# Digitalization of the Ex-Core Neutron Flux Monitoring System for APR1400 Nuclear Power Plant
## 1 Introduction
The host computer communicate with the board via the Computer-Aided Measurement And Control (CAMAC) interface using a direct memory access (DMA) channel [2]. Unfortunately, the maximum rate of pulse processing by the DGF-4C is around 50,000 counts per second per channel, which is slow for the APR1400-specific digital ENFMS. An instrumentation and high voltage power supply provider for nuclear and particle physics in Italy, Construzioni Appareechiature Elettroniche Nucleare (CAEN SpA, Viareggio, 55049 Italy), provides high-speed waveform digitizers and various kinds of modular digital pulse processing electronics which meet IEEE standards for nuclear and particle physics. The real-time digital data processing transforms the row sequence of samples into compressed data that preserve the information required, thereby minimizing the event data size [3; 4]. The French Atomic Agency (CEA) and its industrial partner Technicatome (Villiers-le-Bacle, Ile-de-France, France) developed a fully digitalized wide range neutron monitoring system, named MARINE (after the French acronym for automated neutron measurement), for experimental and commercial nuclear power plants. 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. Mirion Technologies in Germany (Munich, Germany) developed the digital neutron flux and reactor gamma monitoring system proTK which includes the source and intermediate range monitoringnodule, the wide range monitoring module, the power range monitoring module, the flux distribution monitoring module, as well as local and average power range monitoring module. A block diagram of the wide and power range monitoring instrumentation is shown in Figure 1c. Bohunice and Mochovce NPPs in Slovakia replaced parts of the neutron flux monitoring systems with TELEPERM-XS. The new neutron flux monitoring systems, which each consists of TELEPERM-XS, SUGAN and non-standard measuring units, have been operating successfully since 1999. Outputs from the detectors are fed into the Hartman and Braun analog units which convert the signals into levels appropriate to the TELEPERM-XS [6]. In China, a digital neutron flux measuring system based high speed data sampling, an FPGA (field-programmable gate array) and the Peripheral component interconnection eXtension for Instrumentation express (PXIe) bus was developed for the HL-2A tokamak which started its construction in 1995 under the national nuclear fusion development program. The FPGA data processing diagram is shown in Figure 1d [7]. Westinghouse (Cranberry Township, PA, USA) in the USA and Toshiba (Yokohama-shi, Kanagawa 235-8523, Japan) in Japan have also jointly developed FPGA-based Start-up Range Neutron Monitor (SRNM), Power Range Monitor (PRM), Oscillation Power Range Monitor (OPRM), and Traversing In-core Probe (TIP) for Boiling Water Reactors [8]. The Korea Atomic Energy Research Institute (KAERI) has adopted the digital wide-range neutron power measurement (DWRNPM) system for the research reactor in KAERI. The DWRNPM system monitors the neutron flux across a range of over 10 decades, processes signals in the form of electric pulses or current through a series of analog circuits and digital processors. Preamplification of the detector signals, pulse shaping, the signal-to-noise discrimination, and the mean squared voltage (MSV) calculation are performed by the analog circuits. On the other hand, pulse counting and dead time correction, wide-range logarithmic signal generation with pulse and MSV signals, and the conversion of the neutron flux information to reactor power information are done by digital signal processor unit [9]. Figure 1: Simplified block diagrams.