I was annoyed that most of the major news outlets incorrectly described Iran’s heavy water plant (which cannot make plutonium) as a nuclear “reactor” (which can).

I was thinking that an excellent blog post would point out that a heavy water plant separates separates heavy water from regular water by distillation, electrolysis or various chemical processes; that heavy water contains deuterium which makes an excellent moderator in a nuclear reactor, and that a heavy water plant DOES NOT MAKE PLUTONIUM.

Then Cheryl Rofer wrote that, and more, at Whirledview

Here are the differences: the heavy water plant produces (distills, most likely) heavy water from regular water. Heavy water contains deuterium, which is an isotope of hydrogen that has more neutrons in its nucleus, which makes it more effective at slowing down reactor neutrons to produce a chain reaction. An enrichment plant raises the amount of uranium-235, the fissionable isotope of uranium, from its natural abundance of 0.7% to reactor grade (about 3%) or weapons grade (greater than 90%). A reactor brings the uranium and heavy water together to produce a controlled nuclear chain reaction, which can be used to produce power and plutonium, another weapons material. The heavy water plant has no radioactivity involved, the uranium in the enrichment process is slightly radioactive, and a reactor is very radioactive.

Oh, and to all those reporters smart enough to understand the D20 would be used in a nuclear reactor, but thought it was only as a coolant … no, you don’t get a cookie for being half right.

Jack Boureston has an interesting discussion about the specifications of the IR 40—the heavy water reactor under construction at Arak, if you, unlike the press, actually care about the details.

Steven Dolley with Platts points out that my comment about the “press” was too sweeping.