Nuclear Reactor Coolant Pump Flywheel Segmentation
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Solution Overview
Problem
Current reactor coolant pump flywheels lack sufficient stability and resistance to thermal expansion and hoop stress, which can lead to balance changes and potential corrosion and contamination issues in nuclear reactor environments.
Innovation Solution
A flywheel design featuring high density segments made from tungsten-based alloys with preselected gaps for thermal expansion and radial loading, coupled with upper and lower pins and cap members to prevent immersion and corrosion, and a key or spline fit to the shaft for stability, ensuring resistance to motion and seismic events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high density segments are used to increase flywheel inertia, then the ability to maintain rotation during power loss is improved, but thermal expansion and hoop stress effects worsen
Solution Approach 1:
The flywheel is divided into multiple high density segments that can expand independently. Each segment is separated by gaps that allow thermal expansion without creating excessive hoop stress, while still maintaining the overall structural integrity and inertia of the flywheel assembly.
Solution Approach 2:
Different regions of the flywheel have different properties - the segments are made of high density material for inertia, while the gaps between segments provide thermal expansion accommodation. The pins and interference fits provide localized structural support where needed.
2Stability of the object's composition
If segments are coupled tightly to prevent motion, then stability is improved, but thermal expansion accommodation is reduced
Solution Approach 1:
The tight coupling is achieved through pins and interference fits that connect segments to the inner and outer members, providing stability. Meanwhile, gaps between segments allow thermal expansion, and the pins are positioned to provide radial loading that maintains stability without preventing expansion.
Solution Approach 2:
The interference fit between inner member, segments, and outer member provides a controlled degree of coupling that balances stability with thermal expansion accommodation. The interference fit parameter is optimized to provide sufficient radial loading for stability while allowing gaps to accommodate thermal growth.
3Reliability
If cap members are added to prevent corrosion, then reliability is improved, but device complexity increases
Solution Approach 1:
The cap members serve multiple functions: they seal the high density segments and outer member to prevent solvent immersion and corrosion, provides positive encapsulation during seismic events, and maintain structural integrity. This multi-functionality justifies the additional components.
Solution Approach 2:
The cap members provide protective encapsulation before corrosion or seismic damage can occur. During normal operation, they prevent solvent contact with the high density segments and outer member, and during seismic events, they provide positive encapsulation without relying on friction.
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
The design provides enhanced stability and resistance to thermal expansion and hoop stress, preventing balance changes and corrosion, while maintaining coolant circulation in nuclear reactors, even under extreme conditions.
Implementation Method 1
A preselected gap is provided between each of the number of high density segments. The gap accommodates thermal expansion of each of the number of segments
Implementation Method 2
An interference fit may be provided between the inner member, the segments and the outer member
Implementation Method 3
Flywheels are used in centrifugal pumps to mechanically store potential energy during operation of the pump, which energy may be utilized to maintain rotation of the pump in the event of loss of motive power
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
A flywheel for a pump, and in particular a flywheel having a number of high density segments for use in a nuclear reactor coolant pump. The flywheel includes an inner member and an outer member. A number of high density segments are provided between the inner and outer members. The high density segments may be formed from a tungsten based alloy. A preselected gap is provided between each of the number of high density segments. The gap accommodates thermal expansion of each of the number of segments and resists the hoop stress ef fect/keystoning of the segments.