RADIATION IMPACT ASSESSMENT OF THE PROPOSED WASTE INCINERATOR AT SWAKOP URANIUM S HUSAB MINE

Transcription

1 RADIATION IMPACT ASSESSMENT OF THE PROPOSED WASTE INCINERATOR AT SWAKOP URANIUM S HUSAB MINE May 2018 Document Nr: Dr Detlof von Oertzen PO Box 8168 Swakopmund Namibia Tel: Mob: Fax: Web: info@voconsulting.net

2 Client Client contact details Project & Document title Document number SLR Consulting (Pty) Ltd House Schumacher 6 Tobias Hainyeko Street Swakopmund Namibia Radiation Impact Assessment of the Proposed Waste Incinerator at Swakop Uranium s Husab Mine Document version 4 Date of delivery Submitted on 25 May 2018 Author Declaration Disclaimer Acknowledgements Copyright Detlof von Oertzen, PhD (Physics), MBA (Finance), PrSciNat VO Consulting is an independent technical and management consulting firm registered in Namibia, and the company s focus areas are in energy, environment, and radiation protection/safety. VO Consulting has no interest in the Project other than to fulfil the contract between the Client and us. The present study is based on deliverables which are described in Terms of Reference, as were issued by the Client, specifically for the Project. This Report is based on data and information that has been supplied by third parties. Neither VO Consulting nor the author of this Report make any warranty, express or implied, or assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information contained in this Report that is implicitly or explicitly based on data or information supplied by any third-party provider. VO Consulting and the author most gratefully acknowledge inputs from the following individuals: Werner Petrick and Dr Arnold Bittner of SLR Consulting, for helpful clarifications, comments, suggestions, and discussions; Dr Hanlie Liebenberg-Enslin and Dr Oladapo Akinshipe of Airshed Planning Professionals, for providing model outputs for atmospheric dust concentrations emitted from the proposed incinerator, and helpful discussions; Dr Gunhild von Oertzen, in her private capacity, for the peer review, insightful discussions and helpful suggestions. Full and exclusive copyright rests with VO Consulting, unless indicated otherwise. May 2018 Page 2 of 48

3 Executive Summary Swakop Uranium (Pty) Ltd is the holder of mining licence 171 and associated Environmental Clearance Certificates for the operation of the Husab Mine, which is located in the Namib Naukluft National Park in Namibia s western Erongo Region. SLR Consulting (Pty) Ltd was appointed by Swakop Uranium (Pty) Ltd to undertake an Environmental Impact Assessment for the extension of the Husab Mine s waste rock facilities, and the operation of an on-site waste incinerator. VO Consulting was appointed by SLR Consulting to undertake a radiation impact assessment of the proposed waste incinerator at Swakop Uranium s Husab Mine. Such an assessment is important to quantify the radiation-related impacts and repercussions associated with the operation of such a plant. The proposed waste incinerator is to be located on site at Swakop Uranium s Husab Mine, which is located some 20 kilometres (km) from the town Arandis, some 50 km from Swakopmund, and some 65 km from the port of Walvis Bay, in Namibia s central-western Erongo Region. The rationale for undertaking a radiation impact assessment for the proposed waste incinerator is that to-be-incinerated waste includes materials which may be contaminated with radioactive mineral ore dust and/or uranium concentrate. Upon incineration, such radioactive ingredients are released into the environment, in the form of a) atmospheric emissions from the incinerator s stack, b) embedded radioactive residues in filters which are to be employed as part of the incinerator s pollution control system, and c) solid waste residues in the incinerator. All actual and potential radioactive releases must be managed, to ensure that their impacts remain as low as reasonably achievable, and in compliance with relevant regulatory limits. The present assessment is based on the typical and most likely annual waste composition, assuming worst-case operational emissions from the proposed incinerator, to quantify the radiation-related impacts both for unmitigated and mitigated plant operations. Based on an estimate of waste volumes, as were provided by Swakop Uranium, the annual tobe-incinerated waste consists of approx. 24 metric tons of material contaminated with uranium concentrate, and approx metric tons of material contaminated with radioactive ore dust. By type and degree of contamination, the to-be-incinerated waste includes the following: Contaminant Low degree of contamination Medium degree of contamination High degree of contamination Uranium concentrate ~12 kg/a ~119 kg/a ~594 kg/a Radioactive mineral ore dust ~0.2 kg/a ~2 kg/a ~8 kg/a Relevant atmospheric emissions from the operation of the proposed incinerator will occur in the form of particulate matter emissions. While the operation of the proposed incinerator will also result in gaseous emissions, e.g. carbon monoxide, oxides of nitrogen, sulphur dioxide and select May 2018 Page 3 of 48

