Nuclear Reactor Pump Diffuser Axial Alignment

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Solution Overview

Problem

Existing pumps for circulating heat transfer fluids face challenges in achieving high tightness due to deformation from thermal gradients and require complex maintenance operations, including repair machining and are susceptible to stress corrosion from studs.

Innovation Solution

The pump design features a diffuser flange axially clamped between the thermal barrier flange and the volute, with an external groove and tenon system for axial alignment, eliminating the need for studs and reducing the likelihood of deformation, thereby simplifying maintenance and ensuring stable long-term positioning of the volute, diffuser, and cooling device.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If studs are used to secure the diffuser to the thermal barrier flange, then the diffuser is fixed in position, but the studs are susceptible to stress corrosion cracking and the seal area is deformed by thermal gradients

Engineering Contradiction:

Improvediffuser positioning reliabilityVSAvoidstress corrosion cracking and thermal deformation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent removes the studs entirely from the diffuser assembly, extracting the problematic fastening elements that caused stress corrosion cracking. The diffuser is instead secured through axial clamping between the thermal barrier flange and volute, eliminating the source of stress concentration and corrosion vulnerability.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces a seal as an intermediary element between the diffuser and the flange assembly. This seal mediates the connection, allowing the diffuser to be clamped axially while maintaining sealing functionality without requiring direct stud fastening to the thermal barrier flange.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the seal is positioned in the area deformed by thermal gradients, then the seal is located between the diffuser and thermal barrier flange, but achieving high tightness becomes difficult

Engineering Contradiction:

Improvesealing tightnessVSAvoidthermal gradient deformation

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The seal acts as an intermediary that accommodates thermal deformation while maintaining sealing effectiveness. By positioning the seal in the clamped region rather than directly in the high-gradient zone, and using the axial clamping force, the seal can compensate for thermal movements and maintain tightness.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the sealing mechanism from relying on rigid flange alignment to using axial clamping force. This parameter change allows the seal to maintain contact pressure and tightness despite thermal gradient-induced deformations, as the clamping force compensates for dimensional changes.

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If axial alignment requires repair machining during maintenance, then alignment precision can be achieved, but pump maintenance becomes complex

Engineering Contradiction:

Improveaxial alignment precisionVSAvoidmaintenance complexity

Core Design Contradiction:

Manufacturing precisionVSEase of repair

Solution Approach 1:

The axial alignment features (groove and tenon) are pre-formed during manufacturing to ensure proper alignment between the diffuser and cooling device. This preliminary action eliminates the need for repair machining during maintenance, as the components are designed to self-align through the groove-tenon interface.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The diffuser and cooling device have self-aligning features built into their design. The groove in one component receives the tenon of the other, creating automatic alignment during assembly without requiring external machining or adjustment operations during maintenance.

Inventive Principle:

Principle #25Self-service

4Device complexity

If the diffuser is axially clamped between the thermal barrier flange and volute, then the need for studs is eliminated, but axial alignment must be ensured through other means

Engineering Contradiction:

Improvefastening system complexityVSAvoidaxial alignment precision

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The seal serves as an intermediary that facilitates both the axial clamping function and the alignment function. The seal is compressed between the clamped surfaces, and its geometry helps ensure proper axial positioning of the diffuser relative to the cooling device, combining fastening and alignment functions.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The groove and tenon features create an asymmetric alignment mechanism that ensures proper orientation and positioning of the diffuser relative to the cooling device. This asymmetric geometry prevents misalignment and ensures correct axial positioning without requiring additional fastening elements.

Inventive Principle:

Principle #4Asymmetry

Data Source

PatentEP3390829B1Pump for a heat-transfer fluid and nuclear reactor comprising such a pump

Publication Date: 2021.02.24 FRAMATOME SA

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AI summary

The invention relates to a pump comprising a diffuser (11) having a diffuser flange (51) clamped axially between the thermal barrier flange (31) and the volute casing (5), said diffuser (11) comprising an outer groove (65) surrounding the rotation axis (X). The thermal barrier flange (31) comprises an outer tenon (67) which is inserted in the outer groove (65) and aligns the cooling device (15) and the diffuser (11) axially with one another.