Engineering risk assessments

The hardest part of engineering risk assessment has turned out to be the prediction of the modes of failure. Serious accidents at nuclear installations, such as those at Three Mile Island or at Chernobyl, have been caused by modes of failure that had not been analysed at all. For example, the report of the Presidents Commission on the Accident at Three Mile Island (Presidents Commission, 1979, p9) highlighted that the concentration of the assessment process on more obvious large break scenarios meant that the eventual mode of failure, which was a result of a chain of a number of more minor events, was not even considered. Despite the use of significant resources in the design process, the risk assessment had been unable to characterize the complex system adequately, a system that was totally human-made and defined. In particular, the risk assessment process had not been able to identify modes of failure caused by humans involved in the operations of the reactor behaving in unexpected ways. 

Bagtzoglou AC, Tompson AFB, Dougherty DE (1991) Probabilistic simulation for reliable solute source identification in heterogeneous porous media. Water Resources Engineering Risk Assessment, NATO ASI Series G29 189-201... 

Risk Assessment Institute, (n.d.). American Society of Safety Engineers, Risk Assessment Institute. Retrieved from http //bit.ly/lGYTijl... 

CCPS G-51. 1998. Understanding Quantitative Risk Assessment. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. 

Sundararajan, C. 1992. Structural Engineering Aspects of Plant Risk Assessment. 

Jones, D., Nomenclature for Hazard and Risk Assessment in the Process Industries, Second Edition, Rugby, Wai-wickshire, UK Institution of Chemical Engineers, 1992. 

Wells, G., Hazard Identification and Risk Assessment, Rugby, Warwickshire, UK Institution of Chemical Engineers, 1996. 

The Modeling Engine in THERdbASE has the following model groups 1) Population Distributions, 2) Location/Activity Patterns, 3) Food Consumption Patterns, 4) Agent Releases Characteristics, 5) Microenvironment Agent Concentrations, 6) Macroenvironment Agent Concentrations, 7) Exposure Patterns and Scenarios, 8) Dose Patterns, and 9) Risk Assessment. 

Neill, D.T. et al., 1990b, Omega West Reactor, Level 1, Probabilistic Risk Assessment, Idaho State University, College of Engineering, LANL, LA-UR-90-962. 

I am a physicist who switched to nuclear engineering for my Ph D. My introduction to PSA was as an original participant in the Reactor Safety Study in 1972. Material for this book was first gathered in 1974 for a workshop on what to expect in WASH-1400 (the results of the Reactor Safety Study). Materials were gathered over the years for EPRI, Savannah River Laboratory, and other workshops. A culmination was in 1988 with "Probabilistic Risk Assessment in the Nuclear Power Industry" with Robert Hall as coauthor. This book updates these materials and adds material on PSA in the chemical process industry. I prepared the material for printing using a word processor... 

Risk is often defined as the likelihood of a certain event times a measure of the severity of its consequences. Most risk assessment studies concentrate on estimating the likelihood of certain events. They often concern the release of chemicals, or accidents in engineering projects and the project outcome. In thi.s section, the subject of accidents is not covered. Risk assessment (RA), as a technique, has been adopted by various national governments, by EU, and by OECD.-... 

Banks, W., Wells, J. E. (1992). A Probabilistic Risk Assessment Using Human Reliability Analysis Methods. In Proceedings of the International Conference on Hazard Identification and Risk Analysis, Human Factors, and Human Reliability in Process Safety. New York American Institute of Chemical Engineers, CCPS. 

Henley, E.J. and Kumamoto, H. Reliability Engineering and Risk Assessment. Prentice-Hall, Englewood Cliffs, NJ, 1981. 

Apostolakis, G. Data Analysis in Risk Assessments. Nuclear Engineering and Design, Vol. 71, July 1982. 

The following are some of the factors tliat a consulting engineer should consider in conducting the e.xposure and risk assessment. 

Once tlie system components and their failure modes have been identified, tlie acceptability of risks taken as a result of such failures must be determined. Tlie risk assessment process yields more comprehensive and better results when reliable statistical and probability data are available. In tlie absence of such data, tlie results are a strong function of tlie engineering judgment of tlie design team. The important issue is tliat both tlie severity and probability (frequency) of the accident must be taken into account. 

D. Hendershot, "A Simple Example Problem Illustrating tlie Methodology of Chemical Process Quantitative Risk Assessment," paper presented at AICliE Mid-Atlantic Region "Day in Industry" for Chemical Engineering Faculty, Apr. 15, 1988. 

These challenges are critical to the profession of chemical engineering, the chemical industry, and our country. Risk assessment and management involve input from a multitude of different disciplines. The methodology is rapidly changing and extremely complex and reqrrires both technical input and input from professionals with expertise in legal, economic, judicial, medical, regrrlatory, and public perception issues. 

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