Reactor Head Lift System for Close-Coupled PWR Refueling
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Solution Overview
Problem
Close-coupled Pressurized Water Reactors (PWRs) face difficulties in refuelling due to limited access space, making conventional refuelling methods either impossible or more complex, especially when the reactor pressure vessel and steam generators are connected without any structure in between, which complicates the operation of lift cranes and affects design considerations.
Innovation Solution
A lift head system for the reactor pressure vessel that includes a crane with a winch system, radiation shielding, and a hydraulic jack, allowing for the safe removal and replacement of the reactor head with integrated monitoring and containment features, such as a clam-shell shield and dehumidifier, to manage irradiated components and reduce radiation exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional refuelling methods are used with close-coupled PWRs, then refuelling operations can be performed, but the device complexity and operational difficulty increase significantly due to limited access space
Solution Approach 1:
The reactor head assembly is segmented into removable components including the reactor head, radiation shield, and containment structure. This segmentation allows each component to be independently handled, lifted, and positioned, enabling refuelling operations in close-coupled configurations where space is limited.
Solution Approach 2:
A radiation shield is introduced as an intermediary component between the reactor core and the refuelling environment. This shield provides radiation protection while allowing mechanical access for refuelling operations, effectively mediating between the radioactive core and the external refuelling equipment.
2Ease of operation
If the reactor head is removed for refuelling, then fuel replacement can be performed, but radiation exposure risk increases without proper shielding
Solution Approach 1:
The radiation shield is assembled and positioned around the reactor core before the reactor head is removed. This preliminary action ensures radiation protection is already in place when the head is taken off, allowing refuelling operations to proceed with minimized radiation exposure to personnel and equipment.
Solution Approach 2:
The radiation shield acts as an intermediary barrier that provides radiation protection while permitting mechanical access for refuelling. It mediates between the need for head removal to access the core and the need to protect against radiation during these operations.
3Area of stationary object
If close-coupled configuration is used to reduce plant size, then space is saved, but refuelling operations become more difficult or impossible
Solution Approach 1:
The reactor head and associated components are designed as segmented, removable units that can be lifted and repositioned. This segmentation enables refuelling operations even in close-coupled configurations by allowing the head to be removed and repositioned to provide necessary access space.
Solution Approach 2:
The reactor head assembly is designed with dynamic characteristics, allowing it to be removed, repositioned, and reinstalled. This dynamic capability enables the system to transition between a closed configuration (for operation) and an open configuration (for refuelling), resolving the conflict between compact size and operational accessibility.
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 and safe refuelling of close-coupled PWRs by providing a mechanism to lift and shield the reactor head, reducing the need for complex refuelling cavities and equipment, simplifying the containment structure, and allowing for modular reactor designs while maintaining radiation safety and operational efficiency.
Implementation Method 1
a crane with a winch system, allowing for the safe removal and replacement of the reactor head
Implementation Method 2
radiation shielding, wherein the radiation shielding is connectable to the lift head such that the lift head and the radiation shield encase the reactor pressure vessel head
Implementation Method 3
A lift head system for the reactor pressure vessel that includes a crane with a winch system, radiation shielding, and a hydraulic jack
Data Source
AI summary
A lift head for a reactor pressure vessel comprising a lift head which can be coupled and removed to a reactor pressure vessel head, and radiation shielding. The radiation shielding is connectable to the lift head such that the lift head and the radiation shield encase the reactor pressure vessel head and any head package contents removed from a reactor pressure vessel with the reactor pressure vessel head. The radiation shield may be of a clam shell construction. The lift head may be provided with a mechanism for fastening and unfastening the bolts connecting the reactor pressure vessel head to the reactor pressure vessel. The lift head may be provided with monitoring equipment to monitor the core internals.