Variable Thickness Neutron Shield Panels for Reactor Vessels
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Solution Overview
Problem
Existing neutron shield designs for nuclear reactor pressure vessels face challenges in minimizing temperature differences and strain on attachment means, while also affecting pressure drop and flow turbulence in the downcomer region, as reactors increase in size.
Innovation Solution
The implementation of circumferentially spaced neutron shield panels with variable thickness, constructed from stainless steel, featuring a concave surface facing the core barrel and a convex surface facing the pressure vessel, with the greatest thickness in the center tapering to the sides, and segmented construction to accommodate thermal expansion and coolant flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a steel thermal shield is employed to reduce radiation exposure, then neutron shielding is improved, but temperature differences and thermal expansion strain increase
Solution Approach 1:
The patent applies local quality by using stainless steel panels specifically in the downcomer region where neutron flux is highest, rather than uniformly shielding the entire core barrel. This localized approach provides effective neutron protection while minimizing thermal expansion issues in regions where temperature differences are most critical.
Solution Approach 2:
The patent employs composite materials by combining stainless steel panels with the core barrel structure in the downcomer region. This composite construction allows different materials to be used in different regions - stainless steel where neutron shielding is most needed and temperature control is critical, thereby reducing thermal expansion strain compared to uniform steel shielding.
2Object-affected harmful factors
If neutron shield thickness is increased in high flux regions, then radiation exposure is reduced, but pressure drop and flow turbulence in downcomer increase
Solution Approach 1:
The patent implements local quality by varying the thickness of neutron shield panels based on local neutron flux conditions. Thicker panels are placed in high flux regions while maintaining adequate shielding in lower flux areas, thereby reducing overall pressure drop compared to uniform thick shielding while still providing effective radiation protection.
Solution Approach 2:
The patent applies segmentation by dividing the neutron shield into multiple panels of varying thickness positioned at different locations around the core barrel. This segmented approach allows optimization of shield thickness at each location based on local neutron flux, reducing the overall flow resistance compared to a single uniform thick shield.
3Ease of manufacture
If uniform thickness neutron shield is used, then manufacturing is simplified, but temperature differences and strain on attachment means increase
Solution Approach 1:
The patent applies local quality by making panel thickness vary according to local thermal and neutron conditions. This approach, while slightly complicating manufacturing, significantly reduces thermal expansion strain on attachment means by matching shield thickness to actual thermal loading conditions, thereby improving overall structural reliability.
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 reduces pressure drop and flow turbulence, minimizes temperature differences, and reduces strain on attachment means, effectively shielding the reactor vessel from neutron fluence while maintaining efficient coolant flow and reducing the risk of embrittlement.
Implementation Method 1
neutron shields for shielding nuclear reactor pressure vessels from overexposure to neutron flux
Implementation Method 2
each panel having a generally concave surface facing the core barrel and a generally convex surface facing the pressure vessel inside wall
Implementation Method 3
minimizes temperature differences, and reduces strain on attachment means
Data Source
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AI summary
In a nuclear reactor neutron panels varying in thickness in the circumferential direction are disposed at spaced circumferential locations around the reactor core so that the greatest radial thickness is at the point of highest fluence with lesser thicknesses at adjacent locations where the fluence level is lower. The neutron panels are disposed between the core barrel and the interior of the reactor vessel to maintain radiation exposure to the vessel within acceptable limits.