Radiological Assessment of REX Minerals Hillside Project

Transcription

1 Radiological Assessment of REX Minerals Hillside Project Report prepared by: Trevlyn Radiation and Environment ABN: Report prepared for: REX Minerals LTD 1

2 TABLE OF CONTENTS Contents Report prepared by:... 1 Trevlyn Radiation and Environment... 1 ABN: REX Minerals LTD... 1 List of Figures... 3 List of Tables... 3 Executive Summary... 4 Findings... 4 Acknowledgements... 6 INTRODUCTION... 7 Project Objectives... 7 Project Background... 7 Radiological exposure pathways Ionising radiation Natural Radiation Exposures Inhalation of radon progeny External gamma exposure through mining Inhalation and ingestion Dust Ingestion Drinking water Results Radon Airborne radon concentration Radon emanation Exposure to external gamma radiation Inhalation and ingestion Dust Soil Scrapes Ingestion of radionuclides Dietary Intake Concentration factors Surface water and ground water Surface water

3 Groundwater References Appendices List of Figures Figure 1: Location of the REX Minerals Hillside Project Yorke Peninsula, South Australia Figure 2 Uranium-238 decay series Figure 3 Contour maps for four quarters radon measurement Figure 4 Track etch detector results from February 2012 to January 2013 (mbqm -3 ) Figure 5 Radon cup locations and contour lines displaying emanation values Figure 6 Gamma levels measured at the REX Hillside project over the proposed pit area Figure 7 Soil surface scape sample locations that were collected in association with the PRM s Figure 8 Ratio of 222 Rn flux densities from emanation and airborne radon to 226 Ra soil activity concentrations from the 5 scrape locations (mbq m 3 s -1 )/( Bq kg -1 ), Figure 9 Plot of 222 Rn flux densities vs 226 Ra activity concentration for all sites Figure 10. Location map of the biota samples collected at the Hillside project Figure 11 Surface water and groundwater sampling locations at the Hillside project area Figure U activity concentrations for groundwaters at the Hillside project Figure U activity concentrations for groundwaters at the Hillside project List of Tables Table 1 Description of Passive Radon Monitor sampling sites and their sampling periods Table 2 PRM radon results and average results for Hillside Table 3 Average results for radon emanation data collection on the 25/01/13 (5 cups per site) Table 4 Average absorbed gamma dose rates (µgy h -1 ) for background (five kilometres north of Hillside) and proposed Hillside project pit area Table 5 Results for analysis of the high volume air samples Table 6 Sample scape results from eight locations (Bq/kg) Table 7 Average radon flux densities [mbq m-2 s-1] and associated standard deviations (n=3), soil 226 Ra activity concentration [Bq kg-1] and associated standard deviation due to counting statistics, and 222 Rn/ 226 Ra [(mbq m-2 s-1)/(bq kg-1)] measured at the Hillside project area Table 8 Biota sample physical information collected for Hillside Table 9 Radionuclide results for biota samples Hillside project Table 10 Radionuclide results for the soils taken with the biota samples and from soil scrapes Table 11 Concentration factors for Hillside biota samples Table 12 Radionuclide results for unfiltered surface water results (mbq/l) Table 13 Physical water quality results for groundwater at the Hill side project area Table 14 Radionuclide results for filtered (<0.45 um) groundwater samples mbq/l Appendix A1 Results for gamma radiation survey of REX Hillside proposed pit area

4 Executive Summary Trevlyn Radiation and Environment was commissioned by REX Minerals to determine the baseline radiological conditions at its Hillside Iron Ore Gold Copper Project on the Yorke Peninsula in South Australia. This assessment was needed to determine the current radiological levels at the project so decisions and assurances can be made for mine construction, mine operations and mine closure of the project. Proposed pit terrestrial gamma levels have been derived from a ground gamma survey that was conducted in Airborne radon concentration and radon emanation measurements were conducted and the dust radionuclide activity concentration was measured for the inhalation pathway. Ingestion information was also gathered biota samples being collected from the local area and analysed for radionuclides and the concentration factors calculated. Findings Averaged absorbed dose rate across the pit area from terrestrial gamma radiation is μsv hr -1, which is approximately equal to the background absorbed dose rate of μsv hr -1. There were no areas of above background radiation levels measured during the gamma surveys. Airborne radon concentrations and radon exhalation flux densities across the site were measured using passive radon track etch detectors and charcoal canisters. The annual average radon activity concentration in the air at the Hillside project area was determined to be Bq m -3. During the year monitored the area investigated did not exceed the Australian reference level of 200 Bq m -3 for indoor airborne radon activity concentration in new or existing dwellings. Although it does not apply for outdoor situations, all sites measured across the entire project area at Hillside exhibit airborne radon concentrations below this level throughout the year Radon flux densities from emanation data collection using charcoal cups are low with total radon flux from the site amounts to Bq m -3. The values returned by analysis are low, and are comparable to average global values of 15 to 23 mbqm -2 s -1 (UNSCEAR 1982) and average values for Australia of 22 ± 20% mbqm -2 s -1 (Schery et al 1989). 226 Ra levels were measured in the soil scrapes that were collected. These radon levels correlate with the levels of 226 Ra in soils. The gamma spectroscopy analysis of the airborne dust samples for the dust inhalation pathway were low, or below detectable levels. This pathway may play a more important role if or when the site becomes operational as activities such as mining and Plant operations occur. For the ingestion pathway biota samples have been collected during 2012 from the REX site and surrounding areas. An array of biota samples including meat (fish, rabbit, beef and lamb) and crops (canola, wheat and barley) were collected from the surrounding farms and sent for analysis to Australian Radiation Services laboratories for radionuclide analysis. These analyses included total U, 226 Ra, 210 Po and 210 Pb For the meat and crop samples the radionuclide concentrations were within an order of magnitude of each other with uranium concentrations being higher than the other 4

5 radionuclides. The levels of radionuclides in foodstuffs grown in the local area are generally low (Table 8) and close to the level of detection. Concentration factors were calculated for the biota samples as well as whole-body to tissue concentration ratios. These concentration factors will allow for a full dose assessment for both humans and animals to be conducted in the surrounding areas and provide vital baseline information for any future comparisons. With its relatively low rainfall and long, dry summers, South Australia depends heavily on water flowing down the River Murray to meet its requirements. In the Hillside project local area, drinking water is taken from Swan Reach-Stockwell Pipeline which is supplied from the River Murray. Both groundwater and surface waters were collected from the project site and analysed for radionuclide activity concentrations. The activity concentrations for 226 Ra, 238 U, 234 U, 210 Pb and 210 Po for were measured for the unfiltered surface waters at Hillside. All results for the radionuclides for surface water are low with the uranium levels below the Australian drinking water standards for U of 17 μg per litre (equivalent 210 mbq 238 U per litre. Conductivity results illustrate the high salts in the groundwaters making these waters not fit for human consumption. These levels are to be expected because of the sites relative location to the ocean. There is a trend showing the 238 U and 234 U uranium activity concentration higher over the pit. The levels of 226 Ra activity concentrations are low overall, but there is a slight increase closer to the coastal zone which maybe be caused by radium tendency to be more mobile in higher salt water conditions. 210 Pb and 210 Po activity concentrations in the groundwater are low in the area. The Australian Drinking Water Guidelines recommends guideline values for Radium-226 are both 0.5 Bq/L. Only four from the twelve groundwater samples were below the recommended drinking water guideline values for 226 Ra. This baseline radiological information will serve as a basis for comparison with the subsequently acquired data throughout mine life. This information will be invaluable during mine operation and in particular mine closure and subsequent rehabilitation. The radiological information can also be used in conducting dose assessments for both human and non-human biota. 5

