The gas cooled natural uranium fuel reactors were not first built for the primary purpose of power production but rather for the production of plutonium. At the present state of the reactor art, it is difficult to argue that these gas cooled reactors are any more or less economic or reliable than the water, organic and sodium cooled reactors. Corrosion by coolant is negligible. Coolant doesn't react with fuel or with other core materials. Coolant will not flash into vapor if primary system is ruptured.
Coolant has very low capture cross section.
System can be designated with negative temperature coefficient. Any fuel can be used, including natural uranium. Coolant is cheap. Ordinary leakage can be tolerated. Gas turbine may be employed.