atw - International Journal for Nuclear Power | 2.2024

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44 Environment and Safety Initial review of methods used to determine the size of the Emergency Planning Zone › Mercy Nandutu, Jannat Mahal, Professor Filippo Genco, Professor Akira Tokuhiro, Mr. Chireuding Zeliang 1. Introduction SMRs are defined as reactors with electrical power up to 300 MW per module [1] . Many SMRs are being developed for specialized electrical or energy markets where big reactors would be impractical or too costly. SMRs have the potential to meet the need for flexible power generation for a broader range of users and applications, such as replacing aging fossil power plants, providing cogeneration for developing countries with small electricity grids, remote and off-grid areas, and enabling hybrid nuclear/renewable energy systems. SMRs use modularization technologies to achieve the economics of serial production while reducing building time [1] . Various SMR technologies are being developed in different nations for example SMART for South Korea, KLt-40S for Russia, NuScale for USA, UK SMR for the United Kingdom, DMS for Japan, CAREM for Argentina, and CAP200 for China, to mention but a few [2], [3], [4], [5], [6], [7] . SMRs offer lower and more predictable construction costs, shorter and more modular construction timelines, greater operational flexibility and safety, easier financing and siting, and more market opportunities. SMRs also could load follow and integrate with renewables and other technologies [8] . Currently, more than 80 Small Modular Reactor (SMR) designs are under development for a range of sophisticated uses and deployment phases [9] . Fig. 1. SMR Development by Country as of 2023 Figure 1 provides a comparative view of the number of SMR designs in different countries. As of the year 2023, the highest number of projects for advanced small modular reactor are in China. SMR development is progressing in Western nations with substantial private investment, including participation from small enterprises. The design, safety, and siting features of small modular reactors are unique, and they offer a larger range of applications. SMRs have numerous benefits, but they also have their share of drawbacks, just like any other system. One of the biggest obstacles to the deployment of SMRs is the lack of suitable Emergency Preparedness and Response (EPR) Plan, particularly in terms of the size of Emergency Planning Zones (EPZs). Considering the SMR EPZ sizing, the IAEA established a Coordinated Research Program (CRP) to develop approaches and methodologies for determining the appropriate size of EPZs [10] . It was in fact proposed that the CRP would include assessment of relevant design and safety features of SMRs and the extent of necessary offsite arrangements, by comparing design and site-specific technical basis, provided by SMR developers, nuclear regulators, emergency planners and users/utilities [10] . Upon successful deployment of the Small Modular Reactor Technology, a smaller yet appropriately sized EPZ is expected (stand-alone SMR), and this could result in significant cost savings for licensees without compromising the health and safety of the surrounding public [11] . According to the Canadian Nuclear Safety Commission (CNSC), the objectives of a nuclear emergency preparedness and response plan are [12] ; ⁃ To prevent or mitigate the effects of accidental releases of nuclear substances and hazardous substances on the environment, the health and safety of persons, and the maintenance of security ⁃ To regain control of the situation and prevent the escalation of the accident ⁃ To protect workers and the public from deterministic and stochastic health effects of radiation exposure Ausgabe 2 › März
Environment and Safety 45 ⁃ To provide medical assistance and manage the treatment of radiation injuries ⁃ To protect property and the environment from contamination and damage ⁃ To prepare for the resumption of normal social and economic activity It is important to note that Emergency Planning cannot be discussed without considering nuclear accidents and the relative risks associated with these accidents. In 1975, Professor N. Rasmussen produced a report for the Nuclear Regulatory Commission namely, WASH-1400, ‘The Reactor Safety Study’. WASH 1400 put into consideration the course of events that may arise during a serious accident at conventional modern Light Water Reactors. The report established the radiological consequences of these events and the probabilities at which they occur using the Fault Tree and Event Tree techniques which is known today as part of Probabilistic Risk (or Safety) Assessment (PRA/PSA). It was concluded that risks to individuals posed by nuclear power stations were acceptably smaller than other tolerable risks, in fact a conclusion was also drawn that the probability of