Perhaps I asked too soon... "a pressurized water reactor like most of the reactors in the States is another factor to consider" from josepp's post.

I can see (kinda) that if the heavy water was heated to super and funnelled properly it could spin a turbine without gas formation. Seems odd at first thought, to me. Just never thought of it that way... am a silly engineer by trade, not a make-a-nickel engineer.