SiC Coated Zirconium Cladding with Alumina Interlayer

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Solution Overview

Problem

Current methods for manufacturing zirconium alloy cladding with ceramic-containing coatings face challenges in maintaining fission gas impermeability and preventing corrosion during chemical vapor infiltration, especially at high temperatures, leading to potential fuel rod cladding failures in nuclear reactors.

Innovation Solution

A method involving the application of an oxidation-resistant material, such as Al2O3 or Cr2O3, as a first coating on the cladding, followed by a second coating of SiC reinforced fibers with voids that are filled with SiC material, providing a protective layer capable of withstanding high temperatures and corrosion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If SiC coating is applied to zirconium alloy cladding to withstand high temperatures, then temperature resistance is improved, but corrosion resistance during chemical vapor infiltration deteriorates

Engineering Contradiction:

Improvetemperature resistanceVSAvoidcorrosion resistance

Core Design Contradiction:

TemperatureVSObject-affected harmful factors

Solution Approach 1:

The coating is divided into two distinct layers: an inner oxidation-resistant layer (alumina or chromia) and an outer SiC layer. This segmentation allows each layer to perform its specific function - the inner layer protects during CVI while the outer layer provides high-temperature resistance, resolving the contradiction between temperature resistance and corrosion resistance during infiltration.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The solution uses a composite coating structure combining different materials with complementary properties. The oxidation-resistant material (alumina or chromia) provides corrosion protection during CVI, while the SiC outer layer provides high-temperature resistance. This composite approach allows both requirements to be satisfied simultaneously.

Inventive Principle:

Principle #40Composite materials

2Strength

If SiC fibers are used to reinforce the coating, then strength is improved, but fission gas impermeability deteriorates due to voids between fibers

Engineering Contradiction:

Improvecoating strengthVSAvoidfission gas impermeability

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The coating structure intentionally incorporates SiC fibers creating a porous/reinforced structure for strength, then uses the CVI process to infiltrate and fill the voids between fibers with SiC material. This transforms the porous structure into a dense, gas-impermeable composite that maintains the mechanical benefits of fiber reinforcement while eliminating gas permeability issues.

Inventive Principle:

Principle #31Porous materials

Solution Approach 2:

The SiC fibers are placed in position and the voids are left intentionally empty before the CVI process. The preliminary placement of fibers provides the reinforcement structure, and then the subsequent CVI infiltration fills the voids to create gas impermeability. This preliminary action sequence resolves both requirements.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If end plugs are sealed into cladding to maintain hermetic seal, then reliability is improved, but manufacturing complexity increases at temperatures beyond 1200°C

Engineering Contradiction:

Improvehermetic seal reliabilityVSAvoidmanufacturing complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The oxidation-resistant inner coating layer acts as an intermediary between the metal end plugs and the SiC outer coating. This intermediate layer facilitates the sealing process by providing a compatible interface that enables hermetic sealing of end plugs at high temperatures while simplifying the manufacturing process through controlled deposition sequences.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 solution effectively encapsulates the cladding, enhancing its resistance to oxidation and corrosion, maintaining fuel rod geometry and preventing fuel loss, even under extreme conditions, thus ensuring the cladding's integrity during normal and accident conditions in nuclear reactors.

Implementation Method 1

providing a first exterior coating of oxidation resistant material on the exterior surface of the cladding

Methodology Applied

Scientific EffectOxidation resistance: Oxidation

Implementation Method 2

depositing a SiC material to at least partially fill the voids formed between at least a portion of the SiC reinforced fibers

Methodology Applied

Scientific EffectChemical vapor infiltration: Chemical Vapour Deposition

Data Source

PatentEP3117439B1Ceramic reinforced zirconium alloy nuclear fuel cladding with intermediate oxidation resistant layer

Publication Date: 2019.05.15 WESTINGHOUSE ELECTRIC CORP

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AI summary

The invention relates to compositions and methods for coating a zirconium alloy, e.g., ceramic-containing, cladding tube for use with fuel rods in a nuclear water reactor. The coating includes an intermediate oxidation resistant layer and a SiC containing layer at least partially deposited on the intermediate oxidation resistant layer. The SiC containing layer can include a plurality of fibers. The invention provides improved capability for the zirconium alloy cladding to withstand normal and accident conditions to which it is exposed in the nuclear water reactor.