The objective of this Production Test Supplement is to evaluate at a K Reactor the operational aspects of a proposed method for reducing minimum downtime. The proposed method is to partially override the xenon transient with a block of enrichment in the central region of the reactor. The purpose of performing this test at a K reactor in addition to the original test at one of the older reactors, is to examine the operational aspects unique to a K reactor and to evaluate the feasibility of the method for reducing minimum downtime at a reactor of that type. It is expected that differences in operating techniques will be indicated at the K plant because of its greater size, of different speed of control restrictions and of the variation in the reactivity effectiveness of enrichment, rods, and poisons. The experience at B Reactor with the use of enriched core to reduce minimum downtime indicates the feasibility of proceeding with a similar test at one of the K reactors.