On December 9, 2013, an electrical transformer exploded in the switchyard at the Arkansas Nuclear One (ANO) Unit 2 nuclear power station. The explosion caused a fire that lasted more than an hour before it was contained and extinguished. This was the second significant accident this year at Entergy Corp’s two unit atomic power station located near Russellville, Arkansas.
The nuclear industry and the Nuclear Regulatory Commission immediately played down the significance of the nuclear power plant accident as occurring in the “non-reactor portions of the plant.”
However, transformer explosions are significant because theynot only result in fire but generate large, high-velocity missiles that can slam into other equipment and combustibles. For example, Entergy’s Palisade plant in Michigan has large hydrogen gas storage tanks located just 30 feet from those main transformers. Only within the past few years Palisades installed a missile barrier to shield that explosive equipment.
Significant accidents can and do occur at nuclear power stations on the “non-reactor side” that can impact reactor safety operations, potentially adversely. An earlier accident in March 2013 at ANO Unit 1, shutdown for repairs, occurred on the “non-reactor” side where one worker was killed and eight more injured when a heavy load crane moving replacement equipment failed and dropped a 600-ton main turbine generator stator at Unit 1. That accident caused a loss of offsite power to Unit 1 and also caused Unit 2 to hit the breaks in an automatic reactor SCRAM from full power. Unit 1 temporarily lost decay heat cooling of the reactor core before the emergency diesel generators quickly restored emergency power.
Fires at nuclear power plants are equally significant. According to the U.S. Nuclear Regulatory Commission, fire represents 50% of the risk from an accident that leads to reactor core damage. To make matters riskier, ANO is currently operating on a large number of exemptions from NRC fire code for non-compliances with fire protection requirements regulating the safe shutdown of the reactors in the event of a significant fire.