The quantity of tritium we're talking about here is about 100 kg. That will rapidly be mixed into air within a short distance of the plant. It's not going to form some coherent blob that can penetrate 100 km of atmosphere.
Once in the troposphere, hydrogen of any kind will be oxidized to water within a couple of years, and then rain out. Of more concern would be accident processes that would cause it to be oxidized immediately. For example, any fire or exposure of hot materials to air would cause associated tritium to react.
This is all unrealistic anyway, since the plant will not have 100 kg of tritium on hand at any time. That's about the amount consumed in a year, but the reactor could not afford to have any substantial amount sitting around, decaying, or else the breeding ratio will be too low.
I think we have mostly been talking past each other as I don’t disagree.
Anyway, for a more detailed description of what I was expecting. A least initially it’s going to act just like hot air. Hydrogen’s is 7% the density of air so Tritium is presumably 21% the density of air. Which is similar to air at 2000f without the particulate matter of smoke.
About 100kg should be roughly 500 cubic meters depending on temperature, but a more reasonable limit of ~10kg is still close to 50 cubic meters of gas. If we are talking a sudden release from say a pressurized tank rupturing outside that’s going to from an invisible but mushroom shaped blob and rise. Where a detonations mushroom cloud stops rising as the temperature cools, this thing only slows as it mixes with air which isn’t that fast. The troposphere is only ~8miles up so it’s likely to reach the stratosphere mostly intact.
If we’re talking a venting pipe or something that releases gas more slowly then you get much faster mixing. However, baring the slowest of leaks we are still likely talking going up hundreds of feet at a minimum and more likely miles before it dispersed enough to act like the rest of the atmosphere.
In the absolute worst case, you still get a lot of vertical mixing of the atmosphere from thermals and rapid dispersion from the wind which doesn’t slow down. Within days you’re talking thousands of cubic miles of atmosphere. So, a short term evacuation of those down wind might happen, but they should be able to return in days.
Once in the troposphere, hydrogen of any kind will be oxidized to water within a couple of years, and then rain out. Of more concern would be accident processes that would cause it to be oxidized immediately. For example, any fire or exposure of hot materials to air would cause associated tritium to react.
This is all unrealistic anyway, since the plant will not have 100 kg of tritium on hand at any time. That's about the amount consumed in a year, but the reactor could not afford to have any substantial amount sitting around, decaying, or else the breeding ratio will be too low.