HTGR Multi-Lobed Prism Fuel Element Geometry
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Solution Overview
Problem
Existing high temperature gas-cooled reactor (HTGR) designs are slightly under-moderated, leading to inefficient fuel usage due to suboptimal geometry and moderator distribution.
Innovation Solution
The introduction of a multi-lobed prism configuration for fuel elements with a taller and thinner shape, allowing for increased moderator material accommodation and more efficient core geometry, which includes a central trunk of moderator material surrounded by elongate fuel elements, optimizing the ratio of moderator to fuel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional hexagonal fuel element geometry is used, then manufacturing and assembly are straightforward, but the moderator-to-fuel ratio is suboptimal leading to inefficient fuel usage
Solution Approach 1:
The reactor core is segmented into multiple columns of fuel elements arranged in a multi-lobed annular configuration, allowing optimized moderator distribution in the central and peripheral regions while maintaining manageable assembly complexity through modular column structures
Solution Approach 2:
The fuel element geometry transitions from traditional two-dimensional hexagonal plans to a three-dimensional multi-lobed annular arrangement with varying radial and axial dimensions, enabling enhanced moderator-to-fuel ratio through optimized spatial distribution
2Quantity of substance
If fuel element cross-sectional area is increased, then fuel capacity increases, but fuel element weight increases making handling more difficult
Solution Approach 1:
The fuel element dimensions are optimized by changing the aspect ratio parameter, using taller and thinner elements with reduced cross-sectional area, which decreases weight while maintaining fuel capacity through extended length rather than increased width
3Productivity
If more moderator material is added to improve moderation, then fuel efficiency improves, but core volume increases
Solution Approach 1:
Moderator material is strategically distributed with higher concentrations in the central region and at peripheral locations where it provides maximum moderation benefit, optimizing fuel efficiency without requiring uniform increase of moderator throughout the entire core volume
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 configuration enhances fuel efficiency by increasing the proportion of moderator material, reducing fuel element weight, and simplifying fuel handling, thereby reducing costs and complexity while maintaining or improving reactor performance.
Implementation Method 1
A moderator is a material that absorbs energy from neutrons through a series of collisions, but which does not absorb the neutrons. The resulting low energy neutrons have a much greater probability of producing more fission events in the nuclear fuel.
Implementation Method 2
The fuel elements are surrounded by other identically-sized graphite blocks. In some designs, the fuel compacts are accommodated in one set of channels, and helium cooling gas flows in a separate set of cooling channels.
Data Source
AI summary
The disclosure relates to a high temperature gas-cooled reactor core including a plurality of elongate fuel elements arranged in the form of a multi-lobed prism. Each prismatic fuel element includes an elongate prismatic body and a plurality of elongate fuel channels located within the prismatic body, wherein the cross-sectional area of each prismatic fuel element in a plane parallel to the bases of the prismatic fuel element is no more than 800 cm2 and wherein a ratio of the height of the prismatic body to its greatest width is greater than or equal to 3.0.