As I told you yesterday, the Nuclear Regulatory Commission has issued a reassessment of the safety significance of a March 31, 2013, accident at the Arkansas Nuclear One plant. The new assessment finds that the accident was of “substantial safety significance.”
An article today on the industry website World Nuclear News provided new details on the incident:
Unit 1 of the two-unit plant was taken offline in early 2013 for refuelling and refurbishment work which required the removal of the generator stator. In late-March, the gantry used to remove this from the turbine hall collapsed, sending the 525-tonne component crashing through a hole in the floor to a heavy transport vehicle below. One contractor was killed and eight other workers were injured.
The dropped stator ruptured a water pipe in the transport vehicle bay, causing flooding in unit 1. Certain electrical systems shared by both reactors were damaged and unit 2 automatically shut down. Unit 2 remained without power for some four minutes, with normal grid power supply restored after about ten hours. Unit 1 was without offsite power for six days.
The new NRC assessment also addresses the causes of the accident:
The NRC has now concluded that (plant owner) Entergy “approved a design for the temporary hoisting assembly that was not supported by detailed drawings, specifications, evaluations and/or certifications.” In addition, Entergy failed to review associated calculations to ensure that the assembly was designed to support the projected load. It also failed to carry out a load test on the lifting assembly in all configurations for which it would be used.
It also determined that Entergy “did not ensure adequate supervisory and management oversight of the contractors and other supplemental personnel involved with the stator lift, and this contributed to the event.”
It’s hard to imagine that this cause assessment will not figure into liability for the death and injuries caused by the accident.
Here’s a link to the WNN article: http://www.world-nuclear-news.org/RS-Unsuitable-crane-lead-to-Arkansas-accident-2506144.html