Vented Nuclear Fission Fuel Module for Cladding Integrity

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Solution Overview

Problem

Nuclear fission reactors face challenges with fuel rod swelling, cracking, and rupture due to the accumulation and pressure exerted by fission product gases and solids, which can lead to cladding breaches and uncontrollable release of radioactive materials.

Innovation Solution

A vented nuclear fission fuel module system that includes a nuclear fission fuel element capable of generating fission products, with a valve body and valve for controllably venting gaseous fission products into a reactor vessel, utilizing a flexible diaphragm and removable cap to manage pressure and prevent cladding damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If fission products are retained in the fuel element, then fuel rod swelling and cracking increase, but radioactive containment is improved

Engineering Contradiction:

Improvefuel rod integrityVSAvoidradioactive containment

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A vent valve system acts as an intermediary mechanism between the fuel element interior and the reactor vessel. The valve remains closed during normal operation to maintain containment, but can be opened to release fission products when pressure exceeds a threshold, thus mediating between the conflicting requirements of containment and pressure management.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system changes the operational parameter of the vent valve from a static closed state to a dynamically controllable state. The valve transitions between closed and open positions based on pressure conditions, allowing the system to adapt to changing internal pressure parameters while maintaining both containment and structural integrity.

Inventive Principle:

Principle #35Parameter changes

2Stress or pressure

If fission product gases are vented continuously, then pressure buildup is prevented, but reactor efficiency decreases

Engineering Contradiction:

Improveinternal pressure controlVSAvoidreactor efficiency

Core Design Contradiction:

Stress or pressureVSProductivity

Solution Approach 1:

The vent valve operates periodically rather than continuously - remaining closed during normal operation and opening only when pressure threshold is exceeded. This periodic action prevents continuous venting that would reduce reactor efficiency while still managing pressure buildup effectively.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The vent valve system is designed to automatically respond to pressure conditions without external intervention. When internal pressure exceeds the threshold, the valve self-activates to release pressure, then closes again, providing self-regulating pressure management that maintains reactor efficiency.

Inventive Principle:

Principle #25Self-service

3Reliability

If a venting system is added to the fuel element, then fuel rod integrity is improved, but device complexity increases

Engineering Contradiction:

Improvecladding breach preventionVSAvoidfuel module structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The vent valve system is nested within the existing fuel element structure. The valve is integrated into the fuel rod design, with the valve body, diaphragm, and cap components arranged in a compact nested configuration that fits within the fuel element geometry, minimizing additional structural complexity.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The vent valve utilizes a flexible diaphragm as a key component. This thin film element provides the pressure-sensing and actuation function, replacing more complex mechanical pressure sensors and actuators. The flexible diaphragm responds to pressure differential by deflecting to open or close the valve aperture, simplifying the overall valve mechanism.

Inventive Principle:

Principle #30Flexible shells and thin films

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

The system effectively reduces the risk of fuel rod swelling and cracking by allowing controlled release of fission products, maintaining reactor integrity and preventing radioactive contamination.

Implementation Method 1

When the internal pressure exceeds the sum of the external pressure and the spring force, the diaphragm deflects to a second position that opens the valve aperture

Methodology Applied

Scientific EffectPressure differential: Pressure Gradient

Implementation Method 2

a spring means in said valve body for urging said diaphragm toward said closed position

Methodology Applied

Scientific EffectSpring force: Spring

Data Source

PatentUS9721677B2Nuclear fission reactor, a vented nuclear fission fuel module, methods therefor, and a vented nuclear fission fuel module system

Publication Date: 2017.08.01 TERRAPOWER LLC

AI summary

Illustrative embodiments provide a nuclear fission reactor, that includes a reactor vessel, a nuclear fission fuel element capable of generating a gaseous fission product, a valve body defining a plenum for receiving the gaseous fission product, and a valve in operative communication with the plenum for controllably venting the gaseous fission product from the plenum.