A system is safety-critical if its malfunctioning could have catastrophic consequences for people, property or the environment, e.g., the failure in a car's braking system could be potentially tragic. To produce such type of systems, special procedures, and strategies, that permit their safer deployment into society, should be used. Therefore, manufacturers of safety-critical systems comply with domain-specific safety standards, which embody the public consensus of acceptably safe. Safety standards also contain a repository of expert knowledge and best practices that can, to some extent, facilitate the safety-critical system’s engineering. In some domains, the applicable safety standards establish the accepted procedures that regulate the development processes. For claiming compliance with such standards, companies should adapt their practices and provide convincing justifications regarding the processes used to produce their systems, from the initial steps of the production. In particular, the planning of the development process, in accordance with the prescribed process-related requirements specified in the standard, is an essential piece of evidence for compliance assessment. However, providing such evidence can be time-consuming and prone-to-error since it requires that process engineers check the fulfillment of hundreds of requirements based on their processes specifications. With access to suitable tool-supported methodologies, process engineers would be able to perform their job efficiently and accurately. Safety standards prescribe requirements in natural language by using notions that are subtly similar to the concepts used to describe laws. In particular, requirements in the standards introduce conditions that are obligatory for claiming compliance. Requirements also define tailoring rules, which are actions that permit to comply with the standard in an alternative way. Unfortunately, current approaches for software verification are not furnished with these notions, which could make their use in compliance checking difficult. However, existing tool-supported methodologies designed in the legal compliance context, which are also proved in the business domain, could be exploited for defining an adequate automated compliance checking approach that suits the conditions required in the safety-critical context. The goal of this Licentiate thesis is to propose a novel approach that combines: 1) process modeling capabilities for representing systems and software process specifications, 2) normative representation capabilities for interpreting the requirements of the safety standards in an adequate machine-readable form, and 3) compliance checking capabilities to provide the analysis required to conclude whether the model of a process corresponds to the model with the compliant states proposed by the standard's requirements. Our approach contributes to facilitating compliance checking by providing automatic reasoning from the requirements prescribed by the standards, and the description of the process they regulate. It also contributes to cross-fertilize two communities that were previously isolated, namely safety-critical and legal compliance contexts. Besides, we propose an approach for mastering the interplay between highly-related standards. This approach includes the reuse capabilities provided by SoPLE (Safety-oriented Process Line Engineering), which is a methodological approach aiming at systematizing the reuse of process-related information in the context of safety-critical systems. With the addition of SoPLE, we aim at planting the seeds for the future provision of systematic reuse of compliance proofs. Hitherto, our proposed methodology has been evaluated with academic examples that show the potential benefits of its use. / AMASS

As more systems are becoming embedded hardware-based, challenges regarding software safety and considerable consequences of their failure arise. Various safety standards assure certain safety aspects of systems, addressing areas including testing. The safety standards chosen for this thesis are ISO/IEC/IEEE 29119-2 & 3, IEC 61508-1 & 3, ISO 13849-1 & 2, and ISO/IEC/IEEE 12207:2017. This thesis tackles the problem of compliance with safety standards by utilising a lightweight assessment method, leading to recommendations for improving the test process of an industrial control system. A case study is performed on an automation company to achieve the objectives of this thesis. The method used for the qualitative data analysis results in recommendations regarding the compliance of the company's test process with selected safety standards. As the final step, the execution of a focus group research leads to the industrial evaluation of the recommendations and assessment results. The company's development process fully complies with 22% and fails to comply with 58% of the extracted requirements from the selected safety standards. Furthermore, the thesis results in recommendations for improving the test process of an industrial control system. As a result of performing the case study, a method for a lightweight assessment of the development process of industrial control systems is achieved. The generic method follows five steps, firstly tabulating the data to attain assessment criteria and items, used by the assessment step to get a compliance degree per requirement. The analysis step comes next to shed light on areas of strength and weakness, leading to recommendations. The final step evaluates and refines the recommendations according to the results of a focus group. Further development of the method used in this thesis can lead to a generic method for assessing development processes, concerning safety standards, using limited resources.  The results of this generic method can lead to recommendations for test process improvements of control systems via safety standards.

