Occupational Radiation Protection in the Uranium Mining and Processing Industry

By IAEA

This Safety Report has been developed as part of the IAEA programme on occupational radiation protection to provide for the application of its safety standards in implementing a graded approach to the protection of workers against exposures associated with uranium mining and processing. The publication describes the methods of production associated with the uranium industry and provides practical information on the radiological risks to workers in the exploration, mining and processing of uranium. It is a compilation of detailed information on uranium mining and processing stages and techniques, general radiation protection considerations in the relevant industry, general methodologies applicable for control, monitoring and dose assessment, exposure pathways, and radiation protection programmes for a range of commonly used mining and processing techniques.

• Language: English
• Publisher: International Atomic Energy Agency
• Release date: Jun 5, 2020
• ISBN: 9789201065223

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Occupational Radiation

Protection in the

Uranium Mining and

Processing Industry

SAFETY REPORTS SERIES No. 100

Occupational Radiation

Protection in the

Uranium Mining and

Processing Industry

INTERNATIONAL ATOMIC ENERGY AGENCY

VIENNA, 2020

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© IAEA, 2020

Printed by the IAEA in Austria

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STI/PUB/1890

IAEA Library Cataloguing in Publication Data

Names: International Atomic Energy Agency.

Title: Occupational radiation protection in the uranium mining and processing industry / International Atomic Energy Agency.

Description: Vienna : International Atomic Energy Agency, 2020. | Series: IAEA safety reports series, ISSN 1020–6450 ; no. 100 | Includes bibliographical references.

Identifiers: IAEAL 20-01304 | ISBN 978–92–0–106919–1 (paperback : alk. paper) | 978–92–0–162019–4 (pdf)

Subjects: LCSH: Radiation — Safety measures. | Uranium mines and mining. | Industrial safety.

Classification: UDC 614.876:553.495 | STI/PUB/1890

FOREWORD

The Fundamental Safety Principles, IAEA Safety Standards Series No. SF-1, and Radiation Protection and Safety of Radiation Sources: International Basic Safety Standards, IAEA Safety Standards Series No. GSR Part 3, establish the principles and basic requirements for radiation protection and safety applicable to all activities involving radiation exposure, including exposure to natural sources of radiation. International radiation safety regulations have been applied at uranium mines for over forty years. Even though radiation safety regulations in many uranium producing countries are among the most comprehensive and stringent, there is still scope to enhance protection of occupationally exposed workers in terms of improving mechanisms to reduce occupational exposure, achieve informed personal behaviours and apply best engineered controls and other aspects.

Uranium mining companies take active steps to reduce radiation doses and to control exposures wherever they can. They often voluntarily adopt the most recent international requirements and recommendations on dose limits and occupational radiation protection before they become part of national regulations. Enhancing radiation protection of workers on an industry wide and global basis supports the implementation of internationally consistent standards and approaches with regard to the protection of workers.

In 2011, the IAEA initiated the Information System on Uranium Mining Exposure (UMEX) to enhance radiation protection of workers in uranium mining and processing. As a first step, the IAEA conducted a global survey to evaluate worldwide occupational radiation protection. Following an analysis of the results, the IAEA has been able to identify both good practices and opportunities for improvements. This publication presents the results of the questionnaire and identifies actions to assist industry, workers and regulatory bodies in implementing the principle of optimization of protection. This publication also presents information on uranium mining and processing methods, radiation protection considerations, monitoring, dose assessment and radiation protection programmes for the range of commonly used mining and processing techniques.

The IAEA is grateful to all who contributed to the drafting and review of this publication, in particular I. Ženatá (Czech Republic). The IAEA officers responsible for this publication were P.P. Haridasan and H.B. Okyar of the Division of Radiation, Transport and Waste Safety.

EDITORIAL NOTE

Although great care has been taken to maintain the accuracy of information contained in this publication, neither the IAEA nor its Member States assume any responsibility for consequences which may arise from its use.

This publication does not address questions of responsibility, legal or otherwise, for acts or omissions on the part of any person.

Guidance provided here, describing good practices, represents expert opinion but does not constitute recommendations made on the basis of a consensus of Member States.

The use of particular designations of countries or territories does not imply any judgement by the publisher, the IAEA, as to the legal status of such countries or territories, of their authorities and institutions or of the delimitation of their boundaries.

The mention of names of specific companies or products (whether or not indicated as registered) does not imply any intention to infringe proprietary rights, nor should it be construed as an endorsement or recommendation on the part of the IAEA.

