Cold Spray Chromium Coating for Nuclear Fuel Rod Cladding
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Solution Overview
Problem
Zirconium alloys in nuclear reactors react rapidly with steam at high temperatures, producing hydrogen that can lead to explosive atmospheres and fission product dispersion, necessitating a corrosion-resistant barrier to prevent such reactions.
Innovation Solution
A cold spray method is used to deposit chromium or chromium-based alloys onto zirconium alloy substrates, forming a barrier coating by heating a carrier gas and propelling particles at high velocity to achieve a desired thickness, which is then annealed for improved ductility and radiation resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chromium particles are deposited using conventional thermal spray methods, then corrosion resistance is improved, but the high melting point and brittleness of chromium make successful deposition difficult
Solution Approach 1:
The invention changes the key parameter of particle velocity from conventional thermal spray levels to hypersonic velocities (Mach 2-5). This parameter change allows chromium particles to deform and bond effectively despite their high melting point and brittleness, resolving the deposition difficulty while maintaining corrosion resistance
Solution Approach 2:
The invention replaces conventional thermal spray mechanisms with a hypersonic particle injection system. Instead of relying on thermal softening of particles, the system uses kinetic energy from hypersonic velocities to achieve particle deformation and bonding, enabling successful chromium deposition
2Reliability
If zirconium alloy cladding is used in nuclear reactors, then fission product containment is improved, but rapid steam reaction at high temperatures produces hydrogen that creates explosive hazards
Solution Approach 1:
The invention introduces a chromium coating as an intermediary barrier between the zirconium alloy cladding and the steam environment. This intermediate layer prevents direct contact between steam and zirconium, eliminating the harmful hydrogen generation reaction while preserving the fission product containment function
Solution Approach 2:
The chromium coating is applied in advance to create a protective barrier that prevents the harmful steam-zirconium reaction before it can occur. This preliminary protective action stops hydrogen generation at its source while allowing the zirconium cladding to maintain its primary containment function
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
The chromium coating significantly reduces steam-zirconium reactions, preventing hydrogen generation and maintaining the fission product boundary, enhancing the integrity and longevity of nuclear reactor components.
Implementation Method 1
spraying the carrier gas with entrained particles onto a substrate at a velocity of 800 to 4000 ft./sec. (about 243.84 to 1219.20 meters/sec) to form a coating on the substrate
Implementation Method 2
powderized coating materials are deposited with substantial velocity on a substrate in order to plastically deform the particles into a flattened, interlocking material that forms a coating
Implementation Method 3
heating a pressurized carrier gas to a temperature between 200° C. and 1200° C.
Implementation Method 4
The coating is effective in blocking hydrogen diffusion from the substrate
Data Source
AI summary
A zirconium alloy cladding tube for use in a water cooled nuclear reactor under normal operating conditions and under high temperature oxidation conditions is described. The cladding tube has a coating uniformly deposited thereon. The coating, which may be up to 300 microns thick, is selected from the group consisting of chromium, a chromium-based alloy, and combinations thereof.