In this study, combustion and smoke characteristics according to the aging of class 1E cables in nuclear power plants were analyzed through a cone calorimeter test. In the case of combustion characteristics, during the early period, which was the first peak of the heat release rate, the peak value of the non-aged cable was higher by approximately 20-50 kW/m² than that of aged cables. However, in the mid-late periods, which was the second peak, the value of the aged cables were higher than the non-aged cable due to the decrease in flame retardant performance with aging deterioration. In addition, the duration of the char layer of the aged cables was shortened by 200 s than that of the non-aged cables due to the unstable formation of char layer. The total heat release measured was approximately 1.4 times higher in the aged cables than in the non-aged cables. In the case of smoke characteristics, the smoke production rate and total smoke release show a similar trend with the heat release rate and total heat release. The total smoke release of the aged cables was measured to be higher than that of the non-aged cables. The tendency of the smoke factor increased with aging deterioration, and the values of the smoke factor in the aged cables beyond 4 years were approximately 1.76-2.0 times different from those in the non-aged cables. Consequently, the smoke risk increased with aging deterioration. Therefore, the risk of heat and smoke release increased as aging progressed.

The responsibility mental model (RMM) is an important factor in an effective cooperation system that affects decision-making, role adjustment, and performance. For this purpose, 186 firefighters from an off-site fire brigade and 65 firefighters from an on-site fire brigade participated in the study. We compared the levels of the RMM for a fire at a nuclear plant and analyzed whether the RMM is shared internally in each fire brigade through latent profile analysis. The results showed that the responsibility of on-site fire brigades is prioritized for fire liability in nuclear plants. Both brigades identified the heterogeneity of the RMM. Firefighters from the off-site fire brigade were divided into three groups of thinking they have ‘more responsibility’ (11%), ‘shared responsibility’ (36%), and ‘less responsibility’ (53%) than their cooperation partner. Firefighters from the on-site fire brigade were divided into two groups of ‘more responsibility’ (48%) and ‘shared responsibility’ (52%). The result that each fire brigade does not share a homogeneous RMM suggests the ambiguity of roles in the cooperation system. The need for infrastructure for cross-organizational collaboration and coordination is discussed.

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