A Comparative Overview of Thermal Hydraulic Characteristics of Integrated Primary System Nuclear Reactors

A number of new designs of nuclear reactors have emerged in the last decade in attempts to achieve very high levels of safety and to enhance the economical competitiveness of nuclear power with alternative ways of electricity generation. For example, a review of development status of advanced light water reactor (LWR) designs is found in IAEA-TECDOC-1391 [1]. It includes small-tomedium size modular nuclear reactors that meet the demands, not only from already industrialized nations but, in particular, from developing countries which have smaller grids and more limited financial investment capabilities. In this context, the medium size reactors refer to those generating electricity in a range of 300 to 700 MWe and the small size reactors less than 300 MWe following the IAEA’s definition. A more specific and comprehensive review of the innovative small-to-medium-sized nuclear reactor designs is going to be published in the IAEA TECDOC series [2]. In this article, among the small-to-medium sized advanced pressurized water reactor (PWR) designs, focus is placed on the Integrated Primary System Reactors (IPSRs) or integral type PWRs, all looking at the near term deployment. Many of them are based on well-proven PWR technology; however there are several concepts that require additional RD and a simplified compact design where the primary coolant paths are formed within the reactor pressure vessel (RPV). This paper presents a review of small-to-medium-sized, pressurized-water-cooled nuclear power reactors whose major primary coolant systems are integrated into a reactor pressure vessel, the concepts categorized as Integrated Primary System Nuclear Reactors (IPSRs). Typical examples of these proposals of interest in this review are CAREM, SMART, IRIS and IMR, all of which are being aimed at the near term deployment. Emphasis is placed on thermal hydraulic aspects. A brief characterization of the IPSR concepts is made and comparisons of plant key parameters are shown. Discussions will follow for the core cooling under rated power conditions and natural circulation heat removal on the basis of the design data available in the public domain.