Conceptual design of a pressure tube light water reactor with variable moderator control

This paper presents the development of innovative pressure tube light water reactor with variable moderator control. The core layout is derived from a CANDU line of reactors in general, and advanced ACR-1000 design in particular. It should be stressed however, that while some of the ACR-1000 mechanical design features are adopted, the core design basics of the reactor proposed here are completely different. First, the inter fuel channels spacing, surrounded by the calandria tank, contains a low pressure gas instead of heavy water moderator. Second, the fuel channel design features an additional/external tube (designated as moderator tube) connected to a separate moderator management system. The moderator management system is design to vary the moderator tube content from "dry" (gas) to "flooded" (light water filled). The dynamic variation of the moderator is a unique and very important feature of the proposed design. The moderator variation allows an implementation of the "breed & burn" mode of operation. The "breed & burn" mode of operation is implemented by keeping the moderator tube empty ("dry" filled with gas) during the breed part of the fuel depletion and subsequently introducing the moderator by "flooding" the moderator tube for the "burn" part. This paper assesses the conceptual feasibility of the proposed concept from a neutronics point of view.