Stabilizing Reactive Sodium in Nuclear Fuel Pins

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Solution Overview

Problem

The disposal of spent sodium-bonded nuclear fuels requires invasive and complex processing to stabilize reactive sodium metal, increasing costs and safety risks due to potential uncontrolled chemical reactions.

Innovation Solution

A method and apparatus that puncture the cladding of a fuel pin to inject a reaction gas, reacting with the sodium to form a stable compound, with a monitoring system to ensure complete reaction and sealing to confine the product, thereby stabilizing the sodium without disassembly or extensive processing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional complete assembly chopping and electrometallurgical processing is used to stabilize sodium, then the sodium is fully stabilized, but the processing becomes invasive, complex, and costly

Engineering Contradiction:

Improvestability of sodiumVSAvoidprocessing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The fuel pin is divided into segments by creating multiple puncture holes in the cladding, allowing reaction gas to be introduced at multiple points. This segmentation enables the stabilization process to be performed in-situ without complete disassembly, reducing processing complexity while achieving thorough sodium stabilization throughout the fuel pin

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The sodium metal is extracted from its reactive metallic state and converted into a stable compound through chemical reaction with introduced gas. This extraction of reactivity transforms the hazardous sodium metal into stable sodium compounds (such as sodium oxide or sodium carbonate) that can be safely disposed of without further processing

Inventive Principle:

Principle #2Taking out (Extraction)

2Reliability

If conventional complete disassembly and processing is performed, then sodium stabilization is achieved, but disposal costs increase

Engineering Contradiction:

Improvestability of sodiumVSAvoiddisposal cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The fuel pin structure itself is utilized as the reaction chamber, with the cladding serving as both the containment vessel and the structure into which puncture holes are made. The system uses its own existing structure rather than requiring external processing equipment and disassembly, thereby reducing disposal costs while achieving sodium stabilization

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The chemical state of sodium is changed from reactive metal to stable compound through controlled chemical reaction parameters. By adjusting gas flow rate, temperature, and reaction time, the process achieves complete stabilization without requiring the invasive processing and associated costs of conventional methods

Inventive Principle:

Principle #35Parameter changes

3Productivity

If reactive sodium metal is present in spent fuel, then the fuel can be disposed of directly, but uncontrolled chemical reactions create safety risks

Engineering Contradiction:

Improvedisposal speedVSAvoidsafety risk from uncontrolled reactions

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The highly reactive nature of sodium metal, which poses safety risks, is converted into a benefit by utilizing its reactivity in a controlled manner. The same reactivity that causes safety concerns is harnessed to rapidly convert sodium to stable compounds through controlled reaction with introduced gas, eliminating the hazard while maintaining fast processing speed

Inventive Principle:

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

Solution Approach 2:

An inert or controlled atmosphere is created within the fuel pin by introducing specific gases that react with sodium to form stable compounds. This controlled atmospheric environment prevents uncontrolled reactions with moisture or air that would occur during conventional handling, thereby eliminating safety risks while enabling direct disposal

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

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 stabilizes reactive sodium metal within the fuel pin, reducing the risk of uncontrolled reactions and simplifying the disposal process by confining the stable compound, thus enhancing safety and reducing costs.

Implementation Method 1

A reaction gas is injected into the fuel pin through the injection passage to react with the reactive sodium metal to form a stable sodium compound

Methodology Applied

Scientific EffectChemical reaction: Chemical Bonding

Data Source

PatentUS9105364B2Apparatuses for stabilizing fuel containing reactive sodium metal

Publication Date: 2015.08.11 GE HITACHI NUCLEAR ENERGY AMERICAS LLC

AI summary

A method of stabilizing a fuel containing a reactive sodium metal may include puncturing a cladding of a fuel pin enclosing the fuel containing the reactive sodium metal to form an injection passage and an extraction passage. A reaction gas may be injected into the fuel pin through the injection passage to react with the reactive sodium metal to form a stable sodium compound. A ratio of a product gas and a remaining quantity of the reaction gas exiting the fuel pin through the extraction passage is subsequently measured, wherein the product gas is a reaction product of the reaction gas and the reactive sodium metal within the fuel pin. Once the measured ratio indicates that a reaction between the reaction gas and the reactive sodium metal is complete, the injection passage and the extraction passage are sealed so as to confine the stable sodium compound within the fuel pin.