Advanced multi-physics simulation for reactor safety in the framework of the NURESAFE project

Since some years, there is a worldwide trend to move towards “higher-fidelity” simulation techniques in reactor analysis. One of the main objectives of the research in this area is to enhance the prediction capability of the computations used for safety demonstration of the current LWR nuclear power plants through the dynamic 3D coupling of the codes simulating the different physics of the problem into a common multi-physics simulation scheme. In this context, the NURESAFE European project aims at delivering to the European stakeholders an advanced and reliable software capacity usable for safety analysis needs of present and future LWR reactors and developing a high level of expertise in Europe in the proper use of the most recent simulation tools including uncertainty assessment to quantify the margins toward feared phenomena occurring during an accident. This software capacity is based on the NURESIM European simulation platform created during FP6 NURESIM project which includes advanced core physics, two-phase thermal–hydraulics, fuel modeling and multi-scale and multi-physics features together with sensitivity and uncertainty tools. These physics are fully integrated into the platform in order to provide a standardized state-of-the-art code system to support safety analysis of current and evolving LWRs

Validation of the System Thermal Hydraulics Code Athlet for the Simulation of Transient Lead-Bismuth Eutectic Flows

International audienceWithin the European SESAME project, system thermal-hydraulics (STH), computational fluid dynamics (CFD) and coupled 1D-3D thermal-hydraulic simulations were carried out for Generation IV nuclear systems. The Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) gGmbH participated in the project with activities related to the development and validation of CFD and coupled CFD-STH codes. The TALL-3D facility, operated by the KTH Royal Institute of Technology in Stockholm, is designed for thermal-hydraulic experiments with lead-bismuth eutectic (LBE) coolant. A well-instrumented, partially heated test section with cylindrical form is installed in the primary circuit, which is domain of complex 3D flow and heat transfer phenomena. Three different experiments were calculated within a benchmark, organized by KTH: two with coupled programs and one with STH stand-alone code. This paper focuses on the analysis of the observed thermal-hydraulic flow phenomena during the TG03.S310.01 experiment and the comparison between ATHLET predictions and data.and the comparison between ATHLET predictions and data

Development and application of computational fluid dynamics approaches within the European project THINS for the simulation of next generation nuclear power systems

Today computational fluid dynamics (CFD) is widely used in industrial companies, research institutes and technical safety organizations to supplement the design and analysis of diverse technical components and large systems. Such numerical programs are applied to better understand complex fluid flow and heat transfer phenomena. In the last decades there is an increasing interest in the nuclear community to utilize such advanced programs for the evaluation of different nuclear reactor safety issues, where traditional analysis tools show deficiencies. Within the FP7 European project THINS (Thermal Hydraulics of Innovative Nuclear Systems), CFD and coupled 1D-3D thermal-hydraulic simulations are being carried out. These are dedicated to the analysis of the thermal-hydraulics of gas, liquid metal and supercritical water cooled reactors. Such concepts utilize innovative fluids, which have different properties from the ones used in the current nuclear reactors. In order to improve the thermal-hydraulic predictions of their behavior, CFD development, application and validation activities are performed within THINS. This overview paper highlights some of the CFD related work within the European project

Blind simulations of NACIE-UP experimental tests by STH codes

In the frame of the SESAME project, a benchmarking activity was proposed to validate the existing system thermal-hydraulics codes for Heavy Liquid Metal reactors. More specifically, blind simulations on three well-defined experiments were carried out on the NACIE-UP facility, using CATHARE by ENEA, ATHLET by GRS, RELAP5-3D by University of Roma and RELAP5/Mod3.3 by University of Pisa. The numerical models were calibrated in terms of system thermal losses and gas enhanced circulation by means of the outcomes from specific experimental preliminary tests. The present discussion expose, compare and analyze the numerical results of some representative parameters (primary lead-bismuth eutectic (LBE) mass flow rate, temperatures and pressure) charaterizing the system behaviour in transiet scenarios in a “pre-test” blind numerical assessment