131I decays with a half-life of 8.0197 days with beta and gamma-ray emissions. 131I decays by P into ,31Xe which is a stable isotope. 131I decay is accompanied by the emission of gamma-rays as shown in Figure 1-2. 131I decays 100% by beta decay to different excited levels of 131Xe. The 131Xe then releases energy by emission of one or more gamma rays with different energies [30].

P-decay 100% 131, (8.02070 d) C^ =0 9708

i (332.10% 0.7229 j (3.0.65% 0.6669 / P 7.27% 2 V 0.6370

v1 V 0.4048 \, p 80.90% x v f \ t w 0.3644 y &o.05% \ 1 >' 0.3411

]/ M.48% N f >' 0.1639

>f \ ' Ni 0.0802

v ^' N ' ' > / s ' N I 131X e (Stable)

Figure 1-2: U1I Beta Decay Scheme Showing Gamma Rays Produced [30].

The most intense gamma-ray has energy of 364.489 keV with a branching ratio of 81.7%, followed by 636.989 keV at 7.17% and 284.305 keV at 6.14%. Information about the activity of 131I is usually

13 taken from the peak at 364 keV because it has the largest branching ratio of the three most intense peaks

1.5.3 Sources of1}1I in the Environment

Nuclear accidents, such as those at Chernobyl and Fukushima [40], have caused the largest releases of 131I into the environment. It is estimated that the 131I loading in the reactor at Chernobyl at the time of the accident was 3 1 x 1018 Bq [33]. This release was so large that 131I was detected in seaweed samples (Fucus) on the Pacific shores of North America, 15 000 km away from the Chernobyl site The largest fraction of short-term and long-term dose from accidental releases and fallout from atomic bomb tests is from iodine isotopes [41] 131I is routinely administered as a radiopharmaceutical and is found at measurable levels in the environment mainly in sewer system waste and in hospital waste [42] Radiopharmaceutical therapy involves the treatment of an individual with radiation, often in the form of an open source, which can be administered either orally or intravenously. Treatment of thyroid cancer and hyperthyroid using 131I is one of the most common forms of radiopharmaceutical therapy Therapeutic doses of 131I commonly range from 150 to 7400 MBq, the larger doses being for ablation of thyroid remnants or to treat metastases in patients with thyroid cancer [42-45]. The best way to reduce contamination to patients and others is to avoid collection of the waste and therefore all human waste enters the sewage system. In patients with normal thyroid function, approximately 60 to 90% of the administered 131I solution is excreted in the urine within 24 hours Analysis of a database of more than 250 administrations of 131I for thyroid cancer shows a median effective biological half-life of at least 14 h, with substantial variation [46]. In Manitoba, in 1994, 261 patients with hyperthyroidism and 27 patients with thyroid cancer were treated with 131I activities in the range of 185 to 1100 MBq and 942 to 6530 MBq, respectively. The total amount of 131I activity administered was 164 000 MBq Using the assumption that 50% of the 131I is from hyperthyroid patients and 95% (much greater since the thyroid has been removed) of the 131I from thyroid cancer patients would eventually be excreted in to the sewer system, 111 000 MBq of activity was released into the environment in 1994 [47] At wastewater treatment plants in Finland, radionuclides of various origins were detected in the sludge The activity of 131I varied from 108-250 Bq kg' dry weight The highest activity in the sewage sludge and in the water was caused 14 by the medical use of 131I. The highest activity of 131I detected in crude sludge was approximately 94 Bqkg1[48].

1.5.4 Levels and discharges of1311 from Victoria General Hospital in Halifax

At Victoria General Hospital, in Halifax, patients with thyroid diseases are treated with 131I. Table 1-4 outlines the number of patients treated with 131I for both hyperthyroid therapy and thyroid ablations.

Table 1-4: Administered Dose to Thyroid Patients and Estimate of Discharge to Sewer of U1I in Halifax [35].

Total UT Dose Number of Estimate of U1I Administered Year Patients Discharge to to Patients Treated Sewer (/GBq) (/GBq) 2006 68 316 133 2005 50 231 77 2004 56 257 106 2003 49 227 111 2002 34 147 103

Only those patients that are treated as inpatients are included in the estimate of 131I loadings that are discharged into the sewer. The outpatients come from locations all over the province of Nova Scotia and are therefore not included in the estimate of 131I that would eventually be discharged into Halifax Harbour.

15 1.6 Seaweeds

1.6.1 Ion Uptake Pathways in Seaweeds

The mechanisms of ion uptake in plant systems are very complex There are many factors that affect nutrient uptake rates, which include 1 Physical factors such as light, temperature, water motion and desiccation of the plant; 2 Chemical factors such as concentration of the nutrient and the molecular form of the element; and 3. Biological factors including the surface area to volume ratio, hair formation, type of tissue, the age of the plant, its nutritional history and interplant variability Ion uptake pathways in seaweeds can be due to adsorption, passive transport, facilitated diffusion or active transport The biochemistry of the transfer of iodine has been extensively considered, although studies have placed greater emphasis on metal ions Precise mechanisms of iodine uptake are still the subject of research It is accepted that passive diffusion and facilitated diffusion, the latter involving specific structures on the cell membrane, are involved However, transport in seaweeds and iodine uptake in Fucus is thought to be primarily an active process [49, 50]. In pursuant work, it is sufficient to accept that the rates of uptake and loss are a function of the concentration of iodine in seawater and within the plant cells

1.6.2 Iodine in the Environment and in Seaweeds

Iodine has atomic number 53 and occurs in nature as a single stable isotope, 127I. In nature, iodine is found in the form of iodides (I), lodates (I03) and organoiodides (I-R) and at low levels in soils, bodies of water, and in terrestrial plants In seawater, iodine concentrations range from 0 03 to 0.05 |Xg g' [51, 52] Iodine is concentrated by the thyroid gland of mammals and is essential in human health for growth and development [53] It has been known since the nineteenth century that seaweeds have high iodine content; however, the biochemical pathways of iodine accumulation and its significance are stall not fully understood [54, 55] Iodine is taken up by seaweeds in the form of

16 iodides [50, 56]. Litde is known about the iodine-concentrating mechamsms or about the biological functions of iodine in kelp and other marine plants. Only one aspect of halogen metabolism, the production of volatile halocarbons, has attracted attention, because these compounds and in particular the lodinated forms have a significant impact on the chemistry of atmosphere [57]. Marine algae concentrate iodine to levels between 55 and 3000 |ig g Iodine levels in Fucus (rock weed) are as high as 0 17 % dry weight by mass [50] The purpose of iodine accumulation in seaweeds is soil unknown. Since iodine has antibacterial properties, it is suspected that iodine in seaweeds may be used as a defence mechanism against predators such as protozoans and bacteria [50, 58]. Microchemical imaging of iodine distribution in the brown alga laminana digitata shows that the peripheral tissue is the main storage compartment of iodine [55]. This location supports the theory that iodine is used as a defence mechanism, since the iodine can be easily remobilized for potential chemical defence and antioxidative activities. Iodine has also been shown to be a stimulant and in some cases essential for growth and reproduction in some brown algae [59].

1.6.3 Bioaccumulation oj"Radionuclides in Seaweeds

Often, detection of a release of low activity radiation is difficult once the radiation has been diluted in the atmosphere or in bodies of water. Using plants that bio-accumulate radiation can therefore prove to be a useful tool when looking for low level releases. Amchitka Island (part of the Aleutian Islands) was a United States Department of Energy test site for three underground nuclear test shots from 1965 to 1971 [60]. A study was conducted to determine the levels of radionuclides in eight marine species of algae. Many different radioisotopes were studied including 137Cs, 129I, ^Co, 1S2Eu, ^Sr, "Tc, 24]Am, 238Pu, 239Pu, 240Pu, 234U, 235U, 33eV, and 2MU [60]. For most isotopes studied, Fucus had the highest levels of radionuclides, with some radionuclides being an order of magnitude higher in Fucus compared to other algae species. It was concluded that the genera of mterodal Fucus are better accumulators and should be used as bio-indicators for monitoring Fucus is frequendy used as a bio-indicator of radionuclides in the marine environment [60, 61]. The accumulation of radionuclides in seaweeds is a complex process that is controlled by many factors including environmental conditions, health and age of the plant and concentration of the radionuclide in the environment. The concentration of the radionuclide in the surrounding environment is the most important factor when considering a specific species of seaweed. When determining the uptake,

17 some care should be taken when using Fucus since different structures have different uptake rates. The holdfast, a root-like structure that anchors aquatic plants, can take up radionuclides over several years. In contrast, the blades, leaf-like structures, reflect the uptake that has occurred over the last few weeks [62]. The coastal distribution of 131I was measured in Fucus located in the northern hemisphere originating from Chernobyl. The 13,I concentration ranged from 31.7 Bq g1 dry weight in Asko, Sweden to 0.3 Bq g' dry weight in St. John's, Newfoundland, 18 days after the release from Chernobyl [50]. 131I was detected in Ecklonia radiata, a subtidal kelp, near Perth, Australia at an average concentration of 0.009 Bq g \ The source of the 131I was from medical use at a local hospital in Nedlands, Western Australia [63]. In 1999, controlled releases of 129I at the nuclear fuel reprocessing plant of Compagnie Generale des Matieres Nucleaires (COGEMA), La Hague, in the English Channel reached 1.8 TBq. Samples of seaweed species taken 5 km away from the pipe outlet had 129I ranges of 20-150 Bq kg1 dry weight in Fucus serratus and 80-740 Bq kg1 dry weight in Laminara digitata [60]. 129I:127I ratios determined for Arctic marine algae collected between 1930 and 1993 have increased as much as three orders of magnitude and Fucus from the Northeast coast of Ireland are two orders of magnitude higher than Fucus from the West coast. Both of these increases are due to the releases from Sellafield in the United Kingdom and La Hague, France, which released an estimated amount of 1400 kg of ,29I in the late 1980s to early 1990s [64-66].

1.6.4 Fucus Gardneri

The brown seaweed Fucus (commonly known as rockweed) is an intertidal seaweed that is found in Canada on both coasts in the cold temperate waters. Fucus is the most common seaweed in the northern hemispheric waters. It is found in the mid to high intertidal waters. Fucus plants reach 40 cm in length. They have many branches and display a noticeable midrib running the length of the flattened branches, as shown in Figure 1-3 [67, 70]. The tips of the plant branches are often inflated, which helps to keep the plant buoyant during high tide. When the plant reaches maturity, the tips contain the conceptacles (cavities) that bear the egg and the sperm [71]. Since Fucus is easily harvested at low tides, it can be used as a biological monitor for releases of radioactive iodine into the environment [50]. The accumulation of iodide by species of Fucus has been studied. A study of the accumulation of iodide by Fucus ceranoides found that, after 15 minutes, two grams of Fucus ceranoides tissue had taken up approximately 50% of radioactive 131I from 50 mL of seawater held at 18 room temperature (18°C) [72]. Understanding the rate mechanism is thus important, as reviewed in the next Section.

Figure 1-3: Fucus Gardneri Seaweed [67-70].

1.7 Reaction Kinetics and Thermodynamic Equilibrium

Kinetics is the study of the rate of reactions. The rate of the reaction is described using the rate of change of the reactants and/or the products. For reaction rates that are of 2ero order, the concentration of the reactants or the products does not affect the rate and the reaction proceeds at a constant rate. Zero order kinetics may be described by considering the simple reaction given in Equation (2):

19 A->B (2)

For this zero order reaction, the rate is constant. Thus, for a zero order reaction, the rate of change of [A] can be described by Equation (3):

d[A] (3) K — 7~"~ dt

Rearranging and integrating Equation (3) provides Equation (4):

r[A] rt d[A] = -kdt (4) J\A\n J0

For a zero order reaction, the rate of change is linear and the rate of change of [A] is described by Equation (5):

[A] = [A]0 - kt (5)

Consideration of Equation (2) for a first order reaction, in which the rate of change is dependent on [A], [A] provides a reaction rate which changes with time as described in Equation (6):

dlA] m= «> dt

Integrating Equation (6) gives Equations (7) to (9):

cWd\M (' = -kdt (7) W'[A]o [A] Jo

In[y4]-ln[i4]0 =-kt (8)

kt [A] = [A]0e- (9)

20 Figure 1-4 shows the expected shape for a zero and a first order reaction based on Equation (2), with respect to a decrease in [A] as a function of time.

• Zero Order

First Order

5 10 15 20 25 Time /(Arbitrary Units)

Figure 1-4: Shape of Zero and First Order Reactions with Respect to [A] as a Function of Time.

It is evident from Figure 1 -4 that the change in [A] is linear for a zero order reaction. A first order reaction sees a progressive decrease in rate of change with [A] = 0 being achieved at infinity. Higher order reactions are not part of the scope of this thesis and therefore will not be discussed. Pursuant to the research done, reactions that follow first order kinetics and that approach equilibrium are discussed. In many instances, the possibility of a reverse reaction is ignored. Such an assumption is valid for very large equilibrium constants, where the relative rates of forward and reverse reactions differ by many orders of magnitude. However, for a reaction approaching equilibrium, both the forward and reverse reactions are important. First order kinetics may be considered using the simple equilibrium expressed in Equation (10): A r± B (10)

The rate of change of [A] is due to the transformation of A into B, represented by the rate constant kf, in the forward direction. However, the rate of formation of A by the transformation of B must

21 also be considered, which is represented by kb, the rate constant in the backwards direction. The net rate of change is therefore described by Equation (11):

*¥1 =-k,[A] + kb[B] (11)

At the beginning of the reaction, when [B] — zero, the initial [A] can be expressed as [A]0 Moreover, at any time (t), the concentrations of A and B can be expressed by Equation (12):

[A] + [B] = [A]0 (12)

Substitution of Equation (12) into Equation (11) yields Equations (13), (14) and (15):

^-=-kf[A] + kb([A]0 - [A]) (13)

= -kf[A]+kb[A]0-kb[A] (14)

= -(kf + kb)[A]+kb[A]0 (15)

For the initial condition [A] = [A]oJ the solution of this first order differential is expressed by Equation (16) (see Appendix B for steps from Equation (15) to Equation (16) [73]:

+ (kb + kf e-(*/ *»)t\

Equation 16 can be expressed graphically for arbitrary values of kf and kb. Figure 1 -5 shows the time dependence of [A] and [B] with time.

22 1 f-

3 • • 0.5 • [A] o • ID • [B]

u O • U

a _ 4 6 8 10 12 14 Time /(arbitary units)

Figure 1-5: First Order Equilibrium Reactions.

As t», [A] and [B] reach their equilibrium values, giving rise to Equations (17) and (18):

kb[A]0 M.= (17) and

kf[A]0 [B]M = [A]0 - [A] = (18) (*/ + kb)

When the reaction is in equilibrium, the ratio of the concentration of the product over the concentration of the reactant gives the equilibrium constant Keq Taking the ratio of Equations (17) and (18) allows the expression of the equilibrium constant K in terms of [A]OD and [B]oo or kf and k,,, Equation (19):

K -Bl (19) 6q " [A]c

The above equation has significance because it relates the equilibrium constant, a thermodynamic quantity, to the rates of the reaction. Therefore, if the rate of one of kf or kb can be measured experimentally, the other can be determined if the equilibrium constant is known.

23 1.8 Gamma-Ray Spectroscopy

Gamma ray spectroscopy is an analytical technique used to detect gamma-ray emitting radionuclides from a given material Isotopic data can be obtained since the gamma-rays can be identified based on their energy, measured in electron volts (usually keV or MeV). Using a calibrated system, activity can also be determined for each radioisotope measured Intrinsic semiconductor detectors, especially high punty germanium detectors (HPGe), are used to detect low level gamma radiation in environmental samples The superior resolution of an HPGe over that of a sodium iodide (Nal) detector makes possible the identification of radionuclides, which have associated gamma-rays that differ in energy by relatively small amounts [74] Detector efficiency is important in the detection of the low level of activity, which is typically found in environmental samples. The efficiency is measured by taking the ratio of the number of measured gamma-ray counts to the number of actual gamma-rays emitted by the source being measured The relative efficiency of a HPGe is usually expressed as its relative efficiency to that of a 3" x 3" Nal detector The size and dimensions of the crystal determine the efficiency of an HPGe and therefore the larger the crystal, the more efficient the detector Some large volume HPGe detectors can now be constructed to achieve relative efficiency exceeding 100% [75]. The absolute efficiency of a detector is determined for a specific counting geometry by counting a multinuclide source of known activities. It is important to realize that both the sample and detector geometry influences the efficiency calculation. The location of the sample in relation to the detector, the sample size and shape all contribute to a specific efficiency for a specific counting geometry Figure 1-6 is a comparison of three counting geometries. All of the sources were placed in contact with the detector, but varied in size and shape For a point source, as shown in Figure 1-6, the efficiency is greatest since the activity is in close contact with the detector Mannelli containers maximize detector sample interaction by incorporating a concentric lip which sits around the body of the detector (Figure 1 7)

24 0.18

0.16 A

0.14 • \

0.12 1 -t— 5" e at 1 _ _ _ _ u 0.1 E 1 ui 1 Point Source a> \ | 0.08 1 1 LMarinelli Beaker 1 \ • 1 L Bottle 0.06 * V * N r. %. 0.04 • *. **•* ^ 0.02

200 400 600 800 1000 1200 1400 1600 1800 2000 Energy (/KeV)

Figure 1-6: Effect of Different Sample Geometries on Efficiency [76].

Figure 1-7: 450mL Mannelli Beakers used for Increased Counting Efficiency of Samples on an HPGe Detector [77].

25 Thus, a 1 L marinelli beaker is more efficient than a 1 L bottle since the shape of a marinelli is such that the detector is surrounded by the sample and the sample is in contact with both the detector end cap and the sides of the detector. For environmental samples, a marinelli beaker is often employed since it improves the efficiency over using a conventional bottle. Also, since the activity desired is based on a per mass basis, counting as much of the sample as possible is desirable. Moreover, since the activity maybe heterogeneously distributed, larger samples are more representative. For environmental samples, where the activity per unit mass is low, it is not practical to count a small sample such as one that would represent the size of a filter paper. Although activity detected per unit mass would increase using the latter, the absolute mass analysed would be small. The type of detector used affects the shape of the efficiency curve. For p-type detectors, which have electron acceptor impurities, a thick lithium contact is on the outer surface of the crystal and a thin, ion-implanted contact is on the inside. This thick coating decreases the efficiency of the detector at energies below 100 keV. In such circumstances, the detector is surrounded by an aluminum cap, since no benefit is gained from using a low energy efficient beryllium window. For an n-type detector, which has electron donor impurities, the contacts are reversed and therefore the low energy efficiency is greater. Thus an n-type detector makes use of a thin beryllium window on the end cap to allow low energy gamma-rays to reach the detector. The activity of a sample is a measure of the number of disintegrations of a nuclide from its active state. The units of measure for activity are the curie (Ci) and the becquerel (Bq). One curie is based on the activity of one gram of ^Ra and is equal to 3.7 x 101C disintegrations per second. The becquerel is simply defined as one disintegration per second. Therefore, one Ci equals 3.7 x 1010 Bq. To calculate activity using gamma-ray spectroscopy, Equation (20) is used. A = ~k <20> where A is the activity in Bq, n is the net number of counts under the peak of interest, £ is the efficiency of the detector at the energy of the peak of interest, / is the branching ratio for the gamma-ray at the peak of interest and tc is the live time count in seconds. Detector dead time, which is the ratio of the live time to the real time, is kept to a minimum, ideally less than 5% and is accounted for by the analysis programs.

