Hatch Mechanical Locking System for Steam Generator Maintenance

Solution Overview

Problem

The existing access hatch sealing mechanisms in pressurized water reactor nuclear steam generators require costly and time-consuming welding for maintenance access, which introduces risks of radioactive material leakage and creates loose parts that can damage U-tubes, necessitating a more reliable and efficient sealing solution.

Innovation Solution

A mechanical locking mechanism featuring a retractable pin holder and lock nut system, with a redundant cleat locking mechanism, allows for easy access and secure sealing of removable access plates, enabling maintenance in a less caustic environment without creating loose parts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If welding is used to seal access hatches, then the seal reliability is improved, but the maintenance time and cost increase significantly

Engineering Contradiction:

Improveseal reliabilityVSAvoidmaintenance time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The locking mechanism is divided into separate modular components including a locking pin, pin holder, and receiving socket that can be independently assembled and disassembled. This segmentation allows the hatch to be securely locked without welding while enabling quick maintenance access by simply removing the mechanical fasteners.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent replaces the welding process (thermal/chemical joining) with a mechanical locking system consisting of a locking pin, pin holder, and receiving socket. This mechanical substitution eliminates the time-consuming welding operation while providing reliable sealing through precise mechanical engagement of the components.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If welding is used to seal access hatches, then the seal reliability is improved, but the cost increases significantly

Engineering Contradiction:

Improveseal reliabilityVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The locking mechanism is divided into separate modular components including a locking pin, pin holder, and receiving socket that can be independently assembled and disassembled. This segmentation allows the hatch to be securely locked without welding while enabling quick maintenance access by simply removing the mechanical fasteners.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent replaces the welding process (thermal/chemical joining) with a mechanical locking system consisting of a locking pin, pin holder, and receiving socket. This mechanical substitution eliminates the time-consuming welding operation while providing reliable sealing through precise mechanical engagement of the components.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If welding is used to seal access hatches, then the seal reliability is improved, but the risk of radioactive material leakage and loose parts damage increases

Engineering Contradiction:

Improveseal reliabilityVSAvoidradioactive material leakage risk

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent extracts the movable locking components (locking pin and pin holder) from the hatch structure itself, making them separable parts that can be removed without compromising the integrity of the hatch body or creating loose parts inside the containment area. The locking mechanism operates from the exterior, preventing radioactive material leakage risks associated with welding operations.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the welding process (thermal/chemical joining) with a mechanical locking system consisting of a locking pin, pin holder, and receiving socket. This mechanical substitution eliminates the time-consuming welding operation while providing reliable sealing through precise mechanical engagement of the components.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS8670514B2Hatch mechanical locking system

Publication Date: 2014.03.11 WESTINGHOUSE ELECTRIC CORP

AI summary

A locking mechanism for securing hatches internal to a steam generator that is made up of only mechanical locking elements with fully captured moving parts. The mechanism employs a locking pin with redundant mechanisms to secure the pin in the closed position. The moving parts of the device can be attached directly to a removable hatch so that installation and repairs that may be required can be performed outside of the pressure vessel of the steam generator.