4 volatile organic compounds, the present assessment does not consider any of these in further detail as they do not contribute to radiation-related impacts. The quantification of particulate matter emissions, and their potential radiation-related impacts, considers two distinct particle size fractions, namely respirable particulate matter (abbreviated PM2.5) and thoracic particulates (abbreviated PM10). Radioactive atmospheric dust emissions of the type PM2.5 and PM10 are highly relevant in radiation-related impact assessments, as they are readily inhalable, in which case they have negative health repercussions for humans. The proposed incineration process also results in radiation-relevant solid waste. Such waste is contained in filters, filter cartridges or similar pollution control elements, or liquids used in a stack scrubbing process, as well as solid waste residues in the incinerator s chambers, s.a. ash and slag. Based on the above observations, the radiation-related impacts associated with the proposed waste incinerator are mainly associated with the generation of atmospheric particulate matter emissions, as well as radioactive solid waste residues. Atmospheric emissions are the result of a transfer of radioactive substances from the incinerator s primary to the secondary chamber, from where they are passed through filters (provided that such mitigation measures are applied) or without passing through filters (in case of unmitigated operations) via the stack into the environment. Solid waste arises in the form of ash and slag in the chambers of the incinerator, as well as in the filter assemblies (e.g. filter cartridge, or bag filter) that are applied under mitigated plant operations. As part of unmitigated operations, solid waste residues are emitted by way of atmospheric emissions via the stack, while a fraction of such waste will remain in the form of residues in the chambers of the incinerator as well as the incinerator s stack system. Both the radioactive atmospheric emissions and solid waste residues arising from the operations of the proposed incinerator are hazardous, because of the ionising radiation that such substances emit, and because of the toxicity associated with (mainly) uranium-bearing compounds, and other toxic emissions. Because of the potential radiation-related risks from atmospheric and solid waste products it is imperative that health-related impacts are quantified, and managed. This assessment computes worst-case incremental inhalation doses which are associated with the atmospheric emissions from the stack of the proposed incinerator, using average annual particulate matter concentrations for both unmitigated and mitigated plant operations, assuming that emissions occur in the form of uranium concentrate dust only. These assumptions yield the highest possible incremental inhalation doses of all operational configurations, and are therefore worst-case assumptions. The rationale for such assumptions is that in case the risks associated with mitigated/unmitigated operational scenarios are found to be acceptable, then all other operational options are acceptable too. The incremental inhalation exposure dose resulting from the continuous operation of the proposed waste incinerator, under worst-case operational emissions, are summarised below. Under mitigated plant operations, very small incremental inhalation exposure doses are incurred by public members of the critical group, who are assumed to reside at the on-site construction camp, as well as by occupationally exposed persons working at/close to the proposed incinerator. May 2018 Page 4 of 48

5 Receptor type Annual Inhalation Dose Increment Unmitigated operations Mitigated operations Regulatory Annual Exposure Dose Limit Public 0.7 msv.a msv.a -1 1 msv.a -1 Occupational 1.0 msv.a msv.a msv.a -1 The associated impact significance rating for mitigated operations of the proposed incinerator is summarised in the table below: Activity Impact Severity Duration Scale Consequence Probability Significance Incinerator is operated with mitigation measures Exposure dose due to inhalation of atmospheric emissions containing radioactive dust L M L L L LOW The magnitude of the incremental exposure doses necessitates the permanent application and use of mitigation measures, to limit atmospheric emissions from the proposed incinerator. This implies the installation and use of a pollution control system designed to limit stack emissions. In addition, radiation protection measures must be taken to limit potentially negative impacts resulting from the exposure to ionising radiation originating from the atmospheric dust and radioactive solid waste generated through the operations of the proposed waste incinerator. This necessitates that Swakop Uranium s Radiation Management Plan (RMP) is updated, to include the radiation-related aspects introduced as a result of the operation of the proposed incinerator. Also, radiation-related public and environmental monitoring must be initiated prior to the commencement of operations of the proposed incinerator, to strengthen the baseline data of relevance to the atmospheric pathway. Specifically, inhalable dust concentrations must be monitored, and the radionuclide content of such dust must be determined. Once the proposed incinerator is commissioned and operations commence, radiation-related monitoring must focus on determining incremental exposure doses incurred as a result of plant operations. Solid waste generated by the proposed incinerator primarily occurs in the form of ash and slag, which contain radioactive residues, as well as radioactively contaminated filters. All such radioactive solid waste products must be regularly removed from the plant, and then disposed of. The process and specific actions required to clean the incinerator, replace filters, and dispose of the solid waste generated by the plant must be described in the updated RMP, and must be quantified in a special waste inventory that must be kept current. Disposal of such solid waste must be undertaken in compliance with national provisions, and in conformity with the stipulations by the National Radiation Protection Authority and other relevant state actors. May 2018 Page 5 of 48

6 Table of Contents 1 INTRODUCTION BACKGROUND RATIONALE EIA PROCESS SCOPE OF WORK OF THIS ASSESSMENT APPROACH SCOPE OF THIS REPORT LEGAL AND REGULATORY CONTEXT BACKGROUND INTRODUCTION RADIATION PROTECTION RADIATION RISKS LEGAL AND REGULATORY REQUIREMENTS NATIONAL RADIOLOGICAL PROTECTION STANDARDS REGULATORY DOSE LIMITS EXPOSURE TO NATURAL BACKGROUND RADIATION RADIOACTIVITY BACKGROUND INTRODUCTION EXPOSURE TO NATURAL BACKGROUND RADIATION (NBR) THE PROPOSED WASTE INCINERATOR AND WASTE STREAM LOCATION INCINERATOR TYPE TO-BE-INCINERATED WASTE QUANTITIES AND CHARACTERISTICS RADIOACTIVE CONTENT OF THE TO-BE-INCINERATED WASTE RADIATION-RELEVANT ATMOSPHERIC EMISSIONS GENERATED RADIATION-RELEVANT SOLID WASTE GENERATED RADIATION-RELATED IMPACTS INTRODUCTION ATMOSPHERIC EMISSIONS FROM THE PROPOSED INCINERATOR SOLID RADIOACTIVE WASTE FROM THE PROPOSED INCINERATOR IMPACT SIGNIFICANCE RATING 37 7 RECOMMENDATIONS INTRODUCTION UPDATING THE EXISTING RADIATION MANAGEMENT PLAN RADIATION PROTECTION AND RADIATION MANAGEMENT MEASURES CONCLUSIONS 44 APPENDIX A: IMPACT SIGNIFICANCE FRAMEWORK 45 APPENDIX B: CALCULATING EXPOSURE DOSES 46 REFERENCES 47 May 2018 Page 6 of 48

