Nuclear Fuel Assembly Top Nozzle Guide Pin Instrument Insertion

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Solution Overview

Problem

In-core instruments inserted through the top head of a nuclear reactor often interfere with control rod assemblies due to the lack of a structured path, and there is a risk of reactor core substances leaking when inserted through the bottom.

Innovation Solution

Guide pins with axially formed guide holes are used to align the top nozzle of a nuclear fuel assembly with the upper core plate, allowing in-core instruments to be inserted through these holes without straying from a predetermined path and avoiding interference with control rod assemblies.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If in-core instruments are inserted through the top head of a nuclear reactor, then the risk of reactor core substances leaking is reduced, but interference with control rod assemblies occurs

Engineering Contradiction:

Improveprevention of reactor core substances leakageVSAvoidinterference with control rod assemblies

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The top nozzle is divided into multiple regions: a central region for control rod assemblies and peripheral regions for in-core instrument insertion. The guide pins further segment the insertion paths, creating dedicated channels that separate instrument insertion from control rod operations, thereby eliminating interference while maintaining leak prevention

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Guide pins are introduced as intermediary components that mediate between the top nozzle and in-core instruments. These guide pins provide predetermined insertion paths through the upper core plate, ensuring instruments are positioned accurately without interfering with control rod assemblies while maintaining the integrity of the top nozzle structure

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If in-core instruments are inserted through the bottom of a reactor vessel, then interference with control rod assemblies is avoided, but reactor core substances may leak through the insertion hole

Engineering Contradiction:

Improveinterference with control rod assembliesVSAvoidprevention of reactor core substances leakage

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

Instead of inserting instruments from the bottom of the reactor vessel, the insertion path is inverted to go through the top head of the reactor. The top nozzle structure with guide pins provides a sealed insertion path from the top, achieving both leak prevention and avoidance of control rod interference by reversing the traditional insertion direction

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS10692613B2Nuclear fuel assembly top nozzle having in-core instrument insertion structure using an upper core plate hollow guide pin

Publication Date: 2020.06.23 KEPCO NUCLEAR FUEL CO LTD

AI summary

The present invention relates to a top nozzle and a nuclear reactor in which an in-core instrument, which is supposed to be inserted through a top head of a nuclear reactor, is inserted through a guide pin for an upper core plate. In a nuclear reactor including guide pins for aligning a top nozzle for a nuclear fuel assembly with an upper core plate of a nuclear reactor, a guide hole (210) is axially formed through the guide pins (200) and in-core instruments (10) are inserted through the guide holes (210).