a complete core meltdown is approximately 1 in 20,000 per reactor year [13], [14], [15] . Despite the significance and relevance of this new method introduced in the WASH-1400 report, a storm of criticism and several questions were raised years after its release. As soon as the report was published, several reports that either peer reviewed the methodology or judged the probabilities and consequences of various nuclear accidents at commercial reactors were developed [16], [17], [18] . To this date, several PRA related studies have been performed to assess the risks associated with nuclear power plants. In more recent years (at NuScale Power), C. Williams et al, in her study to integrate defense-in-depth metrics into new reactor designs explains an approach for augmenting the traditional defense-in-depth philosophy with quantitative risk data from plant specific PRA in such a way that is well structured, can be used consistently and allows for a clear acceptance criterion [19] . 2. Emergency Planning Zone Emergency Planning zones define the areas beyond the boundary of a reactor facility, in which implementation of operational and protective actions are or might be required during a nuclear emergency, to protect public health, safety, and the environment [20]. In 2015, the Nuclear Energy Institute published a white paper that provides a proposed approach for re-evaluating the size of the plume exposure pathway EPZ and the ingestion exposure pathway EPZ for SMRs. The paper argued that SMR designs have a significantly reduced potential for accident-related offsite releases, and therefore, the consequences from an accident involving an SMR facility are expected to have a limited impact on public health and safety. A suggestion was made that the EPZ size for an SMR facility should be determined using a dose/distance approach based on appropriate protective action guidelines established by Federal agencies, and that considers the consequences from a spectrum of accidents. Moreover, the paper also identified proposed changes to existing regulations and guidance documents to support the implementation of scalable EP requirements for SMR facilities. The proposed approach in this paper maintains consistency with the safety philosophy applied to large light water reactors, i.e., a framework that is technology-neutral, dose-based, and consequence-oriented [21]. 2.1 Regulatory History and Policy Considerations governing EPZ for SMR The USNRC has a compilation of a few documents that provide the regulatory history associated with NRC‘s consideration of establishing a scalable, dose-based, and consequence-oriented plume exposure pathway (PEP) emergency planning zone (EPZ) for small modular reactors (SMRs) [22] . It also summarizes the staff’s evaluation of potential policy issues associated with use of mechanistic source terms in DBA dose analyses and siting. Each nuclear power plant‘s EPZ size and shape is determined individually, considering specific site conditions, distinctive geographical features of the area, and demographic information. EPZ-specific strategies offer a solid foundation to introduce further measures outside the planning zone in case highly improbable events occur [35] 2.2 Radiological Safety People‘s perception of nuclear power plants‘ safety has been impacted by the historical nuclear accidents (Three Mile Island plant, Chernobyl, Fukushima Daiichi), which raised questions about the safety of nucler reactors. The lesson learned from the Fukushima accident is that it is necessary to emphasize the safety of nuclear power plants to enhance public acceptance of nuclear power and reduce the public’s fear of radiation (effects); some called “radiophobia”. Several researchers have conducted experiments that highlight the importance of thoroughly validating the anticipated safety features of SMRs. Consequently, it can be inferred that Small Modular Reactors (SMRs) have the capacity to provide improved radiological safety and robustness in the face of unplanned, service disruptions. The quantity and kind of radioactive materials that could be released into the environment after a nuclear accident are referred to as the „source term.“ A study done by Lulik [36] and his team used an empirical approximation to determine the source term based on the expression given as, Vol. 69 (2024)
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Page 4 and 5: 4 Contents Inhalt Editorial Abschie
Page 6 and 7: 6 Calendar Kalender 2024 07.03.2024
Page 8 and 9: 8 Feature: Energy Policy, Economy
Page 18 and 19: 18 Energy Policy, Economy and Law
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Page 76 and 77: 76 Spotlight on Nuclear Law auf Ko
Page 78 and 79: 78 KTG-Fachinfo KTG-Fachinfo 02/202
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Page 88 and 89: 88 Kerntechnik 2024 Technical Sess
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