26 Radioactive decay and detection are random processes and can be defined using a Poisson distribution. Poisson distribution gives the probability of a number of independent events occurring in a fixed time. For gamma-ray spectroscopy, the standard deviation can be approximated from a single measurement where the uncertainty in counting is equal to the square root of the counts [78]. For low level counting of environmental samples, the type of shielding used can help to reduce background radiation. If the shielding is made of lead bricks, they must interlock on all sides in order to prevent radiation streaming. Stteaming occurs when there are small spaces in the lead shielding between the bricks that allow radiation to enter the shielding and subsequently to be detected. It is also beneficial to have the detector crystal as far away from the shielding as possible. The purpose of the lead is to block out gamma-emitting nuclides from materials exterior to the detector. The inner cavity of the lead shielding is often lined with high purity copper and Plexiglas. The inner linings of copper and Plexiglas (lower density materials) reduce the bremsstrahlung or 'braking' radiation by blocking the beta radiation originating from the lead shielding. Figure 1-8 is an illustration depicting the interactions of gamma-rays and x-rays with detector systems in lead shielding.

27 "'"w-, CSCAPE OF y r^~ ONf K X RAV ^ BETA AfiSORBEP "^ sf cf BREMSSTRAHLUNG - e "X '^ ANNIHILATION RADIATION ^V COMPTON SCATTERING PHOTON REFLECTOR

UV PHOTONS . SHIELDING (Produced liom Local E«cr«d Stattt Following lonii»l

Pb X BAY

PHOTOMULTIPUER

PHOTOELECTBON (Emitted 1t9*n C«thod*l

OVNOOE (Secondary Et*cir

Figure 1-8: Interaction of Radiation with Detector Shielding [79].

1.9 Instrumental Neutron Activation Analysis

Instrumental neutron activation analysis (INAA) is a multi-element analytical technique used to determine the concentration of elements in a sample of interest. The technique involves the bombardment of a sample with neutrons (usually thermal neutrons) and the absorption of a neutron in the nucleus of the atom. If a neutron is absorbed, the nucleus forms a compound nucleus in an excited state. The nucleus will de-excite to a more stable configuration by releasing a prompt gamma-ray. The resulting nucleus is either stable or radioactive. If radioactive, the nucleus will decay by beta emission usually accompanied by gamma-rays. Gamma-rays emitted have specific energies,

28 which can be used to identify and quantify the elements present in the sample. The gamma-rays are detected by a gamma-ray detector, such as an intrinsic or High Purity Germanium detector (HPGe). For the detection of iodine, the neutron irradiation of 127I, which is the only natural isotope of iodine is used, i.e. 127I(», y)128I- Subsequent decay of 128I produces several gamma-rays, including a prominent gamma-ray at 442 keV. At the SLOWPOKE-2 Facility at RMC, the comparative method of INAA is used, which involves the use of a standard of known concentration compared to the unknown sample. Equation (21) is used to determine the concentration of element in the sample.

An BW(l - e-At0(e-At<0(l - e-At0

The constant B is defined by Equation (22) as:

NA6athl £ ,„„x B = — Ell (22) M

where C is the concentration in (ig g \ X is the decay constant and is equal to ln2/half-life (t1/2) of the isotope, n is the number of net area counts under the peak of interest, ^ is the thermal neutron flux, W is the weight of the sample in grams, /, is the irradiation time (s), td is the decay time (s) from the end of the irradiation to the start of the count and tc is the count time (s). NA is Avogadro's constant, 6 is the isotopic abundance of the isotope of interest,

Since the comparative method makes use of standards of known concentration and these are compared to the unknown samples, a sensitivity constant, B, is used as defined above to simplify the equation since these parameters are constant for both the known and unknown.

29 Chapter 2 Experimental

2.1 Experimental Introduction

The main focus of the experimental work was to determine the absorption of 131I in Fucus gardneri. To achieve this goal, instrument and equipment development was required and a number of supporting experiments were conducted. The following sections describe the practical steps taken to gather data with respect to 131I absorption and related studies. Thus, the neutron source provided by the SLOWPOKE-2 Facility at RMC, and the setup and validation of a shielded gamma-ray spectrometer validated to ISO 17025 standards are initially described. The collection and analysis of field samples of Ascophyllum Nodosum and Saccharina from Shearwater, NS is discussed, as are the methods by which Fucus gardneri was kept alive at RMC for experimentation. Since 131I behaves identically to stable iodine in its absorption, stable iodine measurements were conducted on Fucus gardneri. Parameters relating to 131I exposure, such as source, dilution and detection limits are discussed, followed by a detailed description of Fucus gardneri to ,31I. Finally, in some preliminary experiments, Fucus was exposed to other fission and activation products present in SLOWPOKE-2 reactor container water to investigate the uptake of other radioisotopes in Fucus gardneri.

2.2 Instrumentation

2.2.1 SLOWPOKE-2 Reactor at the Royal Military College (RMC), Kingston

The SLOWPOKE-2 reactor at RMC is a pool type reactor that makes use of light water for both moderation and cooling. The fuel is constructed of low enriched uranium oxide powder enriched to 19.89% 235U and is arranged in a fuel cage consisting of 198 fuel pins sheathed in Zircaloy [80- 82]. The reactor is controlled by a digital software program called SLOWPOKE Integrated Reactor Control and Instrumentation System (SIRCIS). The reactor is licensed to operate at a maximum thermal neutron flux of 1 x 1012 n cm2s\ Five inner irradiation sites are located concentrically around the fuel approximately halfway way through the beryllium annulus, where the neutron flux is

30 maximized. These inner sites are used for irradiation of small samples. An additional 4 sites are located just outside the beryllium annulus. A pneumatic transfer control system and polyethylene tubing are used to transfer samples into the reactor sites and to eject samples from the reactor to a lead receiver [80].

2.2.2 Gamma-Ray Spectroscopy Systems

Many gamma-ray spectroscopy systems were used for the research conducted for this thesis. Gamma-ray spectroscopy systems located in the SLOWPOKE-2 Facility are coaxial HPGe semiconductor detectors supplied by EG&G Ortec (Oak Ridge, USA). Table 2-1 lists the equipment used for gamma-ray spectroscopy. The relative efficiency of the detectors used ranged from 20% to 60% and were either p-type or n-type detectors. Each detector is connected to a multichannel analyser (MCA) (models include DSPEC Plus, DigiDART and DSPEC Pro, manufactured by Ortec) which are calibrated for both energy and efficiency before use. The systems are cooled in one of two ways: either through the use of high purity conducting copper rods (also known as cold fingers) attached to the detector capsule and inserted onto a 30 L dewar containing liquid nitrogen or by an electromechanical cooler called an X-Cooler also supplied by EG&G Ortec. The detectors are surrounded by large lead shields lined with Oxygen-Free High Conducting (OFHC) copper. In some cases, an additional Lucite (polymethyl methacrylate) lining is also used. The software program used to determine radioactivity in the samples was Ortec Gamma Vision Version 6.04 [83]

31 Table 2-1: Ortec Gamma-ray Spectroscopy Detector Models, Relative Efficiency and MCAs Used for Gamma-ray Spectroscopy.

Relative Detector Model Efficiency MCA Used

% GMX-20190-P 20% DSPEC Plus GEM25P 25% DSPEC Plus GMX 35-Plus 35% DSPEC Pro GMX40P4-70-S 40% DSPEC PLUS GEM60P4 60% DigiDART GMX60P4 60% DSPEC PLUS

2.3 Radionuclide Preparation and Instrument Validation

2.3.1 Design and Construction of Detector Shielding for IJOIV Leve/ Counting

A large detector shielding was constructed using specially fabricated lead bricks (Canada Metal (Eastern) Limited, Toronto, ON). The dimensions of the bricks are 15.24 cm x 7.62 cm x 5.08 cm (6" x 3" x 2"). The bricks are fabricated with curved edges, which interlock to adjacent bricks as illustrated in Figure 2-1 and Figure 2-2.

32 Figure 2-1: Lead Brick from Canada Metal Showing the Unique Shape used to Prevent Radiation Streaming.

Figure 2-2: Detector Shielding Showing Lead, Copper and Lucite and the GEM60P4 HPGe Detector Inside the Shielding.

33 The lead shielding is 15.24 cm thick (6") on all sides except the bottom, which is 10.16 cm (4"). The inner cavity of the detector shielding has dimensions (1 x w x h) of 38.1 cm x 38.1 cm x 35.56 cm (15" x 15" x 14") and is lined on all sides, top and bottom with a 0.635 cm QA") layer of Oxygen Free High Conductivity (OFHC) Copper (Canada Metal (Eastern) Limited, Toronto, ON) and a 0.32 cm (1/8") layer of Lucite (acquired from Department of Chemistry and Chemical Engineering RMC, supplier unknown). The lid is split into two sections that open in opposite directions away from one another. The lid can be opened using handles that rotate to turn gears that move each section of the lid along a track. The frame of the casde is fabricated out of steel with cross bracing along the legs and a 10.16 cm (4") steel skirt around the base of the platform, which supports the lead shielding. A 10.16 cm (4") hole is cut through the centre of the bottom of the casde to allow the detector capsule to pass through the shielding into the interior of the enclosure. For further details and a diagram, see Appendix C.

2.3.2 Validation and Detection Limit of 131I on a 60% GEM60P4 HPGe

Validation data were collected with a Smart GEM60P4 HPGe detector in shielding as described in section 2.3.1, with liquid nitrogen used as the cooling mechanism. Linearity is obtained using nominal 18, 37 and 55 kBq sources containing nine radionuclides (Am-241, Cd-109, Co-57, Ce-139, Sn-113, Sr-85, Cs-137, Y-88 and Co-60) and analysing eleven of the resulting gamma-ray peaks. The sources were counted for 2700 s live time. Several 500 mL marinelli geometry sources (model 530GE, GA-MA Associates, Ocala, FL) with 450 mL aqueous equivalent gel and with gel density equal to 1.0 g mLl were used. The sources were NIST traceable and obtained from QSA Global (Burlington, MA) and Eckert and Ziegler, (Valencia, CA ). Detection limit data were obtained from eight replicate analyses of 750 mL of tap water, for which a live count time of 6 hours was used on a marinelli, (model number 538G, GA-MA Associates, Ocala, FL) filled with 750 mL of tap water, placed direcdy in contact with the detector.

The precision and accuracy of the GEM60P4 was determined for three sample geometries. These sample geometries included a 500 mL marinelli filled to an active volume of 450 mL, a Petri dish with an active diameter of 46 mm filled to 15 mL and filter paper with an active diameter of 45-50

34 mm. The sources were counted until a minimum of 10 000 net area counts were collected for each of the principal eleven gamma-ray peaks associated with the nine radionuclides identified above.

Each of these sample geometries was counted eight times in three detector configurations to determine precision and accuracy. The three different configurations included collecting a spectrum while the detector was connected to EG&G Ortec's X-Cooler II inside lead shielding (as described in section 2.3.1) and without lead shielding (Figure 2-3), and collecting a spectrum while the detector was cooled with liquid nitrogen and shielded with lead (Figure 2-4).

Figure 2-3: Smart GEM60P4 HPGe Detector in the Detector Stand while Connected to the X-Cooler II.

35 Figure 2-4: Smart GEM60P4 HPGe Detector in Liquid Nitrogen Dewar and Inside Lead Shielding.

An 13,I source was acquired from Draximage (Kirkland, QC) to determine a detection limit and minimum detectable activity (MDA) for the GEM60P4. The solution of 131I was diluted at Kingston General Hospital imaging services. The initial 10 mL 555 MBq source (06 Nov 2007) was determined to have an activity of 24 MBq (Radionuclide Calibrator, Radcal, Monrovia, CA). Serial dilution in 0.02 M Na2S04 and 0.0002 M NaOH afforded a 2 mL aliquot with activity <10 kBq. Since this material was below the exemption quantity for I, transportation of the solution to RMC could be accomplished. At RMC, the 2 mL solution was diluted using 0.02 M Na2S04 and 0.0002 M NaOH to 500 mL. A 200 mL aliquot was counted in a 250 mL marinelli (model 463316 from GA- MA Associates) using a Smart GEM60P4. Once the activity of the stock solution was known, a low level sample was prepared to determine the detection limit of the 60% HPGe detector. A further 1 in 200 dilution was performed by weight, and a 200 mL aliquot was similarly counted for a six hour live-time count. Eight replicate counts were performed.

36 2.4 Field Sample Collection and Analysis

2.4.1 Collection of Seaweed Samples from Shearwater, NS and Preparation for Shipment

Seaweeds were collected in Shearwater, Nova Scotia in December 2006 by Canadian Forces naval divers under the observation of the author. The divers collected eleven samples consisting of two species of seaweed, later identified as Ascophyllum Nodosum and Saccharina hatissima. The samples were collected at the Shearwater Yacht Club and at points around the Shearwater Jetty (Figure 2-5).

Figure 2-5: Map Showing the Shearwater Jetty, the Location of ERMP Shearwater Sampling.

Divers used rope sacks for sample collection. Samples were transferred to labeled sample bottles on the vessel or onshore. Seaweeds collected were at a depth of <8 m, with most of the samples collected at the surface or from ropes at a depths of <4 m. Field notes pertaining to the sample collection are given in Appendix D.

37 Seaweeds were transferred to the Dockyard Building in Shearwater and isolated from the other organisms that were attached to the plants by a process of physical inspection and removal. The organisms and one small sample of each type of seaweed were transferred to Dr. Christopher Lane (Postdoctoral Fellow in the Department of Biochemical and Molecular Biology at Dalhousie University) for identification. The remaining sample containers were packed into larger coolers. Icepacks were placed between the containers to keep the samples cool during shipment. The samples were shipped to RMC using a courier service under Chain of Custody.

2.4.2 Shearwater, NS, Seaweed Sample Preparation and Counting

Preparation was achieved using a commercial food processor (Cuisinart Mini-Prep). Samples were chopped into fine pieces after which a volume of 200 mL or 750 mL (depending on the amount available) aqueous equivalent of the seaweed was transferred into a graduated cylinder. The mass was determined using a pan balance. The density of the sample was calculated. The sample was transferred into a model 538G marinelli container for 750 mL samples and model 463316 marinelli for 200 mL samples. Prepared marinelli beakers were counted over a 60% GEM60P4 HPGe detector for 6 hours live time. Prior to analysis, samples were stored in a refrigerator to prevent spoiling. The spectra were analyzed for I activity using gamma-rays at 364, 637 and 284 keV.

2.5 Fucus Gardneri Collection and Preservation at RMC

2.5.1 Collection of Fucus Gardneri and Shipment

Fucus gardneri samples were harvested from the western shoreline of Vancouver Island in Bamfield, British Columbia at low tide (Canadian Kelp Resources, Bamfield, BC). Samples were taken in January, March and November of 2008. The following describes the vendor's sample preparation. A sharp blade was used to cut the Fucus near the end of the holdfast. Plants of similar size were sampled with the desired height around 20 cm. The Fucus were cleaned and allowed to air dry at

38 ambient temperatures overnight. The Fucus were packed in a burlap sack and placed in a polystyrene foam cooler for shipment [84]. It is assumed that the 131I content of these plants is negligible.

2.5.2 ArtificialSeawater andAquarium

Artificial seawater was prepared using double deionized water and purchased salts (Fisher Scientific). The required salts and masses necessary to mimic seawater are identified in Table 2-2 [85].

Table 2-2: Artificial Seawater Masses and Concentrations

Mass per 200 L

Concentration H20

Compound /gL* /g NaCl 24.7 4940 KC1 0.671 134

CaCl2 1.03 206

MgCl2.6H20 4.66 933

MgS04.7H20 6.29 1260

NaHC03 * 0.180 36.0 Aqueous I 1 200 '"added aft er the compounds listec above

To obtain a final volume of 200 L, salts were mixed into 40 L of double deionized water in a large open container. The solution was manually stirred until all of the salts had dissolved (ca. 30 min). Thirty five litres of this concentrated solution was put into the fish tank. The volume of the fish tank was brought up to 175 L by adding 140 L of double deionized water. The remainder of the solution (5 L) was placed in a 25 L Nalogene container and the volume was brought up to 25 L by adding 20 L of double deionized water. The water in the fish tank was circulated through a chiller system (Arctica Model DA1500B, Garden Grove, CA) using a submersible pump (HENRI Studio Inc High Tech Pump PS7, Wauconda, IL), for a minimum of 24 hours to ensure that the water was well mixed and cooled to 11°C. Two

39 additional head water pumps were used to help mix the water (Hagen Aqua Clear 20, Montreal, QC). Seawater pH was determined to be 7.7 (Denver Instrument Company Conductivity/pH meter model 220 with a pH electrode #300729.1). Aqueous iodide (Inorganic Ventures, Christiansburg, VA) was added to both the aquarium and stock solution using a 1000 \Xg mL1 solution to ensure the concentration of iodine was 0.05 ug mL \ Lighting was provided by a single 122 cm (48") tube strip light (Hagen, Montreal, QC) for lighting during the daytime period of 7-8 h.

2.5.3 Receipt and Preparation for Introduction into Artificial Seawater Aquaria

Fucus gardneri plants were shipped by Canada Post with a transit time of 2 to 3 days. Upon receipt, usually by afternoon delivery, the seaweed was immediately measured, weighed, given a unique number, tagged and tied to a plastic pipette holder using string ( Figure 2-6). Fucus was placed in a half-full aquarium to allow the plants and pipette holder to stand clear of the seawater for 1 d. After that time, the Fucus was cycled in and out of the seawater for 16 h and 8 h per day by immersion in water and location on the pipette holder, respectively. The Fucus were kept at <13°C, with a maximum water temperature of 11°C [84]. This was achieved through the use of an Arctica Model DA1500B chiller that kept the water cooled and by insulating the top of the aquarium using polystyrene foam. Plants were used after acclimatization for > 1 d.

Figure 2-6: Fucus Gardner!'in Seawater Aquaria Showing Plants Supported out of the Seawater.

40 2.6 Measurement of Stable Iodine in Fucus Gardneri

2.6.1 Instrumental Neutron Activation Analysis (INAA) for the determination of Iodine in Fucus Gardneri

Fifteen samples of Fucus gardneri were prepared for INAA. The samples were dried in a fume hood to constant mass, crushed to fine flakes inside plastic bags. Each sample was prepared in a 1.5 cm3 polyethylene vial, which was then heat sealed using a soldering iron. The samples were double encapsulated in a 7 cm3 irradiation vial, which was also heat sealed using a soldering iron. The samples were transferred using an irradiation controller located in the SLOWPOKE-2 Facility through the pneumatic tube system into an inner site of the SLOWPOKE-2 reactor at RMC. The samples were irradiated in a neutron flux of 5x1011 n cm2 s' for 1 min. The decay time before counting was 2.5-4.6 min. The samples were counted over a 25% GEM25P HPGe detector 11.5 cm from the end cap for 5 min or until at least 1500 net area counts were collected in the 442 keV 128I peak. The comparative technique of INAA was used by irradiating known concentrations of aqueous standards and controls. The samples were analysed for total iodine using EPAA Java software (Ecole Poly technique, Montreal, CA).

2.7 Determination of Surface Area of Fucus Gardneri

All surface areas were determined after the Fucus gardneri plants were used in their respective experiments. Only the surface area of the plants collected in November, 2008 were determined (Plants in the number range 101-150). The surface areas of the plants were determined using software, which counts the number of pixels used to create an image. To calibrate the system, a retort stand was used to hold a digital Canon Power Shot G6 camera Model PSG6 at a constant 30 cm from a photo image plane. Black pieces of paper cut to 25, 50, 100, 175, 200 and 400 cm2 were photographed. The photos were converted to bitmap files using Irfanview software (Irfanview, version 4.28, Jajce, Bosnia). The number of pixels used to create the black portion of the image was determined using the software SCION image (Siconcorp, Frederick, MD, version 4.03).