De acordo com os princípios da proteção radiológica, as práticas que envolvem radiações ionizantes devem ser planejadas e executadas de modo que os valores de doses individuais, o número de pessoas expostas e a probabilidade de exposições acidentais sejam tão baixos quanto razoavelmente exequíveis. Para tanto, faz-se necessário que na execução da dosimetria das radiações sejam utilizados medidores confiáveis de grandezas dosimétricas. Esta confiabilidade depende não só da calibração do medidor, mas também do seu desempenho em determinadas condições de teste. A International Standardization Organization (ISO), com o objetivo de promover a padronização e a coerência metrológica internacional, estabeleceu conjuntos de feixes de raios X de referência para calibração e testes de dosímetros, cuja implantação nos laboratórios de metrologia deve atender a requisitos técnicos específicos. Em baixas energias existem especificidades que precisam ser consideradas tanto na implantação dos feixes de referência quanto na sua utilização em calibração e testes. O presente trabalho faz uma análise dos procedimentos e critérios de implantação das radiações de referência ISO 4037, em baixas energias. Foram realizados experimentos que permitiram cálculos de parâmetros de caracterização dos feixes de referência do Laboratório de Calibração de Dosímetros do Centro de Desenvolvimento da Tecnologia Nuclear (LCD/CDTN). Alternativas às metodologias usuais de determinação da camada semirredutora foram estudadas. Espectros de feixes de referência foram simulados por meio de softwares e comparados com espectros medidos experimentalmente. Condições climáticas distintas foram reproduzidas em laboratório para análise dos seus efeitos sobre os parâmetros dos feixes. Incertezas em relação às medidas de parâmetros de implantação foram avaliadas. Os feixes de baixa energia, de acordo com os critérios da norma ISO 4037, foram considerados implantados, permitindo a revisão dos valores dos coeficientes de conversão de kerma no ar para grandezas operacionais de proteção radiológica. / According to the radiological protection principles, practices involving ionizing radiation must be planned and carried out under the guarantee that the values of individual doses, the number of people exposed to radiation and the probability of accidental exposures are as low as reasonably achievable. Therefore, radiation dosimetry is required to be done with reliable instruments designed for measuring dosimetric quantities. The reliability of the dosimetry depends on both the calibration of the dosimeter and its proper performance under certain test conditions. The International Standardization Organization (ISO), in order to promote international standardization and metrological coherency, established sets of reference X-ray beams for dosimeter calibration and typing-test; they are expected to be implemented in metrology laboratories in compliance with specific technical requirements. At low energies there are specific requirements that need to be considered in both the implementation of the reference beams and their use in calibration and testing. The present study is an analysis of the procedures and criteria for ISO 4037 reference radiation implementation, at low energies. In the Dosimeter Calibration Laboratory of the Development Center of Nuclear Technology (LCD / CDTN), experiments were performed for determining the X-ray reference radiation parameters. Alternatives to the usual methods for half-value layer determination were studied. Spectra of reference beams were simulated with software and compared with experimental measurements. Different climatic conditions were reproduced in the Laboratory for analysis of its influence on the determination of the beam parameters. Uncertainties in the measurements of studied parameters were evaluated. According to the ISO 4037 criteria, the low energy X-ray beams were considered to be implemented; they allowed the determination of the conversion coefficients from air kerma to the operational radiation protection quantities.

Thesis (MPH. ) --University of Limpopo, 2014 / This dissertation reports on findings from a qualitative research that sought to investigate adherence and compliance to radiation safety protocols by radiographers and dental professionals in the Waterberg District. The study also sought to determine the knowledge the participants had on the chronic ill-effects of occupational exposure to radiation, safety protocols and their professional experience in dealing with occupational exposure to radiation. Altogether 60 participants from 8 health institutions in the Waterberg district took part in the study. They were compromised of males and females with ages ranging from 22-60 years. The response rate was 75% (n=45/60). The empirical data of the study shows a consistent yet disconcerting pattern among practitioners about safety compliance, safety protocols and their understanding of long term effect of occupational exposure to radiation. Despite their impressive knowledge of X-rays being a source of ionizing radiation, the level of their understanding of ill-effects thereof was of great concern. The general failure by both professionals in complying with the most basic safety protocols is worrisome. In a nutshell, yet some of the practitioners were found to be greatly exposed to radiation, their daily practices were found not consistent with procedures dictated by the guidelines on the use of medical X-ray equipment. Overall, only 59% of radiographers always wore their dosimeters, a basic monitoring and protective tool to measure their radiation exposure. In the study, only 38% of the dentists were found to be compliant and overwhelmingly alluded this to their employers being unable to supply them with crucial protective clothing, a finding that the researcher cannot dispute as indicated in the responses by the two groups. The failure of the employer in enforcing monitoring and assuring safety to the employees, patients and the general public emerged from this study. Various non-compliance patterns could be attributed to the participants and others to the employer. Protocols as clearly stipulated in R1332 of Hazardous Substance Act 15 of 1973 and other guidelines are not adhered to.