6 Acknowledgements We wish to thank Mr David McLean and Mr Sam Germein from Rex Minerals Compass Resources, who were always helpful in providing logistical support and assisted in sample collection during our field campaign in 2012 and

7 Introduction Project Objectives This baseline radiological report has been prepared by Trevlyn Radiation and Environment (TRE) for REX Minerals Ltd (REX) for exploration and resource definition works being conducted on their Hillside copper/gold project near Ardrossan on Yorke Peninsula in South Australia. Hillside is an Iron Ore Copper Gold (IOCG) project that has small quantities of uranium contained within the mineralisation. This uranium is not of any economic value and concentrations are mostly below the exemption limit for uranium as set out in schedule 4 of the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) National Directory. As such the radiation risks associated with exploration and resource definition at Hillside are low. This baseline study has been designed and the associated report prepared according to this low risk category. This report presents a summary of the pre-development levels of radionuclides and ionising radiation in the environment of the Hillside Project area. The purpose of the baseline radiological monitoring programme was to assess the naturally occurring local radiation levels and concentrations of radionuclides in selected environmental media in order to: Provide an understanding of pre-development spatial and temporal variations in radionuclide concentrations Establish baseline measurements in the area against which changes due to the development of the mine and associated facilities can be assessed Define potential pathways of radionuclide movement and radiation exposure in the vicinity of the site thereby providing a basis for prediction of radiological impact for operational and post-operational phases of mine development Provide radiological information that can be used for a baseline radiological dose assessment for both workers at the site and members of the public living around the site The results of the inter-related radiation monitoring programmes are presented for the following parameters: External gamma-radiation due to terrestrial sources Radon and radon decay products in air Long-lived radionuclides in environmental samples Naturally occurring radionuclides in plant and animal tissue This monitoring data can be combined with information on demography and natural resource usage in order to estimate the radiological exposure of local people, and provide a basis for prediction of exposures during the operational period of the mine and after closure. The recent environmental monitoring and sample collection was conducted over a twelve month period covering any potential seasonal variations. Project Background REX Minerals Ltd is a publicly listed Australian based company formed in 2007 with exploration projects in the Yorke and Eyre Peninsula regions of South Australia. The 7

8 head office of REX Minerals is located in Ballarat, Victoria, with subsidiary offices in Adelaide and on Yorke Peninsula in South Australia. REX is currently finalising a drilling program at their Hillside copper/gold project near Ardrossan on Yorke Peninsula in South Australia as part of Pre-Feasibility and Definitive Feasibility Studies being undertaken successively to report the viability of the project for mining. The Hillside project is located approximately 13km south of Ardrossan on Yorke Peninsula in South Australia in coastal agricultural land (Figure 1). There are two settlements nearby, Pine Point which is approximately 2 km away and Black Point approximately 8km from the site. There are also occupied farming dwellings within a 2 km radius on properties adjacent to the tenements. The project is approximately 80km north west of Adelaide which lies across the Gulf St Vincent; the journey by road is approximately 150km. Figure 1: Location of the REX Minerals Hillside Project Yorke Peninsula, South Australia. The Hillside deposit is approximately 2500 metres long and 800 metres wide at the broadest point, lying close to the surface and extending down to a depth of 500 metres. It lies parallel to the coastline at a distance of approximately 800 metres. The deposit is located in arable cropping land and lies across two previously separate properties which have been recently acquired by REX. The land is cleared and fenced, with belts of vegetation adjacent to several roads that bound and cross the deposit. REX Minerals has acquired the southern property on which the majority of the deposit lies, and the homestead is utilised as the site operational base and accommodates site based REX Minerals administrative and management staff. 8

9 Sheds have been converted for core handling and storage while other personnel operate from transportable office buildings. Running along the eastern edge of the site is the major highway connecting eastern and southern Yorke Peninsula to the rest of South Australia. A road running SW-NE through the deposit connects Ardrossan and Minlaton. Both roads are heavily used by local traffic, with activity on the main road peaking during the summer holiday season. A significant surface outcropping of uranium rich material exists on the shoreline directly east of the Hillside deposit, described in historical documentation as the Dead Horse Bay uranium deposit; while REX Minerals has no intention of conducting any activities proximal to the outcrop, it enhances the understanding of local geology and baseline radiological exposures. Although Hillside is primarily a copper and gold deposit, the average grade of uranium within the inferred resource boundaries is 57ppm with a maximum encountered intersect of 10,100ppm. While the overall concentration of uranium is below that which would trigger the requirement for submission of a Radiation Management Plan, REX has elected to proceed with a radiation risk assessment and Radiological Baseline Study along with development and implementation of a Radiation Management Plan as part of due diligence and good corporate citizenship. The development and implementation of these management tools is an acknowledgement of the sensitivity of the environs in which the Hillside Project is located. REX has undertaken ongoing exploration and development programs within the Hillside Project tenements. The ongoing work has been undertaken with specialist contractors and drilling contractors using diamond and percussion drilling equipment to define the economic resources within the project tenements. The initial phase of the project took approximately 14 months, with finalisation of the pre-feasibility study in November Following this, REX advanced to a Definitive Feasibility Study with a target completion date of November Should the project prove viable, regulatory approvals will be sought and development pursued with construction of the mine beginning no earlier than Should mining activities commence, current resource evaluation estimates that Hillside is expected to have an operational life exceeding 12 years. Specialist and supervisory capabilities are provided by REX Minerals employees including geologists, management and administrative staff In addition to drilling, exploration activities may include any or all of the following: Down hole geophysical logging; Analysis of historical samples; Collection of rock chip samples; Collection of soil samples; Collection of water samples; Various ground geophysical survey techniques (e.g. seismic); and Core cutting. 9

10 The majority of the Geology Field Assistants employed to undertake core handling and logging are supplied by a contractor and work under the direction of REX geological personnel. Radiological exposure pathways Ionising radiation Ionising radiation represents electromagnetic waves and particles that can ionise:, that is, remove an electron from an atom or molecule of the medium through which they propagate. Ionising radiation may be emitted in the process of natural decay of some unstable nuclei. Naturally occurring radionuclides in soil, uranium ore, air etc. emit three types of ionising nuclear radiation: alpha radiation, beta radiation and gamma radiation. All three types of radiation cause either direct or indirect ionisation. The process of ionisation in living matter changes atoms and molecules, at least transiently, and may thus damage cells. If cellular damage does occur and is not adequately repaired, it may prevent the cell from surviving, reproducing or performing its normal functions. Alternatively, it may result in a viable but modified cell. The basic quantity used to express the exposure of material such as the human body is the absorbed dose, for which the unit is the Gray (Gy). However, the biological effects per unit of absorbed dose vary with the type of radiation and the part of the body exposed. To take account of those variations, a weighted quantity called the effective dose is used, for which the unit is the Sievert (Sv). A radioactive source is described by its activity, which is the number of nuclear disintegrations per unit of time. The unit of activity is the Becquerel (Bq). One Becquerel is one disintegration per second. Natural Radiation Exposures All living organisms are continually exposed to ionising radiation, which has always existed naturally. The sources of ionising radiation exposure include: cosmic rays that come from outer space and from the surface of the sun; and terrestrial radionuclides that occur in the Earth s crust as well as in building materials and in air, water and foods and in the human body itself. Some of the exposures are fairly constant and uniform for all individuals everywhere - for example, the dose from ingestion of potassium-40 in foods. Other exposures vary widely depending on location. Cosmic rays, for example, are more intense at higher altitudes and latitudes, and natural concentrations of uranium and thorium in soils are elevated in some areas relative to others. Exposures can also vary as a result of human activities and practices. In particular, the building materials of houses and the design and ventilation systems strongly influence indoor levels of the radioactive gas radon and its decay products, which contribute significantly to doses through inhalation. The average global exposure does not pertain to any one individual, since there are wide distributions of exposures from each source and the consequent effective doses combine in various ways at each location, depending on the specific concentration of radionuclides in the environment and in the body, the latitude and altitude of the location and many other factors. The annual worldwide effective dose is determined by adding the various components, as summarized UNSCEAR, 2000 (Table 6-36). The annual global effective dose due to natural radiation sources is on average 2.4 msv. However, the range of individual doses is wide. In any large population about 65% would be expected to have annual effective doses between 1 msv and 3 msv. About 25% of the population would have annual effective doses less than 1 msv and 10% would have annual effective doses greater than 3 msv 10