41 For sample analysis, individual Fucus plants were pressed between two sheets of Lucite plastic. Photographs were taken in the same manner as the calibration, converted to black and white images and similarly processed. The pixels determined for each plant were then converted to an approximate area. This single sided surface area was then doubled.

2.8 Fucus Gardneri ml Exposure Experiments

2.8.1 Fucus Gardneri 1}1I Uptake Measurements with Varying Parameters

In the following experiments, the Fucus plants were counted using HPGe detectors to determine the 131I uptake. Fucus plants were exposed to 1MI under various conditions fTable 2-3). In general, containers holding a specific volume of artificial seawater were spiked with 13,I solution. Polystyrene containers and ice packs were used to maintain the seawater at temperatures between 8-13°C. The temperatures were measured using a mercury thermometer. With the exception of plants 23 and 24, the seawater was stirred for the duration of the experiment. Fucus plants were added to the spiked seawater. The plants were removed, rinsed 6 times using 50 mL artificial seawater, blotted dry and prepared in a 20 mL petri dish or a 200 mL marinelli for each of the counting time intervals used. In some of the experiments, a 15 mL seawater sample was also counted at each of the time intervals. The samples were counted over a 60% GMX60P4 or a 40% GMX40P4-70-S HPGe detector to determine the 131I activity for counts times ranging from 129-322128 s and 1518-146681 s for Fucus and artificial seawater, respectively. The Fucus was returned to the spiked seawater after each count, where required. All activities were back calculated to the start time for the first count of each experiment.

42 Table 2-3: Experimental Parameters for Fucus GardnerimI Exposure Experiments with Varying Parameters.

No. Days Plant Seawater Initial U,I Water Fucus Seawater Fucus Plant Analysis After Mass(es) Volume Activity Temp Count Count Counting Detector Identification Times /h Receipt /g /L /BqL' /°c Time /s Time /a Geometry of Fucus 0 8,1 7, 2 5, 20 mL 20 1 114 3 3 33 13 2100 21600 NA GMX40P4 70 S 3 3,42 Petri 01,02,03, 1652 200 mL 29 3 413 3 400 9 11 0 4, 0 5,0 6, 600 GMX60P4 88774 mannelli 16 1,2,3,4,5, 200 mL 14 5 41 8 3 340 9 125 600 1518 6173 GMX60P4 6,7 mannelli 200 mL 23 7 19 20 0 05 9 5-10 5 6 322158 NA GMX60P4 mannelli

200 mL 24 7 19 20 0 05 9 5-10 5 24 260335 NA GMX40P4 70 S mannelli 38 125 1,2,3,4,5, 4325 200 mL 44 13 123 3 428 8 13 129-300 GMX60P4 21, 25, 26 146681 mannelli 47 123

43 2.8.2 Measurement of Removal of I from Artificial Seawater by Fucus Gardneri

In the following experiments, only the artificial seawater was counted using HPGe detectors to measure the removal of 131I by the Fucus plants. Five separate experiments were conducted using 6 full plants of Fucus gardneri each isolated in 500 mL of 131I spiked artificial seawater. The seawater was kept between 7-8°C using an insulated cooler and icepacks. The temperature was measured using a mercury thermometer. The seawater and Fucus was stirred using a glass rod or spatula every 15 min. One mL aliquots of the seawater were taken, at least, in 30 ± 2 min intervals and the times were recorded. The samples were counted over one of three HPGe detectors including one 20% GMX- 20190-P HPGe, one 20% GEM25P HPGe and one 35% GMX 35-Plus HPGe calibrated for energy and efficiency in the same geometry as the 1 mL container. The detector on which each individual experiment was counted was kept consistent for all counts. The samples were counted for 300 or 600 s live time. Once the 1 mL aliquot was counted, it was returned to the beaker from which it was taken. Table 2-4 contains the sample identification, mass and initial 131I activity for each experiment. After 24 hours of exposure to 131I spiked seawater, plants 101, 104, 105, 109, 115 and 139 were placed in clean artificial seawater cooled to between 7-8°C. The samples were stirred periodically. One mL aliquots of seawater were taken every 30 min and counted for 10 min over an HPGe detector. After the Fucus had been in the seawater for 19 h, a 15 mL aliquot was counted over an HPGe detector for 15 min to determine the amount of 131I that entered the seawater from the Fucus.

44 Table 2-4: Experimental Parameters for mJ Removal by Fucus Gardneri.

Fucus Mass UII Initial Activity in 500mL Frequency of Sampling /min ID /(g) /(kBq) 65 74 2 40 30 66 20 3 40 30 67 141 40 30 68 22 3 40 30 69 79 2 40 30 70 60 40 30

101 163 50 15 104 22 8 50 15 105 22 50 15 109 27 1 50 15 115 24 50 15 139 18 3 50 15

102 10 7 50 15 119 119 50 15 123 113 50 15 127 10 5 50 15 128 10 3 50 15 132 113 50 15

103 51 50 15 130 54 50 15 140 65 50 15 143 65 50 15 146 52 50 15 147 57 50 15 110 13 8 39 15 111 12 6 58 15 116 12 78 15 117 13 9 97 15 141 128 116 15 144 12 3 136 15

45 2.8.3 Retention qf131I in Fucus Gardneri Under Different Storage Conditions

Nine groups of plants of Fucus gardneri were exposed to 131I. The initial activity of the absorbed I31I for each group of plants was determined by counting the samples in 200 mL mannelh containers (model 463316, GA-MA Associates, Ocala, FL) over a 60% GMX60P4 HPGe detector. The plants were divided into three sub-groups and each group was stored in three different temperature environments (Table 2-5).

Table 2-5: Division of Fucus gardneri Plants into Sub-groups with Different Storage Conditions.

Group Plant Identification Location Duration at location /d Temperature at location /°C

1 1,3,5,6 Refrigerator 8 3-6

2 37,40 Refrigerator 8 3-6

3 8, 48, 50 Refrigerator 8 3-6

4 36,39 Freezer, Refrigerator 1,7 -1 to -5, 3-6

5 2, 22, 49 Freezer, Refrigerator 1,7 -1 to -5, 3-6

6 26,34 Freezer, Refrigerator 1,7 -1 to -5, 3-6

7 7, 25, 30 Fume Hood 8 20

8 4,19 Fume Hood 8 20

9 28 Fume Hood 8 20

The conditions were chosen to mimic possible storage conditions during the shipment of field samples. The conditions included room temperature (approximately 20°C) for the 8 d duration of the experiment, refrigerator temperatures (3-6°C) for the 8 d duration of the experiment, and frozen for one day to -1 to - 5°C and then allowed to thaw and stored for the remaining 7 d of the experiment in the refrigerator After 1, 2, 3 and 8 d, each group of Fucus plants was removed from

46 their current marinelli container, dried with a Kimwipe to remove excess moisture, and transferred to a new clean marinelli container for counting. The samples were counted over a 60% GMX60P4 HPGe detector for 5-25 min to determine the 131I activity.

2.8.4 Fucus Gardneri Exposure to Reactor Container Water

Reactor container water from the SLOWPOKE-2 Facility at RMC was mixed in the reactor container for 4 hours and withdrawn after the reactor had been operating for 52.9 consecutive hours at a flux of 5xl0n n cm2 s'. A 200 mL sample of the reactor container water was counted in a marinelli container over a 60% GMX60P4 HPGe detector to determine the radionuclides present. Three Fucus gardneri plants with masses 57.7 g, 59.9 g and 54.4 g were placed in 1000 mL of reactor container water for 4, 8 and 24 h, respectively, after which they were rinsed with distilled deionized water, placed in a 200 mL marinelli container and counted over a 60% GMX60P4 HPGe detector for 4, 15 and 24 h counts, respectively. The spectra were analysed against a fission product library.

47 Chapter 3 Results and Discussion

The results and discussion in this chapter are divided in two parts. The first part, sections 3.1-3.2, covers the topics of detector validation and detection limit of 131I for the GEM60P4 detector. The second part, sections 3.3-3.7, involves the investigation of 131I bioaccumulation in seaweeds and other fission product uptake in seaweeds.

3.1 Validation of GEM60P4 Detector

Consistent with ISO 17025, validation requires the completion of linearity, detection limit (MDA), precision and accuracy measurements to validate a test method [16]. The validation was conducted on a 60% GEM60P4 HPGe detector in lead shielding described in section 2.3.1 and with liquid nitrogen as the cooling mechanism. The 60% GEM60P4 may be used for gamma-ray spectroscopy measurements in the event of an unexpected release of nuclear material. The configuration in which the detector may be used could be variable since it may be used in non-laboratory conditions. For this reason, measurements for MDA, accuracy and precision were taken in three configurations including with lead shielding using a mechanical cooler, without lead shielding using a mechanical cooler, and with lead shielding and liquid nitrogen.

3.1.1 Unearity

Detectors are calibrated for efficiency using NIST traceable standard reference materials. Sample activities are determined using the efficiency generated by the standard reference materials. It is essential that the count rate increases linearly with calculated activity for the energy range, which is used in the analysis. The linearity of the ratio of the calculated activity to the count rate for increasing activities gives confidence that the software program is accounting for the increase in the dead time when samples with greater activity are counted. Linearity was investigated through a wide energy range of the spectrum from 60-1836 keV. Plots generated express the net area counts for a constant live time count (2700 s) for a specific radionuclide versus the time of count activity determined by Gamma Vision. It was found that the GEM60P4 detector was linear across the full energy region from 60-1836 keV with R2 values of 1.00, Figure 3-1 and Figure 3-2.

48 l.OOE+05 n ACs-137 9.00E+04 -< r R2 = I.OO 661.66 8.00E+04 - / R2 = 1.00 keV -Co-60 7.00E+04 - / // R2 = 1.00 i3 6.00E+04 - 1173.24 keV § 5.00E+04 - • Co-60 H 4.00E+04 - 2 1332.5 S 3.00E+04 i - 1/ R = 1.00 keV < 2.00E+04 - * ^____^ "* ACd-109 z 1.00E+04 - ^— ' 88.03 keV O.OOE+00 - i i () 5000 10000 15000 Activity /(Bq)

Figure 3-1: Linearity Plots for 60% GEM60P4 HPGe Detector. (Energy of gamma-rays and originating radionuclides are shown in the legend).

• Am-241 59.54 keV

X Co-57 122.06 keV

= 1.00 X Ce-139 165.86 keV

• Hg-203 279.2 keV

+ Sn-113 391.69 keV

• Sr-85 O.OOE+00 514.01 keV 500 1000 1500 2000 -Y-88 898.04 Activity /(Bq) keV

Figure 3-2: Linearity Plots for 60% GEM60P4 HPGe Detector. (Energy of gamma-rays and originating radionuclides are shown in the legend).

3.1.2 Background Reduction Due to Detector Shielding

Numerous sources of background radiation external to the detector contribute to the background signal observed in HPGe detectors. This background radiation can be reduced by various forms of

49 shielding and materials. The detection limit reported here is expressed as a Minimum Detectable Activity (MDA) calculated by Gamma Vision-32 software version 6 [83]. An MDA is a measure of the minimum activity, which can be detected above the background signal. The significant factors that influence the MDA include the calibration geometry, the backgrounds (system and source induced), the detector resolution and the particular radionuclide of interest. The calculation of the MDA is also a function of the mathematical formula and the sensitivity threshold chosen by the analyst. The mathematical formula used in this analysis for the peak count rate was the United States Nuclear Regulatory Commission Regulation (NUREG) 4.16 equation (23),

2.17 + 4.66 X ob (23) P= — LT

where P is the peak count rate, o"b is the uncertainty in the background (Appendix E ) and LT is the live time. The peak count rate is converted to an MDA with corrections performed for the relevant library peak equation (24),

P (24) MDA = — Is where / is the branching ratio for the gamma-ray used and fis the efficiency of the detector for a specific geometry for the energy of interest. Gamma-ray spectroscopic MDAs are determined on a per sample basis using instrumental noise and sample size; thus, density attenuation, count time and sample size are incorporated into unique detection limits. Increasing the counting time can reduce the MDA for radionuclides because in Equation (23) the denominator will increase more than the numerator. Also, as sample size decreases, the MDA expressed in activity/mass for a homogeneous sample will increase since less material emitting gamma-rays is present. It is important to note that the MDA at a specific energy is determined using the number of gamma-rays per disintegration for a specific radionuclide at that energy. Therefore, the MDA determined for a specific radionuclide at a specific energy cannot be used as the detection limit for a different radionuclide, which has a gamma-ray peak at that same energy and, thus Equation (24) must be used for each radionuclide.

50 Presented in Table 3-1 are the MDA values calculated after 8 replicate counts of 750 mL tap water (model 538G marinelli), for 6 hours, with three different configurations including: 1. Lead Shielding with liquid nitrogen used for cooling the detector, 2. Lead shielding with an EG&G Ortec X-Cooler II used for cooling the detector, and 3. No shielding with an EG&G Ortec X-Cooler II used for cooling the detector. The lead shielding is that described in section 2.3.1. The average MDA is expressed in Bq.

51 Table 3-1: Calculated MDA in Bq for a Specific Radionuclide at a Given Energy for the GEM60P4 HPGe Detector System.

Radionuclide "'Am ,09Cd 57Co B9Ce mSn 8SSr mCs 88y "Co "Co My

Energy (keV) 59.54 88.03 122.06 165.86 391.69 514.01 661.66 898.04 1173.24 1332.5 1836.06

MDA /Bq Liquid Nitrogen 1.9 ± 3.7 ± 0.11 ± 0.10 ± 0.11 ± 0.10 ± 0.08 ± 0.06 ± 0.08 ± 0.06 ± 0.05 ± withPb 0.1 0.8 0.02 0.02 0.03 0.03 0.03 0.03 0.02 0.02 0.02 Shield X-Cooler II withPb 2.0 ± 4.3 ± 0.12 ± 0.12 ± 0.11 ± 0.09 ± 0.09 ± 0.08 ± 0.06 ± 0.07 ± 0.04 ± Shield 0.2 0.4 0.02 0.02 0.03 0.04 0.03 0.03 0.02 0.02 0.02 X-Cooler II outside of Pb 18± 50 ± 1.3 ± 1.2 ± 1.1 ± 0.85 ± 0.87 ± 0.7 ± 0.8 ± 0.6 ± 0.3 ± Shield 2 5 0.3 0.2 0.2 0.08 0.06 0.2 0.2 0.2 0.1

52 The MDA was reduced when shielding was used to stop naturally occurring radionuchdes. Natural sources of radiation include cosmic radiation, natural radioactive nuclides in the air such as radon and its daughters, and natural radionuclides found on Earth including potassium, uranium, thorium and their daughters. The shielding is used to reduce the number of photons that reach the detector from natural radiation found in materials such as concrete. It is important to note that the shielding and even the detector itself will have some naturally occurring radioactive elements. For all three configurations at energies less than 100 keV, the MDA was approximately 20-40 times higher than those just above 100 keV. Since the detector used had an aluminum endcap (P-type detector), gamma-rays below 100 keV are attenuated. For all energy ranges investigated, the MDA with no lead shielding was an order of magnitude higher than the MDAs with lead shielding. Compton scattering from increased exposure to naturally occurring radiation causes more background noise at lower energies and therefore higher MDAs were realized with no lead shielding (Figure 3-3). If required detection limits are well above the detection limits determined for the three cases investigated, then each configuration is acceptable for gamma-ray spectroscopy. For the purpose of detection of low level radionuclides, the configuration including lead shielding and liquid nitrogen is most preferred. The one problem that arises with the use of liquid nitrogen and lead are their availability in the field. Therefore, if liquid nitrogen and lead are not available, then the use of an X- Cooler without lead is still equally useful for counting. For the detection of low level radionuclides approaching detection limits, the use of shielding material is necessary since low level radiation could go undetected due to the increase in the background signal.

53 10000

1000

100 X-Cooler With Pb -LN2andPb X-Cooler No Pb 10

500 1000 1500 2000 Energy (/keV)

Figure 3-3: Spectra Collected for MDA Showing the Counts Obtained versus Energy for Three Configurations.

3.1.3 Precision and Accuracy

Precision/accuracy data were obtained from eight replicate analyses of an active source of the same density and volume as a particular sample used in a specific test analysis (Table 3-2 - Table 3-7). Precision is defined as the mean deviation of tests from the average result. Percent precision is calculated for each radionuclide from the average of eight replicate counts using equations (25) and (26), SDU ... (25) %Precision = xlOO average where a is the standard deviation (using n-1 degrees of freedom), and ts is the one sided students t- distribution at 95% confidence where ts = 2.365. Accuracy is determined by taking the average activity for each radionuclide from eight replicate counts and determining the percent deviation from the certificate values for each radionuclide.

In general, the precision and accuracy improved when lead shielding and liquid nitrogen were used. The X-Cooler II may have caused some electrical interference. In the configuration which included the X-cooler II without the lead shield, an uninterruptible power supply (UPS) was used. It was 54 suspected that when the DigiDART was plugged into the UPS, an increase in electrical noise affected the spectrum at the lower energy range. Also electrical interferences from the X-Cooler II may have contributed to a slight increase in background noise.

In general, for reliable results using gamma-ray spectroscopy, the configuration of an HPGe detector housed in lead shielding with liquid nitrogen used as the cooling mechanism is the preferred configuration. Since validation of the detection equipment is necessary for consistent results, keeping a detector in a laboratory setting provides the greatest dependability. One must consider each unique situation when making the decision to bring the samples to a detector that is pre- validated in a laboratory setting or to ship the detector to the field where validation measurements should be conducted before the detector is used.

55 Table 3-2: Percent Relative Precision for a Radioactive 450 mL Geometry Source for the GEM60P4 HPGe Detector System.

Radionuclide *iAm "»Cd "Co u»Ce "3Sn «*Sr «7Cs 88Y «Co "Co S8Y

Fnergy (keV) 9.54 8.03 22.06 165.86 391.69 514.01 661.66 898.04 1173.24 1332.5 1836.06

Percent Relative Precision /%

I lqmd Nitrogen with Pb Shield 48 33 36 69 77 25 2 13 36 17 1 3 32

X Cooler 11 with Pb Shield 36 25 26 57 43 175 1 1 26 1 5 10 28

X ( ooler II outside Pb Shield 86 3 84 7 78 112 109 20 6 1 3 71 1 8 21 1 9

Table 3-3: Percent Uncertainty for a Radioactive 450 mL Geometry Source for the GEM60P4 HPGe Detector System.

Radionuclide M'Am «»Cd "Co "»Ce i«Sn <»Sr u'Cs 88V "Co «Co 88V

Fnergy (keV) 59.54 88.03 122.06 165.86 391.69 514.01 661.66 898.04 1173.24 1332.5 1836.06

Percent Relative Uncertainty /%

I lquid Nitrogen with Pb 43 79 32 35 25 05 01 10 33 32 16 Shield

X Cooler II with Pb Shield 47 48 49 14 24 66 16 00 31 31 03

X Cooler II outside Pb Shield 69 152 64 58 09 53 31 05 29 30 20

56 Table 3-4: Percent Relative Precision for a Radioactive Petri Geometry Source for the GEM60P4 HPGe Detector System.

Radionuclide 2«Am "»Cd "Co ««Ce ,uSn MSr t"Cs 8gy «>Co «Co My

Energy (keV) 59.54 88.03 122.06 165.86 391.69 514.01 661.66 898.04 1173.24 1332.5 1836.06

Percent Relative Precision /%

Liquid Nitrogen with Pb 21 12 43 37 61 107 09 35 1 1 07 26 Shield

X Cooler TI with Pb Shield 24 21 43 59 30 102 19 24 13 14 33

X Cooler II outside Pb Shield 48 29 143 121 60 150 08 41 23 22 39

Table 3-5: Percent Uncertainty for a Radioactive Petri Geometry Source for the GEM60P4 HPGe Detector System.

