Nuclear Reactor Startup System Using Preheated Coolant
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Solution Overview
Problem
The startup of natural circulation nuclear reactors can be unstable due to rapid temperature changes when control rods are withdrawn, leading to potential power excursions and increased complexity in reaching operating temperatures, which prolongs the startup period and requires additional supervision.
Innovation Solution
A stable startup system is introduced, comprising a reactor core housed in a reactor vessel with a heat sink and an electrically powered heater to add heat to the coolant before reactor core initialization, creating a temperature difference that drives natural circulation and avoids power excursions by controlling coolant temperature and pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If control rods are withdrawn to achieve core criticality, then the reactor core generates heat, but rapid temperature changes occur leading to potential power excursions and startup instability
Solution Approach 1:
The heater is activated before control rod withdrawal to preheat the coolant to a target temperature. This preliminary heating action prepares the thermal-hydraulic conditions in advance, ensuring that when the reactor core becomes critical and starts generating heat, the coolant is already at an appropriate temperature to absorb the heat without causing rapid temperature changes or power excursions.
Solution Approach 2:
The heater provides a counteracting thermal input before the reactor core generates heat. By preheating the coolant, the system counteracts the potential for rapid temperature changes that would otherwise occur when the core becomes critical, thereby preventing power excursions and stabilizing the startup process.
2Extent of automation
If natural circulation is used for cooling, then operator intervention is reduced, but the tight coupling between nuclear physics and thermal hydraulics makes startup potentially unstable
Solution Approach 1:
The heater acts as an intermediary device that bridges the gap between the passive natural circulation system and the active startup requirements. It provides controlled thermal input that mediates the tight coupling between nuclear physics and thermal hydraulics during startup, enabling stable operation while maintaining passive cooling characteristics.
3Temperature
If the reactor is heated to operating temperature during startup, then criticality can be achieved, but the process takes a long time and requires additional supervision
Solution Approach 1:
The heater preheats the coolant to a target temperature before control rod withdrawal, accomplishing part of the heating requirement in advance. This eliminates the need for prolonged heating during the criticality achievement process, significantly reducing startup time and minimizing the period requiring additional supervision.
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 stabilizes the startup process, reduces the risk of power excursions, and shortens the time to reach operating temperatures, thereby simplifying the startup procedure and increasing reactor efficiency and safety.
Implementation Method 1
an electrically powered heater configured to add heat to the reactor vessel prior to an initialization of the reactor core
Implementation Method 2
a heat sink configured to remove heat from the reactor vessel
Implementation Method 3
The reactor core 6 generates the heat that creates the buoyancy needed to drive the flow through the loop
Implementation Method 4
the reactor core 6 generates the heat that creates the buoyancy needed to drive the flow through the loop
Data Source
AI summary
A nuclear reactor module includes a reactor vessel containing coolant, a reactor core submerged in the coolant, and a heat exchanger configured to remove heat from the coolant. The nuclear reactor module further includes one or more heaters configured to add heat to the coolant during a startup operation and prior to the reactor core going critical.