Innovative Pressure Tube Light Water Reactor with Variable Moderator Control

The features of a reactor based on multiple pressure tubes, rather than a single pressure vessel, provide the reactor with considerable flexibility for continuous design improvements and developments. This paper presents the development of innovative pressure tube light water reactor, which has the ability to advance the current pressure tubes reactors. The proposed design is aimed to simplify the pressure tubes reactors by:

• replacing heavy water by a light water as a coolant and moderator,
• adopting batch refueling instead of on-line refueling.

Furthermore, the design is based on proven technologies, existing fuel and structure materials. Therefore, it is reasonable to expect significant capital cost savings, short licensing and introduction period of the proposed concept into the power production grid.
The basic novelty of the proposed design is based on an idea of variable moderator content in the core and “breed & burn” mode of operation. In order to achieve a practical reactor design build on proven technology, several features of the advanced CANDU reactor (ACR-1000) were adopted. 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 proposed design is basically pressure tube light water reactor with variable moderator Control (PTVM LWR).
This paper presents a detailed description of the PTVM core design and demonstrates the reactivity control and the “breed & burn” mode of operation, which are implemented by the variation of the moderator in the core, from a neutronics point of view.