Design and modelling of underground decay heat removal system for a district heating reactor
Dif, Brahim (2021)
Diplomityö
2021
School of Energy Systems, Energiatekniikka
Kaikki oikeudet pidätetään.
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi-fe2021120759345
https://urn.fi/URN:NBN:fi-fe2021120759345
Tiivistelmä
Decay heat in fission reactors is a main concern from a safety perspective. Adequate removal of decay heat should be maintained under all circumstances to ensure reactor operability within safety limits and mitigating any undesirable consequences. This could be achieved by utilising passive safety which increases the inherent safety characteristics and reliability of the design.
The study carried out in this report investigates the feasibility of a proposed passive decay heat removal system for a 24 MWth nominal power underground district heating conceptual design. The proposed loop utilises air and steam mixture as a working fluid and relies on natural circulation to eject the heat from the containment to the ground as a buffer.
A Comprehensive review of condensation theory in horizontal tubes is provided in the literature review with a focus on the effect of non-condensable gas (NCG) on heat transfer. An analytical study is then performed using a MATLAB script substantiated with relevant correlations to determine the geometrical and operational parameters of the system. The analysis is initially performed for a pure steam case as a baseline then the effect of NCG is considered in a further updated model. This was followed by a numerical simulation using thermal hydraulic code system (TRACE) to study the overall behaviour of the loop. Both analytical and numerical results are compared.
The work presented in this report shows that removal of decay heat up to one month following shutdown is feasible with the proposed decay heat removal system. The presence of NCG in the loop has little to no effect on the condensation process and does not compromise the overall performance of the system significantly.
The study carried out in this report investigates the feasibility of a proposed passive decay heat removal system for a 24 MWth nominal power underground district heating conceptual design. The proposed loop utilises air and steam mixture as a working fluid and relies on natural circulation to eject the heat from the containment to the ground as a buffer.
A Comprehensive review of condensation theory in horizontal tubes is provided in the literature review with a focus on the effect of non-condensable gas (NCG) on heat transfer. An analytical study is then performed using a MATLAB script substantiated with relevant correlations to determine the geometrical and operational parameters of the system. The analysis is initially performed for a pure steam case as a baseline then the effect of NCG is considered in a further updated model. This was followed by a numerical simulation using thermal hydraulic code system (TRACE) to study the overall behaviour of the loop. Both analytical and numerical results are compared.
The work presented in this report shows that removal of decay heat up to one month following shutdown is feasible with the proposed decay heat removal system. The presence of NCG in the loop has little to no effect on the condensation process and does not compromise the overall performance of the system significantly.