Passive Boron Release for Sub-Critical Reactor Control

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Solution Overview

Problem

Existing nuclear reactors rely on control rods for reaction control, which can be costly, complex, and prone to nuisance trips, and there is a need for systems that can maintain safe operation without operator intervention, especially during emergencies.

Innovation Solution

A passive boron injection system is used to control nuclear reactions by releasing boron into the containment vessel during emergencies, and a binary position control rod assembly system is employed to manage power output without mechanical actuators, combined with a control system that adjusts power generation parameters.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If control rods are used for nuclear reaction control, then the reactor can be controlled, but the system becomes costly, complex, and prone to nuisance trips

Engineering Contradiction:

Improvereaction control reliabilityVSAvoidcontrol system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts the control function from mechanical control rods and transfers it to a chemical system (boron injection). The boron injection system is positioned in the containment vessel and can be released to control the nuclear reaction, eliminating the need for complex mechanical control rod assemblies while maintaining reliable reaction control.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the mechanical control rod system with a chemical injection system. Instead of using mechanical actuators to move control rods in and out, the system uses chemical injection of boron into the containment vessel to control the nuclear reaction, thereby eliminating mechanical complexity and improving reliability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of operation

If control rods with mechanical actuators are used, then precise control is achieved, but the system requires operator intervention and is prone to nuisance trips

Engineering Contradiction:

Improveautomatic operation capabilityVSAvoidoperation stability

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The boron injection system is designed to operate automatically without operator intervention. The system includes sensors that detect reactor conditions and automatically trigger boron injection when needed, enabling the system to self-regulate and maintain stable operation without human input or mechanical actuators that could fail.

Inventive Principle:

Principle #25Self-service

3Device complexity

If traditional control rod systems are eliminated, then costs and complexity are reduced, but alternative systems must be implemented

Engineering Contradiction:

Improvecontrol system structureVSAvoidsystem implementation

Core Design Contradiction:

Device complexityVSEase of manufacture

Solution Approach 1:

The boron injection system uses pneumatic or hydraulic mechanisms to deliver boron into the containment vessel. This approach eliminates complex mechanical control rod assemblies while providing a manufacturable alternative that uses well-established pneumatic and hydraulic technologies for actuation and delivery.

Inventive Principle:

Principle #29Pneumatics and hydraulics

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 eliminates the need for control rods, reduces costs and complexity, ensures safe operation during emergencies, and allows efficient power output control, even with loss of power, by using boron injection and power generation system adjustments.

Implementation Method 1

a boron injection system positioned in the open volume of the containment vessel and including an amount of boron sufficient to stop the nuclear fission reaction or maintain the nuclear fission reaction at a sub-critical state

Methodology Applied

Scientific EffectNeutron absorption: Absorption (physical)

Implementation Method 2

the vaporized primary coolant is at at least one of a pressure or temperature sufficient to actuate the latch to release the amount of boron from the boron container into the open volume

Methodology Applied

Scientific EffectPhase change: Phase Change

Implementation Method 3

the vaporized primary coolant is at at least one of a pressure or temperature sufficient to actuate the latch to release the amount of boron from the boron container into the open volume

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS12537110B2Passive chemical injection system for controlling a nuclear reaction by delivering a neutron-absorbing chemical into a containment vessel

Publication Date: 2026.01.27 NUSCALE POWER LLC

AI summary

A nuclear power system has an open volume between containment vessel and a reactor vessel containing a reactor core. Located in the open volume is a container holding a neutron-absorbing chemical in solid form. The container is configured to release the chemical in solid form directly into the open volume in response to a predetermined temperature and/or a predetermined pressure within the open volume. The released chemical can assist in maintaining the reactor core in a sub-critical state.