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For more than 100 years upstreaming has been the dominant raising method for tailings storage facilities in Southern Africa. However, there is a growing view worldwide that upstreaming is inherently less safe than centreline or downstream raising of tailings storage facilities. Considering that more than 90% of the 250 plus operational tailings storing facilities in Southern Africa are upstream raised and cannot economically be converted to, or replaced by, downstream raised facilities, the arguments for and against upstreaming were examined in this study. It was found that no compelling reason exists to ban upstreaming in Southern Africa, provided that failure mechanisms are thoroughly considered to prevent serious design omissions. The ALARP (as low as reasonably practicable) approach is introduced as a practical method to deal with the risk of failure, and its hierarchical application is illustrated. [ABSTRACT FROM AUTHOR]

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Standard limits for harmful chemicals in consumer goods are important for consumer safety and the development of relevant industries. This paper proposes a method for determining content limits of chemicals in consumer goods by extending the "as low as reasonably practicable" (ALARP) principle by adding the impact of price and cost changes. While giving due consideration to the price and cost factors of consumer goods, this method derives such limits by measuring "acceptable consumer risk level" on the demand side and "industrial tolerance to chemical limits" on the supply side to obtain the ALARP area. Through a combination of functional relations between different factors and chemical limits, including consumer welfare, producer welfare, and external cost, a general chemical limit decision model can be created for the determination of the general limits of chemicals. This research provides a new methodology for studying decisions on chemical limits by considering consumer and industry affordability. In the final part of this paper, the feasibility and effectiveness of the proposed method are verified based on data of Bisphenol A used in the production of polycarbonate (PC) toys; the data were obtained from enterprise surveys and consumer questionnaires. Through our method, in this paper, a more suitable determination of harmful chemical substances can be obtained. [ABSTRACT FROM AUTHOR]

Working in high consequence yet low frequency, events Australian fire service Incident Controllers are required to make critical decisions with limited information in time-poor environments, whilst balancing competing priorities and pressures, to successfully solve dynamic large-scale disaster situations involving dozens of personnel within the Incident Management Team, including of front-line responders from multiple jurisdictions. They must also do this within the boundaries of public and political expectations, industrial agreements, and the legal requirement to maintain a safe workplace for all workers, inclusive of volunteers. In addition to these operational objectives, fire services must also provide realistic training to prepare frontline staff, whilst satisfying legislative requirements to provide a safe workplace under legislation that does not distinguish between emergency services and routine business contexts. In order to explore this challenge, in this article we review the different safety standards expected through industrial and legal lenses, and contextualize the results to the firefighting environment in Australia. Whilst an academic argument may be presented that firefighting is a reasonably unique workplace which exposes workers to a higher level of harm than many other workplaces, and that certain levels of firefighter injury and even fatality are acceptable, no exception or distinction is provided for the firefighting context within the relevant safety legislation. Until such time that fire services adopt the legal interpretations and applications and develop true safety management systems as opposed to relying on "dynamic risk assessment" as a defendable position, the ability of fire services and individual Incident Controllers to demonstrate they have managed risk as so far as reasonably practicable will remain ultimately problematic from a legal perspective. [ABSTRACT FROM AUTHOR]

Fiber length is one of the most important quality parameters of cotton fibers. Transcriptomic analyses of developing cotton fibers have identified genes preferentially expressing in fiber elongation stage, but few have been functionally characterized. Here, on the basis of confirmation of the preferential expression profile of GhAlaRP (Gh_A09G1166 and Gh_D09G1172), an alanine rich protein gene, in the rapid elongating fibers, we investigated the role of GhAlaRP in fiber development by generating transgenic cottons with an increased or decreased expression level of GhAlaRP. Our results showed that the fiber length was consistently significantly shorter in both the GhAlaRP-RNAi lines and the alarp mutant generated by genome editing than in the control YZ-1. GhAlaRP was localized on plasma membrane, nucleus and endoplasmic reticulum. The yeast two-hybrid assay and bimolecular fluorescence complementation assay showed that GhAlaRP co-expresses and interacts with GhAnnexin (Gh_D11G2184) and GhEXPA (Gh_A10G2323) that are involved in fiber elongation. Down-regulation of GhAlaRP co-suppressed the expression levels of GhAnnexin and GhEXPA. These results suggest a role of GhAlaRP in regulation of cotton fiber elongation, which could be achieved by regulating the functions of GhAnnexin and GhEXPA.

