rpra6 - RPRA 6. Probabilistic Risk Assessment 1 Engineering...

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Unformatted text preview: RPRA 6. Probabilistic Risk Assessment 1 Engineering Risk Benefit Analysis 1.155, 2.943, 3.577, 6.938, 10.816, 13.621, 16.862, 22.82, ESD.72, ESD.721 RPRA 6. Probabilistic Risk Assessment George E. Apostolakis Massachusetts Institute of Technology Spring 2007 RPRA 6. Probabilistic Risk Assessment 2 Objectives • Identify accident scenarios. • Rank these scenarios according to their probabilities of occurrence. • Rank systems, structures, and components according to their contribution to various risk metrics. RPRA 6. Probabilistic Risk Assessment 3 PRA Steps • Define end states • Identify initiating events • Develop event and fault trees • Quantify RPRA 6. Probabilistic Risk Assessment 4 Example: Nuclear Power Plant PWRs keep water under pressure so that it heats, but does not boil. Water from the reactor and the water in the steam generator that is turned into steam never mix. In this way, most of the radioactivity stays in the reactor area. Courtesy NRC http://www.nrc.gov/reading-rm/basic-ref/students/animated-pwr.html RPRA 6. Probabilistic Risk Assessment 5 NPP End States • Various states of degradation of the reactor core. • Release of radioactivity from the containment. • Individual risk. • Numbers of early and latent deaths. • Number of injuries. • Land contamination. RPRA 6. Probabilistic Risk Assessment 6 The Master Logic Diagram (MLD) • Developed to identify Initiating Events in a PRA. • Hierarchical depiction of ways in which system perturbations can occur. • Good check for completeness. RPRA 6. Probabilistic Risk Assessment 7 MLD Development • Begin with a top event that is an end state. • The top levels are typically functional. • Develop into lower levels of subsystem and component failures. • Stop when every level below the stopping level has the same consequence as the level above it. RPRA 6. Probabilistic Risk Assessment 8 Nuclear Power Plant MLD Insufficient Reactivity Control Insufficient Core-heat Removal Insufficient RCS Inventory Control Insufficient RCS Pressure Control Insufficient RCS Heat Removal Insufficient Isolation Insufficient Combustible Gas Control Insufficient Pressure & Temperature Control Excessive Offsite Release Excessive Core Damage Conditional Containment Failure Excessive Release of Core Material Excessive Release of Non-Core Material RCS pressure Boundary Failure RPRA 6. Probabilistic Risk Assessment 9 NPP: Initiating Events • Transients – Loss of offsite power – Turbine trip – others • Loss-of-coolant accidents (LOCAs) – Small LOCA – Medium LOCA – Large LOCA RPRA 6. Probabilistic Risk Assessment 10 Event Sequence Diagrams and Event Trees • Two different ways of depicting the progression of a scenario....
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This note was uploaded on 11/08/2011 for the course AERO 16.851 taught by Professor Ldavidmiller during the Fall '03 term at MIT.

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rpra6 - RPRA 6. Probabilistic Risk Assessment 1 Engineering...

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