Nuclear Fuel Blends for Reactor Safety
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Solution Overview
Problem
Nuclear reactors face challenges in efficiently utilizing low-fissile content nuclear fuels, such as recycled and depleted uranium, due to their high or low uranium content and impurities, which prevent them from being viable fuels in many reactors, and existing technologies struggle to manage coolant void reactivity and fuel temperature coefficients effectively.
Innovation Solution
The development of fuel bundles for nuclear reactors comprising a blend of recycled uranium with depleted or natural uranium, along with the inclusion of neutron poisons, which are arranged in specific configurations to achieve a fissile content of 235U between 0.9 wt % and 5.0 wt %, providing a negative fuel temperature coefficient, a negative power coefficient, and reduced coolant void reactivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If recycled uranium with high fissile content is used as fuel, then power output is maintained, but coolant void reactivity increases and safety is compromised
Solution Approach 1:
The patent applies parameter changes by precisely controlling the fissile content of recycled uranium to fall within the range of 0.72-1.2 wt% 235U, and by adjusting the blend ratio with depleted or natural uranium to achieve a combined fissile content of 0.9-5.0 wt% 235U. This parameter optimization allows the fuel to maintain adequate power output while reducing coolant void reactivity to acceptable levels, thereby resolving the contradiction between power generation and safety
Solution Approach 2:
The patent employs composite materials by creating a blended fuel composition that combines recycled uranium (with its higher fissile content) with depleted uranium or natural uranium (with lower fissile content). This composite approach allows the fuel bundle to achieve an optimized fissile content distribution that maintains power output while controlling coolant void reactivity, effectively resolving the technical contradiction
2Reliability
If depleted uranium with low fissile content is used as fuel, then coolant void reactivity is reduced, but power output decreases
Solution Approach 1:
The patent applies the merging principle by combining depleted uranium (with low fissile content and low coolant void reactivity) with recycled uranium (with higher fissile content) in specific proportions. This combination allows the fuel bundle to achieve a balanced fissile content of 0.9-5.0 wt% 235U, which maintains adequate power output while preserving the low coolant void reactivity characteristic of depleted uranium, thus resolving the contradiction between safety and power generation
3Ease of manufacture
If natural uranium is used as fuel, then ease of manufacture is improved, but fuel burnup control becomes difficult
Solution Approach 1:
The patent applies parameter changes by precisely controlling the fissile content of the blended fuel to fall within the range of 0.9-5.0 wt% 235U, which is higher than natural uranium (0.71 wt% 235U) but still achievable through relatively simple blending processes. This optimized parameter range improves fuel burnup control while maintaining ease of manufacture through straightforward blending of recycled and depleted or natural uranium, resolving the contradiction between manufacturing simplicity and burnup control
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 solution enables the use of low-fissile content fuels in pressurized heavy water reactors, maintaining power output comparable to natural uranium while reducing coolant void reactivity and improving safety through negative coefficients, thus enhancing fuel burnup control and reducing dependency on fresh uranium supplies.
Implementation Method 1
at least one of the fuel elements is a poisoned low-enriched uranium fuel element including a neutron poison
Implementation Method 2
nuclear reactors generate energy from a nuclear chain reaction (i.e., nuclear fission) in which a free neutron is absorbed by the nucleus of a fissile atom
Data Source
AI summary
Fuel bundles for a nuclear reactor are described and illustrated, and in some cases include fuel elements each having a fissile content of 235U between about 0.9 wt % 235U and 5.0 wt % 235U, and wherein at least one of the fuel elements is a poisoned low-enriched uranium fuel element including a neutron poison in a concentration greater than about 5.0 vol %.