Risk from a compressed toxic gas system: Part 1, Dispersal probability

At the Lawrence Livermore National Laboratory, we have prepared a Safety Analysis Report for the Department of Energy on our Building 332 Plutonium Handling Facility. This SAR includes an analysis of potential accident scenarios which could lead to offsite consequences to the public having not only radiological exposures, but also exposures to toxic gases such as chlorine. This paper presents a risk analysis of pressurized chlorine gas system proposed for use at Building 332. The focus of the analysis is to calculate the predicted frequency of an unmitigated leak of chlorine from the system which could result in the dispersal of the entire contents of the gas cylinder to the environment. Modeled are postulated valve leaks or pipe ruptures occurring anywhere in the distribution system, as well as the potential failure of leak mitigation. The fundamental credibility of this type of accident is established. The importance of a reliable leak mitigation system is demonstrated, and the dependence of the results on less than optimal data is discussed in the context of uncertainty and sensitivity analyses