Online discussion about Hiyari-hat incidents is considered to be effective
activity in order to prevent accidents and foster safety culture and in nuclear power
plants. Nevertheless, if once such a discssion activity stops, it will tend to be died. The
authors proposed a method for promoting incident discussion activity with promoting
participants ¡Çspontaneity by¡È active participant ¡Éand¡È Hiyari-hat sharing system ¡É in
order to avoid death of discussion. The method was practiced being joined by 6 groups of
supervisor of nuclear power plants and validated. From the results, some new guideline
for active participant and some requirement of revision of the system were revealed.