Reactor Nozzle Stub Platform with Shielded Access Window
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Solution Overview
Problem
The existing methods for maintaining nozzle stubs in reactor vessels are inefficient due to radiation exposure limitations and space constraints, leading to increased costs and prolonged work periods, even when performed in an atmospheric environment.
Innovation Solution
A nozzle stub working system that includes a platform unit with an access window, an access window moving device, and a control device to allow for remote operation and automation of work inside the nozzle stub, reducing the need for manual intervention and minimizing radiation exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If maintenance is performed under water with waterproof devices, then radiation exposure is reduced, but device volume and weight increase making handling difficult
Solution Approach 1:
A platform is introduced as an intermediary structure between the worker and the radiation source. The platform includes a shielding wall that blocks radiation, allowing the worker to perform maintenance tasks while positioned in a lower radiation zone. This mediator structure enables work to be conducted with reduced radiation exposure without requiring fully waterproof devices throughout the entire system.
Solution Approach 2:
The maintenance system is segmented into distinct functional zones: a radiation-exposed zone containing the nozzle stub and water environment, and a protected zone containing the platform and worker position. The shielding wall creates a clear boundary between these zones, allowing different operational requirements to be met in each segment while reducing overall system complexity.
2Device complexity
If maintenance is performed in atmosphere with platform, then device waterproofing complexity is reduced, but radiation exposure limits work time and efficiency
Solution Approach 1:
The platform serves as an intermediary base that extends into the radiation field while keeping the worker's main body in a protected position. This allows atmospheric maintenance tools to be used without full waterproofing, while the shielding wall mediates radiation exposure to enable longer work periods and improved efficiency.
3Productivity
If multiple workmen are deployed to improve efficiency, then work period is shortened, but platform space is very narrow limiting the number of workmen
Solution Approach 1:
The platform design utilizes vertical space and three-dimensional positioning to accommodate multiple workmen and equipment. By extending the platform structure vertically and utilizing depth, the system can support multiple operators performing different tasks simultaneously, effectively increasing the functional area without expanding the horizontal footprint.
4Reliability
If work period is extended to accommodate multiple tasks, then thorough maintenance is possible, but cost increases and efficiency decreases
Solution Approach 1:
The platform is pre-configured with all necessary maintenance equipment, tools, and shielding structures before the worker enters the radiation zone. UT inspecting devices, lighting, and other equipment are positioned in advance on the platform, allowing the worker to begin maintenance tasks immediately upon entry without time-consuming setup, thereby reducing overall work period while maintaining quality.
Data Source
AI summary
A reactor vessel that performs work inside a nozzle stub of the reactor vessel, including a platform unit that is provided at an upper portion inside the reactor vessel and includes a substantially cylindrical side wall portion and a bottom portion blocking the lower end of the side wall portion; an access window that is provided at the side wall portion of the platform unit an access window moving device that opens and closes the access window; a working device; and a control device that is provided at the outside of the reactor vessel and controls the access window moving device and the working device, wherein the control device drives the access window moving device to open the access window, drives the working device to perform work inside the nozzle stub, and then drives the access window moving device to close the access window after the performance of the work.