Gadolinia-Modified Uranium Dioxide Fuel for Criticality Control

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Solution Overview

Problem

The increased uranium enrichment in nuclear reactor fuels beyond 5% by weight requires significant design changes and equipment modifications in fuel fabrication, storage, and transportation facilities, leading to increased costs and restrictions, which offset the economic benefits of enhanced fuel cycle efficiency.

Innovation Solution

Adding a slight amount of gadolinia, a burnable poison with a large neutron absorption cross-section, to uranium dioxide powders with uranium enrichment greater than 5% by weight to control the effective neutron multiplication factor, allowing for reduced criticality control measures and increased economic efficiency by minimizing the need for equipment modifications.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If uranium enrichment of reactor fuels is increased beyond 5% by weight to enhance power uprating and operation period extension, then fuel cycle costs are reduced and economic efficiency is improved, but design changes and equipment modifications are required in fuel fabrication, storage, and transportation facilities, leading to increased costs and restrictions

Engineering Contradiction:

Improvefuel cycle efficiencyVSAvoidfacility modification requirements

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent applies parameter changes by controlling the effective neutron multiplication factor (k-eff) to be less than or equal to the maximum value for 5% enriched uranium dioxide systems. This parameter control allows facilities to handle higher enrichment fuels (greater than 5% uranium enrichment) without requiring design changes or equipment modifications, thereby maintaining fuel cycle efficiency improvements while avoiding facility complexity increases

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent converts the potential harm of higher enrichment fuels (increased criticality risk) into a benefit by establishing specific handling conditions that ensure subcriticality. By controlling the effective neutron multiplication factor and implementing specific handling procedures, the system allows higher enrichment fuels to be processed in existing facilities without modifications, thus converting the safety concern into an operational guideline that enables continued use of cost-effective high enrichment fuels

Inventive Principle:

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

2Quantity of substance

If uranium enrichment is increased to reduce the number of fresh fuel assemblies and spent fuel assemblies per unit electricity generated, then fuel cycle costs are greatly reduced, but criticality control restrictions and equipment modifications are required for fuel fabrication, storage, and transportation

Engineering Contradiction:

Improvenumber of fuel assembliesVSAvoidcriticality control restrictions

Core Design Contradiction:

Quantity of substanceVSEase of operation

Solution Approach 1:

The patent applies parameter changes by defining specific operational parameters for handling high enrichment fuels, including controlling the effective neutron multiplication factor and specifying handling procedures. These parameter changes enable facilities to operate with reduced numbers of fuel assemblies (improved ease of operation) while maintaining criticality safety through controlled parameters rather than restrictive regulations

Inventive Principle:

Principle #35Parameter changes

3Reliability

If design changes and equipment modifications are made to handle reactor fuels with uranium enrichment greater than 5% by weight, then criticality safety is ensured, but costs increase and economic benefits are offset

Engineering Contradiction:

Improvecriticality safetyVSAvoidfacility modification costs

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent converts the safety requirement (which would normally demand expensive facility modifications) into a set of operational control measures. By controlling the effective neutron multiplication factor and implementing specific handling procedures, the system ensures criticality safety without requiring design changes or equipment modifications, thereby maintaining ease of manufacture while ensuring reliability

Inventive Principle:

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

Solution Approach 2:

The patent enables existing facilities to self-serve for handling high enrichment fuels by establishing internal control procedures and parameters. Rather than requiring external facility modifications, the system allows facilities to maintain their existing design while implementing controlled handling procedures that ensure criticality safety, thus avoiding additional manufacturing costs

Inventive Principle:

Principle #25Self-service

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 approach enables the handling of reactor fuels with uranium enrichment greater than 5% by weight without the need for extensive facility modifications, maintaining subcriticality and reducing fuel cycle costs by leveraging the reactivity-suppression effect of gadolinia, thus enhancing economic efficiency and operational flexibility.

Implementation Method 1

gadolinia, a burnable poison with a large neutron absorption cross-section

Methodology Applied

Scientific EffectNeutron absorption: Absorption (physical)

Data Source

PatentUS8130896B2Method of controlling criticality of nuclear fuel cycle facility, method of producing uranium dioxide powder, reactor fuel rod, and fuel assembly

Publication Date: 2012.03.06 KK TOSHIBA

AI summary

A method of controlling the criticality of a nuclear fuel cycle facility includes steps of producing a reactor fuel by adding less than 0.1% by weight of gadolinia to a uranium dioxide powder with a uranium enrichment of greater than 5% by weight and controlling the effective neutron multiplication factor of a uranium dioxide system in a step of handling the reactor fuel to be less than or equal to the maximum of the effective neutron multiplication factor of a uranium dioxide system with a uranium enrichment of 5% by weight.