M Radionuclide "'Am «»Cd "Co &>Ce luSn «Sr «'Cs 88Y «°Co Co 8«Y

Fnergy (keV) 9.54 8.03 122.06 165.86 391.69 514.01 661.66 898.04 1173.24 1332.5 1836.06

Percent Relative Uncertainty /%

Liquid Nitrogen with Pb 98 49 127 114 132 150 190 23 20 31 92 Shield

X-Cooler II with Pb Shield 94 54 127 58 55 94 182 43 50 52 90

X Cooler II outside Pb 25 0 43 22 5 35 47 77 176 30 32 41 102 Shield

57 Table 3-6: Percent Relative Precision for a Radioactive Filter Paper Geometry Source for the GEM60P4 HPGe Detector System.

Radionuclide *>Am "»Cd "Co fCe lUSn «Sr t"Cs my "Co «>Co My

Energy (keV) 59.54 88.03 122.06 165.86 391.69 514.01 661.66 898.04 1173.24 1332.5 1836.06

Percent Relative Precision /%

Liquid Nitrogen with Pb 23 24 00 48 44 55 00 31 13 09 48 Shield

X Cooler 11 with Pb Shield 16 31 36 66 51 162 13 41 09 09 16

X Cooler 11 outside Pb Shield 67 49 127 118 39 130 06 55 35 06 1 5

Table 3-7: Percent Uncertainty for a Radioactive Filter Paper Geometry Source for the GEM60P4 HPGe Detector System.

Radionuclide »'Am "»Cd "Co "»Ce i"Sn <»Sr t»Cs sgy "Co MCo 8BY

Fnergy (keV) 59.54 88.03 122.06 165.86 391.69 514.01 661.66 898.04 1173.24 1332.5 1836.06

Percent Relative Uncertainty /%

Liquid Nitrogen with Pb 55 49 46 03 40 10 47 112 95 76 54 Shield

X Cooler 11 with Pb Shield 31 110 40 86 86 15 43 77 59 52 01

X Cooler II outside Pb Shield 45 122 40 150 86 87 30 115 84 70 10

58 3.2 Detection Limit of Ull

Specific to this thesis research is the necessity to determine the 131I detection limit and MDA for a GEM60P4 detector. The lead shielding and liquid nitrogen was used for the configuration as determined in the previous section. The 13,I activity of the initial 10 mL stock solution obtained from Kingston General Hospital was 555 MBq on 6 Nov 2007 according to the label on the container. No uncertainty was available for the initial stock solution. All activities are back calculated to 6 Nov 2007 for comparison purposes. The first dilution of 1 mL of the stock solution from Kingston General Hospital into 500 mL gives a nominal value of 111 kBq mL1. A 2 mL aliquot of the second solution diluted to a final volume of 500 mL gives a nominal value of 444 Bq mL J for the final solution given the identification of Stock Solution #1. A 250 mL marinelli was filled with 200 mL of stock solution #1 with a nominal value of 88.8 kBq for the entire sample (444 Bq mL ' x 200 mL). The results for the average of the three peaks for 131I (the most intense gamma-ray has an energy of 364 keV with a branching ratio of 81.7%, followed by 637 keV at 7.17% and 284 keV at 6.14%) are reported. The activity using the peak at 364 keV only is also reported for interest. Table 3-8 contains the results of the 8 replicate counts conducted over a 60% GEM60P4. The uncertainty for all counts is 3% and is the statistical counting uncertainty only (the main uncertainty). The results in Table 3-8 are reported using one extra significant figure for averaging purposes. The activity of the 200 mL 131I solution using all three peaks was determined to be 94 000 ± 2000 Bq at one sigma (470 ± 10 Bq mL1) back calculated to 6 Nov 2007, which is 6% higher than the nominal value. The GEM60P4 detector was validated using NIST traceable standards and therefore the activity determined by gamma-ray spectroscopy is more accurate than the nominal activity. The activity of 470 ±10 Bq mL' was used to calculate the dilutions required to make a low-level 131I source.

59 Table 3-8: Determination of Activity of U1I Solution used for Detection Limit Determination for the GEM60P4 HPGe Detector System.

131I Activity average of »>I at 364 keV 634,637 & 284 Count Date Activity /(kBq) keV/(kBq) 08-Jan-08 93 6 93 9 08-Jan-08 94 0 94 4 08-Jan-08 93 8 941 09-Jan-08 93 3 93 6 09 Jan 08 93 3 92 8 09 Jan 08 93 6 93 8 10 Jan 08 94 0 94 3 10 Jan 08 93 3 93 5 Average 93.6 93.8 Standard deviation 03 05 Relative Standard deviation % 03 05 Nominal Target 88.8 88.8 Percent Difference from 54 56 Nominal Target

The 200 mL low-level sample was prepared on 10 Jan 2008 by adding 1 mL of the stock solution. The activity of the low level sample at the time of the start of the count was 1.55 ± 0.03 Bq at one sigma on 10 Jan 2008 at 14:12. The detection limit and minimum detectable activity for a six hour count on a 200 mL marinelli geometry counted over the 60% GEM60P4 was determined by counting 8 replicate counts of the prepared aqueous 131I source (Table 3-9). The detection limit is calculated using equation (26), 60 Detection Limit = 2 * SD * ts (26)

where o~ is the standard deviation (using n-1 degrees of freedom) and ts is the students t-distribution, two sided with 95% confidence and t5= 1.895.

Table 3-9: Results for Detection Limit of ml in a 200 mL Marinelli Geometry.

U,I Activity Measurement MDA /Bq /Bq 1 1.56 ± 0.07 0.11 2 1.68 ± 0.07 0.10 3 1.55 ±0.08 0.14 4 1.76 ± 0.08 0.14 5 1.73 ± 0.09 0.13 6 1.69 ± 0.09 0.15 7 1.64 ±0.10 0.16 8 1.62 ± 0.09 0.17 Average 1.65 ± 0.08 0.14 Target 1.55 ± 0.03 NA Standard Deviation 0.07 0.02 Detection Limit 0.28 NA

The MDA is calculated using Equation (23). The average activity of the low level sample was 1.65 ± 0.07 Bq at one a which just overlaps within one standard deviation of the target activity of 1.55 ± 0.03 Bq. The detection limit and MDA for a 200 mL 131I source with density 1 g mL' counted for 6 h over 60% GEM60P4 HPGe was determined to be 0.28 Bq and 0.14 Bq, respectively. Assuming a density of seawater of 1 g mL' this equates to a detection limit of 1.4 Bq kg' and an MDA of 0.7 Bq kg1-

61 3.3 Shearwater Seaweeds Sample Results and Discussion

Samples of seaweed were collected in Shearwater, NS (Eastern Passage) in December, 2006. The seaweeds were collected to confirm the continued presence of 131I in the seaweeds that has been observed by the ERMP program. Prepared mannelli beakers of the seaweed collected in Shearwater were counted over a 60% HPGe GEM60P4. Table 3-10 and Figure 3-4 contain the results.

Table 3-10: Detection of U,I in Seaweeds from Shearwater, NS.

Dry Sample Sample wet %Dry Wet activity Sample # Activity Type* weight /g weight /Bqkg-i /Bqkg-' 1 AN 369 6 33 93103 28 1 1 3 AN 429 6 33 85103 2611 8 AN 3861 26 114 + 06 4412 HP1 AN 123 8 32 28106 912 P AN 76 6 25 10 + 1 43 14

Average 277.1 29.8 8.5 ± 0.7 30 + 2

2 SL 204 9 9 24107 274 18 4 SL 428 2 12 54103 4512 SL (stem and 5 188 3 12 112107 91 15 root)

6 SL 2017 9 20 0 1 0 6 214 16 6Dup SL 213 8 11 20 3 1 0 6 191 16 7 SL 693 6 7 21 1 10 4 319 16 9 SL 719 12 11 3 103 92 13

Average 378.5 10.29 16.2 ± 0.6 175 ±7 *\N=AscophyJIum Nodosum, SL= Saccharins Latissima

62 350.00 op ex 300.00 • Ascophyllum CD Nodosum 250.00 • Saccharina Latlssima < 200.00 ''''•'? ?'• '"* 150.00 '" \ % a; 100.00 Q y-4 50.00

0.00 Jetty Knee Yacht Club Jetty Land Floating Logs

Figure 3-4: Dry weight U1I Activity for Shearwater Seaweeds Sampled Around the Shearwater Jetty.

All of the seaweeds analysed had measureable levels of 131I. The Ascophyllum Nodosum had 131I average activity of 8.5 ± 0.7 Bq kg1 wet weight and 30 ± 2 Bq kg1 dry weight with a range of 2.8-11.4 Bq kg' wet weight and 9-44 Bq kg' dry weight. The Saccharina hatissima had 131I average activity of 16.2 ± 0.6 Bq kg1 wet weight and 175 ± 7 Bq kg1 dry weight, which fell in the range of 5.4-24 Bq kg1 wet weight and 45-319 Bq kg dry weight. Significant ranges in the activities observed in Saccharina hatissima and Ascophyllum Nodosum are noted using both wet and dry weight data. However, it is noted that the former has generally higher levels of 131I, which is consistent with the literature values of dry weight iodine content in Ascophyllum Nodosum and Saccharina hatissima of 275 Lig g' and 574 ^ig g1, respectively [86]. This difference in 131I and total iodine may be due to the difference in surface area of these two types of seaweed because the Saccharina hatissima have a much higher surface area to weight ratio compared to Ascophyllum Nodosum and it has been reported that 50-80% of the total iodine is kept in the peripheral tissue of haminaria digitata [55], which would make one hypothesize that other seaweeds may have a similar distribution of iodine.

Using dry weight iodine content in Ascophyllum Nodosum and Saccharina hatissima of 275 Llg g' and

574 |ig g', respectively, and a concentration of iodine in seawater of 0.03-0.05 \ig g', the equilibrium

63 constant for Ascophyllum Nodosum and Saccharina Latissima based on their dry weight iodine content would be 5500-9170 and 11500-19100 g g', respectively [86]. Using these bioconcentration factors, an estimate of the concentration of 131I in the seawater at the sampling locations in Shearwater using Ascophyllum Nodosum and Saccharina Latissima are 0.003-0.005 Bq kg1 and 0.009-0.015 Bq kg1, respectively. From section 3.2, the detection limit and MDA for 13,I were 1.4 Bq kgJ and 0.7 Bq kg', respectively. The estimates of 131I in the seawater in Shearwater given above are less than the detection limits determined for the equipment and would, therefore, not be detectable by the GEM60P4 HPGe system.

3.4 Sample Receipt and Preparation for Introduction into Artificial Seawater Aquaria

The seaweed used in the I uptake experiments was Fucus gardneri. Fucus gardneri is easily accessible and can be found on each of the coasts in Canada. Fucus, also known by its common name, rockweed, is found in the intertidal region of the shoreline, which makes for easy collection and storage of the samples. In contrast, "the problems of maintaining Saccharina species in inland culture are considerable" [84]. Fucus was collected in the months of January, March and November. The Fucus was sampled from Bamfield, BC, at the same location, and therefore it is fair to assume that the plants are of similar kin. The Fucus usually arrived in the afternoon. The plants seemed to be in good condition with respect to the look, feel and smell of the plants. The Fucus plants sampled ranged in size from 10-28 cm length and 3.8-90.9 g mass. The pH of the artificial seawater was measured at 7.74 before the Fucus was introduced. To ensure that no iodine would be lost, a pH of ca. 8 is desired since iodine is lost at lower pH [87]. Aqueous iodide (1000 |lg mL ) was added to both the aquarium and stock solution to ensure the concentration of iodine was at 0.05 ug mL', a typical value that is found in natural seawater. The plants were immersed into the seawater overnight and taken out of the seawater during the day to mimic tidal rotations. Plants were used after acclimatization for one day under the culture

64 conditions, and most experiments were conducted within a week of receipt to ensure the health of the plants was still stable.

3.5 INAA for the Determination of Iodine in Fucus Gardner!

The concentration of iodine in Fucus gardneri in its stable state can be used to estimate an equilibrium constant with seawater if the concentration of iodine in the seawater is known. INAA was used to determine the concentration of iodine in the Fucus gardneri (Table 3-11).

The average of the results is 290 ± 20 \xg g' dry weight (excluding the results for the "random pieces of conceptacles") with a maximum result of 420 ± 30 fxg ga and a niinimum result of 220 ± 20 |ig g1. The average equates to 0.03% iodine by mass, much less than the high level of iodine levels in Fucus (rock weed) reported as 0.17% dry weight by mass, but in line with other concentrations reported such as Fucus edentatus and Fucus vesiculosis, which have a dry weight concentration reported as 125 ± 0.5 fig g1 and 108 ± 1.2 ng g1, respectively [86]. The random pieces of the conceptacles had a much higher concentration of iodine than the average at approximately 1.5 times as high. Fucus 35 also had elevated iodine, which would make one assume that it was essentially all conceptacles. Assuming an average concentration of iodine in seawater at the sampling location in Bamfield, BC in the range of 0.03—0.05 ^.g g and the average concentration of iodine in the Fucus gardneri reported above, the equilibrium constant for iodine in Fucus gardneri in this study was 5800-9700 times the iodine concentration in seawater. This result compares to the equilibrium constant for Ascophyllum Nodosum of 5500-9170 calculated in section 3.3. Although these are not identical species of seaweed, Fucus gardneri may be compared to Ascophyllum Nodosum since their equilibrium constants for iodine are similar.

65 Table 3-11: Concentration of Iodine in Fucus Gardnen Determined using INAA.

Sample ID Iodine dry plants

/(Mgg-1) Random pieces of conceptacles 440 ± 20 Random pieces of conceptacles Dup 460 ± 30 Above not used in average Unlabelled full Fucus 220 ± 20 Unlabelled full Fucus Dup 280 ± 20 Fucus 10 270 ± 20 Fucus 18 260 ± 20 Fucus 18Dup 270 ± 20 Fucus 21 250 ± 20 Fucus 27 300 ± 20 Fucus 31 300 ± 20 Fucus 31 Dup 350 ± 20 Fucus 32 280 ± 20 Fucus 33 250 ± 20 Fucus 35 420 ± 30 Fucus 35Dup 420 ± 20 Fucus 41 280 ± 20 Fucus 43 260 ± 20 Fw«w 45 240 ± 20 Fucus 46 280 ± 20 Original F»«w 250 ± 20 Original Fucus Dup 250 ± 20 Average 290 ± 20

3.6 Determination of Surface Area of Fucus Gardnen

The surface area of seaweed has a significant effect on the uptake of I31I. It was therefore necessary to determine the surface area of the Fucus gardnen so that the effect of surface area on 131I uptake could be investigated. Small features such as hair formation could not be taken into account by the

66 method used; however, no visible hairs were present on the surface of the Fucus gardmri. The surface area of the plants was determined using software that count the number of pixels used to create an image. The software was calibrated using the number of pixels obtained from known surface areas (Table 3-12). The data was plotted on an x-y scatter graph and the equation of the line determined as well as the R2 fit, Figure 3-5. The fit as expressed as R2 was excellent, 0.99, and therefore the calibration was deemed suitable for use to determine the surface area of the Fucus plants. Software was similarly used to convert Fucus samples to digital images with a determined number of pixels. An example of a digital image of Fucus 119 and the converted bitmap image is shown in Figure 3-6a and b. The surface area for a series of plants was determined from the number of pixels present in bitmap images (Table 3-13). Figure 3-7 illustrates the dependence of the surface area of the Fucus to the mass of plant. It appears that the increase in mass results in a linear increase in surface area. However, when the mass of the Fucus is plotted against the ratio of the surface area to the mass, then a non-zero, negative slope is observed (Figure 3-8). Thus, as the size of the plant increases, the amount of surface area per gram of plant decreases, which suggests that the amount of surface area per gram of plant is greater in plants with a smaller mass. However, the mass-dependent surface area effect is small. For example, considering masses of 6.25, 12.5 and 25 g, which span the present experimental range, the relative decrease in surface areas of 12.5 and 25 g plants relative to 6.25 g is 9.4 and 28%, respectively. The relative decrease of 25 g relative to 12.5 g is similarly 9.4%. Given an R2 coefficient of 0.4422, these differences may be lost in the general variability of data. With these results, the mass of the plant will be used determine the equilibrium constant and the rate constants for each experiment.

67 Table 3-12: Calibration of the Surface area to number of pixels data.

Area/cm2 Pixels 25 10797 50 21856 100 43814 175 74760 200 85931 400 167601

450

400 y = 0.0024x 350 H R* = 0.9995 300

|250 -I

cu < 150

100

50

0 50000 100000 150000 200000 Area /(pixels)

Figure 3-5: Surface Area to Number of Pixels Calibration Plot.

68 Figure 3-6 a&b: Fucus Digital Image (top) and Fucus Bitmap Image (bottom).

69 Table 3-13: Measured Surface Area of Fucus Gardneri.

Plant Identification Number Mass of Plant /(g) Surface Area /(cm2) 101 16.3 316 104 22.8 533 105 22.0 449 109 27.1 563 115 24.0 556 139 18.3 386 102 10.7 270 119 11.9 371 123 11.3 365 127 10.5 312 128 10.3 253 132 11.3 298 103 5.1 158 130 5.4 143 140 6.5 207 143 6.5 163 146 5.2 139 147 5.7 207 110 13.8 357 111 12.6 384 116 12.0 295 117 13.9 320 141 12.8 331 144 12.3 365

70 y = 18.62x + 83.308 700 -R2 = 0.8965

Figure 3-7: Relationship of Surface Area to Mass for Fucus Gardnen.

y = -0.4649X + 32.409 R2 = 0.4422 40 _•„, • he 35 fN E 30 • • u _ • •vw^ o 75 • , 4-* 10 & • • • • A t/l M 0 • — 5 15 +-o< 01 10 u tra i/^i 5

0 1 1 i • " i 1 0.0 5.0 10.0 15.0 20.0 25.0 30.0 Mass /(g)

Figure 3-8: Relationship of the Ratio of the Surface Area to Mass for Fucus Gardnen.

71 3.7 Exposure Experiments

The exposure experiments of Fucus gardneri to 131I in seawater are discussed in 2 sections. In section 3.7.1, exploratory experiments conducted to obtain an overall impression of how the 131I would be absorbed in the Fucus gardneri are discussed. In section 3.7.2, multiple experiments involving many plants conducted to determine average results for the equilibrium constant and reaction rates in Fucus gardneri are reported.

3.7.1 Exploratory Experiments of Fucus Exposure to 1}11 in Artificial Seawater

A summary table of results for the uptake experiments in which the uptake of 131I was measured in the Fucus gardneri plants and measured or calculated for the artificial seawater is given in Table 3-14. All 131I activities are back-calculated to the same reference point for each experiment, which is the start of count time for the first count in each experiment. The 131I activity was measured in the Fucus gardneri plants and in the artificial seawater to confirm that no loss of 131I occurred. The method of measuring the 131I in the Fucus directly requires that the Fucus plants be removed from the seawater and placed in marinelli beakers for counting. This technique was used to confirm that the activities determined for 131I in the Fucus and the seawater were consistent with the amount of 131I in the system and that no 131I is lost from the system. Once this fact was confirmed, the measurement of 131I in the seawater alone could be used and the activity of the 131I absorbed by the Fucus could be calculated as opposed to being measured direcdy. A density of 1 g mL' was used for the seawater. Each experiment is discussed in more detail in sections 3.7.1.1-3.7.1.5 following Table 3-14. As will be demonstrated, the kinetics of uptake of 131I by Fucus gardneri followed first order kinetics approaching equilibrium.

