PROCESS RELIABILITY AND SAFETY UNDER UNCERTAINTIES

Uncertainties in the initial conditions and parameters of process syst ems can lead to large variations in the predicted system performance, sometimes with catastrophic consequences. For systems with non-linear dynamics, often the only generally applicable approach to assess the i mpact of these uncertainties on system performance is a search through the operation and parameter range of interest by direct integration o f the system equations. A methodology is presented that can be used to assess process reliability and safety under such uncertainties much f aster than direct integration. The methodology extends the capabilitie s of a previously developed discrete state transition modeling approac h to include capability for the determination of initial conditions th at lead to desirable system operation. Implementation of the methodolo gy on an example system taken from nuclear reactor dynamics shows that : a) the methodology can handle both small and large uncertainties in system parameters and initial conditions, and b) fast conventional app roaches such as perturbation analysis may lead to the choice of more r estrictive or narrower operational ranges for the system than that req uired by reliability/safety considerations. (C) 1996 Elsevier Science Limited.