Moderator component varies in its effective density or materials:
(under subclass 347) Subject matter wherein (a) the number of atoms of moderator component per unit volume varies in space, or (b) the nature of the composition of the moderator varies in space so as to display a different moderating effect in one zone of the reactor core area relative to that displayed in another zone.
(1) Note. The normal change in coolant density as is found along the length of a fuel assembly in a boiling water reactor is not proper for placement in this subclass. Boiling water reactors are in subclasses 370+.
