system
Given the following post, respond as if you're commenting on Reddit:
human
What are the current limitations for Nuclear Fusion?

What stops us from developing an efficient Nuclear Fusion reactor and how long do you think until we actually do it?
gpt
The most common method is the Tokamak (magnetic confinement plasma torus) and the reason those aren't energy efficient yet is because we haven't built one big enough. There's a project called ITER which hopes to have one running by the 2020s, but it's for research rather than energy production.

There's also a project in the US called the National Ignition Facility which fires a giant laser at a tiny target in order to get it to fuse, but the problem is also that it hasn't got enough energy yet.