11 Inhalation of radon progeny Figure 2 Uranium-238 decay series. Background The radon inhalation pathway has been identified in many studies as the main contributor to public radiation dose received from a practice such as uranium mining and milling. This is particularly true for permanent habitation occurring on or in the immediate vicinity of a mine site. Although this is not a uranium mining operation it still has the potential to generate radon concentrations above background levels. 222 Rn is a radioactive noble gas and a member the natural 238 U decay chain (Figure 2). As the immediate progeny of 226 Ra its production and subsequent soil exhalation rate depends, in part, on the soil 226 Ra activity concentration. It also depends on soil type, soil porosity, soil moisture and the depth of the water table, which impedes the flow of soil gas. Consequently, radon flux densities can show large seasonal variations, due to the vast differences in rainfall between seasons (Lawrence, 2005). Radon diffuses into the atmosphere and decays with a half-life of 3.8 days via a number of short-lived progeny to 210 Pb with a half-life of 22.3 years. In contrast to radon gas, which is immediately exhaled again, some of the radon decay products (RDP) are retained in the soft tissue of the lungs after inhalation and their subsequent alpha decay delivers a dose to the respiratory system. A measure for the dose that may be delivered via the inhalation of RDP is the potential alpha energy concentration (PAEC), which gives a measure for the potential energy originating from the alpha decays of RDP in air. 11

12 Airborne radon concentration shows large seasonal and diurnal variations as well (Bollhöfer et al., 2004; Martin et al., 2004; Lawrence, 2005). These are caused by meteorological parameters such as wind speed and direction, rainfall and humidity and barometric pressure. Day to day variations can be quite large and average daily airborne radon concentrations can vary by a factor of 25 in extreme cases (Bollhöfer et al., 2004). Radiation doses to man from the inhalation of radon progeny can be determined from the radon gas concentration in the air via the following equation: E RDP = h RDP C RDP t With: E RDP : effective dose due to the inhalation of radon decay products [ Sv] h RDP : dose conversion factor [ Sv ( Jh m -3 ) -1 ] C RDP : radon progeny potential alpha energy concentration, PAEC [ J m -3 ] t: inhalation time. The radon progeny PAEC can be determined from the radon concentration measured using an appropriate equilibrium factor: F. Akber and Pfitzner (1994) for example have determined an equilibrium factor of for the Top End of Australia. Extensive measurements in recent years in Europe, the United States, Canada and Japan indicate typical outdoor radon equilibrium factors of between 0.5 and 0.7. These results suggest that a rounded value of 0.6 may be more appropriate for the outdoor environment than an earlier estimate of 0.8. There is, of course, a wide range of values from specific area measurements, which is understandable given the many environmental factors that influence the various radionuclide activity ratios, including the exhalation rates and atmospheric stability conditions. The range of the equilibrium factor for outdoor radon is from 0.2 to 1.0, indicating a degree of uncertainty in the application a typical value to derive equilibrium equivalent concentrations. For any assessment for this project, an equilibrium factor of 0.6 could be assumed. The radon PAEC is then calculated from the measured radon concentration via: C RDP (μj m -3 )= 0.6 C Rn (Bq m -3 )/3700(Bq m -3 ) 20.8 (μj m -3 ) (3) With: C Rn : radon concentration [Bq m -3 ]. The total annual effective dose from radon (a world-wide average value) is 1.1 msv from inhalation of 222 Ra and its decay products present in air from all sources, 0.05 msv from radon gas dissolved in blood, and msv from radon gas in ingested tap water. This equates to a total of 1.15 msv. The estimates for thoron ( 220 Rn) from the 232 Th decay chain are 0.09 from inhalation of thoron and its decay products and 12

13 0.01 from thoron gas dissolved in blood (total = 0.10 msv). This is an order of magnitude lower than radon. The dose conversion factor h RDP recommended by the International Commission on Radiation Protection (ICRP, 1993) is 1.1 Sv ( J h m-3) -1 (for radon in equilibrium with progeny), which translates to 6.18 nsv (Bq h m -3 ) -1. The dose conversion factor recommended by UNSCEAR (2000) is 9 nsv (Bq h m -3 ) -1 for dose calculations from the inhalation of radon in equilibrium with its progeny, assuming an average daily breathing rate of 22.2 m 3 per day for an adult male. This is approximately 45 per cent higher than the ICRP (1993) recommended conversion factor. For the calculation of doses received from the inhalation of radon progeny it is recommended the UNSCEAR (2000) dose conversion factor be assumed in this area for any dose assessments. Radon exhalation To identify major sources of radon on the Hillside project site, radon exhalation flux densities were determined across the site. Soil radon exhalation flux densities were measured using charcoal canisters and Passive Radon Monitors (PRMs) were used to measure airborne radiation. The charcoal canisters or cups are made from brass, with an area of approximately 30 cm 2, and are deployed across monitoring sites, pressed into the ground or adhered to the ground surface using a putty to make an air tight seal and left to collect exhaling radon for several days. Radon is adsorbed onto the activated charcoal and after an appropriate in-growth time of a less than 72 hours, the decay of radon progeny was measured using a NaI(Tl) gamma detector calibrated for the respective cup geometry. A recent study in Northern Australia has shown that the radon exhalation can depend on geomorphological attributes and features of the soil, such as vegetation, soil grain size and porosity. Radon exhalation conversion factors have been determined for geomorphological units in the Northern Australia that allow predicting radon exhalation from given soil 226Ra activity concentration (Lawrence, 2005). Feasibility studies have been performed previously, and found that track etch detectors provide a means to determine average radon gas levels over periods of a few months. They have routinely been used in projects across Australia and worldwide. Airborne radon Passive Radon Monitors are typically small plastic containers that have a plastic film that becomes etched by the alpha particles that strike it. Radon gas is allowed to enter the device through small openings covered by a filter. Once the radon gas is inside, it will decay. The small particles thrown off by the radon gas during decay will hit the plastic detector and cause a tiny dent on the plastic surface. After the deployment period, the device is collected and sent to the laboratory where the plastic detectors are removed and chemically etched to make the small dents easier to see under a microscope. The marks are counted and the number of marks are proportional to the amount of radon gas the device had been exposed to. External gamma exposure through mining The mining process can lead to above background radionuclide concentration and assuming occupation of the site by workers during the life of mine operations and 13

