Radiation Shielding for Nuclear Reactor Vessel Inspection
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Solution Overview
Problem
In nuclear power plants, particularly in pressurized water reactors, the neutron flux detector mounted on the thimble tube within the reactor vessel poses a significant radiation obstacle, making inspections and repairs challenging, and existing radiation shielding methods are inefficient, leading to increased costs and radiation exposure for workers.
Innovation Solution
A radiation shielding method and device that create a shielded region outside the reactor vessel, allowing the neutron flux detector and thimble tube to be moved into this region through a curved conduit, where they are shielded using granular materials within hollow vessels, reducing worker exposure and enabling reuse of the detector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If the thimble tube with neutron flux detector is removed from the reactor vessel, then inspection and repair work can be performed, but the detector cannot be reused due to high radiation exposure
Solution Approach 1:
A radiation-shielded region is introduced as an intermediary space between the high-radiation reactor vessel and the worker area. This shielded region, formed by hollow vessels filled with granular shielding material, allows the thimble tube and detector to be moved for inspection and repair while protecting the detector from excessive radiation exposure, enabling its reuse.
Solution Approach 2:
The shielding system is segmented into multiple hollow vessels that can be independently positioned and filled with shielding material. This segmentation allows flexible configuration of the shielded region to accommodate the thimble tube at different positions and orientations during maintenance operations.
2Object-affected harmful factors
If conventional radiation shielding methods are applied inside the reactor vessel, then radiation exposure is reduced, but the complexity and cost increase due to dedicated shielding vessels
Solution Approach 1:
The shielding system is made dynamic by allowing the hollow vessels to be moved and repositioned as needed. Instead of a fixed shielding structure, the vessels can be dynamically adjusted to follow the thimble tube during its movement in and out of the reactor vessel, reducing the need for complex fixed shielding infrastructure.
Solution Approach 2:
The granular shielding material is designed to be easily removable and reusable. After serving its protective function, the shielding material can be discarded from the hollow vessels and recovered for reuse in subsequent shielding operations, reducing waste and long-term costs.
3Reliability
If the thimble tube is kept inside the reactor vessel, then the detector remains in position, but inspection and repair work cannot be performed due to the thimble tube being an obstacle
Solution Approach 1:
The radiation-shielded region acts as an intermediary workspace that allows the thimble tube to be extracted from the reactor vessel and positioned for maintenance without exposing workers to high radiation. The shielded region maintains the detector's functional integrity while providing accessible workspace for inspection and repair operations.
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 approach effectively reduces radiation exposure for workers, allows for safe and efficient inspection and repair of the neutron flux detector, and lowers the cost of maintenance by enabling the reuse of the detector without the need for dedicated shielding vessels.
Implementation Method 1
shielding is performed such that a hollow vessel is disposed at a predetermined portion of a body to be shielded, a fluid is sent out to the vessel by a fluid sending-out means through a hose while a granular shielding material is supplied to the fluid by a shielding material supply means, so that the shielding material is transferred into the vessel through the hose and the vessel is filled with the shielding material
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A radiation shielding method and a device, and a method of processing a structure, in which a first radiation-shielded region (A1) is provided by disposing a first radiation-shielding device (100) outside a nuclear reactor vessel (41), a neutron flux detector (77) is moved into the radiation-shielded region (A1) through a conduit tube (65) by moving a thimble tube (68) from the nuclear reactor vessel (41), and an inspection/repair work of the nuclear reactor vessel (41) is then performed, so that an amount of radiation delivered to a worker can be easily and sufficiently reduced.