The arc flash in a switchyard with injuries is normally a sign of a safety breakdown (rules broken, poor training, improper or no PPE, unqualified workers, steps missed, etc).
From the NRC report one might think the grounds were put on an energized part. This is not certain but possible. Workers often do not wear much PPE when placing grounds but the system must be verified to be deneergized and grounded BEFORE taking off adequate PPE in OSHA and in NFPA 70E which all nuclear power stations are required to follow. The old way was to turn it off and ground it and testing was almost non-existent. Today there is so much more to creating an electrically safe work condition.
In our training we recommend the following.
Here is thethat implies a grounding on energized parts incident. This is filed by the utility itself and public record. The Fulton Sun criticized Ameren for clamming up but this report is quite helpful and public record. Ameren has to clam up because of legal concerns when anyone is hurt. Sad we live in a world where it is hard to share safety information.
Here are two articles noting issues. These types of incidents rarely will cause an issue in a nuclear power plant. Our experience with Ameren and with nuclear power plants in general is they are the most meticulous in the safety world. Ameren was one of the first utilities to test clothing for arc flash back in 1992-1994.
Article on Saint Louis Public Radio
Article on the