Dynamic Logical Analytical Methodology Versus Fault Tree: The Case Study of the Auxiliary Feedwater System of a Nuclear Power Plant

Cacciabue, Pietro Carlo; Amendola, Antonella; Cojazzi, G.

doi:10.13182/nt86-a33804

Cited by 45 publications

(11 citation statements)

References 4 publications

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“…Following an initiating event, the dynamic event tree approach [5,22] tracks the possible branchings in the system evolution at specified time intervals through simulation. The simulations stop when a specified number of time intervals or the top event are reached.…”

Section: Dynamic Reliability Methodologiesmentioning

confidence: 99%

A concept paper on dynamic reliability via Monte Carlo simulation

Marseguerra¹,

Zio²,

Devooght³

et al. 1998

Mathematics and Computers in Simulation

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The methodologies employed in the probabilistic safety assessment (PSA) of hazardous engineering systems have reached a high level of maturity. However, a few issues are still worth of further investigation in order to increase the confidence in the results obtained. In this view, in the past 5±10 years, researchers in the field of reliability have proposed a more`dynamic' approach to PSA with the aim of addressing issues concerning the possible mutual interactions between the hardware system states and the plant physical evolution. Nonetheless, some objections have been raised against such a dynamic approach, especially against its practical complexity and the lack of a clear definition of the domain of its applicability. In this paper, an attempt to define more precisely the field of application for a dynamic approach is propounded on the basis of the concept of accident duration. The qualitative discussion is supported with examples of postulated severe accidents in nuclear power plants like those investigated in level-2 PSA. The application of Monte Carlo simulation as a tool capable, in principle, of handling all the features of dynamic PSA is illustrated. Monte Carlo algorithms are illustrated aiming at improving the stochastic part of the analysis and the deterministic integration as well, so as to allow for a considerable reduction in the computation times. # 1998 Published by IMACS/Elsevier Science B.V.

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Section: Dynamic Reliability Methodologiesmentioning

confidence: 99%

A concept paper on dynamic reliability via Monte Carlo simulation

Marseguerra¹,

Zio²,

Devooght³

et al. 1998

Mathematics and Computers in Simulation

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“…The presence of these differences even in such a simple case is an argument in favour of a dynamic reliability analysis even if the required efforts (software complexity and CPU time) are undoubtedly larger. The dynamic approach has also been compared with the well-known DYLAM methodology [21]. The results show a good agreement between the two with reference to the tank problem of Figure 4: in this case component #2 has a flow rate Q 2 = Qt/2.…”

Section: Monte Carlo In Dynamic Reliabilitymentioning

confidence: 89%

Approaching Dynamic Reliability By Monte Carlo Simulation

Marseguerra

Zio

1994

Reliability and Safety Assessment of Dynamic Process Systems

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Abstract. The event tree/fault tree methodology is probably the most widely recognized and adopted method for assessing the reliabilty characteristics of a plant. However the methodology might suffer some limitations when treating scenarios in which the dynamics of the system play an important role. In these cases a dynamic approach seems appropriate: such analysis should take into account the mutual effects of the process physical evolution, the operator's performance and the system hardware configuration,. In general this analysis requires large efforts both in the implementation of the relating models and in their evaluation as a function of time, which in tum leads to large CPU times. Therefore, a research effort aiming at developing fast models and more efficient techniques for their evaluation is needed. Moreover the effects of the input uncertainties on the resulting output should be considered, this being particularly true for the Human Reliability Analysis (HRA) both for the operator model and its input data. In this regard the Monte Carlo approach seems to enjoy the desirable features.In this paper we present a Monte Carlo dynamic approach to reliability and compare it to a classical static analysis in which the time-dependent response of the plant and the control are not followed. A simple example shows how in those cases in which the reliability characteristics of the plant strongly depend on the process, the results obtained by the two methodologies are quite different. The simulation allows to take into account some important issues such as components' aging, failures on demand, operator's actions. Here we present a simple model of failures on demand and the effects that these failures have on the reliability of the system. Biasing of such failures is also introduced and in this regard we point out that these techniques in general require a high degree of care and judgment.

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“…Currently, the DETs are the most popular approach to discrete-time dynamic PSA. Dynamical logical methodology (DYLAM) (Amendola and Reina, 1984;Cacciabue et al, 1986;Cojazzi, 1996) is the first methodology proposed that uses DETs.…”

Section: Frontiers In Energy Research | Nuclear Energymentioning

confidence: 99%