Post-Fukushima safety enhancements to nuclear power plants

摘要

The U.S. Nuclear Regulatory Commission has concluded that the accident at Fukushima Daiichi was caused by a long-lasting, complete loss of power due to common-cause failure of electrical equipment following the March 11, 2011, tsunami and to insufficient provision against severe accidents. At Fukushima, the defense-in-depth philosophy in existing worldwide safety standards for nuclear plants essentially stopped with the plant's design-basis accident. When the design basis was exceeded by the severe accident, there were no more defense-in-depth levels to deal with the beyond-design-basis conditions, and the plant operators had to improvise their response with the personnel on hand and the tools available to them. Studies of the Fukushima accident, related near-miss accidents, and existing worldwide nuclear standards are reported herein, along with proposals for standards improvement.