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NuScale SLB analysis with TrioCFD/ATHLET/DYN3D

Grahn, A.; Diaz Pescador, E.; Bilodid, Y.; Kliem, S.

Abstract

The small modular reactor (SMR) NuScale has been modelled in the framework of the EURATOM McSAFER project. The main objective was to demonstrate the feasibility of a coupled approach using a thermal-hydraulic system code (ATHLET), a 3-D reactor dynamics code (DYN3D) and a CFD software (TrioCFD) to model the whole primary coolant loop and large parts of the secondary side of the plant, including the downcomer-integrated, helical-coiled steam generators (SG) and the decay heat removal system (DHRS). The 3-D neutronic calculation of the reactor core was performed with a cross-section library developed with Serpent, and the coolant flow in the downcomer and lower plenum of the pressure vessel was analyzed by CFD. A double-ended, non-isolatable steam line break sequence served as a test case for the code coupling. Simulation results at steady-state show agreement with the reference values from the Design certification Application (DCA) report. The transient simulation shows that the rapid depressurization and boil-off with high steam rates towards the break lead to enhanced primary-to-secondary heat removal. However, the symmetrical arrangement of SGs in the NuScale reactor limits the coolant temperature reduction at the core inlet to prevent a possible power excursion which highlights the inherent safety of this reactor design.

Keywords: small modular reactors; steam line break; thermal-hydraulics; reactor dynamics; system codes; computational fluid dynamics

  • Lecture (Conference)
    Workshop on Core and Plant Simulation with an Emphasis on Fuel Behaviour in Light Water Reactor based Small Modular Reactors, 27.-29.02.2024, Wien, Österreich

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