Regulatory Guide (RG) 1.60 presents the response spectra for the seismic design, especially for the safe shutdown earthquake (SSE), of nuclear power plants. This guide is applicable to a two-step process involving the issuance of construction permits and operating licenses (10 CFR Part 50) as well as the issuance of combined construction and operating licenses (COLs), early site permits (ESPs), and standard plant design certifications (10 CFR Part 52) [1]. New reactor designs, however, require modified design response spectra (MDRS) by broadening the high-frequency range from design response spectra (DRS) in RG 1.60. In order to generate artificial time histories to meet the acceptable criteria described in NUREG-0800 [2], it9s necessary to develop the power spectral density of the MDRS. In this paper, we generate the artificial earthquake time histories of the MDRS for further research.

Recently, more than 70 SMRs have been developed around the world due to their modularity, flexibility, and miniaturization. An innovative SMR (i-SMR) is also being developed in Korea, and operators are planning to apply for a Standard Design Approval (SDA) in 2026 after completing the standard design. Accordingly, regulatory organizations are conducting R&D on regulatory requirements and guidelines for systematic SMR standard design review by referring to IAEA and NRC cases. In terms of security, SMRs are expected to undergo many changes not only in terms of physical security through security systems, security areas, and vital equipments, but also in terms of cybersecurity through new digital technologies, remote monitoring, and automated operation. Accordingly, the IAEA Fundamental Safety Principles (SF-1) require operators to improve the safety of nuclear facilities by considering security requirements, access control requirements, and the results of operational impact assessments based on threats from the design and construction stages. Similarly, the U.S. nuclear regulatory body (NRC) has confirmed the status of security assessment and design considering design basis threats (DBTs) in the NuScale standard design review process, and the Canadian nuclear regulatory body (CNSC) has revised security regulatory guidelines and applied them to the SMR standard design review. Among these various activities related to SMR security, this paper analyzes the major changes in the cybersecurity regulatory guidelines for SMRs recently revised by the CNSC, the Canadian nuclear regulatory body. Compared to the previous guidelines, the Defensive Cybersecurity Architecture (DCSA), including external logical access control, security level and zone communication requirements, verification and validation (V&V) activities during development phases, and system & service acquisition security requirements have been added. Other changes, such as the cyber incident response program, will be analyzed and compared. Through the revised regulatory guidelines, the CNSC has divided cybersecurity levels into four (High, Moderate, Low, and Business), strictly prohibiting remote access to High and Moderate levels, and allowing remote access to Low levels only for maintenance purposes. In addition, the paper will analyze the detailed revisions, such as prohibiting access to the High level from lower levels and allowing only handshaking signals from the Low level to the Moderate level.

공학적 안전설비 공기정화계통의 규제지침인 Reg. Guide 1.52(Rev.3)의 변경사항중 성능시험과 관련 한 운전가능성 시험시간 단축, HEPA 필터 현장누설시험용 시험물질 변경 및 활성탄 성능시험 Methyl Iodidie 투과허용율 상향 변경을 영광 5,6호기에 적용하고자, 모사실험장치와 현장 설비를 활용하여 기술 적 타당성을 확인하는 실험을 수행하였다. 10시간 이상의 장시간 운전가능성 시험을 통해 계통내 습분을 제거하여도 시험후 1∼4일만에 회복됨을 확인하여 운전가능성 시험은 기기적 운전가능성 점검에 적합한 매월 15분 이상의 시험을 수행하는 것이 타당함을 확인하였다. HEPA 필터 현장누설시험용 시험물질 변 경을 위해 DOP와 PAO의 에어로졸 입자크기, 발생량, 누설인지도를 비교한 결과 PAO는 원전에서도 DOP 대체시험물질로 사용 가능함을 확인하였다. 베드깊이 4 인치 이상의 활성탄여과기에 대한 Methyl Iodide의 투과율 허용치가 0.175 %에서 0.5 %로 상향 변경된 것은, ASTM D3803(1989)으로의 활성탄 성 능시험 방법 변경에 따른 것으로서, 30 ℃ 상대습도 95 %에서의 Methyl Iodide 투과허용율 0.5 %가 사용 중 활성탄의 성능을 시험하기에 충분히 보수적인 시험방법임을 확인하였다. 본 실험 결과를 바탕으로 영 광 5,6호기는 인허가변경을 완료하였다.