uranium fuel cell (20GJ), DT fuel cell (10GJ) and charged antimatter fuel cell (300GJ) does seem like a very strange progression.
especially considering the fusion plant consumes 2GW meaning a cell lasts only 5 seconds.
compared with a nuclear reactor consuming 100MW which takes 200 seconds to consume its fuel, and the antimatter reactor consuming 3GW which means it takes exactly 100 seconds to consume its fuel.
it seems to me fusion reactors were also intended to have its fuel last for much longer. maybe it should've been 100GJ or 200GJ.