7 List of Tables Table 1: Main natural background radiation contributors and associated exposure doses Table 2: Particulate emission limit with pollution control system (mitigated operations) Table 3: Typical waste sources and associated volumes to be incinerated per year Table 4: Summary of to-be-incinerated radioactively contaminated waste Table 5: Radioactive contamination per unit mass of to-be-incinerated waste material Table 6: Quantities of different radioactive contaminants in proposed annual waste stream Table 7: Proposed air quality guidelines for particulate emissions in Namibia s Erongo Region. 28 Table 8: SA Listed Activity Subcategory 8.1: thermal treatment of general/hazardous waste Table 9: Mitigated and unmitigated incinerator emissions factors Table 10: Maximum estimated emissions and emission densities Table 11: Modelled unmitigated maximum and average ground level concentrations Table 12: Modelled mitigated maximum and average ground level concentrations Table 13: Incremental annual exposure dose due to continuous incinerator operations Table 14: Impact significance rating for unmitigated operations of the proposed incinerator Table 15: Impact significance rating for mitigated operations of the proposed incinerator Table 16: Inhalation dose conversion coefficients for U-238 for 5 μm AMAD May 2018 Page 7 of 48

8 Abbreviations µg.m - ³ micrograms per cubic metre μm micrometre, i.e metre µsv.a -1 micro-sievert per annum (i.e. one-thousands of a msv.a -1 ) ADMS Atmospheric Dispersion Modelling System AMAD activity median aerodynamic diameter (of particulate matter emissions) Bq Becquerel (rate of radioactive decay expressed as disintegrations per second) Bq.kg -1 Becquerel per kilogram Bq.L -1 Becquerel per litre Bq.m -3 Becquerel per cubic metre DCF dose conversion factor EIA environmental impact assessment IAEA International Atomic Energy Agency ICRP International Commission on Radiological Protection IEC International Electro-Technical Commission ILO International Labour Organisation ISO International Organisation for Standardisation km kilometre LNT linear no-threshold (hypothesis) m metre m 2 square metre m 3 cubic metre ml millilitre, i.e. one-thousands of a litre msv milli-sievert (unit of exposure to ionising radiation; msv = 1 Sv) msv.a -1 milli-sievert per annum MET Ministry of Environment and Tourism MME Ministry of Mines and Energy NBR natural background radiation NORM naturally occurring radioactive material NRPA National Radiation Protection Authority PM10 particulate matter with an aerodynamic diameter of less than 10 micrometres PM2.5 particulate matter with an aerodynamic diameter of less than 2.5 micrometres ppm parts per million RMP Radiation Management Plan Rn radon (including the radioactive radon isotopes Rn 222 and Rn 220 ) ROM run of mine RSO Radiation Safety Officer SU Swakop Uranium Sv Sievert (unit of exposure dose to ionising radiation) Sv.a -1 Sievert per annum TSF tailings storage facility TSP total suspended particulates UNSCEAR United Nations Scientific Committee on the Effects of Atomic Radiation WHO World Health Organisation WRD waste rock dump May 2018 Page 8 of 48

9 1 INTRODUCTION 1.1 BACKGROUND Swakop Uranium (Pty) Ltd is the holder of mining licence 171 and associated Environmental Clearance Certificates for the operation of the Husab Mine, which is in the Namib Naukluft National Park in Namibia s western Erongo Region. SLR Consulting (Pty) Ltd was appointed by Swakop Uranium (Pty) Ltd to undertake an Environmental Impact Assessment for the extension of the company s waste rock facilities, and the operation of an on-site waste incinerator. VO Consulting was appointed by SLR Consulting to undertake a radiation impact assessment of the proposed waste incinerator at Swakop Uranium s Husab Mine. Such an assessment is important to quantify the radiation-related impacts and repercussions associated with the operation of the proposed waste incinerator. Currently, Husab Mine s non-mineral waste is managed as per the company s Environmental Management Plan. As part of a review of Swakop Uranium s waste management strategy, certain amendments to current waste disposal practices were recommended. Amongst others, these recommendations included that an on-site waste incinerator was to be procured, to reduce the volume of special waste that would have to be disposed of. As the operation of a waste incinerator falls beyond the scope of Swakop Uranium s present environmental clearance certificates, an Environmental Impact Assessment was commissioned, to inform the amendments to current practices under the company s Environmental Management Plan. 1.2 RATIONALE In Namibia, holders of mining licenses must submit an environmental impact assessment (EIA) in conformity with the requirements of the Environmental Management Act of 2007 should they wish to introduce material changes to the practices included in their existing Environmental Clearance Certificates. Such an EIA is a requirement when applying for an updated Environmental Clearance Certificate and is issued by the Environmental Commissioner in the Ministry of Environment and Tourism (MET). The rationale for undertaking a radiation impact assessment for the proposed waste incinerator at Swakop Uranium s Husab Mine is that the to-be-incinerated waste would include materials contaminated with radioactive materials. Upon incineration, such radioactive ingredients are released into the environment, for example in the form of atmospheric emissions from the incinerator s stack or embedded in filters applied to clean emissions. Any such releases must be managed, to ensure that their impacts remain as low as reasonably achievable, and in compliance with the regulatory limits. May 2018 Page 9 of 48

