Abstract
This work studied the feasibility of digitalizing the analog Ex-Core Neutron Flux Monitoring System (ENFMS) being used for APR1400 nuclear power plants (NPPs) and as to which strategies and steps must be taken. A fission chamber neutron flux detection and instrumentation model were designed. Its accuracy was evaluated and proven by comparing the model data with data gathered from tests and plant operations. A conceptual design was proposed through a combined structure that digitalizes only part of the system. The detector signal pre-amplification remains in analog form while the other functions such as reactor power calculation as well as signal conditioning and processing will be digitalized. Simulations showed that the true mean squared voltage (MSV) of the digitalized ENFMS maintained a linear relationship between real and estimated reactor power in the wide range compared to averaged magnitude squared value of analog ENFMS. Extended Kalman Filter (EKF) was also utilized for estimating reactor power and reactor period from measurement signals that are contaminated with gamma ray interaction and electric noise. This study proved that the ENFMS can be successfully digitalized as proposed wherein all functional and performance requirements are satisfied. Simulations results demonstrated that the functions and performance can be improved through the use of digital processing algorithms such as EKF and MSV.
Highlights
The analog Ex-core Neutron Flux Monitoring System (ENFMS) has been satisfactorily performing its functions but it was implemented using older technology, subject to obsolescence and aging as well as limiting the possibility of adding new capabilities that could be beneficial to the system
As the industrial base has largely been moving to digital-based systems, traditional analog instrumentation and control (I&C) systems for nuclear power plants (NPPs) have been replaced with digital I&C systems
In Korea, major I&C systems in nuclear power plants have been digitalized with programmable logic controllers (PLCs) and distributed control systems (DCSs) applied to the Advanced Power Reactor 1400 (APR1400) including Shin-Kori NPPs 3, 4, 5 & 6 and Shin-Hanul NPPs 1
Summary
The analog Ex-core Neutron Flux Monitoring System (ENFMS) has been satisfactorily performing its functions but it was implemented using older technology, subject to obsolescence and aging as well as limiting the possibility of adding new capabilities that could be beneficial to the system. XIA Corporation (formerly X-ray Instrumentation Associates, Hayward, CA 94544, USA), a digital data acquisition and processing systems supplier for X-ray, gamma ray and particle detectors in the USA, developed the DGF-4C, a model of the four-channel digital signal acquisition and processing module for nuclear applications. A block diagram of the MARINE is shown in Figure 1b [5] They developed the systems, TELEPERM-XS and SPINLINE, which met the requirements of International Electrotechnical Commission (IEC) Category A I&C safety function and Institute of Electrical and Electronics Engineers (IEEE) Class 1E applications, based on their own digital safety platforms. Bohunice and Mochovce NPPs in Slovakia replaced parts of the neutron flux monitoring systems.
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