STH/CFD coupled simulation of the protected loss of flow accident in the CIRCE-HERO facility

The paper presents the application of a coupling methodology between Computational Fluid Dynamics (CFD) and System Thermal Hydraulic (STH) codes developed at the University of Pisa. The methodology was applied to the CIRCE-HERO facility in order to reproduce the recently performed experimental conditions simulating a Protected Loss Of Flow Accident (PLOFA). The facility consists of an internal loop, equipped with a fuel pin simulator and a steam generator, and an external pool. In this coupling application, the System code RELAP5 is adopted for the simulation of the internal loop while the CFD code ANSYS Fluent is used for the sake of simulating the pool. The connection between the two addressed domains is provided at the inlet and outlet section of the internal loop; a thermal coupling is also performed in order to reproduce the observed thermal stratification phenomenon. The obtained results are promising and a good agreement was obtained for both the mass flow rates and temperature measurements. Capabilities and limitations of the adopted coupling technique are discussed in the present paper also providing suggestions for improvements and developments to be achieved in the frame of future applications

Numerical analysis of the CIRCE-HERO PLOFA scenarios

The present work deals with simulations carried out at the University of Pisa by using the System Thermal Hydraulics code RELAP5/Mod3.3 to support the experimental campaign conducted at the ENEA (Energia Nucleare ed Energie Alternative) Brasimone Research Centre on the CIRColazione Eutettico—Heavy liquid mEtal pRessurized water cOoled tubes (CIRCE-HERO) facility. CIRCE is an integral effect pool type facility dedicated to the study of innovative nuclear systems and cooled by heavy liquid metal, while HERO is a heat exchanger heavy liquid metal/ pressurized cooling water system hosted inside the CIRCE facility. Beside the H2020 project Multi-Purpose Hybrid Research Reactor for High-Tech Applications (MYRRHA) Research and Transmutation Endeavour (MYRTE), a series of experiments were performed with the CIRCE-HERO facility, for both nominal steady-state settings and accidental scenarios. In this framework, the RELAP5/Mod3.3 code was used to simulate the experimental tests assessing the heat losses of the facility and analyzing the thermal hydraulics phenomena occurring during the postulated Protected Loss Of Flow Accident (PLOFA). The modified version Mod. 3.3 of the source code RELAP5 was developed by the University of Pisa to include the updated thermo–physical properties and convective heat transfer correlations suitable for heavy liquid metals. After reproducing the facility through an accurate nodalization, boundary conditions were applied according to the experiments. Then, the PLOFA scenarios were reproduced by implementing the information obtained by the experimental campaign. Sensitivity analyses of the main parameters affecting the thermofluidynamics of the Lead-Bismuth Eutectic (LBE) were carried out. In the simulated scenario, the LBE mass flow rate strongly depends on the injected argon flow time trend. The numerical results are in agreement with the experimental data, however further investigations are planned to analyze the complex phenomena involved

Coupled simulations of the NACIE facility using RELAP5 and ANSYS FLUENT codes

This work deals with the development and preliminarily assessment of a coupling methodology between a modified version of RELAP5/Mod3.3 STH code and FLUENT commercial CFD code, applied to the NACIE (natural circulation experiment) LBE (lead bismuth eutectic) experimental loop (built and located at the ENEA Brasimone research centre). The coupling tool is used to simulate experiments representative of both natural circulation conditions and isothermal gas enhanced (assisted) circulation. Furthermore, an accidental test reproducing an Unprotected Loss of Flow (ULOF) scenario is also simulated and the outcomes are presented. A preliminary sensitivity analysis has shown that, to guarantee a suitable numerical convergence, the assisted circulation tests require a time step one order of magnitude lower compared to natural circulation ones. The comparison between the RELAP5 stand-alone simulations and RELAP5/FLUENT coupled simulations proved the capability to simulate the thermal-hydraulic behaviour of a loop experimental facility for all the examined conditions

Experimental campaign on the upgraded He-FUS3 facility

An extensive thermal-hydraulic experimental campaign was conducted on He-FUS3 helium loop facility to support the conceptual design of HCLL and HCPB Test Blanket System. The experiments were divided into three distinct phases. The first one was dedicated to the evaluation of the new ATEKO Turbo Circulator (TC) performances, identifying its operating limits in terms of supplied helium mass flow as a function of rotational speed, cold by-pass opening and loop pressure. The outcomes were compared with the manufacturer theoretical performance map and with a RELAP5-3D pre-test computation. In the second phase, experiments were carried out to analyze the facility dynamic response in hot conditions and to characterize its main components (TC, heaters, economizer, cooling system and valves). The wide amount of collected data will serve for the development and validation of a numerical model of the facility at TBS conditions. For the third phase, the tests were designed to investigate He-FUS3 behavior in accidental conditions representative of LOFAs and LOCAs scenarios

Validation of SIMMER-III code for in-box LOCA of WCLL BB: Pre-test numerical analysis of Test D1.1 in LIFUS5/Mod3 facility

