Deflection-Limited Rod Contacts for Nuclear Fuel Spacers

Solution Overview

Problem

Conventional nuclear fuel spacers face challenges in maintaining fuel rod positioning under transverse loads, such as sudden impacts or vibrations, which can cause damage due to rigid connections or unpredictable spacing with purely elastic connections, and may result in plastic deformation or reduced coolant flow.

Innovation Solution

The introduction of specialized rod contacts with a combination of deflection-limited elastic and rigid components that provide a controlled degree of movement and resistance to fuel rods, preventing permanent deformation and optimizing fuel rod spacing while maintaining coolant flow.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If rigid rod contacts are used to maintain fuel rod positioning, then positioning stability is improved, but damage from transverse loads increases

Engineering Contradiction:

Improvefuel rod positioning stabilityVSAvoiddamage from transverse loads

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The rod contact transitions from a static rigid connection to a dynamic system where the elastic component can deflect and the rigid component provides controlled stopping. This allows the contact to adapt to transverse loads by permitting elastic deformation within safe limits, then providing rigid support when needed, thereby maintaining positioning stability while reducing damage from unexpected loads.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention changes the mechanical properties of the rod contact by combining two distinct components with different stiffness characteristics. The elastic component provides compliance under normal operation, while the rigid component engages under extreme conditions. This dual-parameter approach allows optimization of both positioning stability and damage resistance.

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If purely elastic rod contacts are used to reduce damage from transverse loads, then damage resistance is improved, but positioning precision deteriorates

Engineering Contradiction:

Improvedamage from transverse loadsVSAvoidfuel rod positioning precision

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The rod contact transitions from a static rigid connection to a dynamic system where the elastic component can deflect and the rigid component provides controlled stopping. This allows the contact to adapt to transverse loads by permitting elastic deformation within safe limits, then providing rigid support when needed, thereby maintaining positioning stability while reducing damage from unexpected loads.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention changes the mechanical properties of the rod contact by combining two distinct components with different stiffness characteristics. The elastic component provides compliance under normal operation, while the rigid component engages under extreme conditions. This dual-parameter approach allows optimization of both positioning stability and damage resistance.

Inventive Principle:

Principle #35Parameter changes

3Object-affected harmful factors

If elastic components are used to allow fuel rod movement, then damage from transverse loads is reduced, but plastic deformation may occur

Engineering Contradiction:

Improvedamage from transverse loadsVSAvoidresistance to plastic deformation

Core Design Contradiction:

Object-affected harmful factorsVSStrength

Solution Approach 1:

The elastic component acts as a pre-designed cushion that absorbs and dissipates the energy from transverse loads through controlled elastic deformation. By engaging the elastic component before rigid contact occurs, the system prevents excessive forces from reaching the fuel rod and spacer, thereby avoiding plastic deformation while still allowing necessary movement.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The invention changes the mechanical properties of the rod contact by combining two distinct components with different stiffness characteristics. The elastic component provides compliance under normal operation, while the rigid component engages under extreme conditions. This dual-parameter approach allows optimization of both positioning stability and damage resistance.

Inventive Principle:

Principle #35Parameter changes

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 solution effectively maintains fuel rod positioning, prevents damage from transverse loads, and simplifies fabrication by using a combination of elastic and rigid contacts that provide desired damping characteristics and support, ensuring reliable operation and efficient coolant flow.

Implementation Method 1

an elastic component and an associated limiting component that limits deflection of the elastic component

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS10176899B2Spacers with deflection-limited rod contacts for nuclear fuel assemblies and methods of making the same

Publication Date: 2019.01.08 GLOBAL NUCLEAR FUEL AMERICAS LLC

AI summary

Nuclear fuel spacers include a deflection-limited elastic rod contact. Spacers may additionally include a rigid contact without elastic functionality. A degree of deflection may be chosen based on plastic deformation threshold, maximum fuel rod movement, anticipated transverse loads related to fuel assembly, inspection, handling, transportation, operation, accidents, and/or any other operating characteristic. Spacers include deflection-limited elastic contacts and/or rigid contacts in several arrangements within the spacer and/or on a single fuel rod. Spacers are compatible with a simple fabrication method that forms rigid, deflection-limiting, and elastic components from a single substrate. Nuclear fuel spacers are useable with several fuel assembly types.