This project has received funding from the European Union's Horizon 2020 research and innovation programme under agreement No 945275

PASTELS Final Symposium - April 23rd-24th, 2024 in Paris-Saclay
Mar. 15 2024

The H2020 PASTELS project will be hosting its Final Symposium on May 23rd-24th, 2024 at EDF Lab Paris-Saclay, France

The PASTELS Final Symposium, as the final event of the project, seeks to present the results of the project and its perspectives after 4 years of work.

Registrations are mandatory to attend this event which will be hosted solely in person in EDF premices. 

  • When? 23-24 May, 2024
  • Where? In-person at EDF Lab Paris-Saclay

The final agenda for the event will be communicated at a later stage.

Should you have any questions or require further assistance, do not hesitate to reach out to us at

Thank you for your interest in PASTELS! We look forward to welcoming you to the Final Symposium and celebrating our collective accomplishments together.

PASTELS project visiting SIET facility
May. 10 2023

As part of its Internal progress review meeting, the PASTELS project visited SIET S.p.A.'s offices, laboratories and experimental facilities.

Representatives of SIET S.p.A. presented the work they carry out within the facility, and the project members were able to exchange, learn and develop ideas with our host.

We thank SIET S.p.A. for their time, hospitality, the consortium's different exchanges, and their answers.

Link to SIET article ➡

Link to SIET website ➡ 

Presentation given by SIET click on download 

PASTELS project - Best Paper Award ICAPP 2023
May. 02 2023

Congratulations to Michaël Montout from EDF, Joonas Telkkä from LUT University and Christophe Herer from IRSN for the best paper award they received during the ICAPP 2023 conference in Gyeongju Korea.

Paper title: PASTELS Project - Overall Progress of the Project on Experimental and Numerical Activities on Passive Safety Systems.

We would also like to congratulate the Project Consortium for their work and involvement in the project, which allowed for such a distinction.

This Award is a sign for the PASTELS project of the importance of the work carried out, and we are thankful to ICAPP 2023 for recognizing our work.


PASTELS: Workshop on Natural circulation passive systems
Mar. 23 2023

The PASTELS consortium organised a workshop at Erlangen hosted by FRA-G on the 22nd and 23rd of March, 2023.

The Consortium gathered 84 participants, and we would like to take this opportunity to thank everyone for participating in the PASTELS two-day workshop.

First day 22/03/2023

The workshop started with an overview of the PASTELS project as well as a presentation of Framatome and the site; following these presentations, the PASTELS project was able to host Martina Adorni from ENEA, who made a presentation titled NEA Activities related to Passive systems, afterwards Haseed Ur Rehman from IAEA presented IAEA's activities of the Use of Passive Safety Systems in Advanced Reactors. 

WP2 took over with the participation of the different institutions included in the WP (IRSN, EDF, ENEA, USTUTT, UJV). The various partners presented their studies on existing separate effect tests and combined effect tests.

During the second part of the afternoon, Thomas Wagner from FRA-G presented the Passive Safety Concept of KERENA and Fulvio Mascari from ENEA presented insights on passive systems modelling for SMR.

WP3 presented the work carried out by FRA-G, EDF, ENEA, CEA, GRS, USTUTT, IRSN, PSI and UJV regarding the PKL experiments with a safety condenser. 

The day ended with a presentation from Sanjeev Gupta from Becker Technologies titled THAI experimental research on the passive safety system.

Second day 23/03/2023

The second day of the workshop started with a presentation regarding the new EURATOM programme presented by ARTTIC, followed by a presentation by Thomas Fuchus (FRA-G) on Simulation and Design Strategy for the Development of Advanced Fuel Pool Cooling Systems.

WP4 presented the PASI experiments with Cold Wall Condenser by the partners involved (LUT, EDF, ENEA, CEA, GRS, IRSN, PSI, UJV). 

The Workshop presentations ended with Marco Caramello (Ansaldo) presentation regarding the Ansaldo experience in analysing and validating passive safety systems for decay heat removal.

The in-person participants were invited to visit the PKL facility at FRA-G.

Presentations made during the PASTELS Workshop are available on the following link.

Feb. 01 2023

The last two experiments in the frame of work package 3 of the PASTELS project were successfully conducted at the PKL test facility in winter 2022/2023. Test P2.1 replicated a cool-down transient under extended loss-of AC-power (ELAP) conditions and demonstrated the employment of the SACO as the ultimate heat sink for the cool-down of the plant. Test P2.2 further extended the database for validation of codes and validation models by the provision of experimental data on maximum SACO heat removal power for different fill levels inside the SACO straight tubes. By means of a parameter study with phases of steady-state operation of the facility and stepwise variation of fill levels inside the SACO straight tubes in between individual phases, test P2.2 explored the maximum heat removal capacity of the SACO for a given SACO straight-tube fill level.

Jun. 22 2022

Pastels project members got together from the 20th until the 23rd at Lappeenranta, Finland, for their internal project review and observe a PASI expirement at LUT.

The project organised a hybrid meeting to include as many people as possible. All the partners took part in the event. Pastels project members exchanged information on the project. They talked about what they have achieved up until now and what is going to happen next.

