(47bf) Resolving Inherently Safer Design Conflicts with Decision Analysis

The Chemical Safety Board (CSB) investigated a fatal explosion at a chemical plant in Institute, West Virginia. The CSB noted that the incident placed at risk a large inventory of methyl isocyanate, the toxic and reactive chemical responsible for the 1984 Bhopal tragedy. The CSB commissioned a study by the National Academy of Sciences (NAS) to investigate the application of inherently safer design (ISD) concepts to the design of the subject chemical plant. One of the findings of the NAS report was the absence of guidance documents to assist the process safety professional when evaluating ISD alternatives. The challenge identified in the NAS report is that process technology alternatives must satisfy multiple objectives, some of which may be in conflict. The NAS panel recognized the potential value of multiattribute utility theory as a basis for evaluating ISD alternatives, but they did not illustrate its use in this report.

In this paper we illustrate the use of multiattribute utility theory (MAUT) as a decision analysis tool for evaluating ISD alternatives. Using the NAS report as the foundation of our study, we show how to use MAUT to evaluate ISD alternatives by formulating utility functions and weights for the decision objectives. A sensitivity analysis is also presented to demonstrate how the final ranking of alternatives varies with the weights. This case study demonstrates that the MAUT technique is an effective tool for resolving ISD conflicts.