Application of Nodal Equivalence Parameters to Prismatic Vhtr Core Analysis
نویسندگان
چکیده
The generation of nodal cross sections and equivalence parameters for prismatic VHTR core components is discussed. For fuel-block cross section generation, a conventional single-block model with a reflective boundary condition is used. A one-dimensional fuel-reflector model is proposed for reflector cross section generation in order to accurately represent the significant neutron spectrum variation at the core-reflector interface. Two-dimensional multi-block models are used for obtaining control rod cross sections for rodded fuel and reflector blocks to best approximate actual spectra in the blocks. The verