Ever is a long time... It's an engineering problem, and it seems prudent to keep working at it until it succeeds, given that the available supply of fissile mat

Ever is a long time... It's an engineering problem, and it seems prudent to keep working at it until it succeeds, given that the available supply of fissile materials is vastly more limited than that of fusible ones. Uranium mining isn't exactly an activity with negligible environmental impact, either.