• Tesi

Abstract
This thesis work analyses some closed loop regulations performed on the Nuclear Island Vent
and Drain System (NIVDS) of the EPR™ reactor. It has been carried on in collaboration with
AREVA NP in the framework of new software validation and their applicability to the
optimization of thermal hydraulic systems automation and automatic regulation.
The purpose of the analysis was to validate state of the art configuration of the used
controllers (Proportional Integral Derivative) and eventually propose a new configuration.
Validation and optimization rely on frequency analysis and stability margins methodology.
First stage of the study was the development of a model of the physical system, both for the
Thermal Hydraulic domain and for the I&C domain. This model was then implemented into
Matlab®/Simulink®, that was the software tool used and also the software to test.
Second stage was the study in the frequency domain of the control loops to get the stability
margins of the state of the art configuration and to inspect a new, possibly improved, one.
This part has been performed using the “Control Systems” toolbox available in Simulink®
which allows linearization of the model.
Last part of the work concerned the time domain analysis of the control loops. This
“validation” stage was necessary because the analyzed process is non-linear. Time domain
analysis was performed using step changes in the set point of the control loops and on main
physical variables that represents a disturbance for the loops.