NTP Burn-Cycle Wait-Time Adjustment for Reactivity Control

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Solution Overview

Problem

Conventional nuclear thermal propulsion (NTP) systems face challenges in reactivity control due to the use of control drums, which can affect system performance and operation requirements.

Innovation Solution

Implementing passive control technologies, such as burnable poisons like Gadolinium (Gd) dispersed in the reactor core and hydrogen pressure control, to minimize mechanical movement of control drums, combined with strategies like extending burn cycle wait times or merging burn cycles, and enhancing temperature feedback mechanisms.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If control drums are used to adjust reactor reactivity, then reactivity control capability is achieved, but mechanical complexity and operational requirements increase

Engineering Contradiction:

Improvereactivity controlVSAvoidmechanical drum movement

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The harmful effect of xenon-135 buildup is extracted and counteracted by introducing burnable poison (gadolinium) into the core. This poison absorbs excess neutrons and mitigates the reactivity depression caused by xenon, allowing the control drum to remain stationary while maintaining reactivity control capability.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Burnable poison is loaded into the core in advance at specific locations and concentrations. This preliminary action provides a built-in mechanism to counteract xenon buildup during operation, eliminating the need for continuous mechanical adjustment of control drums and simplifying operational procedures.

Inventive Principle:

Principle #10Preliminary action

2Productivity

If burn cycles are performed in quick succession, then productivity is improved, but xenon buildup reduces reactivity control effectiveness

Engineering Contradiction:

Improveburn cycle frequencyVSAvoidreactivity control stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The concentration and spatial distribution of burnable poison are carefully optimized to match the expected xenon buildup profile during multiple burn cycles. By adjusting these parameters, the system maintains stable reactivity control even when burn cycles are performed in quick succession, as the poison provides a buffer against xenon-induced reactivity changes.

Inventive Principle:

Principle #35Parameter changes

3Extent of automation

If gadolinium is dispersed in the outer tie tube layer alloy, then passive reactivity control is achieved, but manufacturing precision requirements increase

Engineering Contradiction:

Improvepassive control capabilityVSAvoidgadolinium dispersion concentration

Core Design Contradiction:

Extent of automationVSManufacturing precision

Solution Approach 1:

Gadolinium is dispersed in the outer tie tube layer alloy with a specific concentration range (0-1000 ppm) rather than uniformly throughout the entire core. This localized approach provides passive reactivity control where it is most needed while reducing the overall complexity of manufacturing and allowing for practical tolerances in the dispersion process.

Inventive Principle:

Principle #3Local quality

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

This approach simplifies reactivity control, reduces mechanical drum movement, enhances system performance, and maintains constant reactivity across multiple burn cycles, thereby improving efficiency and reducing mechanical complexity.

Implementation Method 1

A burnable poison can be dispersed in the nuclear reactor core. The burnable poison can include Gadolinium (Gd).

Methodology Applied

Scientific EffectNeutron absorption: Absorption (physical)

Implementation Method 2

hydrogen pressure control, to minimize mechanical movement of control drums

Methodology Applied

Scientific EffectPressure-density relationship: Boyle's Law

Implementation Method 3

enhancing temperature feedback mechanisms

Methodology Applied

Scientific EffectTemperature feedback: Feedback

Data Source

PatentUS12456557B2Adjusting wait time between burn cycles or merging burn cycles

Publication Date: 2025.10.28 STANDARD NUCLEAR INC

AI summary

Passive reactivity control technologies that enable reactivity control of a nuclear thermal propulsion (NTP) system with little to no active mechanical movement of circumferential control drums. By minimizing or eliminating the need for mechanical movement of the circumferential control drums during an NTP burn, the reactivity control technologies simplify controlling an NTP reactor and increase the overall performance of the NTP system. The reactivity control technologies mitigate and counteract the effects of xenon, the dominant fission product contributing to reactivity transients. Examples of reactivity control technologies include, employing burnable neutron poisons, tuning hydrogen pressure, adjusting wait time between burn cycles or merging burn cycles, and enhancement of temperature feedback mechanisms. The reactivity control technologies are applicable to low-enriched uranium NTP systems, including graphite composite fueled and tungsten ceramic and metal matrix (CERMET), or any moderated NTP system, such as highly-enriched uranium graphite composite NTP systems.