14 habitation of the site after mine closure, the baseline average external gamma doses across the whole site should be determined. All potentially affected areas should be surveyed for background gamma levels before operations begin and monitored throughout mine life and beyond. These levels are essential for the accurate calculation of pre, during and post mining dose calculations. Measurements at the Ranger Uranium Mine reported by ERA in 2004 (Supervising Scientist Division Annual Report, 2004) showed that the gamma exposure pathway can be significant for mine workers in pits and for those spending significant time in areas with elevated soil concentrations of radionuclides. The relative contribution from the external gamma pathway can amount to up to two thirds of the total radiation dose received if levels are elevated. The level of external gamma radiation, or the dose rate in micro Grays per hour (μgy hr -1 ), can be measured directly using conventional Geiger Müller tubes, or calculated from the 238 U, 232 Th and potassium 40 K activity concentrations in the soils 1. Inhalation and ingestion Internal exposures arise from the intake of terrestrial radionuclides by inhalation and ingestion. Doses by inhalation result from the presence in air of dust particles containing radionuclides of the 238 U and 232 Th decay chains. The ingestion pathway via the ingestion of foods may be a potential significant contributor to radiological dose if elevated levels of radioactivity are present in the environment. Dust Inhalation intakes of dusts containing uranium or thorium are determined from measurements of the alpha activity associated with airborne dust particles. In mines and processing facilities for which there is a possibility of receiving significant doses from the inhalation of radioactive dust, regular monitoring for airborne radioactive dust should be performed. In deciding on the frequency of this monitoring, the concentrations of radioactive dust, its size distribution and the potential for its inhalation or ingestion should be taken into account. The levels of exposures that are predicted due to the concentrations of radioactive dust will be a key factor in deciding the nature and extent of any individual monitoring programme necessary. Radiological activity in airborne dust generated by mine operations is generally monitored using air sampling techniques in which particles of dust are captured by drawing the air through a filter. Monitoring for dose assessment purposes may be conducted using personal air samplers or workplace air samplers, Personal samplers consist of a small filter holder and a compact, battery powered pump. Dust particles captured on an air sampling filter are analysed by measuring the activities of alpha emitting radionuclides in the 238 U, 235 U and 232 Th series. Gross alpha counting is widely used for routine analysis where there is direct or indirect information about the likely radionuclide composition: for ore dust, unless there is reason to suspect that the ore body is seriously out of equilibrium, it can generally be 1 The derived dose rates are terrestrial gamma dose rates and do not include the cosmic dose rate component. Since the cosmic dose is natural, it does not need to be considered in this assessment. The cosmic dose rate has been determined for Australia and amounts to 0.07 μgy hr

15 assumed that all the radionuclides in the relevant decay series are present in 2 radioactive equilibrium at the time of sampling.. In this study radiometric analysis of individual radionuclides in dust samples were performed. These analyses involved radiochemical separation and high sensitivity measurement techniques, which are more accurate than gross alpha counting methods. Measurements of individual radionuclides were made to characterise the radionuclide composition of the dust from particular sources around the site. Bollhöfer et al (2006) have determined that the dose from the inhalation of mine origin dust in the vicinity of Ranger Uranium Mine is less than 0.01 msv per year. However, this can vary dramatically should activities on site occur such as blasting, drilling and digging, and workers might be exposed to increased levels of radionuclides in the air, or so called long lived alpha activity (LLAA). Measurements at Ranger Uranium Mine reported by ERA in 2004 (Supervising Scientist Division Annual Report, 2004) show that workers such as cleaners or people working in the mill, receive the highest radiation doses (up to three quarters of the total dose) from the inhalation of radioactivity trapped in or on dust. The airborne activity concentration can also be estimated using an equivalent soil concentration S E, defined as the ratio of the concentration of a radionuclide in air C a (Bq m -3 ) to that in the soil C s (Bq kg -1 ) (Nicholson, 1988): S C / C E a s (4) Akber (1992) has determined S E for the Alligator Rivers Region to be ~ (Bq m - 3 air)/(bq kg -1 soil) in the vicinity of Jabiru and Jabiru East. This value however, can vary by orders of magnitude should activities occur that stir up dust and soil particles. From the measured dust long lived alpha activity concentration, C LLAA, the radiation dose received from the inhalation of dust can be determined using: E LLAA = h LLAA C LLAA r t With: E LLAA : effective dose due to the inhalation of dust ( Sv) H LLAA : dose conversion factor ( Sv Bq -1 ) C LLAA : long lived alpha activity concentration (Bq m -3 ) r: breathing rate (m 3 h -1 ) t: inhalation time (h). 2 In nuclear physics, secular equilibrium is a situation in which the quantity of a radioactive isotope remains constant because its production rate (e.g., due to decay of a parent isotope) is equal to its decay rate. 15

16 In most operations in the mining and processing of raw materials, measures are taken for dust control to protect workers against hazards associated with nonradioactive dust. These measures generally restrict the airborne concentrations of radioactive dust sufficiently to meet the requirements for dose limitation. The effective dose from inhalation of 1mg uranium ore of an ore grade of 0.1% U is 0.42µSv (for higher ore grades, the dose increases correspondingly). The 20mSv annual standard is equivalent to 47.6g. This corresponds to a uranium ore concentration in air of 16.5mgm -3 (based on ICRP68 dose factors for insoluble compounds, breathing rate of 1.6m 3 h -1, working time of 1800 ha -1, U-238 in equilibrium with progeny) inhalation of uranium ore dust represents typically 3.2% of the total dose for underground miners, and 6.2% for open pit miners (UNSCEAR 1993). Ingestion The ingestion pathway via foods may be a potential significant contributor to radiological dose during operations and in particular after mine closure when remediated lands are used by local user groups. Site specific baseline data are needed to determine the dose received from the ingestion of foodstuffs growing on site before operations begin and are invaluable in gleaning information from any change in dose, whether perceived or real through mine life and after mine closure. Little work has been done on the uptake of radionuclides into foods across Australia, however a knowledge base exists with the IAEA and various reports. These results are mainly for agricultural products produced in Europe but can be used as default values in any ingested dose assessments. To enable a realistic radiological assessment to be made of the ingestion pathway it is essential to have good information on the importance of local food items in the diet profiles. The site use and the site use expectations of the local user groups after cessation of mining must also be determined. This terrestrial pathway becomes more important, specifically should the site be handed over for agricultural and or human habitation after rehabilitation of the site. Drinking water With its relatively low rainfall and long, dry summers, South Australia depends heavily on water flowing down the River Murray to meet its requirements. In the Hillside project local area, drinking water is taken from Swan Reach-Stockwell Pipeline which is supplied from the River Murray. Local supplies may also be supplemented from rainwater systems, such as tanks etc. For the purpose of this study both surface water and groundwater samples were collected and analysed.. 16