The IAEA has no responsibility for the persistence or accuracy of URLs for external or third party Internet web sites referred to in this book and does not guarantee that any content on such web sites is, or will remain, accurate or appropriate.

The authoritative versions of the publications are the hard copies issued and available as PDFs on www.iaea.org/publications.To create the versions for e-readers, certain changes have been made, including the movement of some figures and tables.

CONTENTS

1. INTRODUCTION

1.1. Background

1.2. Objective

1.3. Scope

1.4. Structure

2. OVERVIEW OF THE URANIUM INDUSTRY AND GENERAL RADIATION PROTECTION

2.1. Global uranium production

2.2. Overall occupational exposure

2.3. Uranium mining and processing stages and techniques

3. GENERAL RADIATION PROTECTION CONSIDERATIONS IN URANIUM MINING AND PROCESSING

3.1. International safety standards

3.2. Scope of regulation

3.3. Responsibilities

3.4. Graded approach to regulation

3.5. Specific aspects of radionuclides in the uranium series

4. GENERAL METHODOLOGY FOR CONTROL

4.1. Occupational health and safety considerations

4.2. Hierarchy of control

4.3. Dose minimization

4.4. Exposure pathways

5. MONITORING AND DOSE ASSESSMENT

5.1. Objectives of a monitoring programme

5.2. Responsibility for the monitoring programme

5.3. Types of monitoring programme

5.4. General dose considerations

6. RADIATION PROTECTION PROGRAMMES

6.1. Exploration

6.2. Underground mining

6.3. Surface mining

6.4. In situ leach mining and processing

6.5. Heap leaching

6.6. Processing facilities

6.7. Non-conventional uranium extraction

6.8. High grade ore mining and processing

6.9. Uranium tailings facilities

6.10. Material in transport

6.11. Decommissioning

Appendix I: SURVEY OF THE INFORMATION SYSTEM ON URANIUM MINING EXPOSURE (UMEX)

Appendix II: EXTERNAL EXPOSURE TO GAMMA RADIATION

Appendix III: RADON AN D RADON PROGENY

Appendix IV: INHALATION OF LONG LIVED RADIONUCLIDES I N AIRBORNE DUST

Appendix V: SURFAC E CONTAMINATION

Appendix VI: INGESTION, WOUND CONTAMINATION AND ABSORPTION

REFERENCES

Annex: IAEA QUESTIONNAIRE ON OCCUPATIONAL EXPOSURES IN URANIUM MINING AND PROCESSING

ABBREVIATIONS

CONTRIBUTORS TO DRAFTING AND REVIEW

1. INTRODUCTION

1.1. Background

Natural uranium is the dominant fuel for global nuclear power programmes, and an increase in the momentum of the prospecting, mining and processing of uranium is inevitable in the future as more countries adopt national nuclear power programmes. The World Nuclear Association¹ reports:

"• In the last 60 years uranium has become one of the world’s most important energy minerals.

• It is mined and concentrated similarly to many other metals.

…….

Uranium is a naturally occurring element with an average concentration of 2.8 parts per million in the Earth’s crust. Traces of it occur almost everywhere. It is more abundant than gold, silver or mercury, about the same as tin and slightly less abundant than cobalt, lead or molybdenum.

The three main methods of producing uranium are underground mining, open pit mining and in situ leaching (ISL) (sometimes referred to as in situ recovery, ISR). Conventional mines, either underground or open pit, are usually associated with a mill, where the ore is crushed, ground and then leached² to dissolve the uranium and separate it from the host ore. At the mill of a conventional mine or at the treatment plant of an ISL operation, the uranium which is now in solution is then separated by ion exchange before being precipitated, dried and packed. The product, uranium oxide concentrate, is also referred to as yellow cake and mixed uranium oxide (U3O8, UO4).

Uranium can also be recovered as a by-product from phosphate fertilizer production and from the mining of other minerals, such as copper and gold, when the ores contain economically exploitable quantities of uranium. In such situations, the treatment process to recover uranium can be more complex.

During uranium mining and processing, workers may be exposed externally to gamma rays emitted from the ores, process materials, products and tailings. Internal exposure can arise from the inhalation of long lived radionuclide dust (LLRD) and radon and radon decay products (RDP), and through absorption, ingestion and wound contamination.

1.2. Objective

The objective of this publication is to provide detailed information to assist regulatory bodies and industry operators in implementing a graded approach to the protection of workers against exposures associated with uranium mining and processing. This information will also serve as the basis for creating a common understanding among various stakeholders (e.g. regulators, operators, workers and their representatives, health, safety and environmental professionals) about the radiological aspects of the various processes involved and the ways in which these aspects can be addressed appropriately and effectively.

