Start-up Subsystem for Nuclear Steam Supply System
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Solution Overview
Problem
Passively safe nuclear steam supply systems lack a method to heat reactor water inventory during start-up, as they do not utilize pumps, which are necessary for conventional systems to achieve the no-load operating temperature and ensure optimal reactivity and turbulated flow.
Innovation Solution
A start-up sub-system that includes an intake conduit, a pump, a heating element, and an injection nozzle to draw and heat a portion of the primary coolant, then inject it back into the primary coolant loop, creating a venturi effect and initiating thermosiphon flow without the need for external pumps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a passively safe nuclear steam supply system is designed without pumps, then safety and reliability are improved, but the ability to heat reactor water inventory during start-up is lost
Solution Approach 1:
The system is divided into two distinct operational modes: a start-up mode using a temporary electric sub-system with pump and heater, and a normal passive mode relying on natural circulation. This segmentation allows the system to have different configurations for different operational phases, resolving the contradiction between safety (no pumps) and start-up capability (needs heating).
Solution Approach 2:
The electric sub-system performs preliminary action during start-up by heating the reactor water inventory to the no-load operating temperature before the passive safety system takes over. This preliminary heating action enables the subsequent passive operation without requiring pumps during normal conditions.
2Productivity
If reactor coolant pumps are used during start-up, then frictional heat can heat the coolant, but external cooling equipment is required to remove the heat during normal operation
Solution Approach 1:
The heating function is extracted from the reactor coolant pump and placed in a separate electric heating sub-system. This allows the pump to be removed entirely from the normal operational configuration, eliminating the need for external cooling equipment during normal operation while maintaining the ability to heat coolant during start-up.
Solution Approach 2:
The mechanical frictional heating method (using reactor coolant pumps) is replaced with an electric heating method during start-up. This substitution allows heating without requiring continuous pump operation, thereby eliminating the need for external cooling equipment during normal passive operation.
3Stress or pressure
If internal heaters are used to increase pressure during start-up, then two-phase equilibrium can be maintained, but the system becomes unsuitable for passively safe designs
Solution Approach 1:
The mechanical pumping system that creates frictional heat and pressure is replaced with an electric heating sub-system that directly heats the coolant. This substitution maintains the ability to achieve no-load operating temperature and pressure while enabling passive safety operation without pumps during normal conditions.
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
Effectively heats the primary coolant to the no-load operating temperature, ensuring optimal reactivity and turbulated flow across the fuel core, enabling safe and efficient start-up of the nuclear steam supply system without relying on frictional heat from pumps.
Implementation Method 1
at least one heating element for heating the portion of the primary coolant to form a heated portion of the primary coolant
Implementation Method 2
an injection nozzle fluidly coupled to the injection conduit and positioned within the riser pipe for injecting the heated portion of the primary coolant into the riser pipe
Implementation Method 3
injecting the heated portion of the primary coolant into the riser pipe... initiating thermosiphon flow without the need for external pumps
Implementation Method 4
a pump fluidly coupled to the intake conduit for pumping a portion of the primary coolant from the primary coolant loop through the intake conduit and into an injection conduit
Data Source
AI summary
A method for heating primary coolant in a nuclear supply system in one embodiment includes filling a primary coolant loop within a reactor vessel and a steam generating vessel that are fluidly coupled together with a primary coolant, drawing a portion of the primary coolant from the primary coolant loop and into a start-up sub-system, heating the portion of the primary coolant to form a heated portion of the primary coolant, and injecting the heated portion of the primary coolant back into the primary coolant loop. The primary coolant may be heated to a no-load operating temperature.