1. The difference between light and heavy elements depends on a particular element.
When two light nuclei are fused together to produce a heavier nucleus, the mass difference is converted into energy.
The issue of fusing Hydrogen into Helium releases a large amount of energy. Fusing heavier elements releases less energy.
Nuclei of heavier elements require additional energy to fuse and fusion reactions require energy rather than produce it.
Heavy elements produce more energy through fission.
Fusion produces more energy if it involves light elements and fission produces more energy if it involves heavy elements.
At the same time the preference is given to reactions that are safe from a control point of view
https://www.energy.gov/ne/articles/f...hat-difference
2. I also want to agree to be fascinated by the degree of cooperation between countries within technological tasks, unprecedented before in history.
It benefits with the speed of solutions, discoveries and technology evolution. These kinds of huge projects need a lot of experts, specialists, and tests to be involved. Hiding information and trying to make it alone would sound like a waste of time, resources and failure.