The paper seeks to present how the methodology, known as formal safety assessment (FSA), manages to identify and verify potential marine hazards by using risk analysis while providing ways to control these hazards in a cost-effective way. This methodology supposes a prior analysis of available data on maritime accidents. Risk assessment is based on the identification of the major causes that would lead to the occurrence of the accident, the probability of their occurrence, and the consequences resulting from the occurrence of the event. Based on the consequences and the probability of the occurrence of the event, the level of risk is determined, depending on which the most effective control and risk reduction options are adopted. Risks are ranked based on ALARP acceptability criteria. [ABSTRACT FROM AUTHOR]

The utilization of risk acceptance criteria (RAC) can help a business to judge whether the risk level concerning any process involved in its working environment is acceptable or not, especially when the risk has a significant societal impact. Thus, the main intention of this study is to make known the current state-of-the-art concerning RACs and to propose new interpretations of it by surveying, for first time, the scientific literature about the RACs associated with the occupational health and safety (OHS) risk-assessment methodologies (RAA). A second objective of this work is the attainment of a prediction for the evolution of the quantity of the publications concerning OHS-RACs, and a third one is the derivation of an algorithm (via a flow-chart) in order to illustrate the process of the formation of new OHS-RACs. The work consists of two parts, (a) exploring and presenting methods of developing RACs in OHS; (b) classifying, analyzing, and benchmarking relevant published scientific articles by surveying the Scopus data base with proper search-hints, through a time interval of 20 years (January2000--December 2019). The review has defined a plethora of RAC-papers with reference to OHS, which is a remarkable percentage in comparison with the other fields aggregated, and this outcome proves that the issue of utilizing RACs is fundamental for the field of OHS. Additionally, it has been deduced that, day after day, there is an increasing tendency for the scientific community to develop and use RACs in the field of occupational safety, as this is evident by their frequent reference to the risk analysis and assessment (RAA) process. Our specific research methodology has been compatible with the PRISMA protocol. A prediction for the evolution of the quantity of the OHS-RAC publications is also given by confirming the Poisson stochastic process. Finally, we propose a generic guideline framework that can contribute to the establishment of new empirically-generated OHS-RACs. [ABSTRACT FROM AUTHOR]

The containment of infectious diseases is challenging due to complex transmutation in the biological system, intricate global interactions, intense mobility, and multiple transmission modes. An emergent disease has the potential to turn into a pandemic impacting millions of people with loss of life, mental health, and severe economic impairment. Multifarious approaches to risk management have been explored for combating an epidemic spread. This work presents the implementation of engineering safety principles to pandemic risk management. We have assessed the pandemic risk using Paté-Cornell's six levels of uncertainty. The susceptible, exposed, infected, quarantined, recovered, deceased (SEIQRD), an advanced mechanistic model, along with the Monte Carlo simulation, has been used to estimate the fatality risk. The risk minimization strategies have been categorized into hierarchical safety measures. We have developed an event tree model of pandemic risk management for distinct risk-reducing strategies realized due to natural evolution, government interventions, societal responses, and individual practices. The roles of distinct interventions have also been investigated for an infected individual's survivability with the existing healthcare facilities. We have studied the Corona Virus Disease of 2019 (COVID-19) for pandemic risk management using the proposed framework. The results highlight effectiveness of the proposed strategies in containing a pandemic. [ABSTRACT FROM AUTHOR]

