Natural Circulation BWR Power Control via Segmented Rod and Water Level Management
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Natural circulation boiling water reactors face challenges in maintaining stable reactor power control and large water level adjustment ranges due to difficulties in fine-tuning reactor power using control rods, which can lead to thermal limit violations and automatic control stoppages.
Innovation Solution
A reactor power control apparatus that integrates turbine control, control rod control, and reactor water level control, using feedback signals to adjust control rod operations and water level settings, preventing large water level variations and allowing for automatic reactivity control, thereby stabilizing reactor power and extending the water level adjustment range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If control rod operation is used for reactor power control, then reactivity adjustment is achieved, but fine adjustment of reactor power is difficult and thermal limit violations occur
Solution Approach 1:
The invention divides the reactor power control function into two separate control mechanisms: control rod operation for coarse reactivity adjustment and reactor water level control for fine power adjustment. This segmentation allows each control method to operate within its optimal range, preventing thermal limit violations while achieving precise power control.
Solution Approach 2:
The invention introduces reactor water level control as an intermediary mechanism between control rod operation and reactor power output. By controlling the water level in the downcomer, the system can fine-tune the reactor power without directly manipulating control rods, thereby avoiding thermal limit violations.
2Measurement precision
If control rod operation and water level control are performed simultaneously, then reactor power control is enhanced, but water level variations become unstable
Solution Approach 1:
The invention performs preliminary action by setting the reactor water level to a predetermined value before control rod operation. This preliminary water level adjustment creates a buffer that prevents excessive water level variations during subsequent control rod movements, ensuring stable reactor power control.
Solution Approach 2:
The invention implements feedback control by continuously monitoring the reactor water level and adjusting the feedwater flow rate accordingly. This feedback mechanism counteracts water level variations caused by control rod operation, maintaining water level stability while enabling precise reactor power control.
3Device complexity
If only control rod operation is used for power control, then reactivity adjustment is simple, but operator burden is great during start-up
Solution Approach 1:
The invention enables self-service control by implementing automatic reactor power control that combines control rod operation and water level control through an automated control system. During start-up, the system automatically coordinates both control mechanisms, reducing operator burden while maintaining control system simplicity.
4Stability of the object's composition
If water level control range is limited, then control stability is maintained, but adjustment range for reactor power is reduced
Solution Approach 1:
The invention applies dynamics by making the water level control strategy adaptive based on reactor operating conditions. The control system dynamically adjusts the water level setpoint and control aggressiveness according to the current reactor state, allowing a wider effective adjustment range while maintaining stability through condition-dependent control parameters.
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 solution enables stable reactor power control with a large water level adjustment range, preventing thermal limit violations and reducing operator burden by combining control rod and water level adjustments, allowing for fine-tuned power control near rated reactor power.
Implementation Method 1
the cooling water is circulated by the natural circulation force which is based on the difference in density (head difference) of the cooling water outside of a core shroud which surrounds the core and the two-phase flow including the steam and the cooling water inside the core shroud
Implementation Method 2
reactivity adjustment of the boiling water reactor (BWR) is performed by inserting a control rod containing a neutron absorber into the core or withdrawing the control rod from the core
Implementation Method 3
adjusting recirculation flow rate (core flow rate) of the cooling water that is also a neutron moderator, through the core
Data Source
AI summary
In order to provide a reactor power control apparatus which can maintain a stable water level when reactivity control based on control rod operation and water level adjustment is performed, this invention comprises a turbine control which calculates the load set error signal from the error between the set target generator power value and the generator power that was fed back and outputs to the turbine control apparatus; control rod control in the natural circulation boiling water reactor which calculates the control rod operation signal and outputs it to the control rod drive control apparatus; water level control inside the natural circulation boiling water reactor which calculates the water level set signal and outputs it to the feed water control apparatus; and the switch determining device which selectively outputs one of the control rod control and water level control based on the generator power that was fed back, the reactor power and water level, as well as switching rules and determination values.