10 1.3 EIA PROCESS The process underpinning the environmental impact assessment related to the proposed waste incinerator at Swakop Uranium s Husab Mine is coordinated by SLR Consulting (Pty) Ltd, who are the environmental assessment practitioners appointed by Swakop Uranium (Pty) Ltd. VO Consulting was appointed by SLR Consulting to undertake the radiation impact assessment for the operations of the proposed waste incinerator. This is to form part of Swakop Uranium s EIA related to the proposed waste incinerator. 1.4 SCOPE OF WORK OF THIS ASSESSMENT The scope of work of the present assessment includes the following: Based on the composition of to-be-incinerated waste, as per the submission by Swakop Uranium (Pty) Ltd, identify, assess, and quantify the sources of radioactive material that are proposed to be incinerated; Based on the results of the air quality assessment for the proposed waste incinerator, identify, assess, and quantify both the unmitigated and mitigated atmospheric emissions resulting from the proposed operations of the incinerator; Based on an assessment of the exposure pathways, identify, assess, and quantify the relevant and significant exposure pathways under current operational realities at the Husab Mine, taking the results of the modelled atmospheric emissions into account; Based on an assessment of the receptors, identify, asses and describe the relevant human and environmental receptors affected by the proposed operations of the incinerator; The results of the above assessments are then integrated to quantify the radiation-related risks and impacts associated with the proposed operation of the waste incinerator at the Husab Mine; and A report will summarise the main findings, conclusions and recommendations arising from the radiation impact assessment. 1.5 APPROACH The present assessment is based on the typical and most likely annual waste composition and worst-case incineration profile at the proposed incinerator at Swakop Uranium s Husab Mine. The incinerator s operations will result in radiation-related impacts. Such potential impacts are quantified, both for unmitigated and mitigated operations, which are then used to quantify the potential radiological impact on people and the environment. May 2018 Page 10 of 48

11 1.6 SCOPE OF THIS REPORT The remainder of this Report is structured as follows: Chapter 2 introduces the legal and regulatory context and requirements of relevance for the radiation impact assessment developed in this report; Chapter 3 provides an overview of global and local natural background radiation and associated exposure doses; Chapter 4 provides an overview of the main radiation-relevant features of the proposed waste incinerator and the to-be-incinerated waste streams; Chapter 5 quantifies the potential radiation-related incremental impacts on persons at or close-by the proposed waste incinerator at Swakop Uranium s Husab Mine; Chapter 6 summarises the impact assessment s impact significance ratings; Chapter 7 summarises the main recommendations; while Chapter 8 presents the conclusions of this radiation impact assessment; Appendix A presents the impact significance rating framework as used in this report; Appendix B describes how public exposure doses are calculated using atmospheric dust concentrations; while the References chapter summarises the reference sources used as part of the present assessment. May 2018 Page 11 of 48

12 2 LEGAL AND REGULATORY CONTEXT This chapter introduces the legal and regulatory context and requirements of relevance for the radiation impact assessment developed in this report. 2.1 BACKGROUND Humans have evolved in the presence of ionising radiation which is emitted from natural sources, including from cosmic radiation, radioactive terrestrial sources, food, water, and the air we breathe. In addition, a variety of man-made sources emitting ionising radiation make additional contributions to the perpetual sea of background radiation in which we live. Certain mining operations, including those undertaken by Swakop Uranium at the Husab Mine, contribute to the natural radiation field to which humans are exposed. In most cases in which radioactive mineral ores are mined, these are crushed, milled, and concentrated, all of which adds to radiation exposures of persons at or nearby such mining, milling, and processing activities. In addition, rock dumps, waste rocks, tailings and process facilities expose radioactive ore to the environment, which contributes to an increase of atmospheric radon and thoron exhalations as well as the concentration of inhalable radioactive dust into the atmosphere. 2.2 INTRODUCTION The International Commission on Radiological Protection (ICRP) has put forward a conceptual model of the processes causing human exposures to ionising radiation [ICRP, 2007]. The model views exposure processes as a network of events and situations with each part of the network starting from a specific source of radiation. This radiation, or the radioactive source material giving rise to such radiation, passes through environmental or other pathways, and in this way may finally expose individuals at or close to the source of such materials, which in turn may lead to an additional exposure to ionising radiation of select individuals. In what is referred to as a source-pathway-receptor model of exposure to radiation, radiation protection can be achieved by acting at the source of radiation, or at the various points along the exposure pathways, and if possible, by changing the location, behaviours and protective measures used by actually and/or potentially exposed individuals. Radiation protection therefore includes all measures, processes and controls applied to minimise the potential exposure to radiation, and such measures are therefore most effectively implemented at the source(s), in the pathway(s) and at the receptor(s). Although not fully supported by empirical evidence for low exposure doses, it is assumed that there exists a proportional relationship between an increment of exposure to ionising radiation May 2018 Page 12 of 48