There is a vital need for India to adopt risk acceptance criteria (RAC) relating to major hazard industries as it attempts to transform into a major global economy over the coming decades. The present work develops a generalized methodology for establishing RAC, and demonstrates its application in the Indian context. Risk levels from a wide range of natural and technological hazards faced by Indian people is analysed vis-à-vis those of select developed and other emerging economies. It is argued that despite the divergence of key risk metrics and socio-economic parameters – per capita GDP, average wage, value of statistical life, and the degree of risk aversion – between India and representative developed economies, it is viable to align the prospective RACs for India with best global guidelines. Based on the ALARP principle, for employees and the public, the intolerable individual risk levels are projected to be 10−3 and 10-4/year respectively, while the broadly acceptable level for both is proposed to be 10-6/year. For the societal RAC, the slope of the benchmark F–N curve is fixed at -1.0, while for a maximum of 10 human fatalities the anchor intolerable and acceptable frequency points are suggested to be 10−3/year and 10-5/year, respectively. It is hoped that these benchmarks would help regulatory intensification, and a strategic mitigation of both technological and natural hazards encountered in India. [ABSTRACT FROM AUTHOR]

Working in high consequence yet low frequency, events Australian fire service Incident Controllers are required to make critical decisions with limited information in time-poor environments, whilst balancing competing priorities and pressures, to successfully solve dynamic large-scale disaster situations involving dozens of personnel within the Incident Management Team, including of front-line responders from multiple jurisdictions. They must also do this within the boundaries of public and political expectations, industrial agreements, and the legal requirement to maintain a safe workplace for all workers, inclusive of volunteers. In addition to these operational objectives, fire services must also provide realistic training to prepare frontline staff, whilst satisfying legislative requirements to provide a safe workplace under legislation that does not distinguish between emergency services and routine business contexts. In order to explore this challenge, in this article we review the different safety standards expected through industrial and legal lenses, and contextualize the results to the firefighting environment in Australia. Whilst an academic argument may be presented that firefighting is a reasonably unique workplace which exposes workers to a higher level of harm than many other workplaces, and that certain levels of firefighter injury and even fatality are acceptable, no exception or distinction is provided for the firefighting context within the relevant safety legislation. Until such time that fire services adopt the legal interpretations and applications and develop true safety management systems as opposed to relying on “dynamic risk assessment” as a defendable position, the ability of fire services and individual Incident Controllers to demonstrate they have managed risk as so far as reasonably practicable will remain ultimately problematic from a legal perspective.

The current paper presents an application of an alternative probabilistic risk assessment methodology that incorporates technical, human, and organizational risks (T-H-O-Risk) using Bayesian network (BN) and system dynamics (SD) modelling. Seven case studies demonstrate the application of this holistic approach to the designs of high-rise residential buildings. An incremental risk approach allows for quantification of the impact of human and organizational errors (HOEs) on different fire safety systems. The active systems considered are sprinklers, building occupant warning systems, smoke detectors, and smoke control systems. The paper presents detailed results from T-H-O-Risk modelling for HOEs and risk variations over time utilizing the SD modelling to compare risk acceptance in the seven case studies located in Australia, New Zealand, Hong Kong, Singapore, and UK. Results indicate that HOEs impact risks in active systems up to ~33%. Large variations are observed in the reliability of active systems due to HOEs over time. SD results indicate that a small behavioral change in 'risk perception' of a building management team can lead to a very large risk to life variations over time through the self-reinforcing feedback loops. The quantification of difference in expected risk to life due to technical, human, and organizational risks for seven buildings for each of 16 trial designs is a novel aspect of this study. The research is an important contribution to the development of the next generation building codes and risk assessment methods. [ABSTRACT FROM AUTHOR]

Risk assessment and management of an individual landslide is the focus and difficulty. This paper analyzes the landslide losses in China from 1995 to 2018, combined with the ALARP approach, to research the risk acceptable model of landslide in China. Meanwhile, the Shiyantan landslide in Mayang county of Hunan Province is exemplified to quantitatively calculate the landslide risks under different conditions, and based on the risk acceptance level to judge whether the risk value is acceptable. The results show that the individual life risk acceptable criteria for Chinese landslide is 5.36 × 10−6/a, the upper and lower limits of the societal life risk (F-N curve) are 10−7/a and 10−8/a, the societal economic risk (F-D curve) are 10−1/a and 10−3/a. In addition, for the risk assessment of Shiyantan landslide, it is shown that the landslide may be damaged under extreme rainfall conditions. Its economic risk is tolerable risk and life risk is unacceptable risk. It is urgent to formulate relevant measures to mitigate the risk. The results can provide a reference for risk assessment and management conducted in other regions and offer a theoretical basis for early warning and forecast of landslide. [ABSTRACT FROM AUTHOR]

