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Analysis of hypothetical channel flow blockage of a tubular fuel assembly in a 10 MWth nuclear research reactor

  • Said M. A. Ibrahim , Mohamed H. Esawy EMAIL logo and Hossam I. Yousif ORCID logo
Published/Copyright: November 7, 2024
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Abstract

Heat removal from the core of nuclear reactors is a crucial safety requirement that needs much analysis and attention. Coolant channel flow blockage is one of the unintentional cases that may influence the required heat removal rate. As a result, unsustainable over heating of the fuel cladding could occur resulting eventually in affecting the fuel integrity. This paper deals with simulating the effect of total channel flow blockage in a single fuel assembly on its steady state thermal hydraulic parameters. Thermal hydraulic calculations are carried out for the much less studied IRT-4M ducted fuel assembly type in a 10 MWth WWR-S tank in pool research reactor. The simulated IRT-4M fuel assembly comprises six rounded rectangular fuel elements in which seven channels are used for cooling. A mathematical model is developed in which all steady state thermal hydraulic parameters and their distributions could be predicted for the blocked and unblocked flow channel cases. Calculations were performed for two separate hypothetical flow channel blockage cases in the innermost channel and the middle channel of the IRT-4M fuel assembly. The results showed that the maximum clad temperatures for the two-flow blockage cases are nearly 127.4 °C, and 132.2 °C, respectively. The temperature increases resulting from a single channel blockage are not high enough to cause fuel damage, although some local coolant boiling might occur. Model validation and results support the model outcomes and its applications in the safety of the research reactor during abnormal operation.


Corresponding author: Mohamed H. Esawy, Reactors Department, Nuclear Research Centre, Egyptian Atomic Energy Authority, Cairo, Egypt, E-mail:

  1. Research ethics: Not applicable.

  2. Informed consent: Not applicable.

  3. Author contributions: S. Ibrahim: Methodology, Validation, Visualization, Formal analysis, Writing (review & editing), Conceptualization, Supervision, Project administration; M. Esawy: Data curation, Software, Methodology, Writing (original draft), Validation, Supervision; H. Yousif: Data curation, Software. All authors have accepted responsibility for the entire content of this manuscript and approved its submission.

  4. Use of Large Language Models, AI and Machine Learning Tools: None declared.

  5. Conflict of interest: The authors state no conflict of interest.

  6. Research funding: None declared.

  7. Data availability: Not applicable.

Nomenclature

Symbols Subscript
A Surface area A Axial or average
Cp Specific heat of water Acc Acceleration
D Diameter B Bulk
DNB Departure from nucleate boiling Ch Channel
DNBR Departure from nucleate boiling ratio Cl Clad
F Friction coefficient Co Coolant
G Mass flux Con Convection
G Gravitational acceleration Crit Critical
H Active length of fuel tubes F Fuel
H Heat transfer coefficient FA Fuel assembly
I Enthalpy Fric Friction
K Thermal conductivity Grav Gravitational
m˚ Mass flow rate H Hydraulic or hot
N Number of fuel I Inside
OFI Onset of flow instability In Inlet
ONB Onset of nucleate boiling L Liquid
P Thermal power M Mixing
P Pressure or perimeter Max Maximum nucleate boiling
PPF Power peaking factor NCB Contribution
T Thickness O Outside
T Temperature S Surface
V Volume Sat Saturation
V Velocity Sp Single phase contribution
Z Axial fuel direction Sub Sub-cooled boiling
Greek symbols Tot Total
Difference Tp Total contribution
µ Dynamic viscosity (kg/m.s) Tube Tube
Nu Nusselt number V Vapor
Pr Prandtl number
Re Reynold’s number
Kinematic viscosity (m2/s)
Φ Heat flux
ρ Density

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Received: 2024-05-28
Accepted: 2024-10-20
Published Online: 2024-11-07
Published in Print: 2024-12-17

© 2024 Walter de Gruyter GmbH, Berlin/Boston

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