123 Chapter V Conclusion and suggestions V.1 Conclusion Design and neutronic analysis of a modular modified CANDLE fast reactor shuffling in radial and axial directions using helium gas as coolant have been carried out. Based on the calculation results and analysis that have been carried out, the following conclusions could be drawn from this research: 1. In this research, a comparison of neutronic studies of fast reactor with modified CANDLE burnup schemes shuffling in radial direction using helium gas, lead bismuth eutectic and liquid sodium coolants has been investigated. The investigation has been done on a 400MWth power reactor and refuelling process every ten years of burnup. The reactor core has been divided into ten regions with the same volume in radial direction. Initial, the fuel was loaded in the first region, and after ten years, it was shifted to the second region, ten years late, the fuel in the second region was shifted into the third region and so on. The fuel in ninth region was shifted into tenth region and the fuel in tenth region has been taken out of reactor core. Based on the results, the utilization of liquid sodium coolant attained on the critical condition faster than that of helium gas and lead-bismuth eutectic coolants. This makes it to be the best coolant. 2. In this research, a 900MWth modular modified CANDLE fast reactor shuffling in radial direction using helium gas as coolant and various fuel volumes fraction 57.5 %, 60%,62.5% and 65% and refuelling process every ten years of burnup has been designed. The helium gas has been selected as a coolant due to that, helium has high thermal conductivity, has a large specific heat capacity, lower neutron absorption cross-section, does not become radioactive upon exposure to neutron radiation, low boiling point and it is inertness gas comparing to the other gases. In the same way like on designing a 400MWth power using various coolants, the reactor core has been divided into ten regions with the same volume directed radially. The fuel was initially placed in the first region, and after ten years of burnup, it was transferred to the second region, and after another ten years, it was transferred to the third 124 region. This technique was applied to all ten regions, and the fuel in the tenth region was removed from the core. SRAC was employed to perform the neutronic calculations with JENDL 4.0 as nuclear data library. The results show that a small amount of fuel volume fraction causes an increasing rate of burnup level and a decreasing rate of effective multiplication factor. The highest average discharge burnup level is about 370GWd/Ton HM or 37%HM for the fuel volume fraction of 57.5% and the lowest average discharge burnup level is about 328GWd/Ton HM or 32.8%HM for the fuel volume fraction of 65%. 3. In this research, a gas cooled fast reactor employing modified CANDLE shuffling in axial direction strategy was designed.