Risk Analysis and Design: Probabilistic Safety Assessment for the Replacement Research Reactor in Australia

J. BARÓN; J. NÚÑEZ MC LEOD; S. RIVERA

Bariloche

Congreso; 2do Congreso Latinoamericano de Calidad en la Industria del Petróleo y del Gas; 2004

Instituto Argentino del Petróleo y del Gas

In July 2000, a contract was signed by the Argentinian company INVAP S.E. for the design, construction and commissioning of a replacement research reactor (RRR) to be build in Lucas Heights, near Sydney, Australia.  Among the different studies needed for this reactor, INVAP contracted CEDIAC to prepare the Probabilistic Safety Assessment (PSA) for the RRR in support of the application for the construction licence. The PSA is complementary to the deterministic Safety Analysis, attempting to determine all the possible individual failures and combinations of failures that may contribute to the risk of the installation.  The risk estimation is performed with a probabilistic methodology, using generic data for component failures and models on human reliability. Besides the basic objective of the PSA, which is the quantitative evaluation of the risks associated with the RRR, and its comparison to the regulatory objectives, the PSA studies have been performed in parallel with the basic engineering phase of the project.  Therefore, preliminary results from “the risk point of view” were used as input to the design process, thus permitting improvements to be made to the design, and resulting in an effective reduction of the residual risk. To perform the PSA studies several methodological developments were made, in order to obtain a representative list of internal and external initiating events, to treat component and human-related failures, to consider common-cause failures, and to consider some specific aspects of the design (i.e., fail-safe components, passive systems, and lack of need for support systems). The PSA studies were performed to obtain not only quantitative estimations of the risk, but also quantitative estimations of the uncertainty associated with them. The overall results of the PSA indicate a very low residual risk for the RRR, providing the fulfillment of the most stringent Australian and Argentinian standards on the field.  Besides, the developed tool (living PSA) allows for the analyses of different operation alternatives, different maintenance schemes and different personnel structures.  Minor design changes can also be evaluated, always looking at the plant from the risk point of view. Altogether, the PSA proved to be a valuable tool to increase the safety level of the RRR, and this was possible because the interaction between the PSA performers and the designers was straightforward.