Bimetallic Cladding Resolves FCCI in Nuclear Fuel

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Solution Overview

Problem

Fuel-cladding chemical interaction (FCCI) in nuclear reactors leads to degradation of fuel elements due to chemical reactions between fuel and cladding components, resulting in reduced mechanical properties and cladding breaches, which are exacerbated by extended service time at high temperatures, particularly in traveling wave reactor applications.

Innovation Solution

The use of bimetallic and trimetallic claddings with a carbon-doped vanadium alloy layer and a structural steel layer, or a vanadium alloy layer with a steel liner, separated by an intermediate layer, to reduce chemical interactions and enhance the mechanical properties of the cladding, thereby preventing fuel-cladding chemical interaction and maintaining structural integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a single-layer steel cladding is used, then the structural strength is sufficient, but fuel-cladding chemical interaction causes degradation of mechanical properties and cladding breaches

Engineering Contradiction:

Improvecladding mechanical strengthVSAvoidcladding integrity

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The cladding is divided into multiple functional layers: an inner vanadium alloy layer that resists chemical interaction with fuel, an intermediate layer that prevents interdiffusion, and an outer steel layer that provides structural strength. This segmentation allows each layer to specialize in one function, resolving the contradiction between chemical resistance and mechanical strength.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention uses composite cladding structures combining different materials (vanadium alloy, nickel/chromium/zirconium intermediate layer, and steel) to achieve properties that no single material could provide alone. The composite structure provides both chemical inertness and mechanical strength simultaneously.

Inventive Principle:

Principle #40Composite materials

2Duration of action of moving object

If extended service time at high temperatures is required for traveling wave reactor applications, then energy production increases, but fuel-cladding chemical interaction is exacerbated leading to cladding degradation

Engineering Contradiction:

Improveservice lifeVSAvoidchemical interaction degradation

Core Design Contradiction:

Duration of action of moving objectVSObject-affected harmful factors

Solution Approach 1:

An intermediate layer of nickel, chromium, or zirconium is introduced between the vanadium alloy and steel layers to prevent harmful interdiffusion. This intermediary layer blocks the migration of iron and nickel into the fuel and fission products into the cladding, enabling extended service life without chemical degradation.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention changes the chemical composition parameters of the cladding by incorporating vanadium alloy with specific carbon content (0.1-0.5 wt%) and controlled impurity levels. This parameter optimization enhances resistance to chemical interaction while maintaining structural integrity over extended periods.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If a multi-layer cladding structure is implemented, then fuel-cladding chemical interaction is reduced, but device complexity increases

Engineering Contradiction:

Improveresistance to chemical interactionVSAvoidcladding structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The harmful interdiffusion processes are extracted and isolated by introducing a dedicated intermediate layer that specifically targets and blocks the migration of reactive species. This extraction of the harmful interaction mechanism allows the inner and outer layers to focus on their primary functions.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Different regions of the cladding are assigned different material properties optimized for their specific functions: the inner layer provides chemical inertness, the intermediate layer provides diffusion barrier properties, and the outer layer provides mechanical strength. This local optimization resolves the contradiction between performance and complexity.

Inventive Principle:

Principle #3Local quality

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 proposed cladding configurations significantly reduce fuel-cladding chemical interaction, minimizing mechanical property degradation and cladding breaches, ensuring the structural integrity and extended service life of nuclear fuel elements, even at high temperatures and peak burnups.

Implementation Method 1

a third layer of nickel, nickel alloy, chromium, chromium alloy, zirconium or zirconium alloy between the first layer and the second layer

Methodology Applied

Scientific EffectDiffusion barrier: Diffusion Barrier

Implementation Method 2

a second layer of at least 90% vanadium; and a third layer of nickel, nickel alloy, chromium, chromium alloy, zirconium or zirconium alloy between the first layer and the second layer

Methodology Applied

Scientific EffectCarbon doping: Dopants

Data Source

PatentUS10109382B2Steel-vanadium alloy cladding for fuel element

Publication Date: 2018.10.23 TERRAPOWER LLC

AI summary

This disclosure describes various configurations and components for bimetallic and trimetallic claddings for use as a wall element separating nuclear material from an external environment. The cladding materials are suitable for use as cladding for nuclear fuel elements, particularly for fuel elements that will be exposed to sodium or other coolants or environments with a propensity to react with the nuclear fuel.