Canned Motor for Molten Salt Reactor Using Solid Copper Bars
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Solution Overview
Problem
Molten salt reactors face challenges with high-temperature operation, corrosion, and radiation, which affect the reliability and longevity of pumps and motors due to the aggressive nature of molten salts and high radiation levels, leading to issues with insulation, dynamic seals, and the inability to use permanent magnets or suitable insulation materials.
Innovation Solution
A canned rotodynamic flow machine with solid copper bars for stator windings, ceramic spacers for insulation, and active magnetic bearings, allowing for operation at high temperatures without dynamic seals and using the working fluid for cooling, thereby increasing mechanical stability and reducing leakage risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If permanent magnets are used for the electric motor driving the pump, then the motor can provide sufficient torque and power, but the magnets start to irreversibly lose their magnetism at high operating temperatures of molten salt reactors
Solution Approach 1:
The patent replaces permanent magnets with an electromagnetic motor system where the magnetic field is generated dynamically through electrical current in stator windings. This substitution eliminates the temperature-dependent magnetic properties of permanent magnets while maintaining the necessary motor torque through electromagnetic induction, allowing reliable operation at molten salt reactor temperatures.
Solution Approach 2:
The patent changes the operating parameters of the motor system by using electromagnetic fields generated through controlled electrical current rather than relying on fixed magnetic properties. This parameter change allows the motor to maintain sufficient torque at high temperatures where permanent magnets would fail, as the electromagnetic field strength can be adjusted independently of temperature.
2Ease of repair
If dynamic seals are used in pumps, then the pump can be disassembled and maintained more easily, but dynamic seals are not available for the temperature range and aggressive environment of molten salt reactors and are much less reliable than static seals
Solution Approach 1:
The patent extracts and eliminates the dynamic seal component from the pump design by using a canned motor configuration where the motor is sealed within the pump housing. This removal of the dynamic seal eliminates the reliability issues associated with seals in high-temperature, corrosive environments while the entire canned motor assembly can be replaced as a single unit, maintaining ease of repair.
Solution Approach 2:
The patent merges the motor and pump into a single integrated canned motor assembly where the motor is sealed within the pump housing. This combination eliminates the need for dynamic seals between moving and stationary parts, as the entire assembly operates as a sealed unit. The merged design maintains ease of maintenance through modular replacement while achieving the seal reliability required for molten salt reactor conditions.
3Reliability
If the electric motor is cooled below the operating temperature of the molten salt, then the motor can operate reliably, but the salt vapor deposits on cold surfaces within the dynamic seal or motor, resulting in shorter life-cycle and increased risk of radioactive material release
Solution Approach 1:
The patent changes the temperature parameter of the motor to match the molten salt operating temperature. By heating the motor to the same temperature as the molten salt rather than cooling it below, the patent eliminates the temperature differential that causes salt vapor deposition. This parameter change allows the motor to operate reliably without generating harmful deposits, as the entire system operates at uniform high temperature.
4Temperature
If suitable insulation materials are used for stator windings, then the motor can operate at high temperatures, but there are no suitable insulation materials that can handle the operating temperatures and conditions of molten salt reactors
Solution Approach 1:
The patent replaces the need for high-temperature insulation materials by using a canned motor design where the stator windings are sealed within the canned motor housing. This substitution protects the insulation from direct exposure to the aggressive molten salt environment while allowing the motor to operate at high temperatures. The sealed configuration isolates the insulation materials from corrosive conditions that would otherwise degrade them.
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 solution enables reliable operation at high temperatures, extends equipment life, and reduces the risk of radioactive material release by using solid copper bars for stator windings and active magnetic bearings, eliminating the need for dynamic seals and oil lubrication.
Implementation Method 1
an induction or reluctance motor or generator comprising a stator and a rotor, the rotor being operably coupled to the impeller, the stator comprising stator windings for inducing a magnetic field that penetrates the rotor
Implementation Method 2
Heat can be extracted from such reactors by pumping the molten salt in a loop between the 'core' and a heat exchanger
Implementation Method 3
Heat can be extracted from such reactors by pumping the molten salt in a loop between the 'core' and a heat exchanger with the reactor power being directly proportional to the temperature drop across the heat exchanger
Data Source
AI summary
A canned rotodynamic flow machine (1) configured for operating with a working fluid such as molten salt of a molten salt nuclear reactor. The stator windings are formed by one or more electrically conductive solid bars (12).