17 Results Radon Table 1 gives the locations of the passive radon monitors and their exposure time from the 1 st February 2012 to the 24 th January The locations are shown in Figure 3. Table 1 Description of Passive Radon Monitor sampling sites and their sampling periods. Sample Eastings Northings System Quarter 1 No. Quarter 2 No. Quarter 3 No. Quarter 4 No. ID Exposure Days Exposure Days exposure Days exposure Days M GDA94 1-Feb-12 to 29 Apr Apr 12 to 26 Jul Aug 12 to 30 Nov Nov to 24 Jan M GDA94 1-Feb-12 to 29 Apr Apr 12 to 26 Jul Aug 12 to 30 Nov Nov to 24 Jan M GDA94 1-Feb-12 to 29 Apr Apr 12 to 26 Jul Aug 12 to 30 Nov Nov to 24 Jan M GDA94 1-Feb-12 to 29 Apr Apr 12 to 26 Jul Aug 12 to 30 Nov Nov to 24 Jan M GDA94 1-Feb-12 to 29 Apr Apr 12 to 26 Jul Aug 12 to 30 Nov Nov to 24 Jan M GDA94 1-Feb-12 to 29 Apr Apr 12 to 26 Jul Aug 12 to 30 Nov Nov to 24 Jan M GDA94 1-Feb-12 to 29 Apr Apr 12 to 26 Jul Aug 12 to 30 Nov Nov to 24 Jan M GDA94 1-Feb-12 to 29 Apr Apr 12 to 26 Jul Aug 12 to 30 Nov Nov to 24 Jan M GDA94 1-Feb-12 to 29 Apr Apr 12 to 26 Jul Aug 12 to 30 Nov Nov to 24 Jan M GDA94 1-Feb-12 to 29 Apr Apr 12 to 26 Jul Aug 12 to 30 Nov Nov to 24 Jan M GDA94 1-Feb-12 to 29 Apr Apr 12 to 26 Jul Aug 12 to 30 Nov Nov to 24 Jan EX GDA94 1-Feb-12 to 29 Apr Apr 12 to 26 Jul Aug 12 to 30 Nov Nov to 24 Jan

18 Figure 3 Contour maps for four quarters radon measurement 18

19 Airborne radon concentration Airborne radon concentrations were also measured across the site. Whereas in conventional radon gas monitors radon decay products are filtered out of the ambient air before it enters the active volume of the instrument, radon decay product monitors collect airborne radon decay products on filters and directly determine radon decay product concentrations by measuring their subsequent alpha decays. The study at Hillside used passive radon monitors (PRM) or track etch detectors to measure the geographical variation of airborne radon concentration. Feasibility studies have been performed previously and have shown that PRM s provide a means to determine average radon gas levels over periods of a few months. They are routinely used for monitoring in homes and within the mining industry across Australia and worldwide. Thirteen locations for the placement of the PRM s were chosen (Figure 3). The monitors were place in aerated plastic containers at approximately 1.7 metres from the ground and left for up to three months in the field. Both deployment and collection times were recorded. Upon collection this information along with the deployed PRMs and background monitors were sent to Radiation Detection Systems (Adelaide, Australia) for counting. Table 2 gives details of locations and exposure times. Table 3 shows the results as concentration contours of the airborne radon concentration measured using the PRMs. Figure 4 displays all results for the twelve month study with quarterly exposure periods displayed as lines and the average across the four periods displayed as a bar chart Average 1st Qtr 2nd Qtr 3rd Qtr 4th Qtr Figure 4 Track etch detector results from February 2012 to January 2013 (mbqm -3 ) Highest radon concentrations were measured at sites M2 and M3 which are in the northern area of the project area. These results are only marginally higher and may be attributable to statistical and counting errors as well as natural fluctuations. The gamma readings in Table 3 also indicate there is no elevated gamma activity in these areas and the background levels are low. Most countries have reference levels for radon concentration in dwellings above which measures should be taken to reduce the risk from inhalation of radon progeny. In Australia this reference level amounts to 200 Bq m -3. Although it does not apply for outdoor situations, all sites measured across the entire project area at Hillside exhibit airborne radon concentrations below this level throughout the year. Diurnal variation in airborne radon concentrations was not measured in this study. 19

20 Table 2 PRM radon results and average results for Hillside Sample Q1 Q2 Q3 Q4 Average SD Gamma error ID Bqm -3 Bqm -3 Bq m -3 Bq m -3 µgy h -1 M M M M M M M M M M M EX Average Standard SD error 2.76 Overall SD 3.73 Radon emanation Baseline and environmental radon is examined in several ways in order to provide a holistic picture of radon concentration and distribution. Complementing passive air sampling for radon decay products, a radon emanation study using activated charcoal cups was conducted at Rex Minerals Hillside site as part of the pre-mining baseline radiation study. These monitors were used to capture naturally emanating radon during a four day exposure period and were externally analysed to determine emanation concentrations for each monitoring location, with results normalised across the cohort of monitors used at each site. In order to determine natural radon exhalation from soils, this form of monitoring exploits the adsorptive properties of activated charcoal in order to trap radon emanating from the ground. The carbon is analysed by means of gross alpha count using a sodium iodide detector as soon as possible after the monitoring period ceases. This measurement can be used to calculate the radon exhalation from the monitoring location. In a practical sense, the activated carbon is housed inside small brass cups, which are inverted and sealed into the soil at the monitoring location. These monitors give a single point measurement; in order to increase the statistical robustness of collected 20

21 data, monitors are deployed in small cohorts at a number of randomly determined locations for each monitoring site. Ten locations were selected to give good coverage over all parts of the proposed Hillside operational layout, although restricted access to some farming properties resulted in an alteration to initially planned coverage (Figure 5). Five monitors were exposed at each of ten monitoring sites across the area of the proposed pit, processing plant and stockpiles. Some issues were encountered with acquiring permission to access properties that will eventually form part of the Hillside mine lease but which currently remain under the ownership of local landholders. The lack of access to these sectors required some adjustment of originally planned monitoring locations, but good coverage of operational areas was still achieved. The monitoring was conducted during mid-summer when soil moisture in the area is expected to be a minimum. Dry soil is beneficial to representative emanation measurement as moisture can inhibit the natural emanation rate of radon from soil. Cups were deployed by TRE and Rex Personnel at ten sites selected to give optimal coverage of different areas of the proposed Hillside operation including the mine pit, processing plant and stockpiles. At each site five cups were deployed in locations randomly determined, and the location of each cup was logged using GPS coordinates and marked with a flagging pin. Time and date of deployment was recorded for each cup. The method for installation of cups is standard: a sealed cover is removed, exposing the activated charcoal and the cup is then sealed into the ground with the open end facing down, exposing the charcoal to the soil. At all Hillside monitoring locations, soils were loose and sandy, and highly cultivated as the deposit lies in agricultural land that has been cropped for many years. Stone has largely been raked from surface soils over years of cropping activity and soils are uniform. These soil characteristics eliminated issues encountered in monitoring campaigns conducted in areas with rock or densely packed soils. The locations selected for monitoring included two sites over the pit, two in the area of the proposed processing plant, three over the proposed waste rock piles, one off the planned operational area and one in the centre of the current operational base, behind the structure currently in use as a core handling shed. Monitoring commenced on January 25 th 2013 and the cups were exposed in situ for a period of four days. They were recovered by REX personnel working to a written standard, and the time and date of recovery recorded. Recovery involves the removal of the cup from soil and replacement of the sealed cover, minimising exposure to atmospheric radon and ensuring that measured adsorption of radon onto the charcoal can be properly ascribed to exhalation during exposure to soil. Following recovery, the cups were couriered to Safe Radiation for analysis. For this form of monitoring, analysis involves removal of the activated charcoal from each brass cup and for analysis by a calibrated sodium iodide gamma spectroscopy system. The analysis gives total adsorbed radon which can then be used in combination with exposure time to give a radon concentration value. 21

