Heterogeneous Heavy Water Reactor Core Design for Thorium Fuel
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Previous heavy water reactor core designs using thorium-based fuels have not been able to achieve simultaneously high fuel burnup, high fissile utilization, and high conversion ratios while meeting design goals of high core-average power densities and safety characteristics, particularly due to neglecting alternative design options beyond homogeneous cores and neutron absorbing poisons.
Innovation Solution
A heterogeneous reactor core design for heavy water reactors, featuring separate seed and blanket fuel regions with varying compositions of UO2 and ThO2, and optionally PuO2, arranged in checkerboard or annular patterns, with a central displacer tube to reduce coolant void reactivity, allowing for improved fissile utilization and sustainability of the thorium fuel cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If homogeneous core designs are used, then device complexity is reduced, but fuel burnup and fissile utilization cannot be simultaneously optimized
Solution Approach 1:
The core is divided into distinct homogeneous regions (e.g., inner core, outer core, reflector zones) with different fuel compositions and arrangements. Each region is optimized independently for its specific function, allowing the inner core to maximize power density while the outer core optimizes for burnup, thereby resolving the contradiction between operational simplicity and fuel utilization efficiency.
Solution Approach 2:
Different regions of the core are assigned different fuel characteristics (enrichment levels, fuel types, geometric arrangements) tailored to local requirements. The inner core uses higher enrichment for power generation, while outer regions use lower enrichment optimized for burnup, enabling simultaneous optimization of multiple performance parameters without increasing overall design complexity.
2Reliability
If neutron absorbing poisons are added to reduce void reactivity, then safety characteristics improve, but fuel burnup and fissile utilization deteriorate
Solution Approach 1:
Instead of adding neutron-absorbing poisons to the fuel, the design extracts this function to dedicated control elements and reflector configurations. The fuel composition remains optimized for burnup and fissile utilization, while safety is achieved through separate neutron absorption mechanisms that do not interfere with fuel performance.
Solution Approach 2:
Control rods and reflector materials serve as intermediary elements that provide neutron absorption for safety control without being mixed into the fuel itself. This separation allows the fuel to maintain optimal composition for high burnup while external components provide the necessary neutron absorption for safety.
3Power
If high fissile content fuel is used, then power density increases, but conversion ratio decreases
Solution Approach 1:
The core is segmented into power-generating zones with higher fissile content and breeding zones with lower fissile content. The inner core regions are optimized for high power density using higher enrichment fuel, while outer regions are optimized for neutron economy and conversion ratio, allowing both objectives to be achieved simultaneously in different spatial locations.
Data Source
AI summary
A channel type heterogeneous reactor core for a heavy water reactor for burnup of thorium based fuel is provided. The heterogeneous reactor core comprises at least one seed fuel channel region comprising seed fuel channels for receiving seed fuel bundles of thorium based fuel; and at least one blanket fuel channel region comprising blanket fuel channels for receiving blanket fuel bundles of thorium based fuel; wherein the seed fuel bundles have a higher percentage content of fissile fuel than the blanket fuel bundles. The seed fuel channel region and the blanket fuel channel region may be set out in a checkerboard pattern or an annular pattern within the heterogeneous reactor core. Fuel bundles for the core are also provided.