13 and the resulting increment of the associated risk from such an exposure. The assumption is further that there exists no threshold for the onset of such risks. This is the essence of the socalled linear no-threshold (LNT) hypothesis, which suggests that the risk association with exposure to radiation increases linearly as the exposure dose increases. Today, the LNT hypothesis underpins the formulation of most radiation protection measures and processes and applies across the potential chain of exposure from the source, via one or several pathways to the actual or potential receptor(s). Today s radiation protection officer identifies those parts of the chain of exposure that are most relevant and amenable to the application of effective exposure controls by separating the total exposure dose into its various contributing parts, which in turn allows targeted interventions for each such contributing element. Individuals are subject to several types and categories of exposure. A mine worker who is occupationally exposed because of the particular work that is being undertaken on a mining site is also exposed to naturally occurring environmental sources of ionising radiation. Similarly, a member of the public is exposed to ionising radiation from the natural background radiation, plus an incremental contribution due to other sources of radiation in his/her immediate environment, including radioactive dust, as well as radon and thoron progeny entering the environment from nearby mining site(s), as well as the food and water that is consumed, and the exposure to a variety of man-made source of radiation. 2.3 RADIATION PROTECTION Radiation protection measures are most effective when applied in the immediate environment in which risks to exposure exist. For example, the incremental dose that ordinary members of the public may be exposed to from operations such a uranium mine needs to be minimised to such an extent that potential exposure doses do not exceed the applicable national dose limit. Likewise, occupational exposures of workers at a practice which processes radioactive ores must be minimised at the place of work, where particular occupational exposure dose limits apply. As far as regulatory controls are concerned, each distinct exposure group, such as for example members of the public or occupationally exposed persons, are treated separately, and are subject to separate regulatory provisions. And because potential public and occupational exposure categories require different protection measures and approaches, separate control measures and dose limits (over and above the specific contribution due to natural background radiation) apply to each of these exposure categories. The present assessment focuses on the potential exposure contribution resulting from the operation of the proposed waste incinerator at Swakop Uranium s Husab Mine. Primarily therefore, this assessment considers how exposures arising from the operation of the incinerator affect exposure doses of persons who spend time on site, irrespective of whether these are members of the public or Swakop Uranium staff members. May 2018 Page 13 of 48

14 2.4 RADIATION RISKS Radiation protection practices in the mining industry focus on minimising the so-called stochastic effects of ionising radiation. Stochastic effects are not associated with a particular exposure threshold, in contrast to the so-called deterministic effects of ionising radiation, which are certain to occur if a certain exposure threshold is exceeded. Stochastic radiation effects are probabilistic in nature and may ensue if a cell (for example in the body of an occupationally exposed worker) and with it the genetic make-up of the affected cell is modified rather than killed. Such modified cells may, in time, develop into a cancerous growth. In most cases where persons are exposed to low levels of radiation, the body's repair, and defence mechanisms active at the cellular level render it unlikely that cells are irreparably modified. This is indeed most often the case in an occupational setting in which low-level radioactive ores are mined and processed. There is no actual proof that a threshold dose exists below which cancerous growth will no longer form. While the probability of occurrence of such cancers is higher for higher doses, the severity of any cancer resulting from irradiation is independent of the dose that caused it. This implies that potential exposures of workers or members of the public must be kept as low as reasonably achievable, and below the dose limit as is applicable to each such exposure group, as specified by the national regulatory authority. In contrast, deterministic effects resulting from the exposure to radiation have a well-defined threshold of occurrence. If an individual incurs an exposure dose above such a threshold value, their impacts on the receptor are well-known and can be predicted with certainty. However, deterministic effects from the exposure to ionising radiation do not occur in ordinary mining operations dealing with low-grade radioactive ores, as typical exposure thresholds of 100 msv or more are not readily exceeded in most of such operations. 2.5 LEGAL AND REGULATORY REQUIREMENTS The present assessment is guided by the requirements of Namibia s Atomic Energy and Radiation Protection Act, Act No. 5 of 2005 [Act, 2005], and the relevant regulations under the Act, i.e. the Radiation Protection and Waste Disposal Regulations, No. 221 of 2011 [Regulations, 2011]. Namibia s legal framework as pertaining to radiation-relevant aspects is substantially based on the following international guidance documents: the recommendations contained in the Basic Safety Standards of the International Atomic Energy Agency (IAEA) [IAEA, 1996], [IAEA, 2004] and [IAEA, 2014]; and those by the International Commission on Radiological Protection (ICRP) (refer to [ICRP, 1993], [ICRP, 1995] and [ICRP, 2007]). May 2018 Page 14 of 48

15 The above frameworks recognise that human health and the environment must be protected against the potentially adverse effects resulting from the exposure to ionising radiation, as do for example arise when handling, mining, milling, and processing of mineral ores that contain naturally occurring radioactive materials. 2.6 NATIONAL RADIOLOGICAL PROTECTION STANDARDS In Namibia, the Atomic Energy and Radiation Protection Act, Act No. 5 of 2005 [Act, 2005], and the Radiation Protection and Waste Disposal Regulations [Regulations, 2011] under this Act [Regulations, 2011], describe the statutory and regulatory radiation protection and control measures applicable to individuals and entities dealing with sources of radiation. The National Radiation Protection Authority (NRPA) was established under the Act and is responsible for setting and overseeing the criteria applicable to radiation protection in Namibia. The proposed waste incinerator at Swakop Uranium s Husab Mine will have to comply with the national regulatory requirements for radiological protection, which are underpinned by the following elements: justification of practices; exposure dose limitation; optimisation of protection and safety; and dose constraints. The pertinent elements of the Namibian radiological protection standards are summarised in the sub-sections below Justification of Practices Regarding the justification of practices, regulation 9 of the Regulations under the Act states the following (verbatim quotes are presented in italics, and are cited from [Regulations, 2011]): 9. (1) No practice or source within a practice may be licensed or registered unless it produces sufficient benefit to the exposed persons or to society to offset the radiation harm that it might cause, taking into account social, economic and other relevant factors. (2) The applicant for the licence or registration concerned must provide sufficient information to the Director-General relating to the benefits and the harm to support the justification of the practice. May 2018 Page 15 of 48