72 Table 3-14: Summary of Results for Fucus Exposure to U1I in Artificial Seawater.

Activity in Equilibrium R2 of First Time Activity in Artificial Constant order After Plant Seawater Initial U'l Water Analysis Fucus at Plant Seawater at (non- equilibrium Receipt Mass(es) Volume Activity Temp Times end of Identification end of equilibrium kinetics of Fucus /g /L /Bq L' /°c /h Experiment Experiment results in linear plot /d /BqgT1 /BqgT1 brackets) 0.8,1.7, 2.5, 20 1 11.4 3 3.33 13 0.20 0.0025" NA(8) NA 3.3,4.2 0.1,0.2,0.3, 29 3 41.3 3 400 9-11 0.4, 0.5, 0.6, 20.3 0.08 250* 0.995 16 1,2,3,4,5, 14 5 41.8 3 340 9-12.5 14.4 0.14' 103 0.990 6, 7, 48 23 7 19 20 0.05 9.5-10.5 6 0.0044 0.000046» NA(96) NA 24 7 19 20 0.05 9.5-10.5 24 0.016 0.000035' 460 NA 38 12.5 24, 1,2,3,4,5, NA.NA, 44 13 12.3 3 428 8-13 24, 0.38 63 21, 25, 26 NA 47 12.3 23 a = Obtained Dy calculati on, *the te mperature o F the seawate r at equilibrium was 23°C, therefore the equilibrium constant was affected.

73 Details of the six experiments conducted are provided in the following sub-sections. The initial six exposure experiments of 13,I and Fucusgardneri were conducted as a preliminary investigation. From these experiments, parameters could be determined for 131I uptake experiments in which multiple plants were investigated at one time using measurements of 1311 activity in the seawater only. In each case, kinetic data are described. For each experiment, the uncertainty is reported at one SD and includes the statistical counting uncertainty only.

3.7.1.1 Investigative Experiment Using Fucus Plant Number 20

Fucus 20 was exposed one day after receipt of the Fucus and therefore would be relatively healthy. This was the first experiment conducted and was an investigative experiment. The activity was determined, as shown in Table 3-15 and plotted in Figure 3-9.

Table 3-15: Activity of Plant 20 Uptake of ml. 131I Activity Uncertainty at Time/ (h) /(Bq) one SD 0.8 0.70 0.07 1.7 1.5 0.1 2.5 1.77 0.08 3.3 2.0 0.1 4.2 2.3 0.1

3

i S 2 * ^1.5 • 1 * # < 0.5 * 0 • 1 i 1 1 1 1 1 1 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 Exposure time /(hours)

Figure 3-9: Uptake of mI by Fucus 20 Showing an Exponential Shape. 74 Fucus 20 was not exposed long enough to the niI spiked seawater to reach equilibrium in the 4.2 hours of the experiment; therefore, an equilibrium constant cannot be calculated. Also, the amount of 131I used in the seawater was very low, 3.3 Bq kg' and therefore the counting time had to be relatively long. This required the Fucus be out of the seawater for an extended period of time, which could have affected the uptake of the 131I since the Fucus would warm up to temperatures greater than 13°C. However, the amount of 131I absorbed by the Fucus in 4.2 hours was 23% of the total initial ,31I in the system. Also, by the shape of the plot, the uptake was assumed to be a first order kinetic process as discussed in section 1.7 and Figure 1-5. Since the reaction did not go to equilibrium, it is not possible to determine if the reaction follows a first order equilibrium model using equation (28):

lnlw7^iTJ = (kf+kb)t (27)

131 where [A] is the concentration of I in seawater in Bq mL', kf is the rate constant in the forward direction, kb is the rate constant in the reverse (backward) direction, and t is time. Appendix B contains the relevant derivation. Plotting Equation 28 versus time gives a graph with a slope equal to the sum of the rates of reaction kf + kb

3.7.1.2 Investigative Experiment Using Fucus Plant Number 29 and Measuring I Activity Removal from Seawater

Counting the Fucus direcdy for the uptake of I could have an effect on the health of the plant since it must be repeatedly removed from the seawater for counting and therefore may warm up to ambient temperatures. The aim of this experiment was to determine if an aliquot of seawater could be counted to indirectly determine the 131I accumulation in the Fucus. Fucus 29 exposure took place 3 days after the receipt of the samples. Both the plant and a 15 mL aliquot of seawater were counted to investigate both the accumulation of the 131I into the plant and the removal of 131I from the

75 seawater. The total ,31I in the system was preserved within experimental uncertainty indicating that no 131I was lost to the surroundings (Table 3-16). For Fucus 29, the uptake was measured over a short amount of exposure time (36 min). The 131I in the Fucus was also measured at 16 h. However, the temperature of the seawater had increased to 23°C and therefore the amount of 131I absorbed by the Fucus would be increased due to the increase in temperature since the uptake is an active process. For the first 36 min, the plot appears to follow a linear function; however, as is illustrated by Figure 3-1 Oa & b, the function is exponential. Using equation (28) the activity for Fucus 29 was plotted to confirm first order equilibrium kinetics with R2=0.995 (Figure 3-11).

Table 3-16: Activity of Uptake of U1I by Fucus 29.

Time mI Fucus Uptake U1I in Seawater Total U1I in system /h /Bq /Bq /Bq 0.1 53 ±3 1200 ± 100 1200 ± 100 0.2 98 ±5 1080 ± 90 1200 ± 100 0.3 135 ±7 1110 190 1300 ± 100 0.4 160 ± 10 930 ± 80 1100 ±90 0.5 200 ± 10 1040 ± 90 1200 ± 100 0.6 227 ±9 920 ± 60 1150 ±70 16 840 ± 30 250 ± 20 1090 ± 50

76 1400

1200

1000 1 i S. 800 * >• *^ • Activity in Seawater | 600 < • Activity in Fucus 400 • 200 fg 0 I () 5 10 15 20 Exposure time (hours)

1.40E+03

1.20E+03 f 1.00E+03 i * i i s S. 8.00E+02 >• B 6.00E+02 • Activity in Fucus u < • Activity in Seawater

4.00E+02 • w 2.00E+02 • • • •

0.00E+00 ) 0.1 0.2 0.3 0.4 0.5 0.6 0 7 C Exposure time (hours)

Figure 3-10 a & b: Uptake of U1I by Fucus 29 and Removal From Seawater.

77 y = 0.5149x + 0.0119 Ft2 = 0.995

kf+kb • Linear (kf + kb)

Figure 3-11: Activity of ml in Seawater Plot of Equation (28) with Time for Fucus 29 Suggesting First Order Equilibrium Kinetics.

3.7.1.3 Time Required to Approach Equilibrium

The purpose of the next experiment was to determine the time required to reach equilibrium. Once the time to equilibrium was determined, more regimented experiments could be developed to obtain more data in a shorter time scale. Fucus 14 was exposed to 131I five days after receipt. Both the plant and a 15 mL aliquot of seawater were counted to determine both the accumulation of the 13,I into the plant and the removal of 131I from the seawater (Table 3-17). Figure 3-12 illustrates the shape of the uptake. Again, for this experiment, the 131I in the system was preserved giving greater confidence that the Fucus does not need to be measured directly to determine the uptake of 131I. Also, the 131I uptake by Fucus 14 in Figure 3-12 appears to follow a first order kinetic process that approaches equilibrium within hours. Again, using equation (28), the uptake follows a first order equilibrium model with R2=0.990 (Figure 3-13).

78 Table 3-17: Activity of Uptake of U,I by Fucus 14.

Time F»aw ,3,I Seawater niI Total 13,I in

/(h) Activity /Bq Activity /Bq system /Bq 1 171 ± 5 830 ± 60 1000 ± 70

2 293 ±7 710 ± 60 1000 ± 70

3 389 ±9 600 ± 50 990 ± 60

4 460 ± 10 490 ± 40 950 ± 50

5 510 ± 10 500 ± 50 1000 ± 60

6 520 ± 10 390 ± 40 910 ± 50

7 540 ± 10 370 ± 30 910 ± 50

48 600 ± 10 NA NA

1000 900 800 — 70° £ 600 2- 500 • Activity in Seawater | 400 < •Activity in Fucus 300 200 100 0 4 Time /(h)

Figure 3-12: Uptake and Consequent Removal of U1I from Seawater in Fucus 14 Suggesting First Order Equilibrium Kinetics.

79 y = 0.3484x + 0.0139 R2 = 0.99

Fucus 14 1311 Uptake •Linear (Fucus 14 1311 Uptake)

Time (/h)

Figure 3-13: Activity of U1I in Seawater Plot of Equation (28) with Time for Fucus 14 Illustrating First Order Equilibrium Kinetics.

3.7.1.4 Uptake for Three Combined Plants, Fucus 38, 44 and 47

On the 13th day after receipt, three Fucus plants were exposed together in one container with 3 L of artificial seawater spiked with 1285 Bq of 131I. The purpose of this experiment was to determine if similar plant masses would have similar uptake rates and final [131I]. The plants used were numbers 38, 44 and 47 weighing 12.5, 12.3 and 12.3 g, respectively. The plants were counted individually to determine the uptake of each plant. In this experiment, both the plants and a 15 mL aliquot of seawater were counted to determine both the accumulation of 13,I into the plant and the removal of 131I from the seawater. For a third time, the 131I was preserved in the system and therefore it was determined that the uptake of 131I in the Fucus could be determined indirectly by measurement of 131I in the seawater. The results of the uptake are given below in Table 3-18 and Figure 3-14. The mass of three plants were almost identical and therefore the variation in the total uptake of 131I by each plant could be compared. The uptake was almost within one SD and overlapped within 2 SD uncertainty at equilibrium. Also, the total ,31I in the system remained constant within one SD uncertainty. This experiment can only be treated qualitatively, since the 131I solution is influenced by removal from all three plants. However, because plant masses are similar and uptakes are consistent, the analysis of individual plants is acceptable as a first approximation.

80 Table 3-18: Activity of Uptake of ml by Fucus 38, 44 and 47.

Time F»f»j 38 Fucus 44 Fucus 47 Seawater Total 13!I in system /h 13,I Activity /Bq ,3,I Activity /Bq ,3,I Activity /Bq 13,I Activity /Bq ,3,I Activity /Bq 1 55 ±2 53 ±2 46 ±2 970 ± 70 1120 ±80 2 89 ±4 98 ±4 76 ±3 900 ± 60 1160 ±70 3 134 ± 5 132 ±5 115 ±4 760 ± 60 1140 ±70 4 162 ±6 146 ±6 142 ±5 690 ± 50 1140 ±70 5 199 ± 7 150 ±6 166 ±6 630 ± 40 1140 ±60 21 340 ± 10 276 ±9 273 ± 8 270 ± 20 1160 ±50 25 320 ± 10 310 ± 10 278 ±9 260 ± 20 1160 ±50 26 295 ±9 300 ± 10 287 ±9 260 ± 20 1150 ±50

1.20E+03

1.00E+03

g 8.00E+02 "I*. • Plant 38 1o 6.00E+02 %. -4-» • Plant 44 a. A Plant 47 f 4.00E+02 XBqin3L 2.00E+02

0.00E+00 0 5 10 15 20 25 30 Time /(h)

Figure 3-14: Uptake of U1I by Fucus 38, 44 and 47 Illustrating Similar Uptake based on Mass of Plant.

81 3.7.1.5 Uptake in Fucus Gardneri with a Low Initial Concentration of I in Seawater

An experiment was conducted to see if a low level of activity 0.05 Bq L' in a larger volume of seawater (20 L) could be absorbed by the Fucus to a level measurable by gamma-ray spectroscopy. Two plants were used: Fucus 23 and Fucus 24. Both plants were placed in individual containers containing 20 L of artificial seawater spiked to 0.05 Bq L' 131I. Fucus 23, which weighed 19.0 g, was exposed for 6 hours and absorbed 0.083 ± 0.009 Bq of 131I with a concentration of mI in the plant of 0.0044 ± 0.0005 Bq g'. Fucus 24, which weighted 19.0 g, was exposed for 24 hours and absorbed 0.30 ± 0.02 Bq of 13,I with a concentration of ,31I in the plant of 0.016 ± 0.001 Bq g1. The total amount of 131I in the 20 L was 1 Bq and therefore Fucus 23 absorbed 8.3% of the total initial ,31I in the 20 L. Fucus 24 absorbed 30% of the total initial 131I in the 20 L. Approximating the density of seawater at 1 g mL , a comparison can be made with the seawater and the Fucus. Comparing the concentration of 131I in seawater to 131I in Fucus at the end of the experiment, on a mass basis, gives a ratio of 1:96 for Fucus 23 in 6 h and a ratio of 1:460 for Fucus 24 in 24 h. Therefore, for a very low concentration of 131I in seawater, using Fucus as a bioindicator for !31I after approximately 12 hours is reasonable.

3.7.1.6 Summary of Investigative Experiments

These initial 131I uptake experiments confirmed that the process of uptake is a first order kinetic process that approaches equilibrium within hours. Since there is no 131I lost from the system, measurements on the seawater can be conducted and the 131I absorbed by the Fucus gardneri can be determined indirecdy by calculation. Levels of 131I in seawater below the detection limit for the GEM60P4 are absorbed by the Fucus on the order of hours to levels measurable by gamma-ray spectroscopy. Using this information, experiments were developed to measure the equilibrium constant and rates of reactions in Fucus gardneri that involved measuring the 131I removed from the seawater only, allowing the plants to remain in the seawater.

82 3.7.2 Equilibrium Constant and Reaction Rates for 131I and Fucus Gardneri

3.7.2.1 131I Uptake in Fucus Gardneri

In the following experiments, only the artificial seawater was counted to measure the removal of 131I by the Fucus plants. This method allowed for a more rapid way to measure the uptake of 131I in Fucus because the plants did not have to be removed from the seawater for counting. Also the health of the plants during the course of the experimentation would be improved because the plants could be maintained at temperatures below 13°C. The amount of I absorbed by the Fucus was determined by calculation. The rate constants, kf and kb, and the equilibrium constant, Keq were calculated using Equation (28). Table 3-19 contains the data for equilibrium constants and the reaction rates for each experiment based on wet weight for the Fucus and Table 3-20 contains the results based on dry weight. When field samples are taken as part of the ERMP, results are reported on a wet weight basis because a quick turnaround time is required [8, 16]. The seaweed samples have high moisture content, therefore the time required to dry the samples would delay the reporting of results. The uncertainty calculated was for the activity only. This uncertainty was between 5-10% for all experiments. Appendix F contains the activity determined for each experiment.

83 Table 3-19: Experimental Results for U,I removal by Fucus Gafdneri Based on Wet Mass.

»'I Final »H Final Activity "'I Initial "'I Final Activity Mass/ ["'I] in ["T| in Reaction Reaction Reaction Surface absorbed m Activity m Activity tn absorbed m Surface Fucus g1 FioiMcm2 Rates Rate Rates Fucus ID Mass /g Area Fucus by Rz Seawater Seawater Fucus by Area / Wet/("'I] /[•"I] in kf + lq, k k„ /cm2 difference f /Bqml ' /Bqml.1 difference gem2 tn seawater seawater /hi /h> /h< /Bq ml ' /cm2 ml,1 ml ' Wet 65 74 2 1781" 84 16 458 19 0 042 28 12 1 14 080 1 10 0 0388 66 203 487" 81 13 1668 69 0 042 127 53 0 49 0 99 0 49 0 0039 67 14 1 338' 78 13 2324 97 0 042 181 76 040 100 040 0 0022 68 22 3 535' 78 10 1514 63 0 042 146 61 0 36 0 98 0 36 0 0025 69 79 2 1901- 79 23 354 15 0 042 16 06 0 81 0 94 0 76 0 0486 70 6 144" 76 21 4585 191 0 042 220 92 0 22 0 97 0 22 0 0010 101 16 3 316 57 22 1084 56 0 052 50 26 0 54 0 95 0 53 0 0106 104 22 8 533 54 18 791 34 0 043 44 19 080 0 92 0 78 0 0178 105 22 449 61 23 880 43 0 049 39 19 0 62 0 69 0 60 0 0155 109 271 563 58 18 730 35 0048 40 19 084 0 89 0 82 00204 115 24 556 63 21 872 38 0 043 41 18 0 98 0 92 0 96 0 0232 139 183 386 63 28 961 46 0 047 35 17 0 64 0 78 0 63 00180 102 107 270 62 30 1508 60 0040 51 20 0 67 0 67 0 65 0 0128 119 119 371 64 25 1636 53 0 032 65 21 0 66 0 66 0 65 0 0101 123 11 3 365 74 31 1928 60 0 031 63 20 0 68 0 88 0 67 0 0107 127 10 5 312 58 32 1230 41 0 034 38 13 0 69 0 85 0 68 0 0178 128 10 3 253 62 33 1383 56 0041 42 17 0 68 0 68 0 67 0 0161 132 11 3 298 63 36 1200 45 0038 33 13 0 57 0 83 0 55 0 0165 103 51 158 60 37 2260 73 0032 61 20 0 50 0 76 0 49 0 0080 130 54 143 61 32 2679 101 0038 85 32 0 32 0 83 0 32 0 0037 140 65 207 64 34 2370 74 0031 70 22 0 42 0 79 0 41 0 0058 143 65 163 55 26 2258 90 0040 88 35 0 17 0 76 0 17 00019 146 52 139 66 32 3304 123 0037 104 39 0 33 0 83 0 33 0 0031 147 57 207 73 34 3434 95 0 028 100 28 0 36 0 60 0 36 0 0036 110 138 357 51 16 1269 49 0 039 81 31 0 63 0 93 0 63 0 0077 111 12 6 384 69 21 1911 63 0 033 91 30 0 35 0 95 0 35 0 0038 116 12 295 98 33 2699 110 0041 81 33 0 60 086 0 59 0 0073 117 139 320 122 35 3146 137 0 043 90 39 0 56 0 57 0 55 0 0061 141 128 331 152 44 4204 163 0039 95 37 0 42 0 92 0 41 0 0043 144 123 365 169 42 5146 173 0 034 122 41 0 51 0 91 0 51 0 0042 Average 17 431 NA NA NA NA 0 039 78 30 0 57 NA 0 55 0012 SD 17 403 NA NA NA NA 0 006 46 19 0 22 NA 0 21 0011 %SD 99 94 NA NA NA NA 15 60 63 38 NA 38 94 * Calculated result using the calibration of the mass to the surface area Figure 3 7

84 Table 3-20: Experimental Results for U1I removal by Fucus Gardneri Based on Dry Mass. 131I Final Activity "'I Initial »'I Final ["'I] in absorbed in Dry Activity in Activity in Fucus g1 Fucus ID Fucus by Mass /g Seawater Seawater Dry/P'I] difference /BqmL' /BqmL' in seawater /BqmL1 mL' Dry 65 98 84 16 458 215 66 26 81 13 1668 989 67 24 78 13 2324 1066 68 34 78 10 1514 960 69 9.9 79 23 354 125 70 1.2 76 21 4585 1099 101 2.4 57 22 1084 331 104 34 54 18 791 293 105 3.3 61 23 880 258 109 41 58 18 730 268 115 36 63 21 872 276 139 2.7 63 28 961 232 102 1.6 62 30 1508 340 119 18 64 25 1636 430 123 1.7 74 31 1928 420 127 1.6 58 32 1230 253 128 1.5 62 33 1383 277 132 1 7 63 36 1200 223 103 1.0 60 37 2260 305 130 11 61 32 2679 424 140 1.3 64 34 2370 352 143 1.3 55 26 2258 440 146 1.0 66 32 3304 522 147 1.1 73 34 3434 501 110 2.1 51 16 1269 539 111 19 69 21 1911 608 116 1.8 98 33 2699 542 117 2.1 122 35 3146 602 141 1.9 152 44 4204 635 144 1.8 169 42 5146 811 Average 2.6 NA NA NA 480 S.D. 2.1 NA NA NA 270 % S.D 83 NA NA NA 56

The average equilibrium constant for Fucus gardneri is 78 ± 46 mL g' based on wet weight and 480 ±

270 mL g' based on dry weight. The average rate constants kf +kb, kf and kb are 0.57 ± 0.22 h ', 0.55 ± 0.21 h' and 0.012 ± 0.011 h', respectively. Using these rate constants the time that is required to approach equilibrium is given in Table 3-21.

