"You're not recycling the reactor rubble, the contaminated water or soil." I wonder why is that, why can't all of it be molten and run through enriching turbin

"You're not recycling the reactor rubble, the contaminated water or soil." I wonder why is that, why can't all of it be molten and run through enriching turbines. Is it because of too low of a radioactive mass proportion of said material rendering that economically unfeasible?