Low Temperature Nitrate Salt Oxidation of Graphite Nuclear Fuel

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Solution Overview

Problem

Current methods for processing used graphite-based nuclear fuel elements are inefficient and costly, particularly due to the need for high-temperature incineration and mechanical crushing, which can contaminate low-level waste with high-level waste and generate expensive containment requirements.

Innovation Solution

A reduced-temperature method using a nitrate salt to chemically oxidize the graphite matrix and carbide layers of nuclear fuel elements, allowing for the separation of carbon and ceramic encapsulation materials before breaching the silicon carbide layer, thereby preventing contamination and reducing waste generation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If high temperature incineration is used to remove carbon materials, then the carbon encapsulation materials are effectively removed, but the cost increases significantly and low level waste becomes contaminated with high level waste

Engineering Contradiction:

Improveremoval effectivenessVSAvoidprocessing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent changes the temperature parameter from high temperature (incineration) to low temperature (400-700°C) chemical oxidation using nitrate salts, achieving effective carbon removal while reducing processing costs and preventing waste contamination

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the mechanical/thermal process of high temperature incineration with a chemical oxidation process using nitrate salts, which selectively removes carbon materials at lower temperatures without contaminating waste streams

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Productivity

If mechanical crushing is used to process fuel elements, then the matrix and particle outer layers are broken down, but fines are generated requiring expensive containment procedures

Engineering Contradiction:

Improveprocessing efficiencyVSAvoidcontainment cost

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

The patent replaces mechanical crushing with chemical oxidation using nitrate salts, which dissolves carbon materials into solution rather than generating solid fines, thereby eliminating the need for expensive containment procedures while maintaining processing efficiency

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If high temperature processing is used to remove carbon materials, then the carbon is effectively eliminated, but the silicon carbide layer is breached causing low level waste contamination

Engineering Contradiction:

Improvecarbon removal effectivenessVSAvoidwaste contamination

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the temperature parameter to a lower range (400-700°C) and uses chemical oxidation with nitrate salts, which selectively removes carbon materials while preserving the silicon carbide containment layer, preventing waste contamination

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent converts the potential harm of silicon carbide layer breach into a benefit by using low temperature chemical oxidation that selectively attacks carbon materials while leaving the silicon carbide layer intact, thus preventing contamination

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 method efficiently removes carbon and ceramic materials at lower temperatures, enabling the safe disposal of low-level waste and reducing the need for costly containment procedures, while maintaining the integrity of the fuel kernel for further processing.

Implementation Method 1

the nitrate salt can react with the graphite to chemically oxidize the graphite to carbon dioxide

Methodology Applied

Scientific EffectChemical oxidation: Oxidation

Implementation Method 2

contacting the carbide layer of a fuel particle with a an alkali metal hydroxide and a nitrate salt... The carbide can react with the alkali metal hydroxide and this nitrate salt to remove the carbide

Methodology Applied

Scientific EffectChemical reaction: Chemical Bonding

Data Source

PatentUS20170301423A1Low Temperature Chemical Processing of Graphite-Clad Nuclear Fuels

Publication Date: 2017.10.19 BATTELLE SAVANNAH RIVER ALLIANCE LLC

AI summary

A reduced-temperature method for treatment of a fuel element is described. The method includes molten salt treatment of a fuel element with a nitrate salt. The nitrate salt can oxidize the outer graphite matrix of a fuel element. The method can also include reduced temperature degradation of the carbide layer of a fuel element and low temperature solubilization of the fuel in a kernel of a fuel element.