85 Table 3-21: Time Required to Reach Equilibrium Based on Reaction Rates kf and kb.

% To Equilibrium Completion 95 99 99 9 Time/h 5±2 8±3 12±5

Therefore, it would take 5, 8 and 12 hours for the Fucus gardnen to reach 95%, 99% and 99.9% of their equilibrium constant value, respectively The standard deviation of the equilibrium constant is 60%, which is large, but expected for a biological process. The rate constant 1% is much greater than

131 kb, which means that the reaction heavily favours the forward direction of I in the Fucus gardnen

Large standard deviations of ca. 40, 40 and 100% were determined for the rate constants \ +kb, kf and kb . The percent standard deviation for kb is much greater than that for kf because the order of magnitude for kf is greater than kb. Therefore, changes in the rate constant for kb result in a greater percent standard deviation even though the absolute standard deviation is smaller, 0 011 h versus 0.21 h \ There are many factors that affect the uptake rate in living systems The large uncertainty is most likely due to the physiology differences in the Fucus, such as health, age and stage of reproduction cycle. Regardless of the fact that the standard deviation is large, the results can still be useful to determine the equilibrium constant and rate constants in Fucus gardnen. It is important to note that the equilibrium constants and rate constants calculated are based on the initial rapid uptake (<5 hours) of 13,I and do not account for the long term uptake over days or weeks. This difference is the probable reason for the difference in the equilibrium constant for Fucus gardnen calculated by INAA of 5800-9700 (based on dry weight of Fucus) because this range is based on stable iodine Since 131I has a half-life of 8 d, an equilibrium constant such as that achieved by stable iodine is not possible because the [ I] is constandy decreasing due to radioactive decay. For Fucus gardnen, a bioehmination half-period has been estimated at 10.3 days and a total half period has been estimated at 4 5 days [50], which means that, after 10.3 days, half of the 13,I has been lost by means of biological processes and after 4.5 days half of the total 131I is lost by radioactive decay and biological processes. In Halifax Harbour, there is a constant influx of 131I due to medical procedures conducted at Victoria General Hospital; therefore, there is a constant supply of 131I, which explains why it is detected in seaweeds regularly

There is a linear relationship R2= 0.954 (Figure 3-15), for the equilibrium constants derived using mass of the Fucus and surface area of the Fucus. The strong linear relationship results from the fact

86 that the dependence of the surface area on the mass was also a linear relationship. Neither the equilibrium constant nor the rate constants are dependent on the mass of the Fucusgardneri. The dependence of the equilibrium constants and the rate constants on mass are plotted in Figure 3-16 - Figure 3-19. In these figures, there is no strong correlation between mass and the constants. The random distribution of equilibrium constants likely results from the individual physiology of the Fucus plants.

10.0 y = 0.0401X - 0.091 ^ « 9.0 R2 = 0.9542 ^ i? 8.0 +s>^ 1 7.0 \ 6.0 4. s' ^ § 50 u . y< E 4.0 •= 3.0 y^' w + =5 2.0 - ^ tr JT~ w 1.0 4^ 0.0 () 50 100 150 200 250 Equilibrium Constant /(mL cm 2)

Figure 3-15: Relationship of Equilibrium Constants Calculated using Mass of the Fucus and Surface Area of the Fucus.

87 250 r-

.!? 200

£ 150 c o u E 100 3

3 50 111 rv**

20 40 60 80 100 Mass/(g)

Figure 3-16: The Dependence of the Equilibrium Constant on Mass.

1.20

1.00

_ 0.80 ,0.60 4 + • «>•• 0.40 t+ 0.20

0.00 20 40 60 80 100 Mass/(g)

Figure 3-17: The Dependence of Rate Constants kf + kb on Mass.

88 1.20

1.00

0.80

< 0.60

0.40

0.20

0.00 20 40 60 80 100 Mass/(g)

Figure 3-18: The Dependence of Rate Constant kfon Mass.

0.0600

0.0500

0.0400

-; 0.0300

0.0200

0.0100 ±1'

0.0000 20 40 60 80 100 Mass/(g)

Figure 3-19: The Dependence of Rate Constant kb on Mass.

89 3.7.2.2 I Loss from Spiked Fucus Gardneri to Seawater

The purpose of this experiment was to determine the loss of 131I to seawater from Fucus gardneri containing 131I. After 24 hours of exposure to 131I spiked seawater, plants 101, 104, 105, 109, 115 and 139 were placed in clean artificial seawater cooled to between 7-8°C. Initial aliquots of this initially clean seawater were analysed over a period of hours; however, the [131I] in the seawater was below the detection limit and no results could be determined for the rate constants. The loss of the 131I to the seawater was slow and was below the detection limit for 1 mL of ,31I counted for 10 min over an HPGe detector. After 19 h, the amount of 131I that entered the seawater from the Fucus was above the detection limit, and was measured by gamma-ray spectroscopy, Table 3-22.

The predicted concentrations of 131I in the Fucus and in the seawater at equilibrium were calculated by equation (28) and (29), respectively.

kf[B]0

... k„[B]0 lA]°°=jkpn^ <29>

131 131 where [B]0 is the initial concentration of I in the Fucus, [BJoois the concentration of the I in the Fucus at equilibrium, [AJ^ is the concentration of the 131I in the seawater at equilibrium and kf, k,, and kf+kb are the averages for the rate constants determined experimentally. Using the equilibrium constant (Keq), the predicted concentration of I in the seawater at equilibrium was calculated. The results for the above measurements and calculations are given in Table 3-22.

90 Table 3-22: Comparison of Experimental and Predicted Results for U1I Spiked Fucus Gardner! Placed in Clean Artificial Seawater.

FucusID 101 104 105 109 115 139 131I Initial Activity in Fucus (Bq g ') 1080 790 880 730 870 960 U1 1 Predicted I in Fucus at Equilibrium (Bq g- ) 1042 762 850 700 840 930 (using Eq. (28)) 131I Final Activity in Fucus (Bq gf1) (based on measured 131I) 980 710 800 660 800 900 m 1 Predicted I Final Activity in Seawater (Bq g" ) 23,13 17,10 19,11 15,9.4 18,11 20,12 (using Eq.(29),Keq) Measured 13,I Final Activity in Seawater (Bq g ') 3.4 3.9 3.4 3.9 3.4 2.3

The predicted results and the experimental results show reasonable agreement for Fucus confirming the fact that 131I favours the Fucus. Consideration of seawater shows that 131I approached equilibrium based on the final activity in the seawater predicted by the equilibrium constant and the rate constant kb, although the systematically lower experimental activities should be further investigated. The Fucus had been exposed for 19 h, longer than the 12 ± 5 h required to approach equilibrium at 99.9% given in Table 3-21. The minimal loss of 131I to the seawater was as predicted by the equilibrium constant where the [131I] is greater in the Fucus gardneri than in the seawater. This result is useful because the seaweed holds on to significant amounts of the 131I even in the absence of 131I in the seawater. Therefore, 131I can be detected in Fucus gardneri long after it is no longer measureable in seawater. This is critical information that can be used to determine sampling strategies for the ERMP and NER programs.

3.7.2.3 Mass Balance Calculation for the Concentration of1311 in Shearwater, NS

It is known that ,31I enters the sewage system from patients treated for thyroid diseases in Halifax and that the sewage enters Halifax Harbour through a series of outfalls [35,88]. A calculation can be made to estimate the approximate level of 131I in seawater located near Shearwater. This result can then be compared to the experimental results found in the previous sections. The sampling location

91 used in the ERMP program for seaweeds in Shearwater, NS is also called the Eastern Passage. Following is a list of the parameters used for the calculation:

• There is one sewer outfall located at Eastern passage that has an average effluent discharge of 0.46 m3 s \ 0.15 m3 s \ of which is raw sewage [88] (Figure 3-20).

• Assuming a 5 km2 area with an average depth of 20 m, the volume of water affected by the sewer outfall is approximately 0.1 km3 or lxlO8 m3.

• In one day, the volume of discharge at Eastern passage is 4 x 104 m3. [88] • In Halifax, a single patient will discharge 2 GBq of 131I to the sewer (Table 1-4: Administered Dose to Thyroid Patients and Estimate of Discharge to Sewer of1311 in Halifax [35] for 2006 data).

• Assuming the discharge occurs in one day and that the 1MI is mixed homogeneously in the lxlO8 m3 seawater, the concentration of 131I in the seawater would be 20 Bq m3 or 0.02 Bq

kg'-

The 131I activity of 0.02 Bq kq' is a reasonable concentration and compares to the estimate of 0.003 Bq kg1 calculated based on the equilibrium constant calculation using the total iodine in Ascophyllum Nodosum and seawater (section 3.3). Using the average equilibrium constant, 78 mL g1 (Table 3-19), for a 1 kg sample of Fucusgardneri, the 131I activity in the Fucusgardneri after one day would be 1.56 Bq kg1. This result is consistent with the amount of 131I found in Ascophyllum Nodosum in Table 3-10. These results are useful because they show that laboratory experiments can give some guidance to the prediction of 131I concentrations in field samples. The equilibrium constant proves to be more useful than reaction rates as reaction rates can not be as easily applied in field applications because the system is dynamic. Since the volume of water to which the Fucus is exposed is variable and almost impossible to predict, applying rate constants in field applications is not practicable.

92 BEDFORD BAY BEDFORD HALIFAX • *. BASIN INLET

\ THE NARROWS DARTMOUTH * k* t5 44 W*Vy/ r DC 40 ^ DS V HALIFAX ^^ / J DK J»- , GEORGES ISLAND *3& EASTERN 7rf» / PASSAGE 4t NORTHWEST P ARM * 8>r

9^ 44 36 YORK REDOUBT

HERRING

1j 5 COVE >*.

km 63 40 63^36 63 32' Sewage outfalls are identified by arrows.

Figure 3-20: Map of Halifax Harbour Showing Sewage Outfalls.

93 i. 7.3 Retention of I in Fucus Gardneri under Different Storage Conditions

Seaweed samples can often experience shipping delays. The time between shipment and receipt of samples at the laboratory can be many days. It is imperative that samples arrive in a timely manner because some radioisotopes have half-lives on the order of hours and require analysis within days of sampling. It is also desirable to analyze seaweed samples within a few days after sampling because they begin to perish quickly. An experiment to determine the retention of 131I in Fucus gardneri was performed to determine if the storage conditions of the plant would have an impact on the retention of 1MI. The Fucus were subjected to different environmental conditions. These conditions were chosen to mimic what might happen during shipment of the samples. Following are the results describing the changes in activity over an 8 day period for the three storage conditions. All activities are back-calculated to the date and time of the first count for each storage condition. The results in Figure 3-21 and Figure 3-22 show that there was no measurable loss within the uncertainty of the experiment of 131I from the plants after 8 d regardless of the conditions. Note that individual plants were given unique numerical identifiers and that the numerical codes presented here represent the plant samples combined to provide suitable sample mass. Therefore, the method of storage of the seaweed samples does not result in a loss of 131I.

94 4.00E+00 • 1_6_3_5 i • 37_40 I 1 8_48_50 00 ;; ex CO x 39_36

X2_22_49 '•> i u < i • 26_34 +7_25_30

:: I -4_19 2.00E+00 T i_t i- 0 10 -28

Time/(d) Average (all plants)

Figure 3-21: Results of U1I Retention for all Samples, where Sample Identifiers Represent Combination of Uniquely Numbered Plants.

3.5

CO 3 ii >• T T T 1 1 i

2.5 4 5 Time /(d)

• Average (fridge) • Average (frozen) Average (room temp)

Figure 3-22: Average of Results for U1I Retention for Different Storage Conditions.

95 3.7.4 Fucus Exposure to Reactor Container Water

NCVs and NPVs regularly visit ports on both the East and West coasts of Canada. In the event of a leak of nuclear material, the uptake of fission and activation products by seaweeds could be useful to catch small leaks that would not be detectable in seawater. An investigation into the fission and activation products absorbed by Fucus gardneri was conducted. Reactor container water from the SLOWPOKE-2 reactor at RMC was withdrawn and used to expose Fucus gardneri to the low level of fission products contained in the water possibly similar to the levels expected near a berth. There are many ways the radionuclides absorbed in the Fucus gardneri can be interpreted. Many decay chains are present from the decay of the fission products. Parent radionuclides decay into daughter radionuclides. Depending on the half-life of the radionuclides decaying, conditions such as secular equilibrium may be established. Since the purpose of this experiment was to simply determine which fission and activation products are absorbed by Fucus gardneri, the half-life of the actual radionuclide was used and conditions of parents decaying into daughters was not considered to determine actual activities of each radionuclide. In Figure 3-23, the radionuclides found in the Fucus gardneri exposed to 1 L of reactor container water after 4, 8 and 24 h are shown. The activity of each radionuclide contained in 1 L of reactor container water is also plotted for comparison. All activities are back- calculated to the time of the initial count for a 1 L reactor container water sample. Radionuclide activities below the MDA are plotted with a black border. The data with uncertainty is tabulated in Appendix G. The percent of activity absorbed by Fucus gardneri from 1 L of reactor container water is given in Table 3-23. Results in red are calculated using one or more MDA results and are reported for interest only. In general, for long lived radionuclides, the longer the Fucus is exposed, the greater the concentration of radionuclides taken up by the Fucus. However, for many of these radionuclides, the uptake occurs in the first 4 hours. For shorter lived radionuclides, the activity decays more rapidly; therefore, a radionuclide that is present in the 4 or 8 hour exposure may not be detected in the 24 hour exposure because too many half-lives have past. For example, for 88Kr, the half-life is only 2.8 minutes and therefore it is only detected in the 1 L reactor container water sample because, within approximately 22-28 minutes, the 88Kr had reached nine half-lives, and may be assumed to have completely decayed away. For radionuclides detected in the Fucus and not in the reactor container water, the main cause could be due to the larger Compton background in the reactor container water spectrum. In it, there is higher overall radioactivity (the total reactor container water

96 activity at time of count was 68000 Bq kg1 compared to 21000, 14000 and 7000 Bq kg1 for the Fucus exposed for 4, 8 and 24 h, respectively) resulting in a higher MDA for each radionuclide, which is the case for ^Co where the MDA was 35 Bq kg' in the reactor container water, a result greater than the reported result for each of the other Fucus exposures to reactor container water experiments. Based on the above results, Fucus gardneri is an excellent bioindicator to determine the dispersion of fission products in the event of a nuclear release. It is certainly suggestive that further study will demonstrate the ,31I release from and NPV should be accompanied by significant levels of other bioaccumulated radionuclides in aquatic plants.

97 14 Hour Exosure Fucus 8 Hour Exposure Fucus 124 Hour Exposure Fucus • 1 L Reactor Container Water

1.00E+05

pa

Figure 3-23: Fission and Activation Product Back-calculated Activity Measured in Bq in 1 L of SLOWPOKE-2 Reactor Container Water and in Fucus Gardneti. (MDA data is shown with a black border.) 98 Table 3-23: Percent Activity for Each Isotope Detected in Fucus Gardner/ from 1 L of Reactor Container Water Back-calculated to the Same Reference Date and Time. (MDA- based data is shown in red.)

Nuclide 4 Hour Exposure Fucus 8 Hour Exposure Fucus 24 Hour Exposure Fucus % Total Activity in Fucus Iodines

131J 14 16 19

133! 15 16 15

135! 20 34 43

Metals 20 19 21 24Na 4S 51 54 MMn 59 66 610 "Mn 30 2" 28 ooCo 49 60 61 91Sr

4 1.4 1.4 "Mo 6 24 2 ,03Ru 10 11 10 110mAg 38 39 40 I40Ba 34 ""8 230 ,40La 524 03 0 2 138Cs 67 61 56 ^Np Noble Gases 0.3 0.2 0 0 «Ar 1.6 1.1 0.4 85Kr

SSmKj. 6 0 48 81 IT 68 2500 88Kr 2 0 1.7 1.1 133Xe 4.0 5.1 4.7 135Xe 14 9 3 3 1 135mXe

99 Chapter 4 Conclusions & Recommendations

4.1 Conclusions

The uptake of 131I in Fucusgardneri follows a first order equilibrium process that comes to equilibrium within hours. This information is important for ERMP and NER sampling strategies because samples of seaweed can be taken hours after a suspected leak of nuclear material. Using gamma-ray spectroscopy to measure the content of 131I in seaweed, levels which are not detectable by measuring the seawater alone can be detected. The average equilibrium constant for Fucus gardneri is 78 ± 46 mL g' based on wet weight and 480 ±

1 270 mL g based on dry weight. The average rate constants kf +kb, kf and kb are 0.57 ± 0.22 h \ 0.55 ± 0.21 h1 and 0.012 ± 0.011 h1, respectively. These results have large uncertainty, but should be expected since the physiology of the individual plants would have a large effect on the results. The equilibrium constants determined using mass and the surface area of the individual Fucus gardneri plants show a linear relationship, R2 = 0.95. Therefore, the mass of the plant can be used to compare individual plants eliminating the need to determine surface area which is time consuming and has an immeasurable uncertainty. The range of the Fucus gardneri masses used was large 5.1 — 71 g; however, the equilibrium and rate constants were not dependent on the mass of the Fucus gardneri used and therefore the size of the plant sampled in the field can be variable. This fact makes sampling of Fucus gardneri easier for the NER team who may not take plants of similar size even if requested.

The forward rate constant, kf, is much greater than reverse rate constant, kb, which means that the reaction heavily favours the forward direction of 131I in the Fucus gardneri. These results are useful because they demonstrate that the !31I has a high partition coefficient for 131I in seaweed even in the absence of 131I in the seawater. Therefore, 131I can be detected in seaweed long after it is no longer measureable in seawater. Seaweed samples can be stored for up to one week in temperatures ranging from -5°C to 20°C without any loss of 131I, indicating that samples may be kept for later analysis, as necessary. These results provide critical information that can be used to determine sampling strategies for the ERMP and NER programs.

