Fuel Assembly Lifting Device with Debris Retention Flow
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Solution Overview
Problem
During the shutdown and maintenance of nuclear reactors, debris particles such as metal chips and wires tend to accumulate in the reactor vessel due to reduced water flow, which can cause defects in fuel rods and other components, as existing debris filters are insufficient to retain particles during lifting operations.
Innovation Solution
A device with a pump that maintains a controlled water flow of at least 0.5 m/s through the fuel assembly during lifting, ensuring debris particles are retained within the debris filter, and a collecting member to capture any particles that pass through, with the option to reverse the flow for deposition in a water pool for collection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the fuel assembly is lifted upwardly during shutdown and maintenance, then the fuel assembly can be removed from the reactor vessel, but the water flow through the fuel assembly is reduced or reversed causing debris particles to fall out from the debris filter and accumulate in the reactor vessel
Solution Approach 1:
A pump is activated before and during the lifting operation to maintain water flow through the fuel assembly in the upward direction. This preliminary action ensures that debris particles are kept trapped in the debris filter at the lower end of the fuel assembly before lifting begins, preventing them from falling into the reactor vessel during the lifting process.
Solution Approach 2:
The pump maintains continuous water flow through the fuel assembly throughout the entire lifting operation. This continuous action ensures that the debris filter remains effective during the complete lifting process, preventing intermittent particle release that would occur if flow were interrupted or reversed during lifting.
2Quantity of substance
If debris particles are allowed to accumulate in the reactor vessel during shutdown, then particle removal mechanisms are overwhelmed, but maintaining high water flow to prevent accumulation increases energy consumption
Solution Approach 1:
The pump is activated before lifting begins to establish adequate water flow through the fuel assembly. This preliminary action traps debris particles in the debris filter before they can accumulate in the reactor vessel, preventing the need for more intensive particle removal operations later and reducing overall energy consumption during the shutdown process.
Solution Approach 2:
The invention converts the potentially harmful effect of reduced water flow during lifting into a benefit by using the pump to maintain flow. The pump's energy consumption is justified by the prevention of debris accumulation in the reactor vessel, which would otherwise require more energy-intensive removal operations and pose safety risks.
3Use of energy by moving object
If the water flow through the fuel assembly is reduced during lifting, then energy consumption is decreased, but debris particles are no longer retained and fall out from the debris filter
Solution Approach 1:
The pump maintains continuous water flow through the fuel assembly throughout the entire lifting operation, ensuring that debris particles are continuously trapped in the debris filter. This continuous action prevents harmful particle release into the reactor vessel while managing energy consumption through controlled flow rates.
Solution Approach 2:
The pump flow rate is optimized to maintain adequate water flow velocity for particle retention while minimizing energy consumption. By adjusting the flow parameter to be sufficient for trapping particles but not excessively high, the system achieves a balance between preventing harmful particle release and reducing energy usage during the lifting operation.
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
Significantly reduces the accumulation of debris particles in the reactor vessel by maintaining a sufficient water flow to prevent particle release during lifting and transport, ensuring a cleaner reactor environment and preventing contamination of the transport path.
Implementation Method 1
a pump (32) arranged to create a flow of water through the fuel assembly and the conduit member (31)
Implementation Method 2
it is known to provide some kind of debris filter in the lower part of the fuel assemblies
Implementation Method 3
The force which is created by the flow and retains the debris particles in or immediately beneath the debris filter
Data Source
AI summary
The invention refers to a device and a method for handling a fuel assembly (3), which comprises a number of fuel rods extending between a lower part and an upper part of the fuel assembly, a debris filter located in the lower part of the fuel assembly and a casing surrounding the fuel rods. The device comprises a lifting device (15) for engaging, during a lifting operation, a fuel assembly located in a reactor vessel (1) and lifting the fuel assembly upwards and out from the reactor vessel. A conduit member is connected to the upper part of the fuel assembly. A pump (32) creates a flow of water through the conduit member and the fuel assembly during the lifting operation. The flow has such a size that possible debris particles contained in and/or immediately beneath the debris filter at least are retained in and/or immediately beneath the debris filter during the lifting operation.