Petroleum products, which are required to keep the 'wheels' of industry and commerce turning, are distributed from the various refineries to their destinations throughout the country on a daily basis and the mode and extent of transportation or conveyance of these products is varied. This distribution activity predominantly takes place by means of road tanker, pipeline as well as rail tanker and quantities during transit could vary from a few hundred litres to many thousands of litres per trip. Road tanker transportation is considered to be the most vulnerable form of distribution means and this poses a high risk in terms of the potential for being involved in an accident. The risk potential associated with the road transportation of these fuels, from an environmental point of view, is aggravated due to: *The conveyance of bulk loads, *non-roadworthiness of many vehicles, *inconsistency in vehicle condition checking systems and in the application of *safety systems, *poor road conditions, *driver fatigue, *hi-jacking threats, *the level of incompetence or unsuitability of drivers, *the inconsistency in driver training programs, *the vulnerability of the tankers being subject to collision and accidents. The potential exists for road tankers involved in accidents to leak or spill large quantities of petroleum products which in turn could result in catastrophic environmental consequences (such as leaking large quantities of fuel into sewers, plantations, rivers and streams thus causing much ground and water pollution). Also, during an accident the fuel leaking from a road tanker may ignite causing it to burn for several hours before it is finally brought under control and extinguished. This may result in much air pollution as well as damage to the surrounding ecological systems. Subsequent explosions could further result in severe loss of life and associated fires which in turn could cause more environmental degradation and damage. For the purpose of this dissertation, focus was specifically placed on the introduction of internal company control measures that a "supplier” company (such as Natref (Pty) Ltd) could implement to check whether petroleum product distributors are complying with predetermined criteria aimed at reducing the potential for accidents involving road tankers. The measuring of how these controls have an effect in the bigger scheme of things in terms of reducing accidents and environmental degradation was very difficult to determine because it was not possible to extract from the distributors how many of their vehicles were actually involved in incidents during the study period. As a result it was not possible to determine whether the improved control measures had an effect on the number of accidents incurred by the vehicles that were effected by the improved application of the standards. The study thus focused primarily on the effect that the implementation of an inspection system could have in progressively reducing the number of defects found on road tankers wanting to gain access to Natrefs site as well as measuring whether an improvement in compliance to standards actually took place. This study was conducted over a period of 22 months and involved the development and implementation of a new procedure and training course, implementation of an inspection checklist, improved reporting methods as well as improved the overall environmental awareness of the employees involved in the checking and inspection process. It is however assumed that the implementation and ongoing enforcement of the company standards has assisted in contributing towards minimising the potential for pollution exposures arising from accidents and in so doing minimising environmental degradation to a larger or lesser extent. / Thesis (M. Environmental Management)--North-West University, Potchefstroom Campus, 2004.

