Safety for Particle Accelerators

Front matter

Particle Acceleration and Detection

Thomas Otto

Safety for Particle Accelerators

Preface

Particle accelerators have received ever growing attention since their invention in the 1930s. They have developed from one-of-a-kind facilities for fundamental research to a wide range of facilities with specialized applications. Their use in fundamental research is no longer limited to nuclear and particle physics. Synchrotron light sources are, despite their diminutive name, full-fledged particle accelerators and serve material science, chemistry, and biology. Spallation neutron sources employ the most powerful proton accelerators (measured by the product of beam intensity and maximal beam energy) so far constructed. Medicine employs scores of compact electron linear accelerators with a limited energy range (E < 25 MeV), and the advent of proton and heavy ion therapy has led to the construction of specialized synchrotron facilities. Industry uses accelerators, for example, in the production of semiconductors, for the sterilization of medical equipment, and for the polymerization of plastics.

The extension of fundamental research facilities to large national or transnational organizations led to a simplified access of researchers to accelerators. These users are not specialized in accelerator technology and related fields, but they have diverse academic and technological backgrounds. The entry of accelerators into the medical field enhances the demand for reliable and safe operation in the interest of patients and medical staff alike. In industry, finally, the emphasis is on reliability and costeffectiveness. In short, accelerators are used by many non-specialists as a tool which must conform to regulations and standards like other means of production.

International bodies and national regulators define stringent technical and organizational criteria for the safe use of technical facilities and equipment, targeted to protect clients, users, and the environment alike from harm. These regulations apply naturally to particle accelerators. Operators and users are legally obliged to implement regulations and morally bound to respect recommendations as much as technically feasible.

Occupational safety is concerned with controlling the hazardous effects of professional activities for workers, the public, and the environment. Occupational safety draws essential information from physics, chemistry, engineering, occupational health, and environmental protection for providing an optimal, appropriate protection vi Preface from occupational hazards. For particle accelerators, occupational safety creates the conditions for obtaining research, medical, or business objectives in a safe and responsible manner without creating harm for workers, the public, and the environment.

This book gives an overview of the vast subject of safety at particle accelerators. It is targeted at managers, scientists, engineers, and users at accelerator facilities. It serves also as a first introduction for safety professionals who take up work at a particle accelerator or who are generally curious on safety in these facilities. The book is organized into five chapters. Chapter 1 gives a working definition of hazard and risk as an essential introduction to occupational safety. Chapter 2 briefly introduces particle accelerators and then describes safety aspects of their core technologies: magnets, cryogenics, radiofrequency, lasers, and beam interception. Chapter 3 treats safety topics connected to accelerator beams and ionizing radiation. In Chap. 4, safety hazards also occurring in major industries are described in their relation to particle accelerators: electrical and mechanical safety, pressure vessels, fire safety, occupational noise, and environmental impact. The concluding Chap. 5 closes the loop opened in Chap. 1 with a more detailed description of the safety process, it gives an overview of safety organization in accelerator centres, and describes beam safety and functional safety, a concept frequently employed at accelerators.

At around 150 pages, the book cannot be exhaustive, but presents an overview of the subject to the interested reader. References are given to recent literature, preferably to documents freely available on the Internet or as links to websites. All references were up to date at the time of publication; however, occupational safety is a rapidly evolving field. References to regulatory context (directives, laws, standards) may change rapidly, and the reader is warned to check all references for validity before applying them in a real-world accelerator facility.

Safety is based on science and engineering, but it is not a hard science. The “human factor” and the personal viewpoint inevitably enter in risk assessments and in the implementation of mitigation measures. I regularly profit from the collaboration with fellow occupational safety specialists when defining the best risk control measures within a limited budget of money, time, and manpower. The responsibility for this book’s content, including any mistakes, is nevertheless solely my own. The opinions expressed in the book do not always reflect policies of my employer, the European Organization for Nuclear Research, CERN.

This book is dedicated to Marta, my wife and greatest support. Thank you!

Stay safe and healthy.

Geneva, 2020 Thomas Otto

Acknowledgements

A picture says more than a thousand words, and I thank all organisations and companies who allowed me to reproduce their photographs and illustrations in this book:

CERN and PSI for the right to use several photographs of their facilities.

IBA in Louvain-La-Neuve (BE) (Fig. 2.1).

The European Commission’s Directorate-General for Employment and Social Affairs (Fig. 2.21).

The International Electrotechnical Commission (IEC) for permission to reproduce information from its International Standards (Fig. 2.23). IEC has no responsibility for the placement and context in which the extracts and contents are reproduced by the author, nor is IEC in any way responsible for the other content or accuracy therein.

Lawrence Berkeley National Laboratory (USA), D.E. Groom, S.R. Klein, for Fig. 3.1 from the Review of Particle Physics.

RadPro International GmbH in Wermelskirchen (DE) (Figs. 3.7 and 3.8).

Public Health England (PHE) (Fig. 3.9).

ELSE NUCLEAR S.r.l. in Busto Arsizio (IT) (Fig. 3.10).

The Swiss Occupational Accident Insurance SUVA in Luzern (CH) (Fig. 4.2). The UK Health and Safety Executive (HSE) (Fig. 4.15). This Figure is published under Open Government License (OGL), https://www.nationalarchives.gov.uk/ doc/open-government-licence/version/3/.

Finally, a big thank you goes to Hisako Niko from Springer, who accompanied this book from the beginning and who was always very patient with my requests for yet another delay.

