If the surrounding body of water is permanent, I would not be all that concerned about radiation. If the stack was any shorter, it might as well be a flare pit.
Assuming you won't be able to get near it while it's flaring, I am inclined to go out there with UT apparatus and see what metal you have available to work with. If it's in any way salvageable, cut below and above the kink and weld a 2 foot piece into the middle, and remove the guy wires.
Otherwise, by visual observation of the facility in the background, I don't think I would be devoting a lot of time to coming up with a low cost fix for this somewhat toasted piece of pipe.
If shutdown outage is the issue, then in my opinion the best thing you can do at this point is take the guy wires down and let the thing last as long as it lasts. The minute you are forced to work on it, it looks like replacement is the best option.