ANALYSIS OF A 2-INCHES GUILLOTINE BREAK OF THE DVI LINE IN AN IRIS-LIKE DESIGN BY USING ASTEC CODE

Today the LWR passive Small Water Reactors (SMR) are one of the key design options for the deployment of nuclear technology considering their inherent safety due to the use of passive mitigation strategy (e.g. use of passive systems, etc). The integral nature and the passive mitigation strategy of these reactors require the analysis and the characterization of the phenomena characteristic both in design and beyond design basis accidents conditions. In the framework of deterministic safety analyses for integral small modular reactor a nodalization of IRIS-like SMR was developed by using the severe accident ASTEC code (study carried out with ASTEC V2, IRSN all rights reserved, [2019]). In particular, the IRIS-like primary/secondary circuit and the safety systems were modeled using CESAR module of ASTEC code, while the containment system was nodalized using CPA module. A 2-inches guillotine break of the Direct Vessel Injection (DVI) line was hypothesized and the effect of the safety systems considered available (ADS, EHRS, PSS, LGMS, EBS) was investigated on the transient progressions. The purpose of this work is to analyze the capability of ASTEC code to simulate the mitigation effect due to activation of the different passive systems and the consequent transient scenario