CRDM Latch Engagement and Holding Separation
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Solution Overview
Problem
Existing control rod drive mechanisms (CRDMs) for nuclear reactors face inefficiencies in energy usage due to the integration of latch engagement and holding functions, which complicates the SCRAM process and increases operational power requirements.
Innovation Solution
The CRDM design separates latch engagement and holding mechanisms, utilizing a self-engaging cam/latch system and an electromagnetic holding system to reduce energy consumption and simplify the latching process, allowing for reliable SCRAM operations without the need for high-energy latch engagement during normal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If latch engagement and holding functions are integrated in existing CRDMs, then the structure is more compact, but operational power requirements increase and the SCRAM process becomes complicated
Solution Approach 1:
The patent divides the latch mechanism into two independent subsystems: a latch engagement mechanism that uses spring-loaded latches to engage with the control rod, and a separate latch holding mechanism that uses an electromagnetic circuit to maintain the engaged state. This segmentation allows each mechanism to be optimized independently, with the holding mechanism consuming minimal power once engaged, while the engagement mechanism provides the necessary force only during the engagement phase.
Solution Approach 2:
The patent extracts the holding function from the engagement mechanism by introducing a separate electromagnetic holding circuit. This extracted holding mechanism maintains the latch in the engaged position using a minimal holding current, while the engagement mechanism can disengage completely during SCRAM operations without needing to overcome residual magnetic forces, thereby reducing overall power requirements.
2Ease of manufacture
If latch engagement and holding functions are integrated, then fewer components are needed, but manufacturing complexity increases
Solution Approach 1:
The patent segments the latch system into distinct engagement and holding components, each with dedicated functions. The engagement mechanism includes spring-loaded latches and cam actuators that are mechanically simple to manufacture, while the holding mechanism uses a standard electromagnetic circuit with movable and fixed pole pieces. This functional segmentation simplifies manufacturing by allowing each component to be optimized and produced independently using standard fabrication processes.
3Reliability
If high-energy latch engagement is used during normal operation, then reliable latching is achieved, but energy consumption increases
Solution Approach 1:
The patent employs spring-loaded latches that are pre-loaded and ready to engage immediately when the control rod approaches the engaged position. This preliminary preparation ensures rapid and reliable engagement without requiring continuous high-energy input. Once engaged, the electromagnetic holding mechanism maintains the position with minimal power, and during SCRAM, the springs automatically drive the latches open without needing additional energy input.
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 separation of functions reduces operational power requirements, enhances manufacturing simplicity, and ensures reliable SCRAM operations by leveraging gravity and electromagnetic forces for latch engagement and holding, respectively.
Implementation Method 1
a holding mechanism comprising an electromagnetic circuit with magnetic poles configured to be drawn together when the electromagnetic circuit is energized to hold the lifting rod and to release the hold on the lifting rod upon de-energizing the electromagnetic circuit
Implementation Method 2
The holding mechanism includes a non-magnetic spacer between the magnetic poles that defines a gap between the drawn together magnetic poles... the gap reduces residual magnetic force and accordingly minimizes delay in releasing the lifting rod upon de-energizing the electromagnetic circuit to initiate SCRAM
Data Source
AI summary
A control rod drive mechanism (CRDM) includes a lifting rod supporting a control rod and a holding mechanism comprising an electromagnetic circuit with magnetic poles drawn together when the electromagnetic circuit is energized to hold the lifting rod. The hold is released upon de-energizing the electromagnetic circuit. A translation mechanism linearly translates the lifting rod held by the holding mechanism. The holding mechanism may include a non-magnetic spacer between the magnetic poles that defines a gap between the drawn together magnetic poles. The translation mechanism may include latches configured to engage an upper end of the lifting rod, and the holding mechanism draws the magnetic poles together to hold the latches engaged with the upper end of the lifting rod. A four-bar cam assembly may be used to cam the latches closed in response to a vertical actuation force applied to the cam bars.