Fuel Assembly Neutron Absorbing Inserts for Power Peaking

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Power peaking in nuclear reactors, specifically in WER-440 reactors, causes pellet-cladding interaction and fuel failures due to axial movement of follower assemblies, which is not efficiently addressed by existing technologies.

Innovation Solution

A fuel assembly design featuring second fuel rods with neutron absorbing inserts, such as Hafnium, positioned in the outermost row of the fuel rod positions closest to the shroud, effectively reducing power peaking by localized neutron absorption without requiring extensive modifications or excessive use of neutron absorbing materials.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If follower assemblies are moved axially to control reactor power, then reactor power can be adjusted for load following, but power peaking occurs in surrounding fixed fuel assemblies causing pellet-cladding interaction and fuel failures

Engineering Contradiction:

Improvereactor power adjustment capabilityVSAvoidfuel rod integrity

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent applies local quality by positioning neutron absorbing inserts specifically in the outermost fuel rods of the follower assembly. These inserts create localized neutron absorption zones at the periphery where power peaking occurs during follower movement, thereby protecting the surrounding fixed fuel assemblies from excessive power excursions while maintaining the follower's power adjustment capability

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The neutron absorbing inserts are pre-installed in the outermost fuel rods to provide preliminary anti-action against power peaking. This preventive measure counteracts the harmful effect of neutron moderation that occurs when the follower moves axially, thereby preventing pellet-cladding interaction and fuel failures before they can occur

Inventive Principle:

Principle #9Preliminary anti-action

2Reliability

If neutron absorbing material is used to reduce power peaking, then fuel rod integrity is improved, but excessive use of neutron absorbing material increases cost and complexity

Engineering Contradiction:

Improvefuel rod integrityVSAvoidfuel assembly structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Instead of uniformly distributing neutron absorbing material throughout all fuel rods, the patent applies it locally only in the outermost fuel rods where power peaking occurs. This selective placement reduces the total amount of neutron absorbing material required while maintaining effectiveness in protecting against power peaking

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses partial action by implementing neutron absorbing inserts in only the outermost fuel rods rather than all fuel rods. This partial application is sufficient to address the power peaking problem at the periphery where it occurs most severely, avoiding the excessive use of materials and simplifying the overall fuel assembly structure

Inventive Principle:

Principle #16Partial or excessive action

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 design efficiently reduces power peaking in surrounding fixed fuel assemblies, preventing fuel failures and maintaining reactor stability during load and frequency follow operations, while being cost-effective and compatible with existing reactor components.

Implementation Method 1

each of the second fuel rods comprises an insert of a neutron absorbing material, wherein the second fuel rods are the only fuel rods of the plurality of the first fuel rods and the second fuel rods comprising the inserts of the neutron absorbing material

Methodology Applied

Scientific EffectNeutron absorption: Absorption (physical)

Data Source

PatentEP4343791B1A fuel assembly, a follower comprising a fuel assembly and a nuclear reactor

Publication Date: 2025.01.01 WESTINGHOUSE ELECTRIC SWEDEN AB

Figure 1
Figure 2~2a
Figure 3

AI summary

A fuel assembly (1, 1') for a follower (2) configured to initiate and control fission reactions in a nuclear reactor (4) is described. The fuel assembly (1, 1') comprises a shroud (3) and a plurality of first fuel rods (5) and second fuel rods (5') positioned in evenly distributed fuel rod positions within the shroud (3). Each of the plurality of the first fuel rods (5) and the second fuel rods (5') has a casing (7) with an inner diameter (d) and a nuclear fuel positioned inside the casing (7). The second fuel rods (5') are positioned in the outermost row of the fuel rods positions closest to the shroud (3) and along the circumference of the shroud (3). Each of the second fuel rods (5') comprises an insert (9, 9') of a neutron absorbing material, wherein the second fuel rods (5') are the only fuel rods of the plurality of the first fuel rods (5) and the second fuel rods (5') comprising the inserts (9, 9') of the neutron absorbing material. A follower (2) and a nuclear reactor (4) are also described.