# Team-Communication Modeling Framework for Multi-Unit Nuclear Power Plant Accident Analysis
## 3 Results and Analysis
### Case Study
#### 3.7.2 The Multi-Unit Accident Scenario  
During our research project, a group of NPP accident prevention experts developed a few multi-unit accident scenarios and using those scenarios, we were able to test the feasibility of our modeling framework and methodology. We selected one scenario to be the case study in this paper; however, we are unauthorized to disclose the full details. Thus, we describe the accident scenario based on its main events, as follows. A certain NPP has six reactors. Due to an earthquake of 0.3 G scale, the power supply to all reactors is lost. The automatic shut-down and power loss are confirmed; an accident type called \"loss of off-site power/LOOP\" is decided. The operational status of some emergency power supply equipment (emergency diesel generator, turbine-driven auxiliary feed-water pump, etc.) is checked. Part of the equipment appears to be not working, and field operators are sent to operate them on site. MCR starts the procedure to diagnose the accident and, upon finding that all AC power sources are lost, proceed to the indicated emergency procedure. Countermeasures, such as opening dump valves, are taken. Reports from the field operators are received, which mention that the power generators are not operable. The accident has entered a prolonged power loss state, and it is decided to be a type called \"extended loss of AC power/ELAP\". MCR follows the corresponding accident guideline to stop unnecessary power load requests for multiple pieces of mobile equipment to the SC, which receives the requests and calls the drivers located outside the site. The drivers arrive at the mobile equipment storage and prepare and drive them to the installation location. SC checks the road for damages and starts removing the debris. TSC is active and oversees the mobile equipment assignments. OSC is active and assigns members to move to mobile equipment installation locations and prepares for installation. EOF is active and takes over the mobile equipment assignments. TSC requests additional mobile equipment for EOF. EOF requests additional mobile equipment to other NPP sites, through SC. SC reports that the other NPP sites agree to send the equipment and EOF assigns the mobile equipment for the whole site. MCR stops the unnecessary load; however, the nuclear core temperature reaches 649 \({}^{\circ}\)C, which is an entry condition to severe accident-management guidelines. While MCR is following the guidelines, mobile equipment arrives (driven by SC drivers) and is installed (with the help of OSC), with permissions from TSC, who acquired the assignments from EOF. Mobile equipment from other NPP sites arrives and is received by SC drivers, who take them to the installation location. The operation of the mobile equipment (by field operators) is successful, the power supply is recovered, and the core cooling is ongoing. The situation is stable, and the accident scenario is finished. 3.7.3. The Application of Team-Communication Modeling Framework  
Among the three models in the framework, two of them, the team-communication investigation model and the performance-factor model, are mostly static, and the remaining process model is dynamic, which represents the specific communication process of an NPP emergency. Although the three models interact (Figure 1), the investigation model and performance-factor model mainly provide input to the process model as influencing and performance factors, respectively (the feedback loops were created to maintain consistency in case the process model contains new influencing/performance factors). The three model concepts were developed at the same time; however, the contents of the investigation model were developed first [29] and followed by the contents of the performance-factor model (Table 1). The contents of the process model depend on the communication activities, which depend on an accident scenario. Thus, the accident scenario described above mainly affects the FRAM-based team-communication process model.