In an article entitled "Trump Inherits a Secret Cyberwar Against North Korean Missiles," the New York Times reports:
Last month, a report on cybervulnerabilities by the Defense Science Board, commissioned by the Pentagon during the Obama administration, warned that North Korea might acquire the ability to cripple the American power grid, and cautioned that it could never be allowed to “hold vital U.S. strike systems at risk.”
The American power grid, of course, provides the primary electricity for running safety and cooling systems at U.S. nuclear power plants, including to atomic reactors as well as high-level radioactive waste storage pools.
Although there are emergency backup diesel generators at U.S. nuclear power plants, in case the grid goes down, these too could be targeted by cyber attackers bent on causing reactor meltdowns, or storage pool fires, at U.S. nuclear power plants. In fact, EDGs at U.S. nuclear power plants have a bad reliability record, even absent an intentional cyber attack!