独立防御層の確率論的リスク評価

抄録

In chemical and nuclear power plants, the safety policies have been established according to the consideration of independent protection layer (IPL). This paper studies risk reduction using the IPL consisting of n layers. For general failure distribution function of plant and IPL, we proposed a general algorithm to estimate the expected numbers of normal trips and accidents caused by IPL failure. The results of this algorithm gave agreement with those had been concluded by Markov analysis in the case of exponential distribution. Moreover, the expected numbers of normal trips and accidents are derived analytically when n≤3. Furthermore, we provided a new quantification method for assessing the risk reduction by the use of IPL. The method is illustrated through application to the risk assessment of nitrobenzene synthesis batch plant.