100 Fucus gardneri is an excellent bioindicator to determine the dispersion of fission products in the event of a nuclear release. Fucus gardneri exposed to reactor container water from the SLOWPOKE-2 Facility absorbs fission products within 4 hours. In the event of a fission release, the uptake of the fission products in Fucus gardneri would qualitatively result in the observation of multiple radionuclides in Fucus. The Fucus gardneri not only absorbed iodine isotopes, but also a range of metals and noble gases. This result also supports the theory that the detection of 1MI alone in seaweed sampled from Shearwater is indicative of a single isotope medical source. Overall, the bioaccumulation characteristics of 1MI and other fission products in Fucus gardneri shows that it is an effective species to be used as an indicator for a release of nuclear material. The bioaccumulation and measurement by gamma-ray spectroscopy of 1MI and other fission products in Fucus gardneri is an efficient way to measure low level releases of radioisotopes. In the event of a dispersion of nuclear material on the East or West coast of Canada, NER teams could sample Fucus located in the area within hours of the release and determine the presence of radionuclides by gamma-ray spectroscopy. Further sampling and analysis could occur hourly or daily over the succeeding weeks, providing a picture of the distribution of radionuclides. Sampling Fucus Gardneri in new locations over time may also help to measure the dispersion rate of radionuclides in the area since the uptake occurs in a few hours. Samples could be taken daily at various locations, counted and mapped to give a picture of the dispersion of radionuclides over time. This information could be used to find the source of the radionuclides if the location of the source is unknown. In locations where no seaweed grows naturally and in the event of a low level release of nuclear material, Fucus gardneri or other species of seaweed could be used. Shipment of seaweed samples to the location and immersion of the samples in potentially contaminated water could give a quantitative result for the activity of the radionuclides present as was demonstrated by the experiments conducted in this thesis. The Ascophyllum Nodosum and the Saccharina Latissima sampled in Shearwater, NS in December 2006 had 131I average activity of 30 ± 2 Bq kg1 and 175 ± 7 Bq kg1 dry weights, respectively. These results confirmed that 131I is present in the seawater and also confirm the routine detection of 131I suggesting that the source is likely medical. The Saccharina Latissima had much higher levels of 131I compared to the Ascophyllum Nodosum, which suggests that for very low level releases of 131I Saccharina Latissima should be sampled rather than Ascophyllum Nodosum since the detection of much lower concentrations of I is likely.

101 The average concentration of iodine in Fucus gardneri determined using INAA is 290 ± 50 u\g g1 dry weight. The equilibrium constant determined for stable iodine in Fucus gardneri using INAA was 5800-9700, based on dry weight for the Fucus. In the event of a long term release of 1MI, these results can be used to make predictions for the concentration of trace 131I in seawater by measuring the 131I concentration in Fucus gardneri by gamma-ray spectroscopy. Determining the concentration of stable iodine in other species of seaweed and in the seawater, in which they are living, could give further confirmation of the 131I concentration in seawater on both the East and West coasts. With regard to the construction of detector shielding, validation and detection limit of 131I, the best configuration for low level detection of 131I and other radionuclides is to use lead shielding and liquid nitrogen since background radiation and electrical interferences are reduced. The 60% GEM60P4 detector performed well for the purpose of detection of 13,I in seaweed samples. The detection limit for a 200 mL 131I source and minimum detectable activity was determined to be 0.28 ± 0.07 Bq and 0.09 ± 0.02 Bq, respectively. This result can be obtained in a 6 hour count time, which is a reasonable turnaround time for environmental samples collected though the ERMP and NER programs. Since laboratory validated equipment is more reliable than equipment used in the field, it might be advantageous to ship samples to a laboratory rather than take readings in the field when a low level release of radiation has occurred.

102 4.2 Recommendations

The sewage outfalls in Halifax Harbour, NS, are well documented. Samples of seaweed should be taken more frequendy during the year to determine the maximum and minimum trends of 131I in seaweed at the sewage outfalls. INAA should be conducted to determine the iodine content of seaweed from Shearwater, NS. With these results, along with the concentration of iodine in the seawater, the equilibrium constants for iodine and the seaweed in their natural state should be determined. Maintaining seaweed in an aquarium is very difficult. Uptake experiments using seaweeds should be conducted near their natural environment. This would eliminate the need to ship and maintain seaweed in an aquarium. Also natural seawater should be used, eliminating the need to make artificial seawater. Uncontaminated seaweeds should be exposed to a large (>1 m3), isolated volume of seawater sampled from Halifax harbour to determine if 131I can be detected in the seaweeds.

More experiments should be conducted that measure kb in Fucus gardneri directly to obtain a result with less uncertainty. This effort would require that the Fucus gardneri has a high initial concentration of ,31I such that the loss to seawater could be measured with a small sample size and in a relatively short counting time. More experiments should be conducted on the uptake of other fission products from reactor container water by Fucus gardneri and the equilibrium constants for those radionuclides should be determined. The experiments on the uptake of fission products by Fucus gardneri could provide more information by extending the exposure time of the Fucus to the reactor container water and increasing the counting time in an attempt to observe any trace radionuclides absorbed.

103 References

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108 61. Brown J.E., Hosseini A., Borretzen P., and Thorring H., "Development of a Methodology for Assessing the Environmental Impact of Radioactivity in Northern Marine Environments" Marine Pollution Bulletin, 52 (2006) 1127-37. 62. Hurtgen C, Koch G., van der Ben D., and Bonotto S., "The Determination of Technetium-99 on the Brown Marine Algae Fucus spiralis Collected along the Belgium Coast" Science of the Total Environment, 70 (1988) 131-149. 63. Marsh K.V., Buddemeier R.W., Wood W., and Smith C, "Radioiodine in Kelp from Western Australia" Journal of Radioanalytical and Nuclear Chemistry, 123 (1988) 199-213. 64. Cooper L.W., Beasley T.M., Zhao X.L., Soto C, Vinogradova K.L. and Dunton K.H., "Iodine- 129 and Plutonium Isotopes in Arctic Kelp as Historical Indicators of Transport of Nuclear Fuel- Reprocessing Wastes from Mid-to-High Latitudes in the Adantic Ocean" Journal of Marine Biology, 131 (1998) 391-399. 65. Keogh S.M., Aldahan A., Possnert G., Finegan P., Leon Vintro L., and Mitchell P.I., "Trends in the Spatial and Temporal Distribution of 129I and 99Tc in Coastal Waters Surrounding Ireland Using Fucus vesiculosus as a Bio-indicator" Journal of Environmental Radioactivity, 95 (2007) 23- 38. 66. Yiou F., Raisbeck G.M., Zhou S.Z., Kilius L.R., and Kershaw P.J., "Improved Estimates of Oceanic Discharges of 129I from Sellafield and La Hague" Proceedings of: The Second International Conference on Environmental Radioactivity in the Arctic, Oslo, Norway August (1995) 113. 67. Dr. Megan Dethier, University of Washington, Friday Harbor Laboratories, and Dr. Susan Williams, University of California-Davis, Bodega Marine Laboratories "Intertidal Ecology of Fucus, San Juan Island, Washington" Photo oi"Fucus" Website: http://faculty.washington.edu/mdethier/Fucus (2011). 68. Biology Department, Sonoma State University Photo of "Fucusgardneri", Website: https://www.sonoma.edU/users/c/cannon/univl02marinebiology.html (2011). 69. UBC Botanical Garden and Centre for Plant Research. Photo of 'Fucusgardneri' Website: http://www.botanicalgarden.ubc.ca/potd/fucus gardneri.jpg (2011). 70. Centre for Phycological Documentation, Decew's Guide, Photo of "Fucusgardneri Si/vd" University Herbarium, UC Berkeley, Website: http://ucjeps.berkeley.edu/guide/brown38.html (2011). 71. Druehl L., Pacific Seaweeds. Harbour Publishing British Columbia Canada (2000).

109 72. Klemperer H.G., "The Accumulation of Iodide by Fucus ceranoides" Journal of Biochemistry 67, (1957). 73. Atkins P.W. Physical Chemistry. Third Edition. Oxford University Press. Oxford. (1987). 74. Knoll G.F. Radiation Detection and Measurement. Second Edition. John Wiley and Sons, Inc. USA. (1989). 75. Ishikawa Y., Shoji K., Takahashi M., and Watanabe T., "High Sensitive Measurements of 137Cs and Other Radionuclides in Environmental Samples Using Germanium Detectors" Journal of Radioanalytical and Nuclear Chemistry, 243 (2000) 367-376. 76. Harb, S., Salahel Din K. and Abbady A., "Study of Efficiency Calibrations of HPGe Detectors for Radioactivity Measurements of Environmental Samples" Proceedings of the 3rd Environmental Physics Conference. Aswan, Egypt 19-23 Feb (2008). 77. GA-MA & ASSOCIATES, INC website : http://www.gamaassociates.com/english/im020003.html 78. Ishikawa, Y., Shoji, K., Takahashi, M., and Watanabe, T., "High Sensitive Measurements of 137Cs and Other Radionuclides in Environmental Samples Using Germanium Detectors" Journal of Radioanalytical and Nuclear Chemistry, 243 (2000) 367-376.Friedlander G., Kennedy J.W., Macias E.S., and Miller J.M., Nuclear and Radiochemistry 3rd Edition. John Wiley and Sons, Inc. New York (1981). 79. Bennett L.G.I., and Lewis B.J., "Introduction to Nuclear Engineering" Class Notes, Department of Chemistry and Chemical Engineering. Royal Military College (2006-2007). 80. The SLOWPOKE-2 Facility at RMC Training Manual for Operation in Automatic Mode for Trainee Reactor Operators. Revision 1.1 (26 Oct 2009). 81. Nielsen, K.S., ed., Annual Report for the SLOWPOKE-2 Facility at the Royal Military CoUege of Canada Kingston, Canada, (2011). 82. Andrews, W. S., Thermal Neutron Flux Mapping around the Reactor Core of the SLOWPOKE- 2 at RMC, MASc Thesis, Department of Chemistry and Chemical Engineering, Royal Military CoUege of Canada, Kingston ON (1989). 83. Software User's Manual. Gamma Vision -32 Gamma-ray Spectrum and MCA Emulator for Microsoft Windows 98, 200, NT and XP. Manual Revision D. USA (2003). 84. Personal communications with Dr. Louis Dreuhl by telephone and email 7 and 25 Jan 2008 and 28 Feb 2008, (2008).

110 85. Personal communication with Christopher Lane. (2006) Seawater also found on Website: http://www.mbl.edU/BiologicalBuUetin/COMPENDIUM/Comp-Appl.html#EX (2006). 86. Martinelango P.K., Tian K, and Dasgupta P.K. "Perchlorate in Seawater Bioconcentration of Iodide and Perchlorate by Various Seaweed Species" Analytica Chimica Acta 567 (2006) 100-107. 87. Baily N.A., Kelly S., "Iodine Exchange in AscophyUum" Biological BuUetin, 109 (1955) 13-21. 88. Buckley D.E., and Winters G.V. "Geochemical Characteristics of Contaminated surficial sediments in Halifax Harbour: impact of waste discharge" Canadian Journal of Earth Science, 29 (1992) 2617-2639. 89. Ames D. P., Bunker M. E., Langer, L. M., and Sorenson, B. M. " The Disintegration of 91Sr and 91mY" Physical Review, 19 (1953) 68-74.

Ill Appendices

112 Appendix A :

Sampling Maps for ERMP Program

Figure A-1: Base Line Study Sample Location Map - Esquimalt, BC.

113 N

wj ;ȤeE ! HD4 HPS HW11 HCTJ Atlantic Ocean S

_—-IMM>T_^ \JlW HUB I cf^Shearwatei r yA MPfc-JT^f "W iri„np It1 \~^ Prt MPV Hoorlno A Xj MCT Mil I

** MD11 H»I ^-

HC10 HWtl sa iicLaa.S

Figure A-2: Base Line Study Sample Location Map - Halifax, NS

114 "^3"

0 0 ^ \tf4 MM^

o ^ MF7 WT JNC1 MP1M81 NWll JF7 U3SUHS9 Ranekfoirt C5 <3= htenoose Bay JL^JNPV Mooring

|NC4 NP3 WB» tWWlAI HG2 NM

Figure A-3: Base Line Sample Location Map - Nanoose, BC.

115 Appendix B : Derivation of First Order Equilibrium Equations

Getting from Equation (15) to Equation (16):

d[A] = -(k + k )[A] + k [A] dt f b b 0 d[A] = dt -(kf + kb)[A] + kb[A]0 1 •ln(-(kf + kb)[A]t + kb[A]0) = t + c -{kf + kb)

ln(-(kf + kb)[A]t + kb[A]0) = -(kf + kb)t + -(kf + kb)c

-(kf + kb)[A]t + kb[A]0 = e-(*/+**)«+(-(*/+*»)*)

fc +fc ~(kf + kb)[A]t + kb[A]0 = e-( / i.)te-(fc/+fc6)c

Att=0,[A]t=[A]o

-(kf + kb)[A]0 + kb[A]0 = e-(*/+*!•)'

k k -(*, + kb)[A]t + kb[A]0 = e< r+ -H-{kf + kb)[A}0 + kb[A]0)

k +k -(kf + kb)[A]t = e-( f ^(-(kf + kb)[A]0 + kb[A]0) - kb[A]0

k e-^ ^(-kf[A]0 - kb[A]0 + kb[A]0) - kb[A]0 [A]t = -(kf + kb)

k k e-( f+ »)t(-kf[A]0 - kb[A]0 + kb[A]0) - kb[A]t [A]t = -(kf + kb)

k +k -kf[A]0e-( r >>> - kb[A]0 [A]t = -(kf + kb)

k +k kf[A]0e< f ^ + kb[A]0 [A]t = (kf + kb)

116 Derivation of Equation 28: A**B

6(1 kb [AU Conditions

T=0 A=A0 B=0

T=t A=A B=B= A0-A T=ao A=Aoo B=Boo= A-Aoo

kr [B]t h [i4]«, = L"Joo A0 — AQO

kb [S]oo — A0 — Bo,— Kf

[B^kf = A0kf - Bmkb

A0kf = B^ikf + kb)

*}£ =-k,[A] + kb[B]

^. =-kf[A] + kb([A]0 - [A])

= -kf[A] + kb[A]0-kb[A]

= -(kf + kb)[A] + kb[A]0 Sub in

K — Kf b V[*L

=-fa + kb)[A] + k,^-[A]0

[A]c = -(*/ + kb)[A] + kf[A]0 ° [*]«

117 [A]0kf = [BUikf + kb-)

1 = -{kf + kb)[A] + [BUikf + kb)

= -(kf + kb)[A] + [A]OB(kf + kb)

d[A] = -{k + k )[A] + [AUdkf + k ) dt f b b d[A] dt = [A] - [AU(-{kf + h)) d[A] = -{k + k )dt [A] - [Al f b

(\n([A]t - Woo) - (ln(M0 - [AU) = ~{kf + kb)t

(ln(^]0 - [AU) - Qn([A]t - [AU) = {kf + kb)t

. [A\0 [A\oo /. . \

118 Appendix C :

Lead Castle Design Parameters

Lead Castle

Dimensions Total Volume of sides (outer dimensions - inner dimensions) Sides 27"x27"x14" Outer Dimensions 10206 in3 0.167246 m3 Interior (hollow) 15"x15"x14- Inner Dimensions 3150 in3 - 0 051619 m3

Volume Sides 0.115627 m3

Bottom 27-x27"x4- Volume Bottom 0.047785 m3

Lid 27-x25"x6- Volume Lid 0.066368 m3 Note: The Bottom will have a hole cut in it. The lid will have slightly smaller dimensions Total Volume 0.229779 m3 along the width to accomidate the track needed Density of Pb 11340 kg/m3 for the lid to open and close. Total Weight of Pb 2805.699 kg

[Total Weight of Lid | 752.6087 Kg

For the Base of the Stand 1. Cross braces on three sides of the stand. At the mid point of the legs (or where it accomidates) a horizontal brace attached. Two sets of diagonal braces extending the full length of the openings * See Diagram Below.

Use 3/4" X1/8" Steel or Rod for cross braces

* Ensure the cross braces do not inhibit the placement of the dewar.

2. On the front side of the castle the braces should be extended so that they are the maximum length possible and such that the dewar and detector can pass without hlnderance into and out of the castle

3. On the base of the stand (where the Pb sits) there needs to be a brace that can be attached to the wall The length of the brace should be 6"? Figure A-4: Detector Shielding Design Parameters.

119 4 A steel skirt can be attached to three sides to prevent bending of the plate (not on the front side)

5 A frame built around the Pb walls 27"x27"x18"(height) The frame should not be tight fitting The frame must be able to support the lid which will open into two pieces at the center The lid weighs 753 Kg

6 The lid of the castle has dimensions 27"x25"x8" high It will open along a track located along the 27' side of the lid There are bearings provided The lid opens in the center and opens and closes like elevator doors The bottom of the lid which is the ceiling of the castle will consist of 1/4" copper sheet The design of the lid can be discussed for support requirements

track

25" Pb Pb

track I

• Bearings (wheels)

Figure A-4 continued: Detector Shielding Design Parameters.

120 Appendix D: Field Notes Pertaining to Sampling of Seaweed Samples in Shearwater

Table A-1: Field Notes Pertaining to Sampling of Seaweed Samples in Shearwater NS.

Location Sample Information The divers were at depths of up to 15 m (48 feet) but could find no samples here They went Jetty End inside the yellow boom (designed to trap oil spills) and through the camber as well Not enough light and the depths are too great A sediment sample was collected at 10 50

Samples were collected from the side of the diving barge that was tied up to the knee of the jetty The seaweeds were attached to the sides of the dock and to the mussels that were Jetty Knee growing along the sides The depths were therefore at around surface level Sample time was from 9 30-9 40 Four sample bottles were collected, one Sacchanna Latissima and three Ascophyllum Nodosum The sampling time was at 11 20 In this area there are diving training ropes (shallow jack stay) attached to the sea floor and the plants like to grow along these ropes There are also Jetty Land buoys that have chains attaching them to the seafloor with plants growing along these Three sample bottles were collected, two Sacchanna Latissima and one Ascophyllum Nodosum which was floating at the surface in the jetty land area Sample time was at 10 38 for approximately 10 mm The samples were taken at depths of 8 m (19 feet) or less Mainly on the white wave breakers Two sample bottles were collected Yacht Club of Sacchanna Latissima One of these bottles will be used for the ERMP plant There was also a sediment sample taken at this location The sampling time was at 11 08 In this area there are log fenders that the seaweeds like to Near Knee grow along The seaweeds grow both below the surface and on the top of the logs This at floating location was sampled because nothing could be found at the end of the Jetty Samples logs were taken off of the logs Two sample bottles were collected one of Sacchanna Labssima and one Ascophyllum Nodosum There were a total of 11 plant samples taken Five Ascophyllum Nodosum and six Totals Sacchanna Latissima

Many of the plants collected in Shearwater were near the surface of the water, often attached to floating objects such as a diving barge, wave breakers or floating logs The seaweeds were 121 also attached to mussels that were attached to the sides of the various sampling locations. The divers commented that a good place to obtain seaweeds was at Rec Cove (around 2 miles away from the Jetty) where the depths are shallower and there is a lot of sunlight. The divers also commented that there does not seem to be as many seaweed species in the winter months as in the summer months. Identification of the seaweeds and the organisms that were attached to the seaweeds (organisms were attached mostly to the Saccharina Latissima) were performed by Christopher Lane [85]. None of the organisms were parasites and therefore do not feed on the seaweed itself. On the surface of the blade of the Saccharina Latissima, there were white spirobids or tube worms. In the roots of some of the seaweed samples were orange organisms called tunicate. A tunicate only uses the seaweed's roots as a place to anchor much like the seaweeds use the mussels for anchoring. There was also an organism (not identified) that is a member of the starfish family that would cover the part of the surface of a blade of some of the Saccharina Latissima samples. This organism affects the uptake of iodine by the Saccharina Latissima since there is not as much surface area in contact with the seawater. Therefore these portions of the samples were avoided during sample preparation for 131I activity determination. Some bright green seaweed also grows from the side of the Saccharina Latissima, which was most likely Viva (a leaf like growth) which looked like a long thin blade.

