Thermal-hydraulics/thermal-mechanics temporal coupling for unprotected loss of flow accidents simulations on a SFR

In the frame of ASTRID designing, unprotected loss of flow (ULOF) accidents are considered. As the reactor is not scrammed, power evolution is driven by neutronic feedbacks, among which Doppler effect, linked to fuel temperature, is prominent. Fuel temperature is calculated using thermal properties...

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Bibliographic Details
Published in:EPJ nuclear sciences & technologies 2016-01, Vol.2, p.2
Main Authors: Patricot, Cyril, Kepisty, Grzegorz, Ammar, Karim, Campioni, Guillaume, Hourcade, Edouard
Format: Article
Language:English
Subjects:
Accidents
Doppler effect
Evolution
Feedback
Fluid dynamics
Fluid flow
Heat transfer coefficients
Hydraulics
Impact analysis
Mass flow
Mathematical analysis
Mechanics (physics)
Nuclear fuels
Physics
Sodium
Temperature
Thermal conductivity
Thermodynamic properties
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Summary:In the frame of ASTRID designing, unprotected loss of flow (ULOF) accidents are considered. As the reactor is not scrammed, power evolution is driven by neutronic feedbacks, among which Doppler effect, linked to fuel temperature, is prominent. Fuel temperature is calculated using thermal properties of fuel pins (we will focus on heat transfer coefficient between fuel pellet and cladding, Hgap, and on fuel thermal conductivity, λfuel) which vary with irradiation conditions (neutronic flux, mass flow and history for instance) and during transient (mainly because of dilatation of materials with temperature). In this paper, we propose an analysis of the impact of spatial variation and temporal evolution of thermal properties of fuel pins on a CFV-like core [M.S. Chenaud et al., Status of the ASTRID core at the end of the pre-conceptual design phase 1, in Proceedings of ICAPP 2013, Jeju Island, Korea (2013)] behavior during an ULOF accident. These effects are usually neglected under some a priori conservative assumptions. The vocation of our work is not to provide a best-estimate calculation of ULOF transient, but to discuss some of its physical aspects. To achieve this goal, we used TETAR, a thermal-hydraulics system code developed by our team to calculate ULOF transients, GERMINAL V1.5, a CEA code dedicated to SFR pin thermal-mechanics calculations and APOLLO3®, a neutronic code in development at CEA.
ISSN:2491-9292
2491-9292
DOI:10.1051/epjn/e2015-50036-x