This was AFAIU a 'dry annealing' on a full scale power reactor: https://inis.iaea.org/records/505bf-gcq02 https://inis.iaea.org/records/505bf-gcq02 and https://

This was AFAIU a 'dry annealing' on a full scale power reactor: https://inis.iaea.org/records/505bf-gcq02 https://inis.iaea.org/records/505bf-gcq02 and https://inis.iaea.org/records/a42j1-np856 https://inis.iaea.org/records/a42j1-np856 Not the whole reactor vessel though, just one critical circumferential weld seam. (As mentioned in the second link, other VVER-440 reactors had previously been annealed, I'm sure one could find information about them as well.)