New state-of-the-art regulatory document has been developed and implemented in Ukraine to present requirements for seismic hazard assessment of nuclear power plant (NPP) sites and seismic resistance of nuclear power units taking into account lessons learnt from the accident at Fukushima-1 NPP. One of the new important regulatory requirements in this document is the extension of the list of mandatory load combinations, which should be considered in assessing seismic resistance of unit components. Advantages and disadvantages of the algorithm proposed by the operating organization to determine the necessity to consider some load combinations in assessing the seismic resistance of pipelines and thermomechanical equipment based on previously performed seismic strength calculations have been analyzed in the paper. The pipelines as well as the thermomechanical equipment of Zaporizhzhya NPP Unit 3, for which seismic strength evaluation was calculated, have been considered. The results of expert seismic calculations of YP13S02 valve of ZNPP-1 and ZNPP-3 have been provided. The paper presents the comparative analysis of the floor response spectra for the lower, middle and high elevations of ZNPP-3 containment with the corresponding floor response spectra of other Ukrainian NPPs and conclusions. The possibility for disseminating results obtained by the operating organization for ZNPP-3 to other units of the Ukrainian NPPs has been analyzed.
In the near future, small modular reactors (SMR) potentially will play a significant role in global sustainable energy development through the growing interest in SMR implementation in both countries with developed nuclear industry (for example, in Ukraine) and countries that only start launching their nuclear energy programs. At present, there are about 50 SMR designs developed using different reactor technologies in various stages of readiness. The novelty and uniqueness of some fundamental decisions that are the basis for the specified designs and the lack of resulting of real testing of such decisions have created challenges related to ensuring nuclear and radiation safety during installation and further operation of SMR. The paper provides general information on the activities of the SMR Regulators’ Forum (Forum) created by the International Atomic Energy Agency (IAEA) and countries that actively consider and address the use of SMR in the national energy sector to ensure efficient cooperation in dealing with the specified challenges. The paper presents the results obtained by Forum working groups, the main purpose of which is to develop common positions on issues that have already arisen or are likely to arise during the expected licensing of SMR designs in a number of countries, in particular: demonstration of comprehensive implementation of defense in depth strategy in design safety justification; use of the graded approach within the licensing process; approaches to defining zones and distances in emergency planning around NPPs with SMR. In addition, the working groups defined the best practice and approach to considering the specified issues in licensing SMR designs. Based on the performed review, the paper provides proposals for using the available Forum results during planning and licensing of SMR designs in Ukraine and states on the need for a detailed study of its further activities.
According to Articles 22 and 24 of the Law of Ukraine “On Nuclear Energy Use and Radiation Safety” and with the aim of improving the regulatory and legal documents regulating nuclear and radiation safety of nuclear installations, the regulation “Requirements for Seismic Resistance Design and Evaluation of Seismic Safety of Ukrainian NPPs: NP 306.2.208-2016” was developed. The paper presents modern requirements included into NP 306.2.208-2016. The emphasis was done on new requirements that were not previously available in PNAE G-006-87, but should be taken into account both in the design of new NPP units and in the assessment/reassessment of seismic resistance of operating units.
Nuclear energy is a strategic Ukrainian industry that produces more than 50% of electricity at present. Over the last decade during the operation of Ukrainian NPPs, the set of technical matters have been found and corresponding tasks shall be decided with engaging of scientific potential of the country. One of such matter is a safety justification of NPP components and structures for the period that is bigger than an initial design one and that is defined as transition from design operation to the long-term operation (LTO). From the end of 2010 to the beginning of 2020, the State Nuclear Regulatory Inspectorate of Ukraine granted 11 licenses for 11 power units based on positive results of the state assessment and review of Periodic Safety Review Reports considering mandatory safety review each ten years. These results became possible due to the coordinated, conscientious and longstanding work of thousands of highly qualified nuclear experts, which led to the fact that Ukraine now has a unique experience in preparation for a transition of various types of WWER-1000 and WWER-440 reactors to LTO. The summarized results and lessons learnt from the practice of transition to LTO are presented in this paper.
Результати впливів потужних землетрусів на АЕС Японії («Кашивазакі-Каріва», «Фукусіма-1») засвідчили, що рівні цих впливів можуть перевищувати прийняті в проекті. У зв’язку з цим розглядаєтьсяпитання впровадження в Україні сучасних міжнародних підходів до оцінки сейсмічної небезпеки майданчиків діючих АЕС на прикладі майданчика Южно-Української АЕС.
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