PASTELS project - overall progress of the project on experimental and numerical activities on passive safety systems
Résumé
Nuclear accidents such as Fukushima Daiichi have highlighted the potential of passive safety systems to replace
or complement active safety systems as part of the overall prevention and/or mitigation strategies. In addition,
passive systems are key features of Small Modular Reactors (SMRs), for which they are becoming almost unavoidable and are part of the basic design of many reactors available in today’s nuclear market. Nevertheless,
their potential to significantly increase the safety of nuclear power plants still needs to be strengthened, in
particular the ability of computer codes to determine their performance and reliability in industrial applications
and support the safety demonstration.
The PASTELS project (September 2020–February 2024), funded by the European Commission “Euratom
H2020” programme, is devoted to the study of passive systems relying on natural circulation. The project focuses
on two types, namely the SAfety COndenser (SACO) for the evacuation of the core residual power and the
Containment Wall Condenser (CWC) for the reduction of heat and pressure in the containment vessel in case of
accident.
A specific design for each of these systems is being investigated in the project. Firstly, a straight vertical pool
type of SACO has been implemented on the Framatome’s PKL loop at Erlangen. It represents a tube bundle type
heat exchanger that transfers heat from the secondary circuit to the water pool in which it is immersed by
condensing the vapour generated in the steam generator. Secondly, the project relies on the CWC installed on the
PASI test loop at LUT University in Finland. This facility reproduces the thermal-hydraulic behaviour of a Passive
Containment Cooling System (PCCS) mainly composed of a CWC, a heat exchanger in the containment vessel
connected to a water tank at atmospheric pressure outside the vessel which represents the ultimate heat sink.
Several activities are carried out within the framework of the project. Different tests are conducted on these
integral test facilities to produce new and relevant experimental data allowing to better characterize the physical
behaviours and the performances of these systems for various thermo-hydraulic conditions. These test programmes are simulated by different codes acting at different scales, mainly system and CFD codes. New “system/
CFD” coupling approaches are also considered to evaluate their potential to benefit both from the accuracy of
CFD in regions where local 3D effects are dominant and system codes whose computational speed, robustness
and general level of physical validation are particularly appreciated in industrial studies. In parallel, the project
includes the study of single and two-phase natural circulation loops through a bibliographical study and the
simulations of the PERSEO and HERO-2 experimental facilities. After a synthetic presentation of the project and
its objectives, this article provides the reader with findings related to the physical analysis of the test results
obtained on the PKL and PASI installations as well an overall evaluation of the capability of the different numerical tools to simulate passive systems.
Domaines
Physique [physics]
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Licence : CC BY NC ND - Paternité - Pas d'utilisation commerciale - Pas de modification