The Counter Effects of the Accident at Fukushima Dai-ichi Nuclear Power Station

The counter effects of the accident at the Fukushima Dai-ichi Nuclear Power Station are discussed in this paper. Though decommission and remediation have been conducted in the facility and surrounding area, ninety thousand residences near the facility are still under the evacuation order. Four nuclear power units have already restarted under the new regulatory framework, but two of them in Fukui prefecture stop the operation due to the provisional disposition declared by Ohtsu district court in Shiga prefecture. Reinforcement of the latter layer of the defense in depth has been improved in many ways. The improvement of decision-making process is very important in latter layers of the defense in depth, in contrast the plant behaviors are automatically decided based on their design in the prior layers.