74 Chapter IV Results and discussions In this Chapter IV, the neutronic analysis results by using SRAC are reported. The reactor core has been divided into 10 regions in radial direction and neutronic calculations have been performed and then the reactor core has been divided into 10 regions in axial direction. The standard sample calculations of Modified CANDLE shuffling in radial direction for the first case whose parameters (describe the value of each parameter) are presented in Table III.1 has been investigated and the standard sample calculations of Modified CANDLE shuffling in axial direction whose parameters are presented in Table III.8 has been investigated. The surveyed samples shuffling in radial direction for the first case whose parameters are mentioned in Table III.2, radial shuffling direction for the second case whose parameters are mentioned in Table III.3 and sample description in radial direction for the second case whose parameters are presented in Table III.4 were also carried out. The surveyed samples shuffling in axial direction whose parameters are mentioned in Table III.9 were carried out. The calculations have been performed in two stages. Fuel cell neutronic calculations and the reactor core calculation. Fuel cell calculations involve the calculations of fuel cell burn up for 100 years by using collision probability method (PIJ), with data collection intervals every two years. Neutronic calculations gave several neutronic features such as burn-up levels, infinite multiplication factor (k inf) integral Conversion ratio values (Integral.C.R.), Fission products (F.P), and atomic density values. While, the reactor core using CITATION calculations give several features such as multiplication factor (k eff) of core and the distribution of relative power density. IV.1 Results of Modified CANDLE shuffling in radial direction In this section, the neutronic analysis results of gas cooled fast reactor designed using Modified CANDLE shuffling in radial direction have been described. IV.1.1. Standard sample results in radial direction for first case Table III.1 illustrates the standard sample parameters. The power output is 900MWth, with fuel, cladding, and coolant volume percentages of 57.5%, 11.5%, and 31%, respectively for standard sample. 75 IV.1.1.1 Burnup level and atomic density of the fission product (FP) Figure IV.1 shows the standard sample's burnup level and atomic density of the fission product (FP). It is shown that at the beginning of life (BOL), the burnup level increased sharply because of the placement of the 1 st region near the tenth region (mostly active region). The regions can be divided into two zones. From 1-5 regions' breeding zones and regions 5-10 burning zones (most active regions) (Irka et al., 2023). After ten years of operation time until about 50 years, the burnup level increases insignificantly. The overall burnup increases considerably after 50 years of burnup until the end of life (EOL).