It will probably work in the short term, but I wouldn't consider it permanent unless you get extraordinarily lucky. Whatever is causing that leak is not going away............there cannot be any leaks with a suitable hose clamp on a proper tube.

If you decide to try RTV, use a very thin layer ...........don't glob it in there............and wait overnight until it's fully cured. If the stuff breaks away, it clogs one of the radiator tubes.........guaranteed.