[mirko22]

One was created in 1960 and ran for 5 years but was shut down under Nixon administration due to various unrelated reasons.

But it was not creating fuel itself and it had some issue with corrosion which would have been fixed. There was not one built since and a lot of documentation was lost but luckily saved by NASA.

In last 10 years more and more people are working on them, specially India and China but also USA (Bill Gates is working on similar thing among others)