This proposal was born in the framework of the collaboration between the DIAEE Nuclear section and ENEA Brasimone research center into the EU H2020 SESAME Project, for the validation of the system code RELAP5-3D© in pool temperature stratification analysis in heavy liquid metal reactor by comparison with experimental data.
In this frame, experimental data from CIRCE-ICE (Integral Circulation Experiments) pool facility at ENEA/Brasimone Research Center test section, which simulates the thermal behavior of a primary system in a HLM cooled pool reactor are available for us. The experimental campaign led to the characterization of mixed convection and thermal stratification in a HLM pool in safety relevant conditions and to the distribution of experimental data for the validation of system codes. The aim of this work is to investigate the capability of the system code RELAP5-3D© to simulate mixed convection and thermal stratification phenomena in a HLM pool in steady state conditions by comparing code results with experimental data, made available by ENEA, simulating the main vessel with a three dimensional component.
In summary, the innovations which this activity aims to achieve are:
- The experimental validation of RELAP5-3D© in natural and gas lift circulation;
- The verification of the capability of the code to reproduce thermal stratification and mixing convection phenomena into the pool.
The target of the proposal is to validate RELAP5-3D© in natural and forced circulation, comparing the simulation results with experimental data carried out during the experimental campaign on CIRCE-ICE test facility. This simulation was already performed by a research team of the ENEA Research Center, using RELAP5© mod 3.3, which is the modified version of the code by Ansaldo Nucleare and ENEA to implement new working fluids, including LBE. The results showed the capability of the code to reproduce the thermal-hydraulics of the primary flow path but highlighted that the system code was not able to reproduce thermal stratification phenomena [1].
One of the most improvement of the new version RELAP5-3D© is the capability to split the volume in three directions (using cylindrical, spherical or squared geometries), using a three dimensional balance equation set, in comparison of the one dimension resolution of the previous version. For this, the main objective of the activity is to investigate the capability of a three dimensional component to simulate thermal stratification and mixing convection phenomena into the pool.
In addition, our team implemented new thermos-physical property correlations of heavy liquid metal, according to the NEA state-of-the-art data [2] through the application of the soft-sphere model [3]. A new progress in this activity, will be the comparison between two different set of property correlations and also the comparison with experimental data.
The innovations of this activity are the code verification and validation (V&V) for the RELAP5-3D© with our modification (fundamental aspect for a nuclear application) and the investigation of the 3D component capability to simulate HLM pool thermal-hydraulics. The experimental validation of the system code may allow the use of RELAP5-3D© with our modification as design tool during the next planned developing phases, in particular for the safety analysis, establishing the best practice guidelines for the safety analysis of a Generation IV LFR pool type reactor.
Moreover the project will improve the experience with the coupled use of RELAP5-3D© and RAVEN [4], which can be used to run in a single job a multi-case sensitivity analysis with a variation of one or more parameters in the RELAP5-3D© basic input file, induced by a Monte Carlo sampling. Raven can also store and post-process all output from RELAP5-3D© and perform an uncertainty quantification with a comparison versus experimental data.
In summary, the innovations that this proposal aims to achieve are:
- The experimental verification and validation of RELAP5-3D© in natural and gas lift circulation of LBE under CIRCE-ICE conditions, with second order metrics, for the old and the new thermos-physical properties correlations;
- The investigation of the capability of RELAP5-3D© to reproduce thermal hydraulic phenomena into the pool of a HLM reactor;
- The improvement of the experience with the coupled use of RELAP5-3D© and RAVEN.
[1] Bandini G, Polidori M, Meloni P, Tarantino M, Di Piazza I (2014) RELAP5 and SIMMER-III code assessment on CIRCE decay heat removal experiments. Nucl. Eng. Des. 281, Jan 2015, 39¿50
[2] OECD/NEA. 2015 Handbook on Lead-bismuth Eutectic Alloy and Lead Properties, Materials Compatibility, Thermal- hydraulics and Technologies. NEA No. 7268.
[3] Balestra P, Giannetti F, Caruso G and Alfonsi A (2016) New RELAP5-3D lead and LBE thermophysical properties implementation for safety analysis of Gen IV reactors Sci. Technol. Nucl. Install. 2016.
[4] Alfonsi A, Rabiti C, Mandelli M, Cogliati J, Kinoshita B. RAVEN and Dynamic Probabilistic Risk Assessment: Software Overview, Proceedings of European Safety and Reliability Conference (ESREL 2014) Wroclaw (Poland), Sept. 14-18, 2014.