Non-linear Dynamical Reliability Analysis in the Very High Temperature Gas Cooled Reactor

Abstract

A dynamic safety assessment has been developed for the passive system in the very high temperature gas cooled reactor (VHTR), where the operational data are deficient. It is needed to make use of the characteristics of the reactor in order to compensate the data shortage and to treat the propagation. Therefore, this paper focuses on the failure frequency construction of the basic events and the advanced method of the propagation. The mass flow rate of the natural circulation in the passive system is related to the fuel temperature which affects to the failure fraction of the fuel. These features are exploited for the failure frequency of the basic event. The non-linear string logic is used due to the simple and tractable algorithm of the passive system instead of the tree concept which is used in the event-fault tree based decision making. The time feedback is applied to the string concept, where the time weighting is adjusted by the operator’s judgment. The result is obtained by 4 cases. 2 cases among them are non-linear transition features of the events using feedback. These are the particular values comparing the other 2 cases of the linear propagations, which are constructing the characteristics of the dynamic resistance-stress method (DRSM). Using the string algorithm, one can make the safety assessment successfully in any other advanced reactor like the VHTR.