Microreactor Control Neutron Absorber Assembly Design
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Solution Overview
Problem
Microreactors face challenges in reactivity control due to limited space and weight constraints, requiring flexible and compact systems for flux control, coolant heating, and re-heating that can function effectively in restricted volumes and varied environmental conditions.
Innovation Solution
A compact, integrated, and multi-functional Control Neutron Absorber (CNA) assembly for microreactors, comprising a neutron absorbing rod, a drive shaft, a heater, and a burnable absorber, which allows for precise reactivity control, shutdown, and thermal management within a small nuclear reactor core, utilizing a double-walled housing for safety and leak detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional flux control mechanisms are used in microreactors, then reactivity control function is achieved, but the device volume and weight exceed the limited space constraints of microreactors
Solution Approach 1:
The patent combines multiple functions into a single integrated control rod assembly that includes the neutron absorber rod, drive mechanism, and heater element all within one compact structure. This merging of functions eliminates the need for separate components, thereby reducing overall volume while maintaining reactivity control capability
Solution Approach 2:
The control rod assembly serves multiple purposes: it acts as a neutron absorber for reactivity control, contains a drive mechanism for positioning, and includes a heater element for thermal management. This multi-functionality allows a single component to replace what would traditionally require multiple separate systems, addressing the volume constraint
2Volume of moving object
If control mechanisms are made compact for microreactors, then space constraints are satisfied, but component accessibility and shielding for radiation sensitive components are compromised
Solution Approach 1:
The patent employs a nested structure where the neutron absorber rod is positioned within a drive mechanism housing, which in turn is contained within the reactor core assembly. This nesting arrangement protects sensitive components like the drive mechanism and electrical connections from radiation damage while maintaining a compact overall volume
Solution Approach 2:
The housing structure provides pre-designed radiation shielding and mechanical protection for the drive mechanism and electrical components before they are exposed to the harsh reactor environment. This beforehand protection ensures component reliability without requiring additional volume
3Reliability
If separate systems are used for reactivity control and thermal management, then each function can be optimized, but the overall system volume and complexity increase
Solution Approach 1:
The heater element is integrated directly into the control rod assembly, combining thermal management functionality with the reactivity control mechanism. This eliminates the need for a separate thermal management system, reducing overall system complexity while maintaining the ability to independently control both reactivity and temperature
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
Enables efficient reactivity control, shutdown, and thermal management in microreactors, reducing initial costs by up to 10% and ensuring safety and performance without sacrificing space efficiency, while allowing for quick restart capabilities.
Implementation Method 1
The CNA rod includes a neutron absorbing rod including a first neutron absorbing material. The neutron absorbing rod is positioned within the inner housing and is configured to move axially relative to the inner housing.
Implementation Method 2
The burnable absorber includes a second neutron absorbing material. The burnable absorber exhibits a neutron absorbing strength that is less than that of the neutron absorbing rod.
Implementation Method 3
The heater is mounted to and positioned radially outward from one or more of the drive shaft and the neutron absorbing rod. The heater is configured to move with the drive shaft and the neutron absorbing rod.
Data Source
AI summary
A Control Neutron Absorber (CNA) assembly for a microreactor that produces nuclear energy is disclosed. The CNA assembly includes a housing, a CNA rod, and a burnable absorber. The housing includes an inner housing and an outer housing. The inner housing is configured to receive a CNA rod. The outer housing extends coaxially with the inner housing and is positioned radially outward and offset from the inner housing defining a cavity therebetween. The CNA rod includes a neutron absorbing rod including a first neutron absorbing material. The neutron absorbing rod is positioned within the inner housing and is configured to move axially relative to the inner housing. The burnable absorber includes a second neutron absorbing material, exhibits a neutron absorbing strength that is less than that of the neutron absorbing rod, is positioned within the inner housing, and is configured to receive the neutron absorbing rod therein.