1.3. Scope

This publication describes the methods of production in the uranium industry and provides practical information on the radiological risks to workers in exploring, mining and processing. This publication also describes the methods of assessing and controlling the radiological risks based on the application of the appropriate IAEA safety standards and good working practices. This information has been compiled from published literature, from unpublished data provided by the contributors to this publication and from numerous experts with extensive experience in the various sectors of the uranium mining and processing industry. Guidance provided here, describing good practice, represents expert opinion but does not constitute recommendations made on the basis of a consensus of Member States.

1.4. Structure

Section 2 provides an overview of the uranium industry and the general radiation protection aspects of various uranium mining and processing methods. Section 3 summarizes the radiation protection principles and considerations that apply to the industry and the application of the international standards, the graded approach to regulation and specific aspects of radionuclides in the uranium decay series. Section 4 addresses the general methodology for control with the introduction of occupational health and safety considerations, the hierarchy of control, dose reduction and exposure pathways. Section 5 explores the arrangements for monitoring and dose assessment of various exposure pathways, and Section 6 presents the occupational radiation protection programmes during the life cycle of different uranium mining and processing methods and stages. The six appendices begin with a description of the Information System on Uranium Mining Exposure (UMEX) survey, which is followed by the methods and analysis of the survey results, and concludes with technical details on the assessment and control of the major exposure pathways.

2. OVERVIEW OF THE URANIUM INDUSTRY AND GENERAL RADIATION PROTECTION

2.1. Global uranium production

With the current interest in nuclear power, there has been an increase in uranium exploration and in the development of new uranium mining and processing facilities in many countries. World uranium production was 55 975 tU as of 1 January 2015 [1, 2]. This uranium production occurred in 16 different countries at approximately 50 different mining and processing facilities. Uranium production has increased by 50% since 2007; and because of this increased demand, the numbers of workers in the uranium mining and processing industry is set to increase substantially within a few years.

In 2012, as part of UMEX, the IAEA developed a questionnaire that was distributed to 36 operators in uranium producing countries. The responses to this first questionnaire were received in 2013. The information in Appendix I is based on the analysis of the questionnaire results from the operating facilities, which comprises 18 operators and accounts for nearly 85% of the global uranium production, and it includes summaries of current practices for monitoring exposures and reporting doses.

Many ISL facilities (also known as uranium solution mining) have operated since the late 1960s (e.g. in Central Asia and the United States of America). In recent years, they have been producing almost half of worldwide uranium supplies, accounting for 48.7% of uranium mined in 2015 [2]. Most uranium mining in Kazakhstan, the United States of America and Uzbekistan is now conducted using ISL methods. ISL mining is also undertaken in Australia, China and the Russian Federation, and ISL operations are being considered in Mongolia and the United Republic of Tanzania [2]. Underground mining (27%), open pit mining (14%), co-product and by-product recovery from copper and gold operations (7%), heap leaching (<1%) and other methods (<1%) accounted for the remaining uranium production [2].

2.2. Overall occupational exposure

Occupational exposure is the exposure of workers in the course of their work, whether full time or part time, as either a company employee or contract worker. Occupational exposure arises mainly from external gamma radiation and the inhalation of LLRD and RDP.

The monitoring practices and dose calculation procedures and assumptions used to estimate worker doses vary according to operations and regulations. Doses can be assessed, for example, from area monitoring and estimates of occupancy times, or be based directly on individual dose measurements. The procedures and assumptions for dose assessment affect not only the estimation of dose by pathway but also the total dose. Thus, it is important to document any assumptions made in estimating and reporting the dose and the values of other key parameters used in calculating the dose. Figure 1 presents the average dose components from the UMEX survey of each pathway of exposure in different types of mining and processing.

The UMEX data for the various operations were combined into four mining methodologies: underground, open cut, ISL and other. Both the underground and open cut mining data were further separated into mining and processing personnel. The other category included exposures from uranium recovery from rehabilitation, wastewater treatment and toll milling. The results of the survey can be summarized as follows:

(a) General observations:

— The dominant uranium mining method was ISL, followed by underground and open cut methods.

— The main process for uranium extraction from ores was acid leaching, followed by alkali leaching.

(b) Assessment of external exposure:

— Most operators used thermoluminescent dosimeter (TLD) methods for the assessment of individual gamma doses.