Abstract One of the four breeding blanket concepts for European DEMO nuclear fusion reactor is the Water-Cooled Lithium Lead Breeding Blanket (WCLL BB). The WCLL in-box LOCA (Loss Of Coolant Accident) is a major safety concern of this component, therefore transient behavior shall be investigated to support the design, to evaluate the consequences and to adopt mitigating countermeasures. To fulfill this objective, at first, SIMMER-III code was improved by implementing the chemical reaction model between PbLi and water. Then, SIMMER-III Verification and Validation (V&V) procedures have been established and conducted to obtain a qualified code for deterministic safety analysis. The verification activity was successfully completed, while the validation activity requires further effort according to the R&D plan set up in the framework of the EUROfusion Project. In view of this, an experimental campaign and a test matrix has been designed in LIFUS5/Mod3 facility performing pre-test analyses of Test D1.1. The preliminarily-defined test matrix will be used for the validation SIMMER-III according to a standard procedure. At the present stage, a pre-test numerical analysis was performed to support future experimental tests. The presented work aims to support the upcoming experimental activity in terms of setting up Boundary & Initial condition, specifying the most important parameters to be measured during tests and calculated by SIMMER-III code during transient and obtaining the best nodalization for the post-testing simulation. In particular, a qualitative analysis of obtained results was performed according to the available data time trends and based on engineering considerations. It aims to interpret the resulting sequence of main events and the identification of phenomenological windows and aspects, relevant to pressure transient and hydrogen production due to the chemical reaction between heavy liquid metal and water

HLMC Fuel Pin Bundle characterization in CIRCE-ICE pool facility

Abstract. This work, carried out at the DICI of Pisa University, in collaboration with ENEA Brasimone R.C., deals with the analysis and a preliminary discussion of the experimental tests performed in the Integral Circulation Experiment (ICE) configuration of the Circulation Eutectic (CIRCE) facility aiming to investigate the heat transfer in fuel rod bundle. The facility test section basically consists of an electrical bundle (FPS) made up of 37 pins arranged in a hexagonal wrapped lattice with a pitch to diameter ratio of 1.8. Along the FPS active length, two sections were instrumented to monitor the heat transfer coefficient along the bundle as well as the cladding temperatures at different ranks of the sub-channels. In particular, forced circulation condition tests were performed imposing a temperature difference through the FPS and a LBE mass flow rate through the FPS. Nusselt number in the sub-channels was calculated as function of the Peclet number and obtained results were compared to Nusselt numbers computed from correlations available in Heavy Liquid Metals (HLM) literature. Results shown that the Nu is slightly lower in the middle section (section 1) if compared with the ones into the upper section (section 3), and that behaviour is probably due to the turbulence of the flow which seems to be fully developed only in the upper part of the fuel pin bundle. Anyway the Nu number, calculated as function of the Pe number in the range Pe~1500÷3000 (forced circulation condition), matches well the numerical correlation available for HLM fuel pin bundle, (i.e. Ushakov and Mikityuk)

Simulation of operational conditions of HX-HERO in the CIRCE facility with CFD/STH coupled codes

Abstract The paper describes the application of a coupled methodology between Fluent CFD code and RELAP5 System Thermal-Hydraulic code developed at the DICI (Dipartimento di Ingegneria Civile e Industriale) of the University of Pisa. The methodology was applied specifically to the LBE-water heat exchanger HERO located inside the S100 vessel of the CIRCE facility, built at ENEA Brasimone Research Centre, to investigate the capabilities of this component. In the proposed methodology, the primary side of the HX-HERO, containing LBE, is simulated by the CFD code, while the secondary side, containing a two phase mixture of water and vapour, is reproduced by the System Thermal-Hydraulic code. During the calculation the two codes exchange, at the coupled boundaries: the bulk temperature and heat transfer coefficient of the ascending water (RELAP5 to Fluent) and the wall temperature at the water side surface of the pipes (Fluent to RELAP5). The coupling technique was tested by comparing the numerical results with the experimental data recently obtained by ENEA; the numerical results predicted well the qualitative trend of the temperature and provided an overall good prediction of the temperature also from a quantitative point of view. It is worth noticing that this good performance remained reliable for all the cases simulated, proving the general applicability of the methodology

Interactive Machine Learning for Embodied Interaction Design: A Tool and Methodology

As immersive technologies are increasingly being adopted by artists, dancers and developers in their creative work, there is a demand for tools and methods to design compelling ways of embodied interaction within virtual environments. Interactive Machine Learning allows creators to quickly and easily implement movement interaction in their applications by performing examples of movement to train a machine learning model. A key aspect of this training is providing appropriate movement data features for a machine learning model to accurately characterise the movement then recognise it from incoming data. We explore methodologies that aim to support creators’ understanding of movement feature data in relation to machine learning models and ask how these models hold the potential to inform creators’ understanding of their own movement. We propose a 5-day hackathon, bringing together artists, dancers and designers, to explore designing movement interaction and create prototypes using new interactive machine learning tool InteractML