Facility siting mitigation decisions should be made in a logical and defensible manner. This article provides a framework for making and justifying facility siting mitigation decisions beginning with presenting risk results in a clear manner prior to identifying practical risk mitigation strategies, highlighting potential source and location risk mitigation strategies, demonstrating how these strategies can be evaluated with examples, and ultimately to quantifying and optimizing the safety‐benefit of each mitigation strategy/combination of strategies. The outcome of this process provides a defensible basis for prioritization and practicality of risk mitigation strategies, or a combination of strategies that reduce facility risk to broadly acceptable levels or as low as reasonably practicable while minimizing expense. [ABSTRACT FROM AUTHOR]

In Norway, the current regulation for permanent plugging and abandonment of offshore wells is prescriptive, where the requirements for the number and size of plugs do not consider the different types of wells. One then disregards the fact that the wells differ with respect to, for example, flow potential. A differentiation between the wells could allow for cost-saving benefits from the least critical wells, which environment. In this regard, a special challenge lies in how much weight should be given to uncertainties and, in particular, the cautionary principle. In this paper, we look more closely into this issue. We conclude that it is not appropriate to use a static approach to manage plug and abandonment operations. As different ways of plugging and abandonment may be appropriate depending on the well situation, the approach should allow different weights to be given to uncertainties and the cautionary principle. Wells with limited flow potential, for example, should not give as much weight to the cautionary principle as wells with high flow potential. We argue for the use of a dynamic approach to manage plug and abandonment operations, ranging from one extreme, where decisions are made with strong reference to expected cost for some plug and abandonment wells, to another, where the cautionary principle is adopted instead for other wells, with a strong reference to leakage consequences (such as environmental aspects). [ABSTRACT FROM AUTHOR]

Accident statistics indicate that the majority of accidents at four categories of human, environment, equipment, and reputation of a community have mainly occurred in the process industries. Amongst them, the Oil and Gas industries have a significant portion, as these industries handle large quantities of flammable, toxic chemicals, and exposure to the high potential of serious accidents. Having considered these issues, it is essential to execute an in place safe system of work in such industries. Permit to work system (PTWS) is one of the most important and effective key of HSE-MS sub-systems, which has a significant role in identifying, predicting, controlling, and eliminating hazards of activities and probable accidents at workplaces. As a question for this research, it is being used in the oil and gas industry. Currently used PTWS method at gas refineries in Pars Special Economic Energy Zone (PSEEZ) is a paper-based management system document, based on the statistical results obtained using the experiences of trustees and experts, which intrinsically contains some defects and deficiencies; consequently it could not provide sufficient and effective barriers. These inherent PTWS errors and faults as the data-based permit to work system (D.B.P.T.W) are leading the operating system to different types of accidents, and finally system failures and catastrophic disasters. Therefore, in this study Bayesian theory was applied for the conditional probability of fault creator cases (FCCs) of PTWS assessment. Fault creator cases analysis in permit to work system with changes in the current PTWS were used (Current Permit to Work, C.P.T.W) in gas refineries by logical management. So that the use of this new method based on historical and interconnected and multi-faceted fault factors communication and also disconformity/capability for immediate and simultaneous informing and discovering on the relevant system components and also according to a Bayesian analysis on seven important and critical variables for both CPTWS and DPTW.S for pessimist and optimist statuses may improve the protection safety layers and it is possible to decease and finally eliminate accidents as low as reasonably practicable (ALARP) level at gas refinery plants.

