Project topics and materials
Get Complete Project Material File(s) Now! »
Traditional fuel and the proposed fuel design
The fuel cladding tube in LWR is approximately 4 metres long containing many fuel pellets stacked end-to-end to form a fuel rod. The packing structure of the fuel in the tube as depicted in Fig.1.1 is considered to be a simple (rod) with gas contained in the annulus between the pellets and the tube and hence it makes the heat transfer phenomenon in the tube easy and straightforward to calculate as discussed in Chapter 5.
The concept of the new design proposed in the study (see Fig.1.2) is to redesign the nuclear fuel in the form of loose coated particles in a helium atmosphere inside the nuclear fuel cladding tube of the fuel elements (see Fig. 1.3). The coated particle fuel being the heat source forms a bed in the cladding tube, which is closed at both ends. The heat generated by the fuel particles through nuclear fission is transferred to the gas filling the space between particles and interstice between particles and the inside tube walls. The heat transfer from the fuel to the tube is the objective of the investigation.
By converting the inside of the cladding into a porous medium, it is necessary to evaluate the heat transfer characteristics inside the medium under natural convective heat transfer conditions. To do this, there is the need to examine and confirm the suitability of using existing correlations in determining the heat transfer phenomenon in the medium noting the peculiarity of the medium. In the past, heat transfer correlations for packed beds have been investigated but the applicability of these correlations is mostly limited to the particular bed materials used in developing them. The applicability and accuracy of these correlations are uncertain.
An earlier review of most models (some of which are discussed in Chapter 3) used in predicting heat transfer in packed beds as presented by [7] reveals that many of the models are highly empirical in nature and applicable under forced convection. It is evident that these correlations do not account for the thermophysical properties of contacting particles and flowing gas, the interstitial gas effect, gas temperature, contact interface between particles, particle size and particle temperature distribution in the medium. This measure is considered vital in heat transfer phenomenon because they are parameters that define the heat transfer effects in the system. The developed correlations are based on flow in the medium. This reason and the one stated earlier annul the suitability of using the developed correlations in the cladding tube. Review and work done by [8], [9] and [10] reveal an increasing use of theoretical modelling in predicting the heat transfer in packed beds. Most work done on heat transfer in porous media summarised by [9], [11] and [12], adopted a microscopic approach considering a finite contact spot between individual particles in the bed and also relating the convective heat effect of the flowing fluid (gas) with the conduction effect between adjacent particles at the contact spot.
1 Introduction
1.1 Background
1.2 Research problem statement
1.2.1 Traditional fuel and the proposed fuel design
1.3 Methodology
1.4 Contribution of the stud
1.5 Proposed nuclear fuel safety enhancement
1.6 Publication
1.7 Chapter outline
2 Porous Structure
2.1 Introduction
2.2 Analysis of packing regions
2.3 Structured (ordered) packing
2.4 Limitations on defining packing structures with porosity only
2.5 Conclusion
3
3.1 Introduction
3.2 Well-known correlations
3.3 Solid and fluid heat transfer models
3.4 Conclusion
4 Test Facility and Experimental Evaluation of Heat Transfer in the Investigating Medium
4.1 Introduction
4.2 Facility configuration
4.3 Particle test sample instrumentation and measurements
4.4 Uncertainty analysis
4.5 Experimental evaluation of heat transfer in the test facility
4,6 Results and discussio
4.7 Conclusion
5 Theoretical: Basic Unit Cell Model
6 Numerical Modelling of Natural Convection Heat Transfer and Transport 105 in an Enclosed Slender Tube Geometrical Model Containing Heated Microspheres
7 Conclusions and Recommendations
References
