Decay Heat Conversion to Electricity in Spent Fuel Pools
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Solution Overview
Problem
Nuclear reactors face challenges in maintaining adequate cooling during accidents due to failures in emergency equipment, leading to inaccessible Ultimate Heat Sinks and increased thermal loading on spent fuel pools, posing risks to safety and public welfare.
Innovation Solution
A decay heat conversion to electricity system that utilizes pressurized fuel racks with integrated heat exchangers and turbine-pump-generator units to convert decay heat into electricity, providing an independent power source and reducing thermal loading on cooling systems by converting spent fuel pool water into superheated vapor, which drives a turbine to generate electricity and pressurizes the cooling fluid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If active cooling mechanisms with electric pumps are used to remove decay heat, then cooling effectiveness is improved, but reliability deteriorates when external power sources fail during accidents
Solution Approach 1:
The patent converts the harmful decay heat that must be removed into a beneficial energy source that drives the cooling system. The decay heat from spent fuel bundles is used to generate steam that drives a turbine connected to both a generator (producing electricity) and a pump (circulating coolant), eliminating the need for external power sources during accidents.
Solution Approach 2:
The cooling system becomes self-powered by utilizing the decay heat it is designed to remove. The system uses its own waste heat to drive the turbine-pump-generator assembly, creating a self-sustaining cooling mechanism that operates independently of external power sources during normal conditions and accidents.
2Power
If emergency equipment is designed to provide onsite electricity for coolant circulation, then cooling capability is improved, but ease of operation deteriorates when equipment fails due to seismic or flooding events
Solution Approach 1:
The patent transforms the decay heat that requires active management into a direct driver of the cooling operation. The steam generated from decay heat directly drives the turbine-pump assembly, eliminating complex control systems and power transmission requirements that could fail during seismic or flooding events.
Solution Approach 2:
The patent combines the turbine, pump, and generator into a single integrated assembly that is directly coupled to the spent fuel bundles. This merged design eliminates multiple connection points and control systems, simplifying operation during accidents while maintaining full cooling capability.
3Loss of energy
If thermal energy is transferred to an Ultimate Heat Sink, then heat removal is improved, but loss of energy occurs when the heat sink becomes inaccessible during accidents
Solution Approach 1:
Instead of viewing decay heat as energy that must be constantly removed and discarded, the patent converts it into a useful energy source that drives the cooling system and generates electricity. This eliminates the need for continuous energy transfer to external heat sinks while maintaining effective cooling.
Solution Approach 2:
The patent introduces a steam turbine as an intermediary between the decay heat source and the coolant circulation system. The decay heat generates steam that drives the turbine, which in turn drives the pump that circulates coolant through the spent fuel bundles, creating a reliable intermediate energy transfer mechanism that does not depend on external heat sinks.
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 system ensures a reliable and independent source of emergency power during off-normal conditions and reduces thermal loading on spent fuel pool cooling equipment, enhancing safety by utilizing decay heat energy conversion, even in the absence of external power sources.
Implementation Method 1
a first heat exchanger formed by a fuel rack configured to be pressurized while containing spent fuel bundles providing a heat transfer containment structure wherein spent fuel pool cooling fluid (i.e. water) may be pressurized. As this fluid flows through the spent fuel bundles it heats up and changes its thermodynamic state into superheated vapor
Implementation Method 2
The super heated vapor then exits the heat transfer containment structure and expands through a turbine-pump-generator system
Implementation Method 3
The super heated vapor then exits the heat transfer containment structure and expands through a turbine-pump-generator system assembled and flanged to the top portions of the fuel rack
Implementation Method 4
A portion of the turbine torque produced while converting decay heat energy contained in the superheated vapor is converted into electricity by a fast compact electric alternator/generator
Implementation Method 5
As colder spent fuel pool fluid enters the suction of the pump it is pressurized into the nozzle of a jet pump positioned at the bottom of the fuel rack. As the fluid exits the nozzle at high pressure and velocity it ensures pressurization
Implementation Method 6
After expanding through the turbine the superheated fluid may condense by venting and mixing with the cooler spent fuel pool fluid
Data Source
AI summary
Various embodiments of a decay heat conversion to electricity system and related methods are disclosed. According to one exemplary embodiment, a decay heat conversion to electricity system may include a spent fuel rack configured to pressurize spent fuel bundles to obtain superheated vapor to drive a turbine-driven pump and fast alternator all submerged with the spent fuel rack and positioned at the bottom of the spent fuel pool for conversion of electricity distributed outside of the spent fuel pool via cables without impairing spent fuel pool operations.