— Most operators monitored each worker’s dose; the remainder monitored selected group averaging and selected individual monitoring to assess doses.

— Approximately half of operations did not use background subtraction, which can lead to a small overestimation of the occupational dose.

(c) Assessment of LLRD and dust sampling:

— Approximately half the operators used area dust sampling values to estimate doses; the remainder used personal dust sampling methods on individual workers.

— Most operators used gross alpha counting methods for assessing alpha activity.

— Most operators used periodic monitoring for the assessment of inhaled dust.

— Most operators did not use routine bioassay; however, some operators used urine analysis.

(d) Monitoring of inhalation of RDP:

— For monitoring RDP, most operators used area RDP monitoring with worker occupancy factors to estimate doses.

— The monitoring methodology used by most operators was workgroup averaging, followed by individual monitoring.

— Most operators did not use background subtraction, which can lead to a small overestimation of the measured dose.

(e) Dose assessment:

— For the dose calculations, most operators followed the time sheet method, while most of the remainder used electronic devices for time measurement.

— Different types of dose conversion factor (DCF) were used by operators for RDP and LLRD exposure pathways; with regard to RDP exposure, however, most operators followed the values recommended by the International Commission on Radiological Protection (ICRP) [ 3 ].

— The approach to DCFs needs to be harmonized, especially in the case of doses arising from RDP.

— To have an accurate LLRD dose estimate, factors such as the particle size distribution of the inhaled dust, solubility factors and radionuclide mixture need to be considered.

2.3. Uranium mining and processing stages and techniques

The life cycle of a uranium mining and processing operation is a complex process which can extend over decades. The life cycle stages include exploration, planning, construction and operation, decommissioning, handover and surveillance (see Fig. 2). The mining method and design parameters have a significant bearing on the occupational exposures, control measures and monitoring that will be necessary.

The design stage of the life cycle is a critical stage of the process in which the mining and processing method and the plant design is optimized. In addition, the design stage needs to take account of conventional and radiation safety requirements, the methods of waste management and the decommissioning approach. There are a range of mining options available, including underground, surface and in situ mining. Processing also has a large range of options and some are integrally linked to the mining method, such as ISL. The mining and processing are generally closely linked and collectively can be called the operational phase.

Occupational exposure is associated with all of the above stages except for the design stage. Poor decisions in the design phase can have major negative impacts on occupational exposure, and these can be difficult to correct during the operational phase. The choice of mining and processing technique is heavily dependent on the ore grade and the characteristics of the ore body. Other important factors include topography, hydrogeology, geotechnical aspects, logistics and the perspectives of interested parties (e.g. the public, indigenous people, regulatory bodies). Therefore, awareness of the impact of the design approach on the control of occupational exposures is a critical aspect.

2.3.1. Exploration

Exploration is characterized by operations in the field to discover and assess the uranium resource. In most cases, the occupational exposures during exploration are expected to be low, due to the limited amount of radioactive material being handled (a few tonnes) and the usually low ore grades involved in most operations. However, there are exceptions where significantly higher grade ores and quantities are involved and, in some cases, where exploration involves trial mining including underground operations. In the past, the radiation protection aspects of exploration have often been ignored. The modern approach is to assess potential radiation hazards and doses through a prospective assessment and then implement an appropriate radiation protection programme.

2.3.2. Underground mines

Underground mines are designed to facilitate the safe and economic extraction of a mineral resource, and the mining approach will in large part be dictated by the geological constraints of the deposit. Uranium mines face the same safety challenges as mines for other minerals, with the additional constraint of dealing with the radiation associated with the ore. However, except in the case of high grade uranium deposits, it is usually typical mining constraints, such as ground conditions and the size and orientation of the ore zone, and not radiation issues, that determine the optimal mining method. Nevertheless, factors associated with controlling radiation need to be incorporated into the design of the mine to extract the uranium ore safely. The exception is mine ventilation, where far more control of ventilation conditions is likely to be necessary than in conventional underground mines to prevent the buildup of radon concentrations.

The basic radiation protection approach of time–distance–shielding serves as a useful way to highlight some of the key issues that need to be considered in the design and operation of underground uranium mines. With regard to ‘time’, the goal is, to the extent possible, to minimize the amount of time workers are in direct contact with the ore. For low grade ore deposits, this design constraint is not as serious as it is for high grade deposits, where it can eliminate or at least severely restrict the use of some mining methods. Other strategies such as the use of remote controlled equipment and shielding (e.g. clean waste rock on