Refuelling Rods for Nuclear Reactor Shutdown Safety
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Solution Overview
Problem
Conventional methods for maintaining a shutdown safety margin in nuclear reactors during refuelling or storage operations rely on toxic and corrosive boric acid solutions, which pose environmental and safety risks.
Innovation Solution
The use of refuelling and/or storage rods made of a second neutron-absorbing material, such as borated metal, which are insertable between fuel rods to reduce the fission reaction rate and maintain a shutdown state, eliminating the need for poisoned coolant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If boric acid solution is introduced to the primary circuit to maintain shutdown safety margin, then the shutdown safety margin is improved, but the toxicity and corrosiveness of the system increases
Solution Approach 1:
The invention extracts the neutron-absorbing function from the coolant system by introducing removable refuelling rods made of neutron-absorbing material (such as borated metal) that can be inserted into or removed from the reactor core as needed. This eliminates the need for continuously poisoned coolant, removing the harmful presence of boric acid while maintaining shutdown capability.
Solution Approach 2:
The refuelling rods are designed as temporary, removable components that can be inserted only when needed for shutdown or storage operations, then removed afterward. This disposable approach allows the use of highly effective neutron-absorbing materials without the long-term environmental and safety concerns of having poisoned coolant circulating continuously through the system.
2Object-affected harmful factors
If refuelling rods made of borated metal are used instead of boric acid, then the safety and environmental impact is improved, but the device complexity increases
Solution Approach 1:
The refuelling rods serve multiple functions: they provide shutdown capability when inserted, can be removed when not needed, and the same rod structure can be used for both shutdown operations and fuel assembly storage. This multi-functionality justifies the added mechanical complexity by eliminating the need for separate systems for different operational states.
Solution Approach 2:
The locking mechanism is designed to automatically secure the refuelling rods in their inserted position, providing passive safety without requiring continuous active control or monitoring systems. The mechanical self-locking feature ensures that once inserted, the rods remain in place without additional energy input or control system intervention.
3Device complexity
If control rods are used alone for shutdown, then the system simplicity is maintained, but the shutdown safety margin is insufficient
Solution Approach 1:
The system combines two types of neutron-absorbing components: conventional control rods made of traditional neutron-absorbing materials and refuelling rods made of borated metal or other highly effective neutron-absorbing materials. This composite approach provides enhanced shutdown safety margin by layering multiple neutron-absorbing mechanisms, where the refuelling rods provide an additional safety margin beyond what control rods alone can achieve.
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 safe refuelling and storage operations without introducing toxic boric acid into the reactor coolant, while providing a cheaper and simpler alternative that does not require the rods to withstand harsh reactor environments.
Implementation Method 1
at least one refuelling rod, made of a second neutron-absorbing material different to the first material, the refuelling and/or storage rod being inserted between the fuel rods to further reduce the rate of the fission reaction
Data Source
AI summary
A nuclear reactor is provided. The reactor including: plural fuel rods containing fissile material; plural control rods, each made of a first neutron-absorbing material, the control rods being inserted between the fuel rods to reduce the rate of a fission reaction of the fissile material and put the reactor in a shutdown state, but being operable to move in and out of the reactor to vary the rate of the fission reaction when the reactor is critical and generating useful power; and plural refuelling and/or storage rods, each made of a second neutron-absorbing material different to the first material, the refuelling and/or storage rods being inserted between the fuel rods to further reduce the rate of the fission reaction and maintain the shutdown state.