16 (3) For the purposes of sub regulation (1), the following practices are deemed not to be justified whenever they would result in an increase in exposure to ionising radiation (a) practices involving food, beverages, cosmetics or any other commodity or product intended for ingestion, inhalation or percutaneous intake by, or in relation to, a human being; or (b) practices involving the frivolous use of radiation or radioactive substances in commodities or products such as toys and personal jewellery or adornments Exposure Dose Limits Regarding exposure dose limits, regulation 10 of the Regulations under the Act states the following (verbatim quotes are presented in italics, and are cited from [Regulations, 2011]): 10. (1) The normal exposure of persons must be restricted so that neither the total effective dose nor the total equivalent dose to relevant organs or tissues, caused by the possible combination of exposures from all practices, exceeds any relevant dose limit specified in Schedule 2, except in the special circumstances contemplated in regulation 11 and as contemplated in regulation (2) Sub regulation (1) does not apply to medical exposures from licensed practices. The relevant dose limits as apply in case of the proposed waste incinerator at Swakop Uranium s Husab Mine are presented in section 2.7 below Optimisation of Protection and Safety Regarding the optimisation of protection and safety, regulation 12 of the Regulations under the Act states the following (verbatim quotes are presented in italics, cited from [Regulations, 2011]): 12. (1) In relation to exposures from any particular source within a practice, radiation safety must be optimised in order to ensure that the magnitude of individual doses (except for the volume of interest in cases of therapeutic medical exposures), the number of people exposed and the likelihood of incurring exposures must be kept as low as reasonably achievable, economic and social factors being taken into account: Provided that the dose to persons delivered by the source must be subject to dose constraints specified in the license condition imposed by the Director-General. (2) A licensee must use, to the extent practicable, procedures and engineering controls based upon sound radiation safety principles to achieve the objective referred to in sub regulation (1). May 2018 Page 16 of 48

17 2.6.4 Dose Constraints Regarding the applicable dose constraints, regulation 13 of the Regulations under the Act states the following (verbatim quotes are presented in italics, cited from [Regulations, 2011]): 13. (1) Except for medical exposure, the optimisation of the radiation safety measures associated with a given practice must satisfy the condition that the resulting doses to members of the critical group do not exceed dose constraints which are equal to the dose limits specified in Schedule 2 or any lower values established by the Director-General. (2) In case of any source that can release radioactive substances to the environment, the dose constraints must be established so that the prospective annual doses to members of the public, including people distant from the source and people of future generations, summed over all exposure pathways, including contributions by other practices and sources, are unlikely to exceed the dose limits specified in Schedule 2 or any lower values established by the Director-General. The relevant dose limits as referred to in Regulations 13(2) above and as are applicable for the proposed waste incinerator at Swakop Uranium s Husab Mine are presented in section 2.7 below. 2.7 REGULATORY DOSE LIMITS The Regulations under the Act distinguish between dose limits that apply to members of the public, and dose limits that apply to occupationally exposed persons [Regulations, 2011]. For members of the public, the inferred average exposure dose of the relevant critical group(s) (as are further defined and discussed in section 5.2) of members of the public over and above the dose from the natural background radiation sources may not exceed the following limits (verbatim quotes are presented in italics, cited from [Regulations, 2011]): The estimated average doses to the relevant critical groups of members of the public that are attributable to practices may not exceed the following limits (a) an effective dose of 1 msv in a year: Provided that in special circumstances, an effective dose of up to 5 msv in a single year may be approved provided further that the average dose over five consecutive years does not exceed 1 msv per year; As the relevant public dose limits are significantly more stringent than the applicable occupational exposure dose limits, the present assessment quantifies the incremental contribution to the applicable public exposure dose from the operation of the proposed waste incinerator at Swakop Uranium s Husab Mine. May 2018 Page 17 of 48

18 3 EXPOSURE TO NATURAL BACKGROUND RADIATION This chapter provides an overview of global and local natural background radiation and associated exposure doses from this radiation field. 3.1 RADIOACTIVITY Not all atomic nuclei found in nature are stable. When unstable nuclei undergo a process of nuclear rearrangement they emit radiation (particles and electromagnetic waves). The process whereby radiation is emitted from atomic nuclei because of nuclear instability is called radioactivity [Von Oertzen, 2018]. The most common types of sub-atomic particles and radiation emitted during radioactive decays of atomic nuclei are alpha particles, beta particles and gamma radiation. Radioactivity is a natural phenomenon, and elements such as uranium, thorium and potassium are naturally occurring radioactive elements. 3.2 BACKGROUND Radiation is travelling energy and manifests itself in the form of electromagnetic waves and subatomic particles [Von Oertzen, 2018]. Every day, humans benefit from the many different forms of low-energy electromagnetic radiation, for example from radio waves, microwaves as used in kitchen appliances and for communications, as well as infrared and visible light. These forms of low-energy radiation are all referred to as non-ionising radiation, because they are not sufficiently energetic to remove electrons from the shells of atoms. Ionising radiation, on the other hand, is associated with high-energy X-rays and gamma rays, as well as alpha and beta radiation as is emitted by radioactive materials. Ionising radiation is sufficiently energetic to strip electrons from atoms, resulting in electrically charged ions. It has long been recognised that large doses of ionising radiation can damage human cells and tissue. Such damage occurs because of direct interactions between radiation and the building blocks of a human cell, as well as indirectly through free-roaming ions that are created at cellular level. 3.3 INTRODUCTION Radioactivity and the effects of ionising radiation on living tissue have been studied for many decades. Today it is well recognised that exposures to large doses of ionising radiation are hazardous to humans. May 2018 Page 18 of 48

