Breed-and-burn reactor standing wave fuel management

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Solution Overview

Problem

Nuclear fission reactors face challenges in managing excess reactivity and achieving efficient fuel breeding and fissioning, particularly in maintaining criticality and maximizing burnup levels without the need for frequent fuel replenishment.

Innovation Solution

The implementation of a breed-and-burn fast reactor design with a standing wave of breeding and fissioning, utilizing movable reactivity control assemblies and neutron absorber assemblies, along with an in-vessel handling system for fuel shuffling, allows for the establishment of a stable breeding and fissioning wave, enabling extended reactor operation without new fuel introduction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If conventional nuclear reactor designs are used, then initial criticality can be achieved, but excess reactivity cannot be managed and fuel burnup levels are limited

Engineering Contradiction:

Improvefuel burnup levelVSAvoidreactor operation complexity

Core Design Contradiction:

Quantity of substanceVSDevice complexity

Solution Approach 1:

The patent implements movable reactivity control assemblies that can be dynamically repositioned within the core, and an in-vessel handling system that actively shuffles fuel assemblies between different radial locations. This dynamic configuration allows the reactor to maintain criticality throughout the fuel cycle while achieving high burnup levels, resolving the contradiction between fuel utilization and operational complexity.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The reactor core is divided into multiple radial locations with different power levels, allowing fuel assemblies to be shuffled between high-power and low-power regions. This segmentation enables different fuel assemblies to be at different stages of burnup simultaneously, maximizing overall fuel utilization while maintaining reactor criticality.

Inventive Principle:

Principle #1Segmentation

2Duration of action of stationary object

If fuel is continuously replenished to maintain criticality, then reactor operation can be sustained, but operational complexity and fuel handling requirements increase

Engineering Contradiction:

Improvereactor operation durationVSAvoidfuel handling ease

Core Design Contradiction:

Duration of action of stationary objectVSEase of operation

Solution Approach 1:

The in-vessel handling system performs automated fuel shuffling operations within the reactor vessel, moving fuel assemblies between different radial locations based on their burnup status. This self-service mechanism extends reactor operation duration without requiring external fuel replenishment, reducing operational complexity while maintaining ease of operation through automated procedures.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The reactor maintains continuous operation by implementing a standing wave pattern where fuel assemblies are continuously shuffled between breeding and fissioning regions. This continuous fuel management approach eliminates the need for shutdowns or external fuel replenishment, extending operational duration while maintaining simplicity through standardized shuffling procedures.

Inventive Principle:

Principle #20Continuity of useful action

3Duration of action of moving object

If chemical reprocessing is used to recycle fuel, then fuel potential life can be extended, but process complexity and cost increase

Engineering Contradiction:

Improvefuel lifeVSAvoidreprocessing process complexity

Core Design Contradiction:

Duration of action of moving objectVSDevice complexity

Solution Approach 1:

The patent replaces chemical reprocessing with a mechanical fuel shuffling system that moves fuel assemblies between different radial locations in the reactor core. This mechanical approach extends fuel life by utilizing fuel at different burnup stages simultaneously, avoiding the complexity of chemical reprocessing while achieving the same goal of maximizing fuel utilization.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

Instead of chemically reprocessing spent fuel, the system recovers value from fuel assemblies by shuffling them to different radial locations based on their burnup status. Fuel assemblies that have reached high burnup in high-power regions are moved to low-power regions where they can continue to contribute, effectively recovering remaining fuel potential without complex chemical processes.

Inventive Principle:

Principle #34Discarding and recovering

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 maintains reactor criticality, achieves high burnup levels, and allows for fuel recycling, extending the fuel's potential life and reducing the need for chemical reprocessing, while ensuring safe and efficient operation.

Implementation Method 1

fissile nuclear fuel material is fissioned in a plurality of fissile nuclear fuel assemblies

Methodology Applied

Scientific EffectNuclear fission: Nuclear Fission

Implementation Method 2

nuclear fuel is bred in ones of a plurality of fertile nuclear fuel assemblies

Methodology Applied

Scientific EffectNuclear breeding: Nuclear Fission

Data Source

PatentUS11482344B2Standing wave nuclear fission reactor and methods

Publication Date: 2022.10.25 TERRAPOWER LLC

AI summary

Disclosed embodiments include nuclear fission reactor cores, nuclear fission reactors, methods of operating a nuclear fission reactor, and methods of managing excess reactivity in a nuclear fission reactor.