Analysis of Initiating Events

Guidelines for the probabilistic safety analysis have been issued recently. In the guidelines, the analysis of initiating events in other operational states than full power is recommended if essential contributions to the total core damage frequency are to be expected. Efforts have therefore concentrated on limited shutdown analysis for a typical PWR and BWR. A low power and shutdown analysis for one PWR has been completed, one for a BWR will be finished soon and a third, major PWR analysis has just been started. 

The possibility of repair during accident situation is yet to be included into Probabilistic Safety Assessment (PSA). A PSA method Includes Event tree (ET) to generate accident scenario and Fault Tree (FT) used to quantify the probability of failure of the Safety Barrier (SB). In literature, there are some examples in which FT analysis has been done for systems with repair components. A FT analysis of phased mission systems has been performed with repairable and non-repairable components (Vaurio 2001). The other FT models with repairable basic events have been proposed based on renewal intensity principle and inclusion-exclusion methods (Yuge et al. 2012 Yuge et al. 2013). However, ET analysis of Initiating Events (IE) with repairable SB has not been dealt before. Therefore this paper proposes a scheme of PSA level-1 for systems with repairable components using a simplified combination of Repairable Event Tree (RET) and Repairable Fault Tree (RFT). 

High intensity femtosecond pulses have already be demonstrated to be of prime importance in the study of ultrafast biological and chemical reactions and specially in the monitoring and analysis of initial events during photodissociation or photoionization processes and photosynthesis (Martin et al., 1983 Gauduel et al., 198, 1983 Breton et al., 1986). In this paper, we will center on the implication of the femtosecond spectroscopy in the monitoring of the fast elementary steps of electron solvation in homogeneous aqueous solution at ambient temperature. 

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