## 4 Discussion
### Emergency Response Teams and Emergency Management System in NPP  
As briefly mentioned in the Introduction, when the MCR team (team of operators who handle routine operations) observes and declares an emergency, emergency response teams are assembled. The structure of emergency response teams is different by country; in this paper, we discuss the South Korean NPP case. According to the South Korean emergency response plan, emergency response organizations are established based on the scale of an accident [78]. The emergency response teams in South Korean NPPs are the technical support center (TSC), operational support center (OSC), additional local (field) operators and sub-contractors, and the emergency operating facility (EOF) [78]. Their functions are discussed as follows:  
* The technical support center (TSC) provides plant management and technical support to the MCR operators and acts as the primary communication center during an emergency. After the TSC is activated, the decision-making responsibility shifts from the MCR to the TSC. * The operational support center (OSC) provides engineering support for chemical, electrical, mechanical, and instrumentation and control systems, maintenance, fire-fighting, rescue activities, and other duties. However, in contrast to the clear chain of command between the TSC and MCR, the OSC's authorities are not definite. If the TSC is present, then it holds the highest authority. If the TSC is not yet active but the OSC is ready, it is not clear who is responsible for decision-making. It is possible to delay decision-making until the TSC is ready. * Additional local (field) operators and sub-contractors may be requested to handle equipment, for example, to move and install portable diesel generators and pumps. * An emergency operating facility (EOF) is assembled when an accident covers more than two units of NPPs or the situation has deteriorated. Similar to the TSC, the EOF provides plant management and technical support. When the EOF is present, it is responsible for top-level decisions. The EOF is located outside of the NPP site as a precaution in case the NPP site becomes dangerous and hard to reach; however, this raises the need for emergency telecommunication devices. Similar to the concern of the OSC, when both the TSC and EOF are active, the chain of command is clear; otherwise, there is a possibility of miscommunications, recalled decisions, repetitive information, decision delays, and other issues related to team and organization inter-communication. Although the emergency response plan defines the teams and their functions, ambiguities persist. Moreover, the effectiveness of the emergency response plan can only be tested during a large-scale exercise, as studied in [79]. The shift in decision-making responsibility, the increasing number of people to interact with, and the stress of facing emergency situations, among others, fuel the need to support efficient and accurate intra- and inter-team communication [78]. As learned from the Fukushima NPP accident, due to the number of organizations and tasks involved, the risk of inadequate communication, improper communication, or even a total communication failure might be higher. Furthermore, the difficulty in verifying and validating an emergency response plan makes the regulators and analysts anxious to refine the plan repeatedly. The efforts to improve the emergency response plan should be accompanied by the creation of a model or framework, such as a team communication model (discussed earlier) and assurance framework, to internally validate the applicability of the plan. Recently, an assurance framework or assurance program has been adopted by large-scale organizations and governments to achieve a high level of safety, reliability, economic benefits, and accountability, among others [80; 81].