Controllable nuclear fusion wasn't some kind of aircraft or cannon, nor was it an atomic missile. Even though it contained the words "nuclear fusion", it wasn't something that was classified.
Therefore, the location of the research unit didn't have to be a secret.
The people involved also didn't have to be classified.
Same with the communication.
This was just like the International Space Station program; these types of large projects often required more than just one country or organization to accomplish. The controllable nuclear fusion project was the same; competition always existed in ITER, but yet, cooperation would still be there.
If going to a meeting meant having to take multiple flights and rides, then this meeting probably wouldn't happen.
When the Chinese Academy of Sciences wanted to research the tokamak, they set up shop around a beautiful island in Lu Yang city.
