We have at least one fusion plant I know of, the UK Joint Torus, which I know have been operating for decades. It operated ("actually sustained fusion") for a

We have at least one fusion plant I know of, the UK Joint Torus, which I know have been operating for decades. It operated ("actually sustained fusion") for a total of four seconds, in 1997. Most of the work involves non-fusion plasmas. http://www.jet.efda.org/wp-content/uploads/jeteuropeansucess.pdf http://www.jet.efda.org/wp-content/uploads/jeteuropeansucess... That was a costly experiment: the resulting radiation -- neutron activation of the structure -- made the reactor inaccessible for 18 months. http://www.iop.org/Jet/fulltext/JETP98037.pdf http://www.iop.org/Jet/fulltext/JETP98037.pdf