An innovative approach for Steam Generator Pressure Control of a nuclear power plant

The main function of the Steam Generator Pressure Control (SGPC) Program is to match the power (heat) generation in the reactor core with the heat removal in the steam generators (SGs). For most of the designs these programs have been over simplified to cater to the limitation of the instrumentation and control, hardware and software. The main objective of balancing the heat generation, transfer and removal gets lost in the process, which leads to reduction in the availability of the nuclear power plant. This is reflected in under utilization of the process and control system provisions to avoid reactor trips on low/high pressure. Most of the transients/accidents have their origin in the mismatch among the heat generated in the reactor core and the heat removal in the SGs. A new Advanced Process Control (APC) based supervisory controller is proposed to ride over the existing SGPC to achieve the goal. This APC makes use of the estimated/measured heat generation-removal error to alter the SGPC set point to tide over the transients after detection. The transients are detected based on the magnitude of this error to activate the APC. After tiding over the transient successfully the control switches back to the existing SGPC. For evaluation of this error additional instrumentation is proposed in the SG tube walls and other structures of the primary system.The Reactor Regulating System (RRS) which manipulates the reactor power, PHT pressure controller and the SGPC must work in a synchronized and optimized fashion so as to avoid a reactor trip following the PCP trip and other transients. With the existing design it is often observed that these control loops conflict with each other, as they are not designed with a multivariable integrated approach. The objective is being fulfilled by developing new supervisory APC logics to ride over the existing Proportional Integral Derivative (PID) controllers of various process loops. The new APC concept/logics formulation and supervisory control details along with performance tests are presented in this paper.

► Most of the transients/accidents have their origin in the mismatch among the heat generated in the reactor core and the heat removal in the SGs.
► The main objective of balancing the heat generation, transfer and removal gets lost due to simplification of SGPC leading to reduced availability.
► A new Advanced Process Control (APC) is proposed to ride over the existing SGPC to achieve the goal of prompt removal of the heat transfer mismatch.
► The APC logic will lead to overall performance improvements and plant availability for all other transients also.