Passive decay heat removal system design for the integral inherent safety light water reactor (I2S-LWR)

The Integral, Inherently Safe Light Water Reactor (l:S-LWR) is an innovative pressurized water reactor (PWR) concept being developed by a multi-institutional team led by Georgia Tech and in eollaboraiion with Westinghouse. under the Department of Energy's Nuclear Energy University Programs Integrated Research Projects (DOR NF.UP IRP). The I²S-I.WR features an integral primary system configuration and is more conducive to the implementation of inherent safety features by eliminating potential accidents. In this paper, a novel passive Decay Heat Removal System (DHRS). is presented, consisting of a primary loop, an intermediate loop and a cooling tower loop. This passive system is designed to remove the I²S- LWR decay heat in the case of emergency heat removal transients, without the need for external power or operator action. The proposed DHR uses atmosphere as ultimate heat sink, to achieve indefinite decay heat removal In this paper, firstly, the design of primary and secondary DHRS heat exchangers is optimized. Then the DHR heat removal characteristics arc studied using live best-estimate thermal hydraulic code RELAP5. The performance of the DHRS concept is investigated in case of Station Black- Out accident Results show that three of the four DHRS trains are sufficient to indefinitely remove the core decay heat successfully, and keep the reactor in a safe state without the need of any other auxiliary active system.