Contents

Contents

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Chapter 1 A) Introduction to Occupational Safety get

Abstract Itis not possible to write a book on Safety at Accelerators, or on occupational safety in general, without a practical understanding of the technical language of the field. Like in other scientific or technical fields, words are used with a specific meaning, often deviating from their everyday use. These terms must be clarified before penetrating deeper into the subject. Central to occupational safety are the terms of hazard, risk, and control. A more detailed description of these concepts is found in Chap. 5.

1.1 Hazard

An informal definition of hazard is simply “something with the potential to cause harm”. In occupational safety, harm manifests itself either by an accident or an occupational illness.

Hazard can be classified by the technical domain it originates from (e.g. mechanical, electrical, chemical, physical, psychosocial hazards). Another way of characterisation is by the vector of the hazard: the potential harm is carried by an equipment (for example machine, tool, experimental apparatus), an activity (for example production, construction, maintenance, dismantling) or a substance, either used in the activity (basic material, catalyser, ...) or produced in the process (exhaust gases, dust, ...). Numerous hazards exist at the workplaces in an accelerator facility: in the accelerator building or tunnel, in workshops, laboratories and in offices. This book puts the focus on specific hazards at particle accelerators, for example magnetic fields, cryogenic temperatures, and ionising radiation. Industrial hazards present in industry and services impact also the construction, operation, and maintenance of accelerators and one chapter is dedicated to them with references to guidelines in occupational health and safety (OHS).

A useful tool to classify hazards is a hazard list, as reproduced in Annex A. It contains both general hazards from industry and business and specific hazards occurring at accelerator sites.

© The Author(s) 2021 1 T. Otto, Safety for Particle Accelerators, Particle Acceleration and Detection, https://doi.org/10.1007/978-3-030-57031-6_1

2 1 Introduction to Occupational Safety

1.2 Risk

The informal definition of risk is “a measure of the probability of a hazard to cause harm, and of the severity of the consequences.” By reducing risk, one reduces the probability or/and the severity of harmful effects and therefore improves safety.

Measure is often meant in a qualitative sense. Risk can be classified on a coarse scale as low, medium, or high. Such a qualitative judgement is based on a good knowledge of the employed activities, equipment and substances and previous professional experience and remains always subjective.

Quantitative risk assessment makes use of published data on failure rates of components or equipment, accident rates and of models for the behaviour of complex systems. It is a specialist’s domain and is employed in high-hazard industries, such as the chemical and nuclear industries [2].

Often a risk assessment will be situated between the purely qualitative and quantitative and it is up to the professional judgement of the safety specialist and the line management to determine the correct level of assessment.

Risk and hazard are often confounded in colloquial language. People speak of a “high risk” activity, but they usually mean a high hazard activity. While there may exist considerable hazards at a workplace, it is the purpose of occupational safety to reduce and control the risk of these hazards in such a way that workers are not harmed and that the integrity of the public and the environment is preserved.

1.3 Control

The goal of occupational safety is the elimination of hazards and the diminution of risks. One speaks in this context of “control” (or control measure). To control a danger at the workplace, one may progress by elimination, install technical protection measures, equip the worker with personal protections or instruct and train them to avoid the hazards. In many cases, the required control for a given hazard or risk is dictated by law and regulations. Where this is not the case, it is up to line management and occupational safety specialists to agree on the appropriate level of control. It shall reduce risk to a level acceptable by management and workers, without impeding the activity (e.g. the operation of a facility, the conduction of an experiment) beyond the necessary, and without causing incommensurate cost. Choosing and implementing an appropriate level of control is a matter of professional judgement, and as such is based on experience.

The European Union has published a directive, a document that the member states must translate in national law, where a hierarchy of controls is first evoked [1]. The directive stipulates that the employer shall take the measures necessary for the safety and health protection of workers. He or she shall implement these measures based on the following general principles of prevention:

(a) avoiding risks.

(b) evaluating the risks which cannot be avoided

(c) combating the risks at the source

(d) adapting the work to the individual, especially as regards the design of work places, the choice of work equipment and the choice of working and production methods, with a view, in particular, to alleviating monotonous work and work at a predetermined work-rate and to reducing their effect on health

(e) adapting to technical progress;

(f) replacing the dangerous by the non-dangerous or the less dangerous;

(g) developing a coherent overall prevention policy which covers technology, organization of work, working conditions, social relationships and the influence of factors related to the working environment;

(h) giving collective protective measures priority over individual protective measures;

(i) giving appropriate instructions to the workers.

This European directive defines a framework for occupational health and safety, based on a few principles. More than 30 years old, it has shown its effectiveness and has not been revised since. Its principles influence all following directives and laws relating to occupational safety. The U.S. National Institute of occupational safety and health has cast the hierarchy of controls in a more useful way [3]. It gives preference to eliminating or replacing a risk, and to collective protective measures. Personal protective equipment, technical instruction and safety training of the workers is designated as the least effective measure in this hierarchy of controls. It is known that the effectiveness of these measures for the reduction of accidents and occupational illness depends on individual factors and is generally lower than the technical measures listed first.

1. Council Directive of 12 June 1989 on the introduction of measures to encourage improvements in the safety and health of workers at work, 89/331/EEC, http://data.europa.eu/eli/ dir/1989/39 1/2008-12-11

2. Directive 2012/18/EU on the control of major-accident hazards involving dangerous substances, http://data.europa.eu/eli/dir/2012/18/oj

3. National Institute for Occupational Safety and Health (NIOSH), Hierarchy of Controls, https:// www.cdc.gov/niosh/topics/hierarchy/#

4 1 Introduction to Occupational Safety

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