19 In 1928, to ensure that the voluntary and accidental exposure to ionising radiation was regulated, the International X-ray and Radium Protection Committee was established. This entity was later renamed the International Commission on Radiological Protection (ICRP), and its main purpose is to establish the basic principles for and to issue recommendations on radiation protection. Today, the ICRP s guidelines form the basis for international as well as national regulations that govern the occupational exposure of workers to radiation, as well as the exposure of members of the public. The ICRP s recommendations have also been incorporated by the International Atomic Energy Agency (IAEA) into its Basic Safety Standards for Radiation Protection, which are published jointly with the World Health Organisation (WHO), the International Labour Organisation (ILO) and the Nuclear Energy Agency (NEA). These standards are used worldwide to ensure that workers who may be occupationally exposed to ionising radiation, as well as members of the public, are protected against actual or potential radiation hazards. In 1955, the General Assembly of the United Nations formed an inter-governmental body known as the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). UNSCEAR is tasked to assemble, study, and disseminate information on observed levels of ionising radiation and radioactivity (both natural and man-made) in the environment, and on the effects of such radiation on humans and the environment. Many of the UNSCEAR reports are regularly used to guide assessments of exposures to radiation. Today s approaches to radiation protection are consistent across the world. Exposure to radiation levels above the natural background are to be justified, kept as low as reasonably achievable, and below individual dose limits, as are specified for workers and members of the public. The Namibian regulatory requirements that govern radiation protection are based on the recommendations of the ICRP and IAEA ([Act, 2005] and [Regulations, 2011]). They imply, amongst others, that a dose limit applies to members of the public, which is set at 1 msv per year (abbreviated as 1 msv.a -1 ) when averaged over 5 years. The dose limit assumes that there is no discernible threshold dose below which there would no longer be a potentially harmful effect due to exposure to ionising radiation. As such, dose limits are an expression of the precautionary approach that guides the application of sources of ionising radiation, including radioactive mineral ores containing uranium, thorium and potassium and others. Amongst others, the regulatory provisions imply that individual exposure doses of members of the so-called critical groups (refer to section 5.2), must be kept as low as reasonably achievable, and that consideration must be given to the presence of other sources of ionising radiation that may cause additional exposure to radiation to members of a given critical group. Also, allowance for future sources and practices must be made, so that the total dose received by an individual member does not exceed the given dose limit over and above the natural background radiation. May 2018 Page 19 of 48

20 3.4 EXPOSURE TO NATURAL BACKGROUND RADIATION (NBR) Natural background radiation, abbreviated NBR, is a natural phenomenon which occurs because of the existence of various natural radiation sources that emit ionising radiation. Amongst others, natural sources of ionising radiation include soils, rocks, and groundwater. Radiation emitted from such sources is called terrestrial radiation. In contrast, radiation of extra-terrestrial origin is called cosmic radiation. Other natural radiation originates from atmospheric radioactive dust, which can be inhaled and/or ingested, as well as from radioactive gases such as radon and associated decay products. In addition, radiation from man-made sources, such as X-ray machines, X-ray fluorescence devices, sealed radioactive sources, radionuclides in equipment and medicines, cigarette smoke and other sources all contribute to the total exposure of a person and the environment to radiation Exposure Dose from Terrestrial Gamma Radiation The contribution of terrestrial gamma radiation sources to the natural background radiation field is quantified by way of a combination of ground- and airborne radiometric surveys. The global average exposure dose rate due to the exposure to terrestrial radiation amounts to some 0.48 msv.a -1, as reported by UNSCEAR [UNSCEAR, 1993]. For Namibia, Wackerle reports dose rates attributable to natural terrestrial radiation that range between 0.5 msv.a -1 and more than 2.5 msv.a -1 [Wackerle, 2009b] Exposure Dose from Cosmic Radiation The contribution from cosmic radiation to the natural background radiation field depends on the geographic location of the receptor. UNSCEAR reports a population-weighted world average exposure dose due to the exposure to cosmic radiation of some 0.38 msv.a -1 [UNSCEAR, 1993]. Namibian exposure doses attributable to cosmic radiation range between 0.3 msv.a -1 at the coast, to approximately 0.7 msv.a -1 in the central highlands [Wackerle, 2009a] Exposure Dose from Radon Progeny Radon, which refers to the isotopes Rn 222 and Rn 220, is a radioactive gas, and is formed in soils through the radioactive decay of radium (Ra 226 and Ra 224 respectively). Radon and its progeny, i.e. the radon decay products, are found in variable concentrations both indoors and outdoors, and exist in most environments inhabited by humans. May 2018 Page 20 of 48