Asset integrity management system (AIMS) outlines the ability of an asset to perform its required functions effectively and efficiently whilst protecting safety under the integrated system. AIMS is drawing attentions more than ever since the maximum valuation of existing assets is the main stream in E&P industry currently under the volatile oil market and AIMS plays an important role on this. On the other hand deteriorations of aging facilities or deviation from the basis of design are common challenges in brown field. Such late stage challenges were eminent issues in the production Asset A and in addition to the rigorous inspection and maintenance program a facility life extension work (FLEW) had launched for the extension of the facility life. At the same time an asset integrity & operation assurance (AI&OA) initiative had been built from the corporate standpoint to propagate the AIMS concept to the production assets. In 2017 an AI&OA survey under AI&OA initiative was conducted focusing on FLEW to observe the status and ensure FLEW was in progress under systematic and competent manners in line with the AIMS. AI&OA framework is a cyclic process stating from the risk identification. As the result of the survey it was acknowledged FLEW needed to reinforce some items such as the risk assessment, organization structure, project execution plan, monitoring and key performance indicator (KPI), technical authorization, document control and project review process. Another AI&OA Survey was conducted in 2018 focusing how FLEW program was conveyed adhering to AI&OA framework and addressing the items pointed out during 2017 survey. 2018 survey result had indicated FLEW program was executed in line with AI&OA framework fulfilling all of requirements. [ABSTRACT FROM AUTHOR]

Well integrity management has been highlighted as a major theme in oil and gas industry after Macond blowout incident in 2010. JX Nippon Oil & Gas Exploration Corporation（"JX Nippon"）has established and implemented systems named JX Well Integrity Management System（"JX WIMS"）and JX Well Delivery Management System（"JX WDMS"）, by which JX Nippon is enabled to effectively manage well integrity risk at any stage of well life cycle. As a part of well integrity management process, thorough audits were carried out on all JX Nippon's operating wells to investigate its degree of compliance with corporate standard. Several wells revealing integrity issues such as not complied well design nor loss of well barrier effectiveness were identified, then those risks were assessed and mitigated accordingly. This paper presents on JX WIMS and an example of achievement on a gas lift producer whose risk was successfully mitigated to ALARP and deemed acceptable for continuing production. [ABSTRACT FROM AUTHOR]

Fire safety engineering designs should comply with the ALARP requirement, meaning that fire safety measures should be implemented to ensure that fire risks are As Low As Reasonably Practicable (ALARP). However, previous approaches have often been contradictory or unclear, especially with respect to the concepts of risk aversion, the valuation of risk to life, the concept of disproportionality, and the need to take into account monetary benefits resulting from life safety investments. First, the As Low As Reasonably Practicable (ALARP) criterion is specified to a societal, risk-neutral, and scalar cost-benefit analysis in the field of fire safety engineering. This is done to overcome the shortcomings in current practice with respect to utilizing the ALARP criterion for Probabilistic Risk Assessment (PRA). Second, the ethical dilemma of the valuation of risk to human lives is addressed by application of the Life Quality Index (LQI), as has been suggested in the field of structural engineering through the recent ISO 2394:2015 standard. Contrary to the existing literature, the proposed interpretation for the ALARP requirement corresponds to an application of the LQI maximum societal benefit criterion. This ensures that safety resources are allocated so as to maximize the number of lives saved, and implies that the ALARP criterion results in stronger minimum requirements for life safety investments, i.e. societal lower bound investment levels. Third, the valuation of costs and benefits by the fire safety engineer is addressed by emphasizing the duty of care, and by specifying a benchmark criterion for the objective, diligent, and competent fire safety professional. This reinforces self-reflection amongst fire safety professionals, and diminishes the need for often unjustified or poorly specified disproportionality factors. Finally, the relationship between fire safety design and private actor cost-optimization considerations is discussed, and the presented concepts are illustrated using three examples. These clarify the application of the presented concepts and demonstrate how the societal ALARP requirement interacts with the (safety) preferences of private investors. The examples highlight the importance of the societal ALARP evaluation and show that this governs the safety investment when the private investor values damages low, applies a high discount rate, or takes into account indirect costs (e.g. aesthetic costs) related to the safety investment. • Application of the ALARP criterion to probabilistic fire engineering design is discussed. • The ALARP criterion is identified as a societal, risk-neutral, and scalar cost-benefit analysis. • The relationship between ALARP and private cost-benefit considerations is clarified. • The societal willingness to pay for reductions in risk to life is derived from the Life Quality Index (LQI). • Examples of potential applications to sprinkler installation and egress width are presented. [ABSTRACT FROM AUTHOR]

