Abstract
In recent years, the trend in small modular reactor (SMR) technology development has been towards the water-cooled integral pressurized water reactor (iPWR) type. The innovative and unique characteristics of iPWR-type SMRs provide an enhanced safety margin, and thus offer the potential to expand the use of safe, clean, and reliable nuclear energy to a broad range of energy applications. Currently in the world, there are about eleven (11) iPWR-type SMRs concepts and designs that are in various phases of development: under construction, licensed or in the licensing review process, the development phase, and conceptual design phase. Lack of national and/or internatonal comparative framework for safety in SMR design, as well as the proprietary nature of designs introduces non-uniformity and uncertainties in regulatory review. That said, the major primary reactor coolant system components, such as the steam generator (SG), pressurizer (PRZ), and control rod drive mechanism (CRDM) are integrated within the reactor pressure vessel (RPV) to inherently eliminate or minimize potential accident initiators, such as LB-loss of coolant accidents (LOCAs). This paper presents the design status, innovative features and characteristics of iPWR-type SMRs. We delineate the common technology trends, and highlight the key features of each design. These reactor concepts exploit natural physical laws such as gravity to achieve the safety functions with high level of margin and reliability. In fact, many SMR designs employ passive safety systems (PSS) to meet the evolving stringent regulatory requirements, and the extended consideration for severe accidents. A generic classification of PSS is provided. We constrain our discussion to the decay heat removal system, safety injection system, reactor depressurization system, and containment system. A review and comparative assessment of these passive features in each iPWR-type SMR design is considered, and we underline how it maybe more advantageous to employ passive systems in SMRs in contrast to conventional reactor designs.
Highlights
The pursuit of the development and deployment of small modular reactors (SMRs) is a persistent and global phenomenon with widespread interest from technology developers, Research and Development (R&D) organizations and potential users
The NuScale Power Module (NPM) core configuration consists of 37 fuel assemblies and adopts a standard 17 × 17 array with the U-235 fuel rods enriched below 4.95%
The nuclear community has been incorporating lessons learned from these major accidents and practical countermeasures to cope with such an accident, which includes the use of passive safety systems (PSSs) [46]
Summary
The pursuit of the development and deployment of small modular reactors (SMRs) is a persistent and global phenomenon with widespread interest from technology developers, Research and Development (R&D) organizations and potential users. (b) decrease the probability of failure for remaining initiators; and, (c) enhanced features to mitigate the consequences [4,10,11,12,13] These classes of SMRs follow the ‘safety-in-design’ philosophy with the objectives to inherently eliminate or minimize potential accident initiators, and to mitigate/counteract the remaining initiators within the design limits by simplified and reliable passive systems. These objectives are realized by integrating the major reactor coolant system components within a reactor pressure vessel, such as steam generators, pressurizer, and control rod drive mechanism.
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