21 Atmospheric radon concentrations are highly variable in time. Radon gas is exhaled from the crystal lattice of uranium- and thorium-bearing ores in which radium is embedded. Once these radioactive gases diffuse into the pore space of the substrate material in which they are embedded they move to the surface of the material and then escape into the atmosphere. The flux of radon isotopes from the soil surface, rocks and tailings facilities is called radon exhalation, and is strongly dependent on the prevailing seasonal and weather conditions and the time of day. In arid environments such as in the Namib Desert in which Swakop Uranium s Husab Mine is located, short-term atmospheric radon concentrations are highly variable. In cold weather conditions, the atmospheric concentration of these gases may increase dramatically once they are trapped in gullies, pits and riverines, which is a phenomenon which is especially prevalent in still-air conditions in the early mornings in winter. Generally, and in direct response to the diurnal variations of pressure and temperature, atmospheric radon concentrations tend to decrease as the sun begins to heat the ground and convection begins. UNSCEAR reports a population-weighted world average exposure dose due to the inhalation of radon progeny amounting to approximately 1.1 msv.a -1 [UNSCEAR, 1993]. The contributions to the total exposure dose from the inhalation of radon progeny have not been quantified across Namibia. However, as part of the Strategic Environmental Assessment undertaken in Namibia s Erongo Region, it was found that the inhalation of radon progeny contributes some 0.45 msv.a -1 to the total exposure dose from natural background radiation [SEA, 2010] Exposure Dose from Radioactive Dust in Air Natural background radiation is also due to the existence of radioactive dust in air. UNSCEAR reports a population-weighted world average exposure dose from the inhalation and subsequent exposure to radioactive dust amounting to some msv.a -1 [UNSCEAR, 1993]. The contribution that radiation from radioactive dust makes to the natural background radiation field has not been quantified across Namibia. However, as part of the Strategic Environmental Assessment in Namibia s Erongo Region, it was found that the inhalation of radioactive dust contributes about 0.04 msv.a -1 to the total exposure dose from natural background radiation sources [SEA, 2010]. Given the limited empirical data on which this exposure dose is based, it is important to note that this value is considered to be indicative rather than definitive. It is noted that the above contribution from radioactive dust is almost seven times larger than the world average value reported by UNSCEAR. Despite this significant difference, it is important to note that radioactive dust only contributes some 2% to the total exposure dose due to the exposure to the natural background field in the Erongo Region and is therefore small. May 2018 Page 21 of 48

22 3.4.5 Exposure Dose from Radionuclides in Food The ingestion of radionuclides as contained in the food we consume, including water and other liquids consumed by humans, also contributes to the total exposure dose from natural background sources of radiation. UNSCEAR reports a population-weighted world average exposure dose due to the ingestion of radionuclides in food and liquids amounting to some 0.31 msv.a -1 [UNSCEAR, 1993]. The contribution that radiation originating from ingested radionuclides contained in food and liquids make to the natural background radiation field has not been comprehensively quantified in Namibia. However, it is generally accepted that the Namibian diet includes a similar composition and concentration of radionuclides as are contained in foodstuff in other parts of the world. As a result, the world average exposure dose of some 0.31 msv.a -1 is assumed to apply for this contribution to the total exposure dose from natural sources as is incurred in Namibia Exposure Dose from Man-made Sources of Ionising Radiation Humans are continuously exposed to ionising radiation of man-made origin. Potential effects due to the exposure to such radiation depend on the intensity and duration of exposure, and the total exposure dose received. Exposure to ionising radiation from man-made sources include, amongst others, medical exposures to X-rays, radiation from radionuclides used in medicine, and those from technical devices such as XRF instruments, as well as smoking, and from ionising radiation emitted from sealed radioactive sources containing radionuclides. In most cases, and as is done on this assessment, man-made sources of ionising radiation are excluded from all further deliberations included in this report. This is justified as such radiation sources are not a natural part of the background radiation field as exists in nature Summary of Exposure Doses due to NBR Table 1 summarises the main exposure contributions from the various natural sources contributing to the natural background radiation [Von Oertzen, 2010], [Von Oertzen, 2018]. Table 1: Main natural background radiation contributors and associated exposure doses Source of Ionising Radiation World Average Exposure Doses due to NBR [msv.a -1 ] NBR Exposure Doses in the Erongo Region [msv.a -1 ] Terrestrial Cosmic Radon Atmospheric dust Food Total Annual Exposure Dose 2.3 msv.a -1 ~ 1.7 msv.a -1 May 2018 Page 22 of 48

23 4 THE PROPOSED WASTE INCINERATOR AND WASTE STREAM This chapter provides an overview of the main radiation-relevant features of the proposed waste incinerator and the to-be-incinerated waste streams. 4.1 LOCATION The proposed waste incinerator is to be located at Swakop Uranium s Husab Mine, which is some 20 kilometres (km) from the town Arandis, some 50 km from Swakopmund, and some 65 km from the port of Walvis Bay, in Namibia s central-western Erongo Region. 4.2 INCINERATOR TYPE As per the information obtained via SLR Consulting, Swakop Uranium has decided to procure and implement the following waste incinerator type Inciner General Incinerator This incinerator is designed for a throughput of 500 kg per hour. It is a top loader and operated as a controlled-air incinerator. As such, the Inciner 8 is a two-staged incinerator, having a primary and secondary chamber. Principal incineration takes place in the primary chamber, while residual incineration and gas cracking takes place in the secondary chamber. The Inciner 8 s operational temperature is at approx. 850 o C. Depending on client specifications, a pollution control system resulting in cleaned flue emissions can be fitted. As per the communications from Swakop Uranium, dated 26 April 2018, a pollution control system meeting the particulate matter emissions as summarised in Table 2 will be fitted to the proposed incinerator. Such fitment results in mitigated incinerator operations, which will be assessed in this Report. In addition, the emissions resulting from mitigated operations are contrasted with unmitigated operations, i.e. in case the pollution control system is not fitted or is not working to specifications. Table 2: Particulate emission limit with pollution control system (mitigated operations) Name of Pollutant Particulate matter Emission Limit with Pollution Control System Fitted to Incinerator 10 mg/nm³ at 273 K and kpa May 2018 Page 23 of 48