The analysis of events initiating potential accidents in heavy water plants

The paper presents an analysis of potential dangerous events (hazards) that can occur in heavy water plants. This analysis is made by hazard and operability studies (HAZOP). The purpose is to detect any undesirable event foreseeable in the plant's operation. Such purpose is achieved by a systematic study of the operations to be carried out for each process step involved and also of the way in which the various involved components interact. The hazard and operability study started by collecting data about the plant's construction and operation. Unwanted events were identified from the deviations from the normal operation, establishing the possible causes of these deviations, the probability of occurrence assessed by the probability level and their consequences for the process and the environment by qualitative terms. After identification of deviations and estimation of consequences, the necessary measures were determined. The HAZOP methodology was applied to heavy water by isotopic H2O-H2S exchange which circulates high quantities of hydrogen sulphide. The data regarding the technological process, the hydrogen sulphide properties, the constructive characteristics of each type of components, as well as the operating mode of the installations permitted the identification of the main types of undesirable events in initiating potential dangerous situations. The HAZOP studies are carried out periodically in order to analyze the efficiency of the proposed measures. (authors)