Integrated Reactor Head Package With Retractable Drive Rods
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Solution Overview
Problem
The removal of the integrated head package (IHP) from the reactor vessel in nuclear power plants requires a large and expensive polar crane due to the need to lift the IHP vertically above protruding drive rods, necessitating a flooded refuelling cavity and increasing containment structure height and cost.
Innovation Solution
An integrated head package with drive rods that can be decoupled from the control rod assembly and retracted into the IHP, reducing the lifting height by eliminating the need to clear protruding rods and refuelling cavity, using adjustable coupling elements and actuators for remote decoupling and retraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the IHP is removed vertically from the reactor vessel, then the drive rods can be accessed for maintenance, but the lift height increases due to protruding drive rods and refuelling cavity requirements
Solution Approach 1:
The drive rods are retracted into the IHP before the IHP is removed from the reactor vessel. This preliminary retraction action eliminates the need for excessive lift height to clear protruding rods, while still allowing maintenance access once the IHP is positioned on the storage stand.
Solution Approach 2:
The drive rods are made movable between extended and retracted positions within the IHP. During normal operation, they extend to control the reactor core. During maintenance, they retract into the IHP to reduce lift height requirements. This dynamic positioning resolves the contradiction between maintenance access and lift height.
2Object-affected harmful factors
If a flooded refuelling cavity is provided to contain radioactive emissions, then radiation safety is improved, but the containment structure height and cost increase
Solution Approach 1:
The drive rods are extracted from the reactor core and retracted into the IHP before removal. This eliminates the need for a flooded refuelling cavity to contain radioactive emissions, as the drive rods are no longer protruding into the refuelling space. The radiation containment function is maintained without requiring excessive containment structure height.
3Reliability
If the drive rods remain connected to control rods during IHP removal, then control function is maintained, but the drive rods protrude and increase lift height requirements
Solution Approach 1:
The drive rods are decoupled from the control rods before the IHP is removed from the reactor vessel. This preliminary decoupling action allows the drive rods to be retracted into the IHP, eliminating protrusion and reducing lift height requirements, while the control function is preserved through the control rods remaining in the reactor core.
Data Source
AI summary
The present disclosure provides an integrated head package for a nuclear power generation system, the integrated head package comprising a closure head, and a control rod drive mechanism housed within a shroud. The control rod drive mechanism comprises at least one drive rod extending through the closure head and having a coupling element for releasably coupling to a control rod assembly within a reactor core. The at least one drive rod is movable to a maintenance/refuelling position in which the at least one drive rod is uncoupled from the control rod assembly and at least partially retracted into the integrated head package. The integrated head package further comprises at least one engagement feature for securing the at least one drive rod in the maintenance/refuelling position.