Accident statistics indicate that the majority of accidents at four categories of human, environment, equipment, and reputation of a community have mainly occurred in the process industries. Amongst them, the Oil and Gas industries have a significant portion, as these industries handle large quantities of flammable, toxic chemicals, and exposure to the high potential of serious accidents. Having considered these issues, it is essential to execute an in place safe system of work in such industries. Permit to work system (PTWS) is one of the most important and effective key of HSE-MS sub-systems, which has a significant role in identifying, predicting, controlling, and eliminating hazards of activities and probable accidents at workplaces. As a question for this research, it is being used in the oil and gas industry. Currently used PTWS method at gas refineries in Pars Special Economic Energy Zone (PSEEZ) is a paper -based management system document, based on the statistical results obtained using the experiences of trustees and experts, which intrinsically contains some defects and deficiencies; consequently it could not provide sufficient and effective barriers. These inherent PTWS errors and faults as the data-based permit to work system (D.B.P.T.W) are leading the operating system to different types of accidents, and finally system failures and catastrophic disasters. Therefore, in this study Bayesian theory was applied for the conditional probability of fault creator cases (FCCs) of PTWS assessment. Fault creator cases analysis in permit to work system with changes in the current PTWS were used (Current Permit to Work, C.P.T.W) in gas refineries by logical management. So that the use of this new method based on historical and interconnected and multi-faceted fault factors communication and also disconformity/capability for immediate and simultaneous informing and discovering on the relevant system components and also according to a Bayesian analysis on seven important and critical variables for both CPTWS and DPTW.S for pessimist and optimist statuses may improve the protection safety layers and it is possible to decease and finally eliminate accidents as low as reasonably practicable (ALARP) level at gas refinery plants. [ABSTRACT FROM AUTHOR]

Abstract There are currently no detailed regulations or guidelines for designing the safety concept for an underground terminal for buses powered by compressed natural gas (CNG). Neither are there any explicit safety targets for this type of facility in legislation or common practice. A dilemma arises both in the land-use planning process and building design process when evaluating whether the safety of such a bus terminal is sufficient. However, there are internationally accepted principles in other sectors that may be useful in defining a safety target in this case. In this paper it is proposed that such a safety target can be quantified using risk acceptance criteria expressed in terms of individual and societal risk. The method developed in this study is based on comparisons with risk acceptance criteria applied in other types of facilities and activities, both nationally and internationally, and required an extensive inventory of these. The method also takes into account the fact that people's perceptions of risks affect their acceptance. The proposed safety target is presented in terms of an upper and a lower F-N curve, and includes the ALARP principle. In addition to this a maximum average risk (PLL) is specified for the facility. A plausibility check was carried out indicating that the risk level defined by the safety target is lower than, or of the same order of magnitude as, many other corresponding risks in society, e.g. in other transport systems. Highlights • Deriving a safety target in a structured way. [ABSTRACT FROM AUTHOR]

JX Nippon Oil & Gas Exploration Corporation has established and implemented JX Well Construction Management System ("JX WCMS")for managing risks associated with well operations throughout well life cycle. Well Delivery Process ("WDP")which is a core part of JX WCMS and is the systematic management process to plan, execute and review well operations has been adopted and implemented by major oil companies since 1990's and some regulatory authorities have started since BP Macondo blowout disaster in 2010, to mandate the application of WDP to any well operations projects. The main objective of JXWCMS is to reduce the well operations risks to ALARP level and prevent any catastrophic incidents or blowout. [ABSTRACT FROM AUTHOR]

