Subtypes of DBEs are : Circumstances like the 2011 Tōhoku earthquake and tsunami were not considered within the design basis of the plant , and so the resulting Fukushima I nuclear accidents were described using this terminology as " beyond design basis " or " non-design-basis " . However , some have claimed that the design basis for tsunami events at Fukushima was incorrect . Accidents caused by poor design , failure to follow listed safety procedures , or other forms of human error are not considered to be beyond design basis accidents . The terminology can be unclear , however , because a poorly handled design basis accident can result in conditions beyond what was considered likely , causing a beyond design basis accident . For this reason , some industry experts have criticized the use of design basis terminology . The Three Mile Island accident and the Chernobyl disaster are examples of design basis accidents becoming non design basis accidents largely due to failures to follow the written operating procedures
Three Mile Island accident
Three Mile Island accident
Design-basis event