Preliminary thermal-hydraulic feasibility evaluation of the Integral Inherently Safe LWR (I~2S-LWR) high power density core

摘要

The Integral Inherently Safe Light Water Reactor (I~2S-LWR) is a novel PWR concept being developed by a multi-institutional team led by Georgia Tech, under the Department of Energy's Nuclear Energy University Programs Integrated Research Projects (DOE NEUP IRP). The I~2S-LWR aims at delivering an electric power of, approximately, 1 GW while, simultaneously, achieving an overall level of safety that is enhanced with respect to GW-class Generation Ⅲ+ LWRs. The adoption of inherent safety features, such as an integral configuration precluding Large Break LOCAs and Rod Ejection Accidents from happening, the use of a fully passive decay heat removal system designed to allow an extended coping time, and the adoption of unconventional materials for the main core components, are the key design features envisioned to allow the I~2S-LWR to achieve the mentioned objectives. This work summarizes a preliminary evaluation of the thermal-hydraulic performance of the I~2S-LWR core, for steady-state full power operation and a Complete Loss Of Flow Accident. Although this evaluation cannot be a substitute for a comprehensive, system-level, safety analysis, it provides key insights to understand the operating conditions, such as the coolant flow rate and its temperatures, under which the power-related objective mentioned above can be achieved, and how these conditions are affected by the plant thermal efficiency and by the flow coastdown characteristic. Also, by calculating the margin to fuel melting, this analysis provides an indication on the safety performance of the main fuel candidates for the I~2S-LWR, i.e.U_3Si_2 and UO_2. Once combined with a comparison between the core overpower required to cause fuel melting for the two fuels, this analysis will provide important insights for fuel material selection and fuel rod design in general.