122 Appendix E: Uncertainty in Background Calculation

The background area uncertainty is the uncertainty in the channels used to calculate the endpoints of the background multiplied by the ratio of the number of channels in the peak to the number of channels used to calculate the background. For wide peaks and low counts per channel, there is high uncertainty in the calculated background [83].

(background area)(peak width) ( (width of low average + width of high average)

123 Appendix F: 131I Uptake Results

Table A-2: Results of U1I Removal from Artificial Seawater By Fucus Gardner!. Fucus 66 Fucus 70 Fucus 68 Fucus 67 Fucus 65 Fucus 69 1011 Activity '•"I Activity 1J1I Activity 1J1I Activity ,J,I Activity 1J'I Activity Time /h /Bq mL"1 /Bq mL1 /Bq mL"1 /Bq mL"1 /Bq mL"1 /Bq mL"1 0 80 89 ± 5% 75 87 1 4% 77 881 5% 78 35 1 5% 84 0914% 78 71 1 4% 05 66 91 ± 5% 75 68 14% 78 29 1 5% 67 61 1 5% 47 82 1 5% 57 93 1 4% 1 54 52 ± 5% 69 41 15% 60 30 16% 59 28 1 5% 27 56 16% 29 89 1 5% 1 5 45 12 ±6% 65 57 1 5% 50 01 16% 48 92 1 6% 19 8417% 25 33 1 6% 2 39 23 ± 6% 58 78 1 5% 43 81 1 7% 41 38 1 6% 12 38110% 18 1017% 25 32 89 ± 7% 52 92 1 5% 35 1418% 35 42 1 7% 10 91 110% 13 8217% 3 28 28 ± 8% 51 00 1 5% 35 03 1 7% 31 68 1 7% 11 18110% 12 4718% 35 23 45 1 8% 47 36 1 5% 26 45 1 8% 30 1617% 9 73110% 12 1218% 4 23 25 ± 8% 45 69 1 5% 27 75 1 8% 26 31 1 7% 1014110% 11 60 1 8% 45 19 50 ±8% 41 03 1 5% 21 5019% 23 93 1 8% 11 12 110% 10 0918% 5 19 58 ±8% 38 60 1 6% 21 2519% 20 72 1 8% 9 041 10% 10 0019% 55 18 98 ±8% 35 32 1 6% 19 41 19% 19 5718% 9 481 10% 9 84 1 9% 6 16 07110% 34 21 1 7% 19 06110% 18 83110% 9 121 10% 7 56111% 21 13 1719% 20 85 1 8% 10 35114% 12 81 112% 1611 110% 22 70 1 7%

90 80 E • 66 70 • 70 i 60 +x m or 68 to 50 anr 40 fr x67 T 30 •d U ?,<) v*s x 65

Figure A-5: Removal of mI from Artificial Seawater by Fucus Gardner! (Plants Represented by Numbers in the Legend).

124 Table A-3: Results of B,I Removal from Artificial Seawater By Fucus Gardneri. Fucus 101 Fucus 104 Fucus 105 Fucus 109 Fucus 115 Fucus 139 1J11 Activity 131l Activity 1011 Activity 1J1I Activity ,0,l Activity ,J1I Activity Time /h /Bq mL1 /Bq mL1 /Bq mL1 /Bq mL1 /Bq mL1 /Bq mL1 0 57 18 ±4% 54 06 ± 5% 61 43 ± 6% 57 77 ± 6% 62 98 ± 5% 62 74 ± 6% 0 25 52 80 ± 5% 50 40 ± 6% 51 27 ± 6% 51 59 ± 6% 53 55 ± 5% 52 36 ± 6% 05 47 51 ± 5% 45 71 ± 6% 46 94 ± 6% 37 24 ± 7% 38 34 ± 6% 43 42 ± 7% 0 75 45 10 ±6% 40 79 ± 6% 45 43 ± 7% 36 95 ± 7% 35 77 ± 6% 43 59 ± 7% 1 37 70 ± 6% 34 02 ± 7% 33 43 ± 8% 26 64 ± 8% 35 01 ± 6% 42 38 ± 7% 1 25 39 65 ± 7% 29 65 ± 7% 36 19 ±7% 26 53 ± 8% 31 51 ± 7% 45 97 ± 7% 1 5 35 09 ± 7% 28 10 ±7% 34 83 ± 8% 22 59 ± 9% 30 57 ± 7% 36 68 ± 7% 2 32 28 ± 8% 27 66 ± 5% 28 22 ± 7% 20 86 ± 7% 24 79 ± 6% 27 78 ± 6% 25 31 15 ±8% 22 18 ±6% 29 58 ± 7% 17 23 ±7% 23 49 ± 6% 34 09 ± 6% 3 26 95 1 8% 20 93 ± 6% 28 05 ± 6% 16 71 ±8% 23 93 ± 6% 27 20 ± 7% 35 26 61 ± 8% 19 03 ±7% 29 24 ± 7% 17 08 ±8% 20 71 ± 6% 30 80 ± 8% 4 25 62 ± 9% 19 15 ±7% 24 92 ± 9% Data lost 21 58 i 6% 26 52 ± 7% 45 25 67 i 8% 20 34 ± 6% 24 03 ± 7% 16 97 ±8% 20 91 ± 6% 23 29 ± 7% 5 25 35 ± 9% 15 98 ±7% 29 65 ± 9% 15 17 ±8% 20 21 ± 6% 25 54 ± 8% 55 21 67 ± 4% 17 56 ±7% 27 04 ± 7% 14 60 ±9% 20 86 ± 6% 25 42 ± 8% 23 21 85 ± 4% 18 01 ±8% 22 71 ±11% 18 19 ±8% 21 11 ±7% 27 59 ± 8%

• 101 • 104 A 105 X109 X115 • 139

0 10 15 20 25 Time (/h)

Figure A-6: Removal of U,I from Artificial Seawater by Fucus Gardnen (Plants Represented by Numbers in the Legend).

125 Table A-4: Results of U1I Removal from Artificial Seawater By Fucus Gardneh. Fucus 102 Fucus 129 Fucus123 Fucus127 Fucus 128 Fucus 132 M1l Activity ,ail Activity 1J,I Activity ,J1I Activity 1011 Activity 1J1I Activity Time /h /Bq mL"1 /Bq mL"1 /Bq mL"1 /Bq mL"1 /Bq mL"1 /Bq mL'1 0 61.82 ±4% 64.29 ± 5% 74.15 ±6% 58.26 ± 6% 61.80 ±5% 63.06 ± 6% 0.25 56.13 ±4% 54.61 ± 5% 66.17 ±6% 53.90 ± 6% 59.33 ± 5% 55.20 ± 6% 0.50 51.45 ±5% 50.38 ± 5% 58.49 ± 7% 48.04 ± 6% 52.55 ± 5% 53.72 ± 6% 0.75 51.61 ±5% 48.72 ± 6% 57.01 ± 6% 49.02 ± 6% 50.52 ± 5% 54.57 ± 6% 1.00 48.41 ± 5% 42.58 ± 6% 52.89 ± 8% 42.19 ±7% 48.08 ± 6% 52.71 ± 6% 1.25 44.32 ± 5% 43.58 ± 6% 48.04 ± 7% 44.63 ± 6% 45.95 ± 6% 48.51 ± 6% 1.50 40.18 ±5% 39.19 ±6% 42.81 ± 7% 40.28 ± 7% 45.95 ± 6% 48.03 ± 7% 1.83 38.69 ± 5% 38.54 ± 6% 46.87 ± 7% 41.32 ±7% 39.87 ± 6% 40.40 ± 8% 2.17 39.68 ± 5% 36.73 ± 6% 39.07 ± 7% 34.74 ± 7% 38.23 ± 6% Data lost 2.50 36.55 ± 5% 34.17 ±7% 42.38 ± 7% 40.03 ± 7% 38.08 ± 6% 37.1019% 3.00 33.98 ± 6% 30.59 ± 6% 37.99 ± 7% 33.04 ± 7% 34.54 ± 6% 36.12 ±7% 3.50 32.71 ± 6% 28.89 ± 7% 39.01 ± 7% 28.22 ± 8% 35.37 ± 6% 38.52 ± 7% 4.00 31.95 ±7% 30.66 ± 7% 39.92 ± 8% 32.86 ± 7% 33.24 ± 7% 37.08 ± 7% 4.50 28.87 ± 8% 28.27 ± 7% 34.40 ± 8% 28.48 ± 8% 34.23 ± 7% 37.36 ± 7% 5.00 30.31 ± 8% 30.03 ± 7% 33.35 ± 7% 29.69 ± 8% 32.43 ± 7% 40.01 ± 9% 5.53 29.55 ± 8% 25.35 ± 7% 30.59 ± 7% 32.43 ± 7% 33.31 ± 7% 35.94 ± 9% 17.4 29.09 ± 8% 27.65 ± 7% 35.85 ± 9% 26.04 ± 8% 31.19 ±7% 37.68 ± 7%

80 • 102 ^-s 70 60 -*-* • 119 $ cr SO a PQ 127 40 1 ^ 30 n * J ^ ? xl28 V -•—n—•—n—^ •- •a 20 xl23

Figure A-7: Removal of U1I from Artificial Seawater by Fucus Gardneh (Plants Represented by Numbers in the Legend).

126 Table A-5: Results of U1I Removal from Artificial Seawater By Fucus Gardneri. Fucus 103 Fucus 130 Fucus 140 Fucus 143 Fucus 146 Fucus 147 1J1I Activity 1311 Activity 1J11 Activity 1J1I Activity 1011 Activity 1J1I Activity Time /h /Bq mL"1 /Bq mL"1 /Bq mL"1 /Bq mL"1 /Bq mL"1 /Bq mL"1 0 60 14 ±5% 60 56 ± 5% 64 48 ± 6% 55 02 ± 6% 66 03 ± 5% 73 44 ± 6% 0 25 49 69 ± 5% 58 96 ± 5% 58 04 ± 6% 54 16 ±6% 61 16 ± 5% 61 44 ± 6% 0 50 49 95 ± 6% 56 27 ± 5% 56 17 ±7% 54 84 ± 6% 59 62 ± 5% 58 09 ± 6% 0 75 48 44 ± 6% 50 44 ± 6% 49 45 ± 6% 46 79 ± 6% 54 87 ± 5% 52 06 ± 6% 1 00 52 46 ± 7% 52 12 ±6% 55 57 ± 6% 48 89 ± 6% 49 94 ± 6% 52 45 ± 7% 1 25 43 20 ± 8% 52 37 ± 5% 50 72 ± 6% 49 52 ± 6% 51 87 ± 5% 55 57 ± 6% 1 50 45 58 ± 7% 49 66 ± 5% 49 38 ± 6% 46 93 ± 6% 48 15 ±6% 50 50 ± 7% 2 00 43 49 ± 8% 50 45 ± 6% 40 63 ± 7% 48 75 ± 6% 45 70 ± 6% 45 36 ± 6% 2 50 43 75 ± 9% 42 48 ± 6% 44 39 ± 8% 41 92 ± 6% 48 14 ±6% 47 89 ± 6% 3 00 42 95 ± 9% 38 39 ± 6% 46 60 ± 7% 37 80 ± 6% 46 15 ±6% 49 60 ± 6% 3 50 45 00 ±10% 42 32 ± 6% 48 69 ± 7% 41 12 ±7% 48 70 ± 6% 43 76 ± 7% 4 00 39 65 ±11% 40 92 ± 6% 38 09 ± 8% 41 17 ±7% 40 07 ± 6% 41 76 ± 7% 4 50 38 39 ± 14% 36 26 ± 7% 38 51 ± 7% 40 66 ± 7% 41 46 ± 6% 43 01 ± 8% 5 00 39 25 ± 14% 42 13 ±6% 39 50 ± 8% 37 78 ± 7% 39 86 ± 6% 43 86 ± 7% 5 50 39 48 ± 14% 35 98 ± 6% 35 46 ± 7% 40 54 ± 7% 35 10 ±7% 41 33 ± 7% 22 37 08 ± 7% 31 62 ± 7% 33 66 ± 8% 25 66 ± 7% 31 67 ± 7% 34 29 ± 8%

Figure A-8: Removal of U,I from Artificial Seawater by Fucus Gardneri (Plants Represented by Numbers in the Legend).

127 Table A-6: Results of U1I Removal from Artificial Seawater By Fucus Gardner/'. Fucus 110 Fucus 111 Fucus 116 Fucus 117 Fucus 141 Fucus 144 1J1I Activity ,J1I Activity 1J1I Activity ,a,l Activity ldll Activity 1J11 Activity Time /h /Bq mL"1 /Bq mL"1 /Bq mL"1 /Bq mL1 /Bq mL"1 /Bq mL"1 0 50 73 1 7% 69 12 ±5% 97 96 ± 5% 122 2915% 151 77 ±4% 168 9314% 0 25 46 31 ± 7% 69 74 ± 5% 94 17 ±5% 103 2615% 137 01 ±4% 152 1314% 0 50 44 32 1 7% 59 97 ± 5% 78 88 ± 5% 88 38 1 5% 121 71 ±4% 124 1814% 0 75 35 76 1 9% 58 501 5% 76 96 ± 5% 81 85 ± 5% 122 7614% 120 2515% 1 00 34 51 ± 9% 54 75 ± 5% 67 52 1 6% 88 85 1 5% 109 8614% 114 61 15% 1 25 28 87 1 9% 50 72 ± 6% 57 54 ± 6% 64 35 1 6% 106 9814% 105 91 15% 1 50 28 23 1 9% 51 62 1 6% 55 47 1 6% 75 05 1 4% 100 0314% 105 9514% 2 00 27 35 ± 8% 43 96 ± 5% 58 59 ± 5% 73 68 1 4% 96 40 1 4% 91 22 1 4% 2 50 25 91 ± 8% 46 26 1 5% 57 09 1 5% 69 47 ± 4% 87 73 1 4% 83 23 1 4% 3 00 25 18 ±7% 37 22 ± 5% 49 56 1 5% 60 38 1 5% 78 64 1 4% 75 20 1 4% 3 50 20 71 ±8% 33 22 ± 5% 43 88 1 5% 59 78 1 5% 75 37 1 4% 69 23 1 4% 4 00 20 29 1 8% 32 64 ± 5% 43 84 ± 5% 50 87 1 5% 66 94 1 4% 65 96 1 4% 4 50 19 41 ±10% 30 01 ± 6% 46 03 ± 5% 49 87 1 5% 67 24 1 4% 60 27 1 5% 5 00 17 8619% 32 72 1 6% 43 58 1 5% 45 74 1 5% 64 68 1 4% 57 59 1 5% 5 50 17 51 ±9% 27 08 ± 6% 41 83 1 5% 45 59 1 5% 60 03 1 4% 54 22 1 5% 22 15 70 ±10% 20 96 ± 6% 33 19 ±6% 34 84 ± 6% 44 14 1 5% 42 33 1 5% 50 8 95113% 18 99 ±7% 30 55 ± 7% 24 73 1 5% 45 45 1 5% 38 1616% 72 17 09 ±7% Data lost 52 41 ±5% 33 91 1 5% 51 03 1 4% 46 1816%

180 o 160 ::•

^H 140 X i 120 II t§ • 110 cr 100 • *•§ • 117 a i 80 -_-• i 111 fr A! • • 4 $ • • X X 1 60 *•X v X X • xll6 u X • 1 1 < X X 1 40 • *141 •••• • • • 20 • • • • • 144 0 0 4 6 8 10 Time (/h)

Figure A-9: Removal of131! from Artificial Seawater by Fucus Gardnen (Plants Represented by Numbers in the Legend). 128 Appendix G: Fission and Activation Product Uptake in Fucus Gardner! Table A-7: Results of Fission Product Uptake By Fucus Gardneri.

1 L reactor Container Water 4 Hour Exosure Fucus 8 Hour Exposure Fucus 24 Hour Exposure Fucus Time Corrected 1 Sigma Time Corrected 1 Sigma Time Corrected 1 Sigma Time Corrected 1 Sigma Nuclide Activity Total Activity Total Activity Total Activity Total Bq Error/(%) Bq Error/(%) Bq Error/(%) Bq Error /(%) Iodines 1-131 7 59E+00 313E+01 1 03E+00 1 51E+01 1 19E+00 4 81E+00 1 44E+00 1-133 2 40E+01 813E+00 3 62E+00 5 68E+00 3 85E+00 3 58E+00 3 62E+00 4 05E+00 1-135 <2 64E+01 5 26E+00 3 65E+01 8 89E+00 1 99E+01 1 14E+01 Metals Na-24 2 70E+03 2 56E+00 5 33E+02 2 42E+00 5 20E+02 2 41E+00 5 68E+02 2 41E+00 Mn-54 <7 70E+00 3 49E+00 8 25E+00 3 93E+00 3 68E+00 413E+00 3 54E+00 Mn-56 4 07E+02 3 28E+00 2 38E+02 2 60E+00 2 71E+02 3 31E+00 <2 48E+03 >12halflives Co-60 <4 01E+00 1 20E+00 2 05E+01 1 08E+00 8 61E+00 1 14E+00 5 37E+00 Sr-91 <4 30E+01 210E+01 4 60E+00 2 59E+01 4 34E+00 2 61E+01 6 47E+00 Mo-99 2 35E+01 5 23E+00 8 28E-01 1 11E+01 3 37E-01 1 12E+01 3 21E-01 8 63E+00 Ru-103 <5 34E+00 <3 37E-01 <1 29E-01 9 78E-02 2 97E+01 Ag-110M <6 20E+00 6 02E-01 2 25E+01 6 53E-01 9 37E+00 6 44E-01 5 71E+00 Ba-140 <2 07E+01 7 84E+00 1 01E+01 812E+00 4 84E+00 8 30E+00 3 65E+00 La-140 <3 25E+00 1 10E+00 1 74E+01 2 54E+00 4 88E+00 7 39E+00 3 09E+00 Cs-138 7 37E+01 9 85E+00 <3 86E+02 <2 52E-01 >12halflives <1 12E-01 >12halflives Np-239 4 84E+01 5 57E+00 3 22E+01 2 09E+00 2 97E+01 1 92E+00 2 73E+01 1 93E+00 Noble Gases Ar41 4 05E+04 2 55E+00 1 19E+02 3 27E+00 9 47E+01 1 19E+01 1 29E-01 >12halflives Kr-85 3 52E+04 3 57E+00 5 75E+02 1 01E+01 3 76E+02 6 65E+00 1 56E+02 8 35E+00 Kr-85M 1 05E+01 1 80E+01 <6 34E-01 <5 03E-01 <8 54E+00 Kr-88 6 76E+01 1 63E+01 <1 80E+01 <4 58E+01 <1 69E+03 Xe-133 2 63E+01 9 29E+00 <5 13E-01 4 45E-01 1 47E+01 2 91E-01 1 56E+01 Xe-135 2 79E+01 7 05E+00 1 11E+00 1 36E+01 1 41E+00 1 26E+01 1 31E+00 2 74E+01 Xe-135M 4 68E+00 3 78E+01 <6 57E-01 >12halflives <4 37E-01 >12halflives <1 44E-01 >12halflives

130 Curriculum Vitae

131 Curriculum Vitae

Name: Kristine Margaret Mattson

Place and Date of Birth: Sudbury, Ontario - April 17 1977

Education: Queen's University Kingston, Ontario Bachelor of Applied Science, Materials and Metallurgical Engineering May 2000.

Royal Military College Kingston, Ontario Master of Applied Science in Nuclear Engineering August 2011.

Current Position: Royal Military College Kingston, Ontario Chemistry/Nuclear Technologist and SLOWPOKE-2 Reactor Operator

132