22 Results for the radon cup monitoring campaign undertaken at Hillside are presented in Table 3. Results from the emanation study gave an average exhalation value of Bq m -3 ± 4.75 Bq m -3. The values returned by analysis are low, and are comparable to average global values of 15 to 23 mbqm -2 s -1 (UNSCEAR 1982) and average values for Australia of 22 ± 20% mbqm -2 s -1 (Scherey et al 1989). Radon emanation in the low concentrations measured at Hillside will not result in a contribution to radiation dose to workers or members of the public that is any greater than that which they would experience in any other environment. Table 3 Average results for radon emanation data collection on the 25/01/13 (5 cups per site). Area Easting Northing Average 222 Rn activity flux Standard (mbq/m3) Deviation Average SE =

23 Figure 5 Radon cup locations and contour lines displaying emanation values 23

24 Exposure to external gamma radiation A baseline gamma radiation survey was conducted at the Hillside project in Gamma levels were measured over the proposed pit area. The pit boundaries were supplied by REX and these boundaries can be seen in Figure 6, along with the measured survey points. The survey was carried out at regular spacing on a north - south, east - west grid over the mineralized zone; this zone covers an area of approximately 2 kilometres in length and 1 kilometre in width. The survey area encompassed the entire pit with over 1200 individual data points taken (Appendix A). The surveyed area consisted of two large paddocks that had been extensively drilled by the REX exploration team for resource identification purposes. These paddocks have historically been cleared and under crop, and the only vegetation present was grass. Survey point distances were between 25m and 50m. Gamma radiation measurements were taken using two RADEYE GX survey meters in conjunction with MC-71 Geiger Mueller tubes with absorbed gamma dose rates measured at a height of 1m above the ground level integrated over a 60 second time interval giving total counts. The geospatial coordinates (UTM WGS 84) of each measurement point were determined by a Garmin GPS 60cx. The precision of each GPS reading is typically ± 5 m. Soil scrape samples were also collected from the project lease area and will be discussed later in this report. A radiological analysis on these samples was performed at the Commonwealth Government Department of Sustainability, Environment, Water, Population and Community Environmental Research Institute of the Supervising Scientist radiological laboratory using high-purity high resolution germanium gamma detectors. The co-ordinates for the background readings can be found in Table 4. Appendix A shows the raw data and the calculated absorbed gamma dose rates. These rates are based on the measured counts and the instruments response as determined from previous calibration against a 137 Cs source (Bollhöfer et al 2009a; Bollhöfer & Fawcett 2009). The reported uncertainty in the calculated dose rates is one standard deviation based on counting statistics alone. Figure 6 gives a representation of the geospatial location of the individual measurement points. This figure also shows the magnitude of the calculated absorbed gamma dose rates (terrestrial component only) using colour contours over the designated survey area. It can be seen from the colour contour plot and the associated calculated absorbed gamma dose rates that radiation levels over the pit area are low. The low gamma dose rates over the mineralized zone are illustrated in a summarized form in Table 4 as standard statistics. It can be seen from the results that the statistical mean over the pit area was µgy hr -1 ; the maximum reading was µgy hr -1 ; and the minimum was µgy hr -1. These measurements are low and when compared to the background levels in Table 1 highlight the low radiological levels of the area. 24

25 Table 4 Average absorbed gamma dose rates (µgy h -1 ) for background (five kilometres north of Hillside) and proposed Hillside project pit area. Min Max Mean Standard Deviation Background Pit The low gamma dose rates are assumed to be caused by two main factors. Firstly, the area does not have high concentrations of naturally occurring radionuclides in the surface materials as is reflected in the results for the surface scrapes in Table 6. Secondly, the ore body and the associated uranium is approximately sixty metres below the surface, with overlying soils shielding and absorbing the gamma radiation. This has led to very low levels of gamma radiation which are reflected in the results of the ground survey illustrated in Appendix A. It should also be noted before any post mining rehabilitation work is conducted that any comparable surveys should be completed during similar climatic conditions. This is because if there is a significant amount of moisture present in the surface and subsurface material, emanation of radon from the ground can be significantly prohibited, thus reducing the response to the radon decay product 214 Bi. The radionuclide activity concentrations in the soils associated with the Hillside deposit surveyed are low. The gamma dose rate over the deposit is also low and is equal to or less then background levels in the area. It is recommended that gamma ground surveys be conducted and completed in all of the proposed mine site areas before construction work begins. 25

26 Figure 6 Gamma levels measured at the REX Hillside project over the proposed pit area 26

27 Inhalation and ingestion Dust Radiation exposure is considered across various pathways, and monitoring systems both in baseline and operational programs are designed to intercept these pathways and gauge the potential for effect on people, animals, biota and ecosystems. For operations targeting ore bodies that have high uranium or mineral sand content, potential exposure to long lived radioactive dust is one of the pathways monitored. At Hillside, the average grade of uranium across the ore body is % (57ppm) and the maximum grade intersected is 1.01% (10100ppm). Extraction and crushing of this ore could potentially result in some emission of dusts containing small amounts of uranium and other naturally occurring radionuclides. As identified in the Radiation Risk Assessment conducted by Paulka Radiation and Environment, potential radiation exposure risks associated with the liberation of dust include: - inhalation of dusts by workers in the mine and processing area; - deposition into the environment and subsequent uptake into the local food chain A pre-mining baseline study of dust and surface soils at the site provides a benchmark for rehabilitation at mine closure, as well as mitigating any concerns amongst the workforce or wider community. Given the location of the deposit in cropping land and in a region dependent on tourism, the assessment of dust during exploration phase provides information that can be communicated to allay any concerns amongst stakeholders in the immediate vicinity of the site and further afield. In order to establish baseline data for concentrations of radionuclides in dust at Hillside, several forms of monitoring and analysis were considered. High volume dust monitoring was undertaken at Hillside by site technical personnel in order to examine total suspended dust. Loaded filters were sent by Trevlyn Radiation and Environment to Australian Radiation Services for analysis (Table 5). Table 5 Results for analysis of the high volume air samples Location Radionuclide Units M1 X1 U-238 (mbq m -3 ) < 0.2 <0.6 (mbq mg -1 ) <4 <7 Ra-226 (mbq m -3 ) (mbq mg -1 ) Th-230 (mbq m -3 ) < 2 < 3 (mbq mg -1 ) < 50 < 40 Pb-210 (mbq m -3 ) (mbq mg -1 ) Be-7 (mbq m -3 ) (mbq mg -1 )

28 The samples were collected using a high volume dust sampler, in which air is drawn over a glass fibre filter trapping any suspended particulate dust onto the filter. Each filter was pre-weighed and then loaded into a cassette in the high volume dust sampler. For monitoring at Hillside, the sampler ran at a sampling rate of 70m 3 h -1 for a period of one day at each monitoring location. Filters from two monitoring locations were selected as offering representational capture of dust arising from operations at Hillside. Following the sampling period, filters were again weighed to ascertain total mass of dust collected during the sampling period. They were then sent to an Australian Radiation Services, an external NATA accredited laboratory, where they were analysed by gamma spectroscopy for radionuclides 238 U, 230 Th, 226 Ra and 210 Pb. Concentrations of these members of the 238 U decay chain are often scrutinised as they give a better understanding of the radionuclide content than simple analysis for the parent, and remove any uncertainty derived from assumptions of secular equilibrium. Results from analysis of the filters indicate that radionuclides in airborne dusts generated during exploration activities at Hillside are present in concentrations that are comparable to background levels in other parts of Australia (Todd 1998). The prescribed radioactivity concentration threshold for naturally occurring uranium (Schedule 4 of the National Directory for Radiation Protection, Australian Radiation Protection and Nuclear Safety Agency, 2011) which is applied by the state regulator in the South Australian Radiation Protection and Control Act, 1982 is given as 1 Bq/g - 1 U-nat, which equates to 80ppm of 238 U. The results from the gamma spectroscopy analysis of the airborne dust samples were very low, or below detectable levels. It should be noted that these results are from the capture of dusts liberated during exploration activities, and while they provide a valuable baseline they cannot be taken as a direct indicator of any airborne dust parameters that may apply during full operation at Hillside. Continuous monitoring should be implemented at perimeter and strategic internal locations to provide data that can be used to capture any trends in dust generation as the project develops. From the results provided by external analysis of airborne dust and soil scrape samples collected at Hillside, it can be concluded that under current operational conditions, the levels of radioactivity in soils at the project are comparable to background in most of Australia and will not pose a risk to workers or to members of public in the area. It is advised that a program of monitoring be maintained as the project progresses through development and operational phases, in order to capture any trends in the generation and impact of dust and to enable any necessary control measures to be identified and implemented. Soil Scrapes Soil scrape samples were taken at eight locations across various areas of the Hillside operation representing proposed pit, processing plant and waste rock dump sites. These samples comprised approximately one kilogram of soil from each location, taken as a vertical section beginning at the surface and to a depth of approximately 5 cm. 28

