Toxic release consequence analysis tool (TORCAT) for inherently safer design plant

Chemical substitution in processes for inherently safer design: pros and cons

The aim of chemical substitution is to replace hazardous chemicals with a less hazardous alternative in a certain product or process to make it safer for human health and the environment. While a lot has been done by researchers, industries and regulatory bodies on chemical substitution for safer products, very little has been reported in the field of safer processes. On the other hand, chemical substitution is one of the core principles of inherently safer design, a concept frequently used in the chemical industry for the prevention of major accidents. This work presents an analysis of implementing chemical substitution methodology for safer processes through inherently safer design. Chemical industries, nowadays, are frequently asked to phase out hazardous chemicals from their processes. This paper provides an insight into the issues and practicability of chemical substitution in processes with the help of case studies and a review of the existing frameworks of inherently safer design.

Development of an inherent system safety index (ISSI) for ranking of chemical processes at the concept development stage

Inherently safer design is the most proactive approach to manage risk, as referred by scientists and experts. Researchers have adopted various methods in evaluating inherent safety indices like parameter-based indexing, risk-based indexing, consequence-based indexing, etc. However, the existing approaches have their limitations. The present paper focuses on establishing an inherent system safety index (ISSI) to evaluate inherently safer design during the concept development stage. The analysis starts by identifying a non-harmful system's inherent safety characteristics and related parameters. Four subindexes, determined from the non-harmful system's characteristics, are established using their relevant parameters. The safety of the chemical process system, the health of workers, and the environment's safety can be assured by selecting relevant parameters. Parameters are scored based on their deviation from the non-harmful condition. The sum of the deviations of the parameters gives the value of the inherent safety index. The case study looks at various routes of Methyl Methacrylate (MMA). According to the present case study, MMA production followed by Tertiary butyl alcohol is the safest route given health, safety, and environmental perspective. This approach helps overcome the limitation of parameter-based indexing, which arises from selecting predefined fixed parameters that become invalid in case of system variation or significant modification of the system. Besides, it considers the complexity and vulnerability that arises from the interaction of various factors|, which increase predetermined risk calculated at the design stage when the system is in operation. The subindices can be used individually if a focus is needed in a definite section of a system with a particular application or a smaller portion. This method is helpful for the industry in designing a safer plant considering the health, safety, and environmental perspective at the concept development stage.

A scenario-based modeling approach for emergency evacuation management and risk analysis under multiple uncertainties

Nuclear emergency evacuation is important to prevent radioactive harms by hazardous materials and to limit the accidents' consequences; however, uncertainties are involved in the components and processes of such a management system. In the study, an interval-parameter joint-probabilistic integer programming (IJIP) method is developed for emergency evacuation management under uncertainties. Optimization techniques of interval-parameter programming (IPP) and joint-probabilistic constrained (JPC) programming are incorporated into an integer linear programming framework, so that the approach can deal with uncertainties expressed as joint probability and interval values. The IJIP method can schedule the optimal routes to guarantee the maximum population evacuated away from the effected zone during a finite time. Furthermore, it can also facilitate post optimization analysis to enhance robustness in controlling system violation risk imposed on the joint-probabilistic constraints. The developed method has been applied to a case study of nuclear emergency management; meanwhile, a number of scenarios under different system conditions have been analyzed. It is indicated that the solutions are useful for evacuation management practices. The result of the IJIP method can not only help to raise the capability of disaster responses in a systematic manner, but also provide an insight into complex relationships among evacuation planning, resources utilizations, policy requirements and system risks.