June 24 The U.S. Nuclear Regulatory Commission
(NRC) said on Tuesday that after a series of investigations, it
has declared a 2013 incident at an Arkansas nuclear power plant
to be of substantial safety significance, the penultimate of
four emergency classifications.
An industrial accident at Entergy Corp's Arkansas
Nuclear One plant in Russellville killed one worker and injured
eight others on March 31 last year, when a generator fell as it
was being moved out of the turbine building.
The accident was initially classified as an unusual event,
the lowest of four emergency classifications, because the
incident caused a small explosion inside electrical cabinets.
The incident caused unit 2 of the plant to automatically
shut down when a reactor coolant pump tripped due to vibrations
caused by the heavy component hitting the turbine building
floor, damaging electrical cables and equipment, leading to a
loss of off-site power.
Unit 1 at the plant was in a refueling outage at the time,
with all of the fuel still in the reactor vessel, safely cooled.
Emergency diesel generators were relied upon for six days to
supply power to cooling systems.
If the diesel generators would have failed, there was no
alternate means of providing electrical power to key
safety-related systems at the plant at that time, due to the
damaged electrical cables and equipment.
"The NRC determined that the lifting assembly collapse
resulted from the plant's failure to adequately review the
assembly design and ensure an appropriate load test in
accordance with its procedures or approved standards," the NRC
NRC held a regulatory conference with Entergy officials on
May 1 and after considering information provided by Entergy,
determined that 'substantial safety significance' was
appropriate to characterize the risk significance of the event
for both Unit 1 and 2.
"The NRC will determine the appropriate level of agency
oversight and notify Entergy officials of the decision in a
separate letter," the statement said.
(Reporting by Anupam Chatterjee in Bangalore; Editing by