Only a small portion of that will be in the reactor at any given time. I would think that there would be some mechanism put in place to limit the spillage in the event of a catastrophic failure. Also when gaseous tritium is released it has the tendency to go straight up and rapidly escapes the atmosphere. Not that releases of it are healthy. Storage as oxide would prove rather more dangerous in the event of a spill.A fusion reactor would likely have on the order of 10 kg of tritium in inventory. If I calculate correctly, this is ~ 100X the radiation released at Fukushima, so an accident that released even 1% of the tritium inventory would be an equal amount to Fukushima. Also, since tritium is easily taken up by the body, it can have significant biological effects.
The intent is to produce the fuel as an ongoing part of operation. Only a small quantity will be needed on site at any given time. I would hope that the operators of fusion plants (if we ever get that far) will keep the inventory of expensive and dangerous fuel to a minimum.