Until it becomes uncontained.
Pyrex container?
It’s really not a big deal. Basically it makes non-radioactive helium and a very tiny amount of low level, very short half-life other waste.
Fusion would be a fantastic power source if contained and perfected. basically water as fuel, basically no waste.
My historical studies of communist governments and their disregard for something called a "safety margin" gives me a decided unease as well.
CC