## 5 Conclusions  
The digitalization of instrumentation and control systems plays a crucial role in reducing operation and maintenance (O&M) costs of nuclear power plants (NPPs). In this study, we focused on ex-core instrumentation systems (EISs), which are essential systems for the safe and secure operation of pressurized water reactor plants. Traditional EISs used in many existing NPPs are composed of multiple analog modules, and particularly in pulse signal processing, many analog modules are required. Therefore, there is a need for digitalization to simplify the configuration and improve maintainability. There are several examples of digitalizing EISs, but they use a microprocessor that is now obsolete. Therefore, state-of-the-art technology is required to digitalize EISs. We conducted a demonstration study using a field-programmable gate array (FPGA) combined with a high-speed analog-to-digital converter to develop and validate a digital algorithm for efficient pulse signal processing, and explored a new method to enhance the efficiency of maintenance work associated with the discrimination characteristics test (DCT). The validation was conducted using a detector emulator and research reactor. As a result, we confirmed that the proposed algorithm can achieve linearity within \(\pm\)5% of the span and response performance with a delay time of 5 ms, which are required for EISs, with a simpler configuration than a traditional EIS. Additionally, by creating a discrimination characteristics graph using pulse height information, we expect to be able to conduct the DCT in a shorter time compared with a conventional method. As for the validation of the digital algorithm, we compared the results obtained in the research reactor to simulated outputs using MATLAB Simulink. The simulated outputs align well with the values obtained from the experiment using the research reactor, and we proved that adding a time constant improves linearity. In conclusion, the digitalization of EISs significantly contributes to reducing O&M costs. The proposed digital algorithm can satisfy the requirements for commercial power reactors and achieve a simpler configuration to improve maintenance. Furthermore, the  
Figure 13: FC spectrum obtained using MCA-8000D. advanced DCT method can reduce workload. In addition, the digitalization of EISs has the potential to further reduce O&M costs and improve convenience for users. We plan to conduct further investigations to determine the potential advantages of digitalization, such as advanced pulse discrimination and condition-based monitoring. These advancements have the potential to further enhance the efficiency and effectiveness of EISs, leading to even greater cost savings and operational improvements in NPPs. This study is a crucial first step towards realizing the potential benefits of digitalizing EISs. The progressing of digitalization in EISs, based on this study, will contribute to significant advancements in the developments of NPPs and the mitigation of global warming. On the other hand, the potential disadvantages of digitalization must also be considered. One such disadvantage is the need to address electromagnetic compatibility (EMC). Digitalization can make systems more susceptible to external noise and can also introduce noise from within the system itself. While this study focused on the development and validation of digital algorithms for EISs, it is necessary to conduct EMC mitigation considerations during the stages of system design and detailed circuit design. R.K. and T.A. conceptualized, designed, and analyzed the system. R.K. and M.S. : software, M.H. : supervision. All authors have read and agreed to the published version of the manuscript. This research received no external funding. Not applicable. The raw data supporting the conclusions of this article will be made available by the authors on request. The authors would like to express their sincere gratitude to [PERSON], [PERSON], and [PERSON] for their great support of the experiment with URT-KINKI.