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Projects / Programmes source: ARIS

Pressurization process during vapour explosion in sodium cooled fast reactors

Research activity

Code Science Field Subfield
2.13.01  Engineering sciences and technologies  Process engineering  Multi-phase systems 

Code Science Field
T160  Technological sciences  Nuclear engineering and technology 

Code Science Field
2.03  Engineering and Technology  Mechanical engineering 
Keywords
sodium cooled fast reactor, nuclear safety, severe accident, vapour explosion, multi-phase flow, heat transfer, vaporization, numerical simulation
Evaluation (rules)
source: COBISS
Researchers (8)
no. Code Name and surname Research area Role Period No. of publicationsNo. of publications
1.  07025  PhD Leon Cizelj  Energy engineering  Researcher  2017 - 2020  963 
2.  33540  PhD Martin Draksler  Energy engineering  Researcher  2017 - 2020  108 
3.  05570  PhD Ivo Kljenak  Energy engineering  Researcher  2017 - 2020  468 
4.  39407  PhD Rok Krpan  Mechanics  Junior researcher  2017 - 2020  45 
5.  14572  PhD Matjaž Leskovar  Energy engineering  Researcher  2017 - 2020  436 
6.  35548  PhD Jure Oder  Energy engineering  Researcher  2017 - 2020  58 
7.  08661  PhD Andrej Prošek  Energy engineering  Researcher  2017 - 2020  600 
8.  29182  PhD Mitja Uršič  Process engineering  Head  2017 - 2020  265 
Organisations (2)
no. Code Research organisation City Registration number No. of publicationsNo. of publications
1.  0106  Jožef Stefan Institute  Ljubljana  5051606000  91,002 
2.  1554  University of Ljubljana, Faculty of Mathematics and Physics  Ljubljana  1627007  34,291 
Abstract
In the frame of safety studies for the innovative sodium cooled fast reactors, it is important to estimate the risk for the environment in case of a severe accident. One of the important issues in core melt progression during a severe accident in the innovative sodium cooled fast reactor is the likelihood and the consequences of a vapour explosion. A vapour explosion may occur when the hot core melt (i.e. molten fuel) comes into contact with the liquid sodium. A strong enough vapour explosion in a nuclear power plant could jeopardize the reactor integrity and so potentially lead to the release of radioactive material to the environment. Consequently, the understanding of the vapour explosion phenomenon is very important for nuclear safety. Indeed, previously performed experiments showed that vapour explosions may occur during fuel-sodium interaction. The applicability of the fuel-coolant interaction codes to cover the fuel-sodium interaction phenomena are currently under examination. One of the goals of the examination is to highlight the needs for research to improve the capabilities of fuel-coolant interaction codes on sodium. In-line with these activities the purpose of the project is to improve the understanding of the pressurization process during a vapour explosion in sodium. Namely, the precise nature of the pressurization process during a vapour explosion is an open issue. Two concepts are currently used in the analytical researches with water. The micro-interaction concept assumes local thermo-dynamical equilibrium mixing of the melt fragments and surrounding coolant. In the direct boiling concept the pressurization is due to the direct boiling at the interface of the melt fragments and coolant. The applicability of the proposed concepts for sodium must be investigated due to the important differences in the sodium and water properties. The investigation of the pressurization process may be supported using analytical research and precise numerical simulations. The main objectives of the project are the following: Analysis of pressurization modelling. The aim is to analyse the heat transfer and the vaporization around the melt. Simulation of vapour explosion in sodium. The aim is to assess the effect of the premixing conditions on the explosion strength and to demonstrate the applicability of the fuel-coolant interaction codes to experiments. By improving the fuel-coolant interaction codes we will obtain simulation tools, which will enable realistic simulations of fuel-coolant interaction experiments with sodium and in future more realistic simulations of reactor conditions, and consequently a more reliable estimation of the vulnerability of sodium cooled fast reactors to vapour explosions.
Significance for science
One of the most important remaining issues in the core melt progression during a sever nuclear reactor accident in current and future nuclear power plants is the likelihood and the consequences of a vapour explosion. To improve the understanding of the vapour explosion, we will improve the pressurization processes understanding and perform unique simulations of the vapour explosion in sodium with the fuel-coolant interaction code. The results of the proposed project will enhance the basis for detailed safety analyses in sodium cooled fast reactors. Safety analyses are necessary for the risk management to be able to implement the optimal severe accident management approaches. The expected results of the project will present a scientific contribution in the field of vapour explosion research related to nuclear safety.
Significance for the country
The results of the proposed project will be the basis for detailed safety analyses in sodium cooled fast reactors. Safety analyses are necessary for the risk management to be able to implement the optimal severe accident management approaches. Therefore, the research directly contributes to the future sustainable stable supply of electricity, to environment protection and public health. The proposed project will enable us to actively participate in the severe accidents researches of the generation IV reactors. The project would enable cooperation in the CEA PLINIUS2 (Platform for Improvements in Nuclear Industry and Utility Safety) platform planned to be built to support research and development activities related to the ASTRID (Advanced Sodium Technological Reactor for Industrial Demonstration) project. Additionally the project will improve possible engagements of the Reactor Engineering Division, Jožef Stefan Institute, in the future calls of the EU EURATOM program Horizon 2020. The proposed project will strengthen our cooperation with IRSN, France. Directly, the results of the proposed project will improve also the understanding of vapour explosions in water. Therefore the research contributes to creating, keeping and improving of own technical knowledge and enhances the independence on foreign expertise in support of safe Krško NPP operation and helps the regulatory body in the inspection of Krško NPP operation and maintenance. All this contributes to the increase of the competitive position of Slovenia.
Most important scientific results Interim report, final report
Most important socioeconomically and culturally relevant results Interim report, final report
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