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In order to explore the risk assessment method of the multi-unit nuclear power plant site, this paper selects the dual-unit plant nuclear site to analyze lose off-site power accident. By combining and improving the single-unit ET/FT model, to establish the dual-unit ET/FT model. From the analysis of the accident sequence, it can be concluded that the common cause failure of equipment is the main challenge faced by the dual-units. Especially the RPC sub-channel in the reactor protection system and the failure of emergency diesel engine circuit breaker. As can be seen from the high proportion of core CD occurring simultaneously in both uints, it has a great significance to study the risk of mult-units sites.

Currently, there is no mature method for calculating the probability of human failure that occurs in multi-unit. In this study, the single-unit HRA is expanded and improved, and we have compiled a method flow suitable for human reliability analysis in multi-unit. This method considers the communication of commands between different organizations and analyzes the equipment shared by multiple units. This research demonstrates the feasibility of the THERP+HCR method to calculate the human-caused failure probability of multiple units. In this paper, the human failure probability of the fifth emergency diesel engine is investigated during a station blackout at a multi-unit site. The calculated failure probability of personnel deploying a fifth diesel-engine between two units is 0.1061, which is higher than the failure probability of a single unit, and the consequences of failure of a dual-unit invocation would be more severe. Due to the uncertainty of some conditions and parameters, the variation of the failure probability after sensitivity analysis ranges from–0.0846–0.2083. Involvement of more organizations during the accident increases the risk of the plant site. Among the most influential factors on the probability of failure are the presence of inspection clauses in the operating procedures and the level of tension of personnel. [ABSTRACT FROM AUTHOR]

:In order to study the corronon reiistance of iitanium alloy surface microstructure in seawater, laser was used to process the microstructure on the titanrnm alloy surface,and a superhydrophobic iitanium alloy surface was obtamed by modifying it with fluoronlane. The prepared sample was immersed in ariiSisial seawater at 40 *C for one day, and the morphology, dement content, and polarization curve changes of the titanmm alloy surface microstructure before and after ariiSisial seawater immerrion were compared. The results showed that there was no change in its morphology, and the oxygen content only increased by 1.1%. However, the open iircuit potential and sflt-corrosion potential did not change before and after immerson nn artificial seawater, with values of 0. 08 V and --0. 07 Viespectivlly. This ndicates that the surface microstructure of superhydrophobic titanmm alloy has good corroson resistance nn artificial seawatee. At the same time, a new Tafll function was constructed to dynamically evaluate the corroson resistance of titanuum alloy surface microstructure nn artificial seawater,providing effective guidance for the corroson resistance evaluation of titanuum alloy surface microstructure nn seawatee. [ABSTRACT FROM AUTHOR]