Petroleum products, which are required to keep the 'wheels' of industry and commerce turning, are distributed from the various refineries to their destinations throughout the country on a daily basis and the mode and extent of transportation or conveyance of these products is varied. This distribution activity predominantly takes place by means of road tanker, pipeline as well as rail tanker and quantities during transit could vary from a few hundred litres to many thousands of litres per trip. Road tanker transportation is considered to be the most vulnerable form of distribution means and this poses a high risk in terms of the potential for being involved in an accident. The risk potential associated with the road transportation of these fuels, from an environmental point of view, is aggravated due to: *The conveyance of bulk loads, *non-roadworthiness of many vehicles, *inconsistency in vehicle condition checking systems and in the application of *safety systems, *poor road conditions, *driver fatigue, *hi-jacking threats, *the level of incompetence or unsuitability of drivers, *the inconsistency in driver training programs, *the vulnerability of the tankers being subject to collision and accidents. The potential exists for road tankers involved in accidents to leak or spill large quantities of petroleum products which in turn could result in catastrophic environmental consequences (such as leaking large quantities of fuel into sewers, plantations, rivers and streams thus causing much ground and water pollution). Also, during an accident the fuel leaking from a road tanker may ignite causing it to burn for several hours before it is finally brought under control and extinguished. This may result in much air pollution as well as damage to the surrounding ecological systems. Subsequent explosions could further result in severe loss of life and associated fires which in turn could cause more environmental degradation and damage. For the purpose of this dissertation, focus was specifically placed on the introduction of internal company control measures that a "supplier” company (such as Natref (Pty) Ltd) could implement to check whether petroleum product distributors are complying with predetermined criteria aimed at reducing the potential for accidents involving road tankers. The measuring of how these controls have an effect in the bigger scheme of things in terms of reducing accidents and environmental degradation was very difficult to determine because it was not possible to extract from the distributors how many of their vehicles were actually involved in incidents during the study period. As a result it was not possible to determine whether the improved control measures had an effect on the number of accidents incurred by the vehicles that were effected by the improved application of the standards. The study thus focused primarily on the effect that the implementation of an inspection system could have in progressively reducing the number of defects found on road tankers wanting to gain access to Natrefs site as well as measuring whether an improvement in compliance to standards actually took place. This study was conducted over a period of 22 months and involved the development and implementation of a new procedure and training course, implementation of an inspection checklist, improved reporting methods as well as improved the overall environmental awareness of the employees involved in the checking and inspection process. It is however assumed that the implementation and ongoing enforcement of the company standards has assisted in contributing towards minimising the potential for pollution exposures arising from accidents and in so doing minimising environmental degradation to a larger or lesser extent. / Thesis (M. Environmental Management)--North-West University, Potchefstroom Campus, 2004.

Intrinsically safe (IS) active power supplies subjected to certain transient load conditions can deliver power to a circuit at significantly higher levels than indicated on their nameplate ratings. During a transient load such as an intermittent short-circuit, energy is transferred from the power supply to the short-circuit and an electrical arc may form when the short-circuit is applied or removed. This poses a spark ignition risk as energy is transferred from the arc to the surrounding atmosphere. Currently various International and Australian Standards define the performance requirements for IS electrical apparatus. A duly accredited laboratory is required to establish the intrinsic safety compliance of an apparatus with the Standards. It involves an assessment of the apparatus and may include testing. The assessment of the apparatus determines adequate segregation, separation, construction, and selection of components. The tests performed on the apparatus include a temperature rise test and in some cases, the sparking potential of the circuit is tested using the spark test apparatus (STA). Testing the sparking potential of active power supplies to establish compliance adds significantly to the time and costs involved in establishing compliance. A new alternative assessment method is proposed in this report to augment or replace the testing phase of the compliance certification process for active power supplies. The proposed alternative assessment method (PAAM) is derived from a determination of the steady-state and transient output characteristics of the active power supply under consideration. Parameters such as peak output current, time constant of peak current decay, and the output voltages at these times are measured from the circuit's output characteristics. These measurements can subsequently be used to derive the topology and component values of an equivalent circuit. The resulting equivalent circuit is then considered like a linear power supply and the sparking potential can be determined using existing assessment methods. This thesis investigates in detail the equivalent circuit of a number of direct current (DC) active power supplies whose transient output characteristics exhibit predominantly capacitive behaviour. The results of the PAAM using the equivalent circuit are then compared with results achieved using the current testing procedure with a STA. A small sample of active power supplies is used to generate data from which a relationship between the current testing procedure and the PAAM can be established. The PAAM developed in this research project can be used as a pre-compliance check by designers, manufacturers, or IS testing stations. A failure of this test would indicate that the active power supply's sparking energy is not low enough to be regarded as intrinsically safe. The PAAM requires fewer resources to establish a result than the STA. The benefits of a simplified spark ignition test would flow on from designers and manufacturers to end users.

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Made available in DSpace on 2014-10-09T12:27:28Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:48Z (GMT). No. of bitstreams: 0 / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP