Multiple-Degree-of-Freedom Sparger Connection for Nuclear Reactor

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Solution Overview

Problem

Reactor pressure vessels in nuclear plants face issues with intergranular stress corrosion cracking in core spray piping, particularly at welded joints, leading to unpredictable leakage and compromised cooling water delivery during a loss of coolant accident, which threatens the structural integrity and fuel clad temperature control.

Innovation Solution

A core spray sparger T-box attachment assembly with a multiple-degree-of-freedom connection system, including an anchor plate, clamp blocks, and a draw bolt mechanism, is introduced to securely clamp the downcomer piping to the shroud, allowing for flexible alignment and reducing stress on welds, thereby preventing leakage and ensuring structural integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If welded joints are used to attach sparger pipes to the sparger T-box, then the structural integrity is maintained under normal conditions, but intergranular stress corrosion cracking occurs leading to unpredictable leakage

Engineering Contradiction:

Improvestructural integrityVSAvoidleakage prevention

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent extracts the problematic welded joints from the sparger T-box assembly and replaces them with a mechanical clamping system. The clamp assembly with draw bolts and clamp blocks provides a non-welded connection method that eliminates the IGSCC vulnerability while maintaining structural integrity and sealing performance.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces an intermediary clamping system between the sparger pipes and the sparger T-box. This intermediary mechanism (comprising clamp blocks, draw bolts, and sealing elements) mediates the connection, providing both mechanical support and leak prevention without relying on vulnerable welded joints.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Strength

If a rigid clamping system is used to secure the sparger T-box, then structural integrity is improved, but stress on the welds increases leading to potential failure

Engineering Contradiction:

Improvestructural integrityVSAvoidweld stress

Core Design Contradiction:

StrengthVSStress or pressure

Solution Approach 1:

The patent employs a dynamic clamping system where the draw bolts can be adjusted to apply appropriate clamping force. The clamp blocks are positioned to distribute stress away from the welded joints, and the system allows for controlled deformation and stress redistribution, preventing stress concentration at vulnerable weld locations while maintaining overall structural integrity.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS9064609B2Mechanical connections and methods

Publication Date: 2015.06.23 GE HITACHI NUCLEAR ENERGY AMERICAS LLC

AI summary

A mechanical connection between adjacent components of a system may include a first component of the system, a second component of the system, and a multiple degree-of-freedom connection between the first and second components. The multiple degree-of-freedom connection may have at least four degrees of freedom. A method for establishing a mechanical connection between adjacent components of a system may include disposing a first component of the system adjacent to a second component of the system, and connecting the first component to the second component using a multiple degree-of-freedom connection. The multiple degree-of-freedom connection may have at least four degrees of freedom.