29 Five soil scrape samples were collected at locations in association with the PRMs and three soil scrape samples were collected in conjunction with the biota samples. All samples were analysed via high resolution gamma spectrometry for their soil 226 Ra activity concentrations. Surface soils across the entire area of the proposed operational site are uniform, loose and sandy after many years of tilling and cultivation as part of farming and cropping activities undertaken over the site. Other isotopes of interest are also measured. Table 6 shows the results of the gamma spectrometry measurements on all eight soil scrape samples. The averages for the radionuclides are low with 210 Pb being an order of magnitude higher but with large errors. Both 238 U, and 226 Ra are below 20 Bq/kg -1. Concentrations of 40 K are an order of magnitude higher in these soils but are still low. On average all radio isotope results for the samples are low. Table 6 Sample scape results from eight locations (Bq/kg) Sample Number 238 U error 226 Ra error 210 Pb error 228 Ra error 228 Th error 40 K error Bqkg - 1 Bq kg -1 Bq kg -1 Bq kg -1-1 Bq Bq kg kg -1 Scrape < Scrape Scrape < Scrape Scrape Biota 01 13* Biota * Biota * Average SD Note * Th -234 result used 234 Th measurements were used to calculate 238 U concentrations in the gamma spectrometry with a better peak resolution being available at the 234 Th energy line in the gamma spectra. It can be seen by direct comparison that results for the scrape samples taken from Hillside lie well below the limit which defines radioactive material. 29

30 Figure 7 Soil surface scape sample locations that were collected in association with the PRM s 30

31 Table 7 shows that the ratio of radon flux densities and soil 226 Ra concentration varies by less than a factor of two. This indicates that the majority of the 222 Rn exhalation is explained by the presence of 226 Ra in the soil. 222 Rn exhalation is a complex phenomenon dependent on a number of parameters, including 226 Ra activity concentration in soil, soil morphology, soil moisture, rainfall and vegetation cover. It has previously been shown (Lawrence, 2005) that soil morphology is an important factor influencing radon flux densities, which is also reflected in the measurements conducted at various non-operational uranium mines. Table 7 Average radon flux densities [mbq m-2 s-1] and associated standard deviations (n=3), soil 226 Ra activity concentration [Bq kg-1] and associated standard deviation due to counting statistics, and 222 Rn/ 226 Ra [(mbq m-2 s-1)/(bq kg-1)] measured at the Hillside project area. Site UTM Eastings UTM Northings UTM Zone 222 Rn flux density [mbq m -3 s -1 ] 226 Ra [Bq kg -1 ] 222 Rn/ 226 Ra N/A 13.5 N/A Figure 8 shows the ratio of 222 Rn flux densities to 226 Ra soil activity concentrations measured at the various sites. There appears to be a correlation emphasizing the dependence of radon flux densities on 226 Ra activity concentration in soil in this area. 35 Bq -1 /kg and mbq/m Ra 226 in soil Radon Cups PRM Ratio cups to Ra 226 in soil Ratio PRM to Ra 226 in soil Location Figure 8 Ratio of 222 Rn flux densities from emanation and airborne radon to 226 Ra soil activity concentrations from the 5 scrape locations (mbq m 3 s -1 )/( Bq kg -1 ), The areas where the soils were taken and where radon levels were measured that were analysed exhibit 222 Rn/ 226 Ra ratios of on average 1-2 (mbq m -3 s -1 )/(Bq kg -1 ) (Figure 9). 31

32 Rn/ 226 Ra Location Ratio PRM to Ra 226 in soil Ratio cups to Ra 226 in soil Figure 9 Plot of 222 Rn flux densities vs 226 Ra activity concentration for all sites. Ingestion of radionuclides Analysis of samples were conducted by Australian Radiation Services (ARS) and prior to all chemistry preparation, the animal flesh samples were freeze dried and all vegetation samples were prepared as received, with no washing. 226 Radium and 210 lead Sample digestion Preliminary preparation was completed in accordance with ARS internal Standard Operating Procedure ARS-SOP-AS312, which is based on the Method DSB-002 (Medley et al 2005). The paper can be downloaded from Radiochemical separation Further sample preparation was completed in accordance with ARS Internal Standard Operating Procedures ARS-SOP-AS304 and ARS-SOP-AS307, for Ra-226 and Pb-210 respectively. Measurement The samples were analysed using liquid scintillation counting, in accordance with ARS-SOP-AS602. Polonium-210 The samples were analysed using alpha spectrometry after preliminary digestion. Uranium-238 Elemental uranium concentrations were determined by ICPMS (Method reference MA-1400.SD.01 Metals) Dietary Intake The closest major community to the Hillside project area is approximately 12 km from the Project area. This community is a farming town and family holiday destination 32

33 with a permanent population of about 1100 people. It is assumed that shop bought food imported from outside the community as well as local produce make up the majority of the local area population dietary intake. Table 8 Biota sample physical information collected for Hillside Biota Easting Northing Fresh Wt (Kg) Wheat Lamb flesh Razor Fish flesh Rabbit flesh Whiting flesh Canola Barley Beef flesh Various samples (Table 8) have been collected during 2012 from the REX site and surrounding areas. An array of biota samples including meat (fish, rabbit, beef and lamb) and crops (canola, wheat and barley) were collected from the surrounding farms and sent for analysis to ARS laboratories for radionuclide analysis. These analyses included total U, 226 Ra, 210 Po and 210 Pb. These are long lived radionuclides and are part of the 238 U decay series. The samples were collected from around the proposed mine area (Figure 10). Table 9 gives radionuclide analysis results for crop and tissue samples (Bq/kg -1 fresh weight) and radionuclide concentrations for the associated soil samples (Bq/kg -1 dry weight) is contained in Table 10. Table 11 gives the calculated concentration ratios (for fresh plant sample vs. dry soil). For the meat and crop samples the radionuclide concentrations were within an order of magnitude of each other with uranium concentrations being higher than the other radionuclides. The levels of radionuclides in foodstuffs grown in the local area are generally low (Table 8) and close to the level of detection. Table 9 Radionuclide results for biota samples Hillside project Tissue 238 u 238 u 226 Ra 210 Pb 210 Po mgkg -1 Bq kg -1 Bq kg -1 Error Bq kg -1 error Bq kg -1 error Wheat < Lamb flesh < < Razor Fish flesh < < Rabbit flesh < < Whiting flesh < <0.4 < Canola < < Barley < < Beef flesh < < Concentration factors ICRP Publication 23 states that the per caput estimate of food supplies for Reference Man or person from Oceania (Table 122, page 349) is 677 kg/yr. The standard person or reference person is a theoretical individual that has perfectly "normal" characteristics. This model is used for much research into radiation safety. For many 33