Introduction This article investigates a practical method of reducing the impact of scattered radiation during a lateral radiographic projection of the elbow. The light beam diaphragm (LBD) is generally accepted to limit ionising radiation using horizontal and longitudinal lead shutters, yet this article evidences further dose limitation by placing lead-rubber inferolateral to the LBD device. Methods Using an anthropomorphic phantom and arm construction scattered radiation was recorded at multiple radiosensitive organs. A 15 cc ionisation chamber (model 10100 AT TRIAD) was placed on each radiosensitive organ (eye, thyroid, breast, testes, spleen and ovaries) measuring exposure rate (μGy/s). Dose readings were recorded before and after the placement of lead-rubber inferolateral to the LBD. A paired two sample t- test was undertaken affirming how likely dose limitation was attributable to chance ( p < 0.05). Results Descriptive and inferential statistics demonstrate dose reduction to radiosensitive organs (right eye 53%, right breast 53%, left eye 39%, thyroid 13%, left ovary 9%, testes 6%, left breast 3% and spleen 2%) upon placement of the lead-rubber inferolateral to the LBD. The paired two sample t- test demonstrated statistically significant dose limitation ( t = 2.04, df = 7, p = 0.04) thus significant for radiographic practice. Conclusion Placement of lead-rubber inferolateral to the LBD limits dose to multiple radiosensitive organs. Right (53%) and left (39%) eye lens, right breast (53%), thyroid (13%), left ovary (9%), testes (6%), left breast (3%) and spleen (2%) statistically demonstrate dose limiting opportunities to patients. [ABSTRACT FROM AUTHOR]

In process industry, SIL determination is a risk assessment process through which target Safety Integrity Levels (SIL) are allocated to Safety Instrumented Functions (SIF). A target SIL represents the significance of the hazard against which the SIF protects the plant. This paper introduces new SIL determination methods by taking an optimization approach. Unlike the conventional methods, which are generally focused on calculating the gap between the existing and tolerable levels of risk, the methods introduced in this paper are aimed at optimizing the marginal cost or the benefit-cost ratio. By incorporating the cost factor into the SIL determination process, these methods deliver the most reasonably practicable solutions that can minimize the risk while taking into account the cost of solution. The new methods are formulated for corporate risk and the risk to community (i.e. ALARP). Both methods are derived for demand and continuous modes of SIF operation. Furthermore, a new Safety Index is introduced to combine the SIL and the average Probability of Failure on Demand (PFD) or Frequency of Failure per Hour (PFH). The application of the mathematical models is demonstrated through a practical example from power industry. [ABSTRACT FROM AUTHOR]

• Safety cases use tools including quantitative risk analysis, layer of protection analysis, risk matrices and cost benefit analysis. • All of these methods do not demonstrate that risks have been reduced so far as is reasonably practicable. • Four suggestions are provided to improve safety case: 1. Demonstrate the tolerability of risks; 2. Demonstrate how legal obligations are addressed; 3. Use consequence-based analysis; 4. Provide regulators with the power to directly change the safety case. Australian major hazard facilities (MHF) are regulated through a 'safety case' regime requiring operators to submit a safety report to the regulator demonstrating all risks have been reduced so far as is 'reasonably practicable'. The Work Health and Safety Act (2019) has codified the definition of what is reasonably practicable, requiring consideration of five matters: the likelihood of the risk; degree of harm; what is known about the risk; availability and suitability of risk control measures; and the cost of the control measures. Thirteen interviews with MHF regulators were conducted across Australia to understand how they regulated safety cases and applied the concept of reasonably practicable. The regulators revealed they relied on the operator to provide the safety case to demonstrate how the facility had reduced risks so far as is reasonably practicable. The regulators stated that the four most common tools used to demonstrate reasonable practicability were: quantitative risk assessment, layer of protection analysis, cost-benefit analysis, and risk matrices. These tools were examined against the five considerations of reasonable practicability. None of these tools addressed all five considerations. Four suggestions are provided to improve the safety case process: 1. Safety case should demonstrate how the risk is acceptable. 2. Safety case should outline how the operator has met their legal obligations. 3. Safety case should place greater emphasis on the use of consequence-based analysis. 4. Regulators should be granted additional powers to enforce their interpretation of what is reasonably practicable. [ABSTRACT FROM AUTHOR]