Segmented Cask System for Nuclear Reactor Internals Removal
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Solution Overview
Problem
Existing methods for dismantling, casking, and removing nuclear reactor core structures are inefficient due to the need for large, heavy casks that require specialized equipment and enlarged openings, leading to increased costs and extended plant outage durations, as they struggle to minimize radiation exposure and maintain existing crane capacity.
Innovation Solution
A method involving the selective dismantling of radioactive components into smaller casks with reduced wall thickness, allowing for compact configuration and transport through existing equipment hatches, using a combination of inner and outer casks with detachable side walls and advanced tooling for bolt removal and radiation shielding optimization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a single large cask is used to house and shield radioactive internals, then adequate radiation shielding is provided, but the cask becomes large and heavy, requiring specialized equipment and enlarged openings
Solution Approach 1:
The patent divides the single large cask into multiple smaller casks that can be used to house and transport radioactive internals. This segmentation allows each cask to be smaller and lighter, eliminating the need for specialized heavy-lift equipment and enlarged openings while still providing adequate radiation shielding through the collective use of multiple casks.
Solution Approach 2:
The patent employs a nested configuration where smaller casks containing radioactive internals are placed within a larger outer cask. This nested structure provides radiation shielding at multiple levels, with the inner casks housing the radioactive materials and the outer cask providing additional shielding, thereby reducing the weight and size requirements for individual casks while maintaining overall shielding effectiveness.
2Object-affected harmful factors
If a single large cask is used to house and shield radioactive internals, then adequate radiation shielding is provided, but the cask requires specialized lifting equipment and enlarged openings
Solution Approach 1:
The patent segments the shielding function across multiple smaller casks rather than requiring a single large cask. This allows the use of standard lifting equipment and existing openings in the containment building, as the smaller casks can be handled by conventional means and do not require specialized heavy-lift equipment or enlarged openings for removal.
Solution Approach 2:
The nested cask configuration allows standard lifting equipment to handle the outer cask while inner casks are positioned within. This nested structure enables the use of existing crane capabilities and standard openings, as the outer cask can be lifted and positioned with conventional equipment while containing the smaller inner casks that hold the radioactive internals.
3Ease of operation
If the equipment hatch is enlarged or an alternate opening is provided to accommodate a large cask, then the cask can exit the containment building, but the building must be restored at great expense
Solution Approach 1:
The patent uses multiple smaller casks that can pass through existing equipment hatches without requiring enlargement. This eliminates the need to break through concrete and rebar to create larger openings, thereby avoiding the substantial restoration costs that would be required to repair such openings after use.
Solution Approach 2:
The nested cask configuration allows the outer cask to be removed through existing openings while containing smaller inner casks. This enables the use of standard equipment hatches without modification, as the nested structure allows the outer cask to be lifted and removed through existing openings that do not require enlargement or subsequent restoration.
4Ease of manufacture
If existing crane capacity is not exceeded, then costs are minimized, but the cask size and weight are limited
Solution Approach 1:
The patent divides the total weight of radioactive internals into multiple smaller casks that can be handled by the existing crane. This segmentation allows the crane to operate within its existing capacity limits while still transporting all the required radioactive materials, thereby minimizing costs by avoiding the need for upgraded heavy-lift equipment.
Solution Approach 2:
The nested cask configuration allows the existing crane to lift and move the outer cask containing smaller inner casks. This nested structure enables the crane to work within its existing capacity by handling the outer cask as a single unit, thereby minimizing costs while avoiding the need for heavier, crane-capable casks.
Data Source
AI summary
A method is provided for removing radioactive internals structural members in the core of a reactor pressure vessel in a containment vessel. The method includes placing a first cask in a first internals assembly, detaching radioactive first internals structural members from second internals structural members in the first internals assembly, placing the detached first internals structural members in the first cask, placing the first internals assembly in a second cask, and removing the second cask containing the first internals assembly and containing the casked detached radioactive first internals members from the containment vessel. The first internal members may be radioactive baffle plates, and the second internals members may be former plates bolted to the radioactive baffle plates. Novel tooling, framework and fixtures facilitate disassembling, moving and storing the radioactive baffle plates.