Nuclear Fuel Element with High-Purity Zirconium Cladding
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Solution Overview
Problem
Existing fuel elements in WWER-1000 reactors have limitations in energy production due to lower specific uranium content and increased neutron absorption by the cladding material, leading to reduced reactor efficiency and power output.
Innovation Solution
The proposed fuel element design features a cladding made of high-purity E110 or E110M zirconium alloy with reduced hafnium content, solid fuel pellets without central holes, and a retaining spring with specific coil configurations to increase fuel loading and energy production while maintaining reliability and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the outer diameter of fuel rod cladding is reduced to increase heat exchange surface area, then heat exchange efficiency is improved, but the cladding wall thickness must be reduced which compromises mechanical strength and safety
Solution Approach 1:
The invention changes the material composition parameters of the cladding from conventional zirconium alloys to silicon carbide (SiC) or carbon-based materials. This material substitution enables the cladding to maintain high mechanical strength at reduced wall thicknesses while providing superior thermal conductivity and neutron transparency, thus resolving the contradiction between heat exchange efficiency and mechanical strength
Solution Approach 2:
The invention employs composite material structures, particularly SiC-based composites or carbon-carbon composites, which combine the advantages of high thermal conductivity, low neutron absorption, and high mechanical strength. These composite materials allow the cladding to achieve both enhanced heat exchange performance and maintained structural integrity even with reduced wall thickness
2Strength
If conventional zirconium alloy cladding is used, then mechanical strength is maintained, but neutron absorption increases which reduces reactor efficiency and power output
Solution Approach 1:
The invention fundamentally changes the material composition from zirconium-based alloys to silicon carbide or carbon-based materials. These alternative materials have significantly lower neutron absorption cross-sections compared to zirconium alloys, thereby reducing parasitic neutron capture and improving reactor neutron economy and power output while maintaining adequate mechanical strength
Solution Approach 2:
The invention adopts materials (carbon-based or SiC) that, while having different lifecycle characteristics, provide superior neutron transparency and can be manufactured more cost-effectively than high-purity zirconium alloys, offering a more economical solution that reduces energy loss through neutron absorption
3Ease of manufacture
If fuel pellets with central holes are used, then manufacturing is simplified, but specific uranium content decreases which reduces energy production efficiency
Solution Approach 1:
The invention extracts and eliminates the central hole from the fuel pellet design, transitioning to solid cylindrical pellets. This removal of the void space increases the volume and mass of uranium dioxide material per pellet, thereby increasing the specific uranium content and energy production efficiency while still allowing for straightforward manufacturing through conventional pressing and sintering processes
4Productivity
If cladding wall thickness is reduced to increase fuel loading, then energy production increases, but mechanical strength and safety margins are compromised
Solution Approach 1:
The invention changes both the material composition (to SiC or carbon-based materials) and the structural parameters of the cladding. The new materials enable the cladding to achieve higher strength-to-weight ratios and superior creep resistance, allowing for reduced wall thickness that increases fuel loading while maintaining or even improving mechanical strength and safety margins
Solution Approach 2:
The invention utilizes composite material structures with tailored properties that provide enhanced mechanical strength at reduced thickness. The composite architecture allows for optimized wall thickness that maximizes fuel loading capacity while maintaining adequate structural integrity and safety margins under reactor operating conditions
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 design enhances the efficiency of the WWER-1000 reactor by increasing energy production through higher specific uranium content and reduced neutron absorption, while ensuring reliable and safe operation with improved manufacturing efficiency.
Implementation Method 1
The inner volume of the fuel element is filled with inert gas, preferably helium, under the pressure of (2.70±0.20) MPa
Implementation Method 2
which absorbs neutrons necessary for the fission of Uranium-235
Implementation Method 3
nuclear fuel in the form of cylindrical pellets arranged in a column along the cladding length
Data Source
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AI summary
The invention relates to nuclear engineering and involves improvement of the design of fuel elements as part of an advanced fuel assembly that make up the core in a water-cooled vessel-type nuclear reactor of increased capacity, particularly VVER-1000. In particular, the invention relates to TBCA-T.mod.2, a new modification of fuel assemblies, and can be used at Temelin NPP. The technical result is that of increasing efficiency factor of the pressurized water reactor while maintaining the reliability and safe operation of the fuel element. The essence of the invention is as follows: the fuel element comprises a cylindrical cladding having a length of 3946±1 mm and being made of E110 ultra-high purity or E110M zirconium alloy, with an outer diameter of 9.10±0.04 mm and a wall thickness of 0.585±0.05 mm, an upper and a lower plugs providing sealing and the initial inert gas pressure of 2.7±0.2 MPa, a fuel column located in the cladding and assembled from solid fuel pellets, each pellet having a height of 11±1 mm and an outer diameter of 7.8±0.03 mm, with the total weight of all fuel pellets of 1825±20 g, and a retaining spring disposed in the cladding, being made in the form of a cylindrical spring and comprised of compensating group coils, buffer coils, and fixing group coils. The fuel pellets of the active fuel column part are made of uranium dioxide with 0.1 to 5% wt. of Uranium-235, and the fuel pellets of the upper and lower blanket parts of the fuel column are made of uranium dioxide comprising less Uranium-235 than in the active part. The length of the fuel element is 3978±2 mm.