The Conceptual Design Study Of A Compact PWR Core Utilizing TRISO Fuel

The aim of this research is to design a compact nuclear reactor by utilizing TRISO fuel in PWR technology. TRISO fuel has been chosen for the current design study because of its superior reliability against the release of fission fragments. The study is focused on the neutronics and steady state thermal hydraulic safety analysis of the designed core to assess the feasibility of utilizing TRISO fuel in PWR technology without any modification in existing PWR design.To accomplish the task a detailed parametric study was carried out to identify the important fuel and core design parameters as a starting point for a complete reactor core design. The designed core was analyzed in the dissertation which comprises of 3 main domains. First is the development of excess reactivity control mechanism. Second is the neutronics design and finally, the steady state thermal hydraulic analysis of the designed core. Transport theory lattice simulation code WIMS-D/4. diffusion theory based computer code CITATION and light water reactor transient analysis code RELAP5 were used for the conceptual design study.An important feature of the design is a novel TRISO fuel particle composition which provides reactivity control technique over the entire fuel cycle. A small amount of Pu-240 with 5.0 w/o has been added in TRISO fuel particle in the place of U-238. The utilization of inventive TRISO fuel particle can completely eliminate the use of soluble boron system and requirement of burnable poison if adequate number of control rods is used. The Soluble Boron Free (SBF) and Burnable Poison Free (BPF) concepts are more viable in small and medium size reactors (SMRs) because it makes the plant simpler and uniform burnup can be achieved throughout the core. The designed core operates at lower temperature and pressure than a standard PWR power reactor because of its specific use (i.e. heating, desalination and limited power production). The reactor power density is also relatively low and the presence of TRISO fuel also ensures further safety under all operating scenarios.The research presented in the thesis revealed that the combination of TRISO fuel in PWR technology results in a more reliable, safer and better nuclear design. The use of small amount of Pu-240 with 5.0 w/o in TRISO fuel particle resulted in a significant reduction of the excess reactivity through out the fuel cycle. The excess reactivity was reduced to only 6.22%Δk/k from 27.00%Δk/k at the start of fuel cycle. The soluble boron system and burnable poison has been completely eliminated from the design due to the enhanced reactivity control of the design. The values of Doppler, moderator and void reactivity coefficients were found-3.34 pcm K-1,-4.90 pcm K-1 and-91.00 pcm%VM-1 respectively.Steady state thermal hydraulic analysis presented in this thesis depicted that the value of minimum departure from nucleate boiling ratio (MDNBR) at rated power and 115%power is sufficiently larger than the nominal value PWR design. The fuel centre line operating temperature of the designed core was only 930℃which is well below than the melting temperature of UO2 and centerline fuel temperature of standard PWR design. It was also observed that the maximum value of total power peaking factor was only 2.10 and the local power peaking factor (LPF) remained less than 2.15 throughout the fuel cycle. The reactor remains critical for at least 550 EFPD with 260 kg of heavy metal fuel inventory.