Periodic Reporting for period 2 - PASTELS (PAssive Systems: Simulating the Thermal-hydraulics with ExperimentaL Studies)
Okres sprawozdawczy: 2022-03-01 do 2023-08-31
The PASTELS project aims to significantly increase the knowledge of passive systems for European nuclear actors. One of the main objectives of the project is to evaluate and improve the ability of several system and CFD codes, used in the nuclear community for design and safety demonstration, to accurately model key physical phenomena for passive systems such as natural circulation loops.
Given the increasing use of passive systems in non-European nuclear power plants, it is essential, especially with the rise of Small Modular Reactors (SMRs) that largely integrate these systems into their design, that the European nuclear community adapts its numerical reference tools to study these promising technologies. This must be undertaken based on relevant and representative experimental data of the passive systems of interest. The SAfety COndenser (SACO) and the Containment Wall Condenser (CWC) are the two innovative passive systems selected for the project.
The project builds on existing combined effects test campaigns obtained in the PERSEO and HERO-2 test facilities (SIET, Piacenza, Italy), but also on new data obtained in full-scale test facilities operating under conditions close to industrial applications that fill the gap in representative experimental data at European level: PKL test facility (Framatome GmbH, Erlangen, Germany) for CESO and PASI test facility (LUT, Lappeenranta, Finland) for CWC.
Numerical and experimental activities are carried out in a step-by-step approach. Through different benchmarks, PASTELS studies model improvements and proposes new coupling methodologies to obtain the benefits of system and CFD scales in the same calculation.
In addition, important knowledge on the behaviour of SACO and CWC is gained by observing their behaviour during the test campaigns.
All the results of the project will contribute to the development of detailed methodological guidelines and a roadmap for the licensing and implementation of these innovative passive system technologies in future European nuclear power plants.
Given the increasing use of passive systems in non-European nuclear power plants, it is essential, especially with the rise of Small Modular Reactors (SMRs) that largely integrate these systems into their design, that the European nuclear community adapts its numerical reference tools to study these promising technologies. This must be undertaken based on relevant and representative experimental data of the passive systems of interest. The SAfety COndenser (SACO) and the Containment Wall Condenser (CWC) are the two innovative passive systems selected for the project.
The project builds on existing combined effects test campaigns obtained in the PERSEO and HERO-2 test facilities (SIET, Piacenza, Italy), but also on new data obtained in full-scale test facilities operating under conditions close to industrial applications that fill the gap in representative experimental data at European level: PKL test facility (Framatome GmbH, Erlangen, Germany) for CESO and PASI test facility (LUT, Lappeenranta, Finland) for CWC.
Numerical and experimental activities are carried out in a step-by-step approach. Through different benchmarks, PASTELS studies model improvements and proposes new coupling methodologies to obtain the benefits of system and CFD scales in the same calculation.
In addition, important knowledge on the behaviour of SACO and CWC is gained by observing their behaviour during the test campaigns.
All the results of the project will contribute to the development of detailed methodological guidelines and a roadmap for the licensing and implementation of these innovative passive system technologies in future European nuclear power plants.
The consortium was able to set up a project management structure to steer the project on an ongoing basis through 3 documents: the management plan (deliverable D1.1) a SharePoint (D1.2) to allow collaborative work between the partners and the data management plan (D1.3).
The project started its technical activities with a bibliographic research on the phenomena related to natural circulation in closed loop (D2.1).
Then, the numerical activity analysis on Separated Effect Test (HERO-2, D2.2) was done during this first period M1-M18, and during the second period M18-M36 for Combined effect Test (PERSEO, D3.2 ). Various numerical tools at the system and CFD scales were used in order to assess the simulation capabilities of natural circulation phenomena. The results of the system codes highlighted the general agreement of the simulation results with the experimental results, but also the difficulties encountered (simulating each test in the closed configuration for HERO-2 with a single input deck...). The CFD codes have also encountered difficulties in performing the various tests, due to the extremely high computational costs/times incompatible with the timeframe for the publication of the final deliverable. Although the results are not entirely satisfactory, this study enabled an initial assessment of the code's capabilities to be made and provided guidelines for improving the experiment and the models.
For the SACO activities, the specifications for the design and construction of this new passive system on the PKL test loop have also been finalised (D3.1). Two sets of tests dedicated have been specified. The first is devoted to sensitivity analyses of the SACO boundary conditions and the second consists of a simulation of a transient scenario - the Station Black-Out (SBO) scenario - and additional sensitivity analyses devoted to the impact of filling the SACO tubes on its performance. The test matrix for phase 1 was performed at the end of this first period (D3.2) and during the second period for phase 2 (D3.4). The results of the phase 1 calculations have been published in the phase 1 deliverable (D3.3) and the results of the phase 2 numerical activities will be available by the end of 2023.
For the CWC, the PASI test matrix was also defined by the consortium (D4.1) and the test facility was modified to accommodate the needs of the test programme (D4.2). A numerical analysis of the PASI pre-tests (D4.3) was carried out using the system codes for model calibration. General agreement on the qualitative results was found with the development of oscillations in the thermosyphon loop. Nevertheless, some differences were observed on quantitative parameters such as power extraction, mass flux ranges during oscillation, etc. The experimental results are capitalised in deliverable D4.4. The overall analysis of the numerical results on the CWC simulations will also be available at the end of 2023 (D4.5).
