Fast Reactor Core Design for Molten Salt Heat Storage
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Solution Overview
Problem
The existing sodium-cooled metal fuel fast reactors face challenges in achieving high coolant exit temperatures and adaptability to molten salt heat storage systems while maintaining core characteristics, as conventional methods either reduce fuel inventory or deteriorate breeding ratios and burnup reactivity.
Innovation Solution
A core design where fuel rods with a predetermined Pu-enrichment of 11 to 13 wt% are densely packed, with larger hollow diameter fuel rods at the core center and smaller diameter fuel rods on the periphery, to flatten output distribution and increase coolant outlet temperature without compromising core characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If Pu-enrichment of outer core fuel assembly is made higher than inner core fuel assembly, then output distribution in radial direction is flattened, but fuel inventory is reduced and core characteristics deteriorate
Solution Approach 1:
The patent applies local quality by varying the hollow diameter of fuel rods according to their position in the core. Inner core fuel assemblies have fuel rods with larger hollow diameters (first hollow diameter) while outer core fuel assemblies have fuel rods with smaller hollow diameters (second hollow diameter). This spatial differentiation allows the outer core to achieve flattened output distribution through geometric configuration rather than increased Pu-enrichment, thereby maintaining fuel inventory and core characteristics.
2Adaptability or versatility
If coolant outlet temperature is increased to 550°C for molten salt heat storage system, then adaptability to heat storage system is improved, but core characteristics may deteriorate
Solution Approach 1:
The patent changes the geometric parameter of fuel rods (hollow diameter) to achieve the desired coolant outlet temperature of 550°C while maintaining core characteristics. By optimizing the hollow diameter configuration, the design achieves flattened output distribution and improved heat transfer efficiency, enabling high temperature operation compatible with molten salt heat storage systems without compromising core performance.
3Temperature
If hollow diameter of fuel rod is increased, then heat transfer efficiency is improved and coolant outlet temperature increases, but fuel density is reduced
Solution Approach 1:
The patent applies local quality by differentiating hollow diameter based on radial position. Inner core fuel rods have larger hollow diameters to maximize heat transfer and achieve high coolant outlet temperatures. Outer core fuel rods have smaller hollow diameters to maintain adequate fuel density and inventory. This spatially differentiated approach allows the system to achieve 550°C coolant outlet temperature while maintaining overall core characteristics and fuel inventory.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enhances adaptability to molten salt heat storage systems by raising coolant outlet temperatures from approximately 500°C to 550°C, minimizing output fluctuations, and maintaining core characteristics, thus improving thermal efficiency and economic viability.
Implementation Method 1
neutrons generated by a nuclear fission reaction occurring within the fuel assembly
Implementation Method 2
neutrons leaked from the core fuel region are absorbed to U-238 within each fuel rod of the blanket fuel assembly
Implementation Method 3
Pu-239 that is a fissile nuclide is newly generated within each fuel rod of the blanket fuel assembly
Implementation Method 4
liquid sodium which is the coolant is filled within the reactor vessel
Data Source
AI summary
There is provided a core of a fast reactor capable of achieving a sodium-cooled metal fuel fast reactor with high adaptability to a molten salt heat storage system, by flattening the output distribution and raising the coolant outlet temperature while suppressing deterioration of the core characteristic. A core of a fast factor is a fuel assembly obtained by densely disposing fuel rods within a wrapper tube, the fuel rod storing, within a cladding tube, hollow fuel in which Pu-enrichment is made to be a predetermined value within a range of 11 to 13 wt %. In the core of a fast factor, a first fuel assembly including a fuel rod with a large hollow diameter of the hollow fuel is loaded on the center side of the core, and a second fuel assembly including a fuel rod with a hollow diameter smaller than the hollow diameter of the hollow fuel of the first fuel assembly is loaded on the circumferential side of the core.