As reported by Anna Fifield in the Washington Post.
In late 2014, a major hack of the South Korean nuclear power industry was reported. The top suspect was the North Korean regime.
As but one of likely many such examples, in response to revelations of cyber-security vulnerabilities at its Palisades atomic reactor in Michigan, Entergy Nuclear has requested exemptions from cyber-security regulations. Dangerously, the U.S. Nuclear Regulatory Commission can be expected to rubber-stamp any such requests.