The project proposed a dissemination and communication plan at the beginning of the project (D5.1) and set up different media to communicate about the project such as a Project public website (D5.2) a LinkedIn account, a pedagogical video…
A dozen papers have been presented to date at various conference, for instance, SNETP forum 2021, NURETH-19 and FISA/EURADWASTE in 2022 and NURETH-20 and ICAPP in 2023, for which the project received a 'Best Paper Award'.
The project also organised an end-user workshop at Framatome Erlangen in March 2023 with 50 participants on site for a total of 80 participants from Europe, North America and Asia.
Finally, the project provided the EC with the legal documents on ethical issues (D6.1) of the test facilities used in the PASTELS project (PKL and PASI operated by LUT and Framatome GmbH respectively).
The project started its technical activities with a bibliographic research on the phenomena related to natural circulation in closed loop (D2.1).
Then, the numerical activity analysis on Separated Effect Test (HERO-2, D2.2) was done during this first period M1-M18, and during the second period M18-M36 for Combined effect Test (PERSEO, D3.2 ). Various numerical tools at the system and CFD scales were used in order to assess the simulation capabilities of natural circulation phenomena. The results of the system codes highlighted the general agreement of the simulation results with the experimental results, but also the difficulties encountered (simulating each test in the closed configuration for HERO-2 with a single input deck...). The CFD codes have also encountered difficulties in performing the various tests, due to the extremely high computational costs/times incompatible with the timeframe for the publication of the final deliverable. Although the results are not entirely satisfactory, this study enabled an initial assessment of the code's capabilities to be made and provided guidelines for improving the experiment and the models.
For the SACO activities, the specifications for the design and construction of this new passive system on the PKL test loop have also been finalised (D3.1). Two sets of tests dedicated have been specified. The first is devoted to sensitivity analyses of the SACO boundary conditions and the second consists of a simulation of a transient scenario - the Station Black-Out (SBO) scenario - and additional sensitivity analyses devoted to the impact of filling the SACO tubes on its performance. The test matrix for phase 1 was performed at the end of this first period (D3.2) and during the second period for phase 2 (D3.4). The results of the phase 1 calculations have been published in the phase 1 deliverable (D3.3) and the results of the phase 2 numerical activities will be available by the end of 2023.
For the CWC, the PASI test matrix was also defined by the consortium (D4.1) and the test facility was modified to accommodate the needs of the test programme (D4.2). A numerical analysis of the PASI pre-tests (D4.3) was carried out using the system codes for model calibration. General agreement on the qualitative results was found with the development of oscillations in the thermosyphon loop. Nevertheless, some differences were observed on quantitative parameters such as power extraction, mass flux ranges during oscillation, etc. The experimental results are capitalised in deliverable D4.4. The overall analysis of the numerical results on the CWC simulations will also be available at the end of 2023 (D4.5).
The project proposed a dissemination and communication plan at the beginning of the project (D5.1) and set up different media to communicate about the project such as a Project public website (D5.2) a LinkedIn account, a pedagogical video…
A dozen papers have been presented to date at various conference, for instance, SNETP forum 2021, NURETH-19 and FISA/EURADWASTE in 2022 and NURETH-20 and ICAPP in 2023, for which the project received a 'Best Paper Award'.
The project also organised an end-user workshop at Framatome Erlangen in March 2023 with 50 participants on site for a total of 80 participants from Europe, North America and Asia.
Finally, the project provided the EC with the legal documents on ethical issues (D6.1) of the test facilities used in the PASTELS project (PKL and PASI operated by LUT and Framatome GmbH respectively).
First, an inventory of the data of interest available in the literature has been established. Experimentally, the first tests on SACO have shown that the system works despite the presence and formation of non-condensable gases in proportions not initially expected and which do not significantly disturb the heat extraction expected when the exchanger was dimmed.
Numerically, the results on HERO-2, PERSEO, PKL and PASI show a generally satisfactory agreement of the system codes with the experimental data. The CFD codes have more difficulties in simulating all the physical phenomena of these systems (condensation in particular), notably because of the much higher simulation cost. This also illustrated the importance of having as much information as possible on the thermal and pressure losses inherent in these experimental loops to correctly condition the input decks of the codes. The latest tests on PKL and PASI show that the SACO and CWC studied in the project are robust enough to extract energy at a good level despite the presence of non-condensable gas (SACO) or with oscillating behaviour (CWC), which underlines the interest in promoting their implementation in future nuclear power plants.
One of the first impact of the project will be the integration of experimental data and reference input decks into the validation database for the codes used as part of the PASTELS project.
In addition, the PASTELS consortium is starting discussions with other projects (SASPAM, EASI-SMR, etc.) to share the knowledge acquired during the project from an experimental and numerical point of view.
Numerically, the results on HERO-2, PERSEO, PKL and PASI show a generally satisfactory agreement of the system codes with the experimental data. The CFD codes have more difficulties in simulating all the physical phenomena of these systems (condensation in particular), notably because of the much higher simulation cost. This also illustrated the importance of having as much information as possible on the thermal and pressure losses inherent in these experimental loops to correctly condition the input decks of the codes. The latest tests on PKL and PASI show that the SACO and CWC studied in the project are robust enough to extract energy at a good level despite the presence of non-condensable gas (SACO) or with oscillating behaviour (CWC), which underlines the interest in promoting their implementation in future nuclear power plants.
One of the first impact of the project will be the integration of experimental data and reference input decks into the validation database for the codes used as part of the PASTELS project.
In addition, the PASTELS consortium is starting discussions with other projects (SASPAM, EASI-SMR, etc.) to share the knowledge acquired during the project from an experimental and numerical point of view.