34 years, the standard person was called reference man because the work assumed a healthy, young adult male. In recent years, reference woman and reference child models have been created, along with variations on body size, age, sex, and race. The concentration factor (CR) for a radionuclide in an organism is defined as the activity of the nuclide per unit weight of the organism, divided by the activity of the same nuclide per unit weight of substrate, where the substrate is the physical medium (e.g., water, food, or soil) from which the organism obtains the nuclide. Deficiencies in the CR approach are known to exist but, in general, its use is likely to be conservative provided locally derived values are used. Details and sampling location for biota collected is presented in Table 8. The concentration factors for the food samples collected at Hillside have been calculated and presented in Table 15. Activity concentrations were calculated using fresh weights of the biota and dry weights of the soil medium. The activity concentration results for the radionuclides analysed in this study and an estimation of a local diet can be used to conduct a theoretical radiological baseline dose assessment for the local inhabitants of the area. Average soil activity concentrations (Table 10) were calculated from the soil scrape analysis results taken over the course of the study. Eight scapes samples were taken and analysed for radionuclides and these results were averaged and used in the calculation of the biota concentration factors. Three of these soil scrapes were collected with the biota samples whilst the other five were collected as part of the dust and soil study. The three soil samples with the biota samples were analysed at ARS laboratory and the remaining samples were analysed at the eriss laboratory in Darwin. Whole-body to tissue concentration ratios (Yankovich et al 2010) which can be used to calculate whole-body activity concentrations of radionuclides in the biota have also been calculated. These results can be used in biota dose assessments for animals. These calculated concentrations ratios are presented in Table 11 and can be used as part of an ERICA assessment. ERICA is a tool used for assessing and estimating exposure of biota, which involves estimating or measuring activity concentrations in environmental media and organisms, defining exposure conditions, and estimating radiation dose rates to selected biota. This information is then used as the basis of the assessment with risk characterisation performed by evaluating the output data from the assessment (estimates of exposure) against effects analyses. This assessment then allows the management of decisions on specific technical issues associated with the execution of the assessment, general decisions relating to the interaction with stakeholders, and post-assessment decisions. Both a baseline human dose assessment for workers at the Hillside project and members of the public living around the project area and an ERICA assessment for biota can be conducted using the data in this report. The activity concentrations for the biota studied and the soils collected is low and is well within Australian background levels of between 30 to 50 Bqkg -1 for soils 34

35 (ARPANSA 2005) and biota levels studied elsewhere in Australia (Martin and Ryan 2004). Figure 10. Location map of the biota samples collected at the Hillside project 35

36 Table 10 Radionuclide results for the soils taken with the biota samples and from soil scrapes Sample ID Th-234 Error Ra-226 error Pb-210 error Ra-228 error Th-228 error K-40 error Bq kg-1 Bq kg-1 Bq kg-1 Bq kg-1 Bq kg-1 Bq kg-1 SCR SCR SCR SCR SCR BSCR BSCR BSCR Mean SD Table 11 Concentration factors for Hillside biota samples Tissue 238 u Conc Tissue to Whole-body 226 Ra Conc Tissue to Whole-body 210 Pb Conc Tissue to Whole-body 210 Po Conc Tissue to Whole-body Factor wholebody 238 U activity factor wholebody 226 Ra activity factor whole-body 210 Pb activity factor wholebody 210 Po activity Calculated Ratio Bq kg-1 calculated ratio Bq kg-1 calculated ratio Bq kg-1 calculated ratio Bq kg-1 Wheat Lamb flesh Razor Fish flesh Rabbit flesh Whiting flesh Canola Barley Beef flesh

37 Surface water and ground water Both groundwater and surface waters were collected from the project site and analysed for radionuclide activity concentrations. Locations of the bores and the surface water collection locations can be seen in Figure 11. There are no permanent streams or creeks at the site and the samples were collected from either dams or drainage lines after rainfall. These samples were analysed using alpha spectrometry and are presented in the following tables. Details of the alpha spectrometry methods are described in Martin & Hancock (2004), Sill (1987) and Medley et al (2005). Surface water The activity concentrations for 226 Ra, 238 U, 234 U, 210 Pb and 210 Po for unfiltered surface waters are presented in Table 12. The uranium levels are low with Australian drinking water standards for U of 17 μg per litre (equivalent 210 mbq 238 U per litre). The location of the surface water sampling points is shown in Figure 10. Table 12 Radionuclide results for unfiltered surface water results (mbq/l) Location ID 226 Ra err 210 Pb 238 U err 234 U err 234/238 U err 210 Po err Hillside Runoff dam 6 5 < Germiens Dam 9 5 < Hillside Gully 12 5 < Aldermans Track 13 5 < Groundwater Physical results for the ground waters are presented in Table 13 and physical locations of groundwater sampling locations are illustrated in Figure 11. Conductivity results illustrate the high salts in the groundwaters making these waters not fit for human consumption. These levels are to be expected because of the sites relative location to the ocean. Figures 12 and 13 illustrate the 238 U and 234 U uranium activity concentration contours and there is a trend showing the higher activities over the pit. The uranium levels are low with Australian drinking water standards for U of 17 μg per litre (equivalent 210 mbq 238 U per litre). 37

38 Table 13 Physical water quality results for groundwater at the Hill side project area Sample ID Cond ph us/cm WBTH WBTH WBTH WBTH WBTH WBTH WBTH WBTH WBTH WBTH WBTH The activity concentrations for 226 Ra, 238 U, 234 U, 210 Pb and 210 Po for the filtered (<0.45um) ground waters are presented in Table 14. Figure 14 illustrates the 226 Ra activity concentration contours over the site. Table 14 Radionuclide results for filtered (<0.45 um) groundwater samples mbq/l Sample ID 226 Ra Err 210 Pb err 238 U err 234 U err 234 U/ 238 U err 210 Po err WBTH < WBTH < WBTH < WBTH < WBTH WBTH WBTH WBTH WBTH WBTH WBTH Sea Water 17 4 < In Table 15 isotopic uranium is reported and the uranium ratios may be used as a diagnostic source signature in the event of any unexpected contaminate movement into the surrounding groundwater s. The uranium ratios can help to indicate source of any uranium contaminate material. In Table 15 the 226 Ra activity concentration results are given for surface waters. Figure 14 illustrates the 226 Ra activity concentration contours at the project area. The levels of 226 Ra activity concentrations are low overall, but there is a slight increase closer to the coastal zone which maybe be caused by radium tendency to be more 38

39 mobile in higher salt water conditions. The Australian Drinking Water Guidelines recommends guideline values for Radium-226 are both 0.5 Bq/L. Only four from the twelve groundwater samples were below the recommended drinking water guideline values for 226 Ra. Table 13 gives surface water 210 Pb and 210 Po activity concentrations while Table 15 presents the groundwater 210 Pb and 210 Po activity concentrations. These results are low 39

40 Figure 11 Surface water and groundwater sampling locations at the Hillside project area. 40

41 Figure U activity concentrations for groundwaters at the Hillside project. 41