PASTELS Participation to the IAEA confencre
Aug. 01 2022

The PASTELS project participates to the IAEA International Conference on Topical Issues in Nuclear Installation Safety (TIC). The TIC-2022 conference is hosted in IAEA Headquarters Vienna, Austria from the 18th until the 21st of October 2022.
Thanks to Christophe Herer from IRSN, Adam Kecek and Ladislav Vyskočil, PASTELS project submitted a paper entitled ” NATURAL CIRCULATION HERO-2 EXPERIMENT SIMULATIONS FOR THE EU FUNDED PASTELS PROJECT”.
If you want to learn more about the conference and registration, follow this link:

Apr. 04 2022

The PASTELS PASI test campaign at LUT University, Lappeenranta, Finland started in March 2022 with the first test, which investigated the effect of loop friction on the open loop flow behavior and heat transfer from containment to the loop. The test was successfully conducted, showing an oscillative loop flow behavior as expected. The downcomer massflow rate is presented in the figure below.

The figure shows how the flow behavior depends on the flow resistance, which was executed by means of closing the shutoff valve in the downcomer line. During the experiment, quasi-steady states were run with six different valve positions starting with the valve fully open. The heat removal loop was able to transfer heat efficiently from the containment vessel to the heat sink and to keep the containment vessel pressure within a safe level. This shows that an oscillating flow can be an efficient heat removal mechanism.

Feb. 02 2022

PASTELS project is happy to announce that it will take part in the upcoming NURETH-19 conference. To follow the presentation given by our project partners make sure to register for the conference.

EDFIRSNCEALUT University and ENEA are gonna be presenting the Passive systems: Simulating the thermal-Hydraulics with experimental studies (PASTELS) on the 9th of March 2022 at 9.00 a.m

Check out the full programme of NURETH-19 by clicking on the following link:

Jan. 31 2022

The PASTELS project has just completed its first P1.1 programme phase on the Safety Condenser (SACO). Therefore, it started the parameter studies on heat transfer for different boundary conditions (variation of the filling level of the SACO pool, presence of non-condensable gases, variation of the core power). We are grateful and proud of the different partners who made this first step possible. The next step is evaluating the various numerical tools of the project on these innovative new test results.

Check out our website to learn more about the project :
PAssive Systems: Simulating the Thermal-hydraulics with ExperimentaL Studies - Home ( )

Jan. 26 2022

The PASTELS phase 1-tests conducted at the PKL test facility this week aims at collecting the first operating experience with a passive decay-heat removal system on the secondary side of a Western-type (Framatome) PWR.
The objective of the experimental activities is to collect experimental data on the heat removal capacity of the SACO in the vertical straight-tube configuration under different boundary conditions and operating states. Both PASTELS phase-1 parameter studies focus on heat transport phenomena in the SACO straight tubes and provide a database for improvement and further development of calculation models in so-called thermal-hydraulic system codes.
The overall goal of the EU-funded PASTELS project is to advance the technical readiness level (TRL) of passive safety systems for future Western-type LWR and improve methodologies and tools applied in the design and safety analysis of such systems.

Jan. 11 2022

The PASI Test Specification is out and currently available on the deliverable section of the webstie. 

Click here to get access



PASTELS project at the International Conference on Topical Issues in Nuclear Installation Safety
May. 01 2022

The PASTELS project is participating this year in the International Conference on Topical Issues in Nuclear Installation Safety
The conference is hosted in Vienna, Austria from the 18th until the 21st of October 2022.
Thanks to Christophe Herer from IRSN, PASTELS submitted an abstract accepted by the Conference and soon will submit the paper.
If you want to learn more about the conference and registration, follow this link:

Jul. 21 2021

Check out our Media Center (Downloads) to know more about WP4 dedicated to the study of Passive Containment Cooling Systems (PCCS) and the development an experimental data base on the PASI test facility operated by the LUT University laboratories. The PASI test specification report introduces the main modelling challenges and presents the test matrix, which is the baseline of future activities

Mar. 19 2021

The PASTELS first public deliverables are now available in the PASTELS Media Centre / Downloads. Go check them out!

Feb. 02 2021

Michael Montout (EDF) was invited to present the PASTELS project at the SNETP Forum 2021 on 3rd February 2021 (9:40 AM CET).

The PASTELS presentation was part of the first technical session, moderated by Pavel Kral (UJV) and Luis Herranz (CIEMAT). This session looked at long term operation and construction, focusing on topics such as hydrogen management, implementation of safety requirements in the post-Fukushima period, perspectives and opportunities for LTO in Europe, etc.

Over 630 participants registered and around 500 participants were actively involved over the 3 days event. All public presentations from the Forum can be downloaded from the SNETP website SNETP FORUM 2021 - Nuclear, an industry of the future - SNETP

Sep. 23 2020

On 24th and 25th September 2020, the 11 project partners gathered online to kick-off the PASTELS project. In the presence of the EC policy officer, Dr. Cristina Fernandez-Ramos, the PASTELS consortium discussed the planning of the first year and the immediate actions after the project start.

During the first day, the Project Coordinator, Michael Montout (EDF) and the WP leaders outlined the overall structure and the management principles. The second day was dedicated to the kick-off of the work packages. These fruitful discussions allowed the team to clarify the interactions among the WPs, the detailed planning, and the expected results.