The primary reactor coolant system concept of the integral, inherently-safe light water reactor

•The primary system of a large scale (∼1000 MWe) integral reactor is presented.•Design criteria for this reactor are introduced.•Components of the primary system (and thus reactor vessel) are detailed.•Concept design level analyses are discussed for pertinent components.

Nuclear power has enormous potential to provide clean, affordable baseload electricity worldwide. The events at Fukushima demonstrated, however, that nuclear safety must be enhanced in order to fully realize the latent potential of nuclear electricity. Small modular reactors, in particular, create significant safety benefits by eliminating large bore piping and the potential for a large-break loss of cooling accident (LOCA). The I2S-LWR is a large-scale power plant concept designed to incorporate the integral reactor benefits previously exclusive to small modular reactors into large reactor systems. This paper presents and discusses the base design of the integral, inherently safe light water reactor (I2S-LWR) primary coolant system, highlighting the impact of five major design constraints and their impact on the design development. Key deviances from the primary coolant system for both current LWRs and SMRs are indicated where appropriate, and key component design drawings of the I2S-LWR integral reactor pressure vessel (RPV) and supporting systems are provided. These include the reactor pressure vessel, reactor coolant pumps, the pressurizer, the microchannel heat exchangers, the decay heat removal exchangers, and the reactor vessel internals. The final integrated design of the primary coolant system described in this paper serves as the base design configuration for the I2S-LWR, while component performance and analyses are described in companion papers in this issue.