Flywheel-Impeller Coastdown for Passive Reactor Coolant Flow
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Solution Overview
Problem
Existing decay heat removal systems for nuclear reactors rely on electrical power to operate pumps, leading to coolant stagnation and potential failures in the absence of electricity.
Innovation Solution
A passive inertial coast down system using a flywheel and impeller to store and release kinetic energy, allowing primary coolant to continue circulating and removing decay heat even without electrical power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrical power is used to drive pumps for decay heat removal, then coolant circulation is maintained, but the system fails when electrical power is lost
Solution Approach 1:
The flywheel is pre-spinned to store rotational kinetic energy before a power loss event occurs. This preliminary action ensures that when electrical power is lost, the stored energy is immediately available to drive the impeller and maintain coolant circulation without interruption.
Solution Approach 2:
The invention converts the harmful effect of power loss into a beneficial passive operation. When electrical power fails, the system transitions to passive mode where the flywheel's stored kinetic energy automatically drives coolant circulation, turning a failure condition into a self-sustaining operation.
2Adaptability or versatility
If a passive inertial coast down system is used, then the system operates without electrical power, but the device complexity increases
Solution Approach 1:
The flywheel and impeller are combined into a single integrated assembly that serves dual functions: the flywheel stores rotational energy and the impeller drives coolant flow. This merging eliminates the need for separate energy storage and fluid drive mechanisms, reducing overall system complexity.
Solution Approach 2:
The flywheel-impeller assembly performs multiple functions: it stores rotational kinetic energy, drives the coolant circulation, and provides passive operation capability. This multi-functionality reduces the number of separate components needed, thereby simplifying the overall system.
3Use of energy by moving object
If the electromagnetic pump stops circulating coolant, then electrical power is conserved, but decay heat builds up in the core
Solution Approach 1:
The flywheel ensures continuous coolant circulation by providing stored rotational energy that drives the impeller immediately upon pump shutdown. This continuity prevents any interruption in heat removal, maintaining safe core temperatures without requiring continuous electrical power input.
Solution Approach 2:
The system uses its own stored kinetic energy in the flywheel to maintain coolant circulation after pump shutdown. This self-service capability allows the system to sustain its own operation without external power input, conserving electrical energy while preventing heat buildup.
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
Enables continuous coolant circulation and decay heat removal for extended periods after the primary coolant pump shutdown, enhancing reactor safety by avoiding coolant stagnation and heat buildup.
Implementation Method 1
a passive system that can operate through principals of rotational energy storage and selective release to continue circulating primary coolant in the event of a loss of electrical power
Implementation Method 2
the kinetic energy stored in the flywheel is released by the impeller, and the impeller causes the primary coolant to continue to circulate
Implementation Method 3
an electromagnetic pump in fluid communication with the primary coolant loop and configured to circulate primary coolant through the primary coolant loop
Implementation Method 4
Coolant is typically forced through passages between fuel elements and control elements to transfer heat generated by fissioning fuel elements to a heat exchanger
Implementation Method 5
fuel elements and control elements are supported in different interrelated arrangements to support a critical reactivity to control the output of the reactor
Implementation Method 6
a passive system that can operate through principals of rotational energy storage and selective release to continue circulating primary coolant in the event of a loss of electrical power
Data Source
AI summary
A nuclear reactor is configured with a primary coolant loop for transferring heat away from the nuclear reactor core. In a shutdown event, the primary coolant pump may stop pumping primary coolant through the reactor core, resulting in decay heat buildup within the reactor core. An inertial energy coast down system can store kinetic energy while the nuclear reactor is operating and then release the stored kinetic energy to cause the primary coolant to continue to flow through the nuclear reactor core to remove decay heat. The inertial energy coast down system may include an impeller and a flywheel having a mass. During normal reactor operation, the flowing primary coolant spins up the impeller and flywheel, and upon a shutdown event where the primary coolant pump stops pumping, the flywheel and impeller can cause the primary coolant to continue to flow during a coast down of the flywheel and impeller.