Research on isotope yield calculation methodology for HFETR

BackgroundThe High Flux Engineering Test Reactor (HFETR) is used to produce various medical isotopes due to its high neutron flux density. The calculation of isotope yield of HFETR needs to consider the characteristics of complex core structure, strong heterogeneity and large changes in radiation environment.PurposeThis study aims to establish a model and method for the accurate calculation of different types of isotope yields by employing a "deterministic fuel management-Monte Carlo particle transport-yield" coupled calculation strategy.MethodsFirstly, the core loading design and burnup calculation through the dedicated fuel management program for the research reactor were conducted to obtain the fuel burnup distribution and control rod positions at each time step along with other parameters. Then, the acquired data was applied to establishing automated full-core refined modeling and conducting neutron transport calculations employing the Monte Carlo method. The reaction rates between various nuclides and neutrons within the sample were systematically determined at each temporal interval. Subsequently, the concentration variations of critical nuclides in subsequent time steps were calculated through iterative coupling of the yield determination algorithm with the Monte Carlo program, and comprehensive evaluations of decay losses occurring during refueling shutdown phases and throughout the post-extraction measurement period were incorporated. Finally, the accuracy of the calculation program was verified by the isotope production experimental results obtained by HFETR.ResultsThe calculation results show that the deviation for the production yield of 89Sr through irradiation of 88Sr is 5.41%, the deviation for the production yield of 32P through irradiation is 4.90%, and the deviation for the production yield of 177Lu through irradiation is 5.66%. All deviations are within 6% compared with experimental results.ConclusionsResults of this study demonstrate that this calculation method improves the accuracy of isotope yield calculation, hence can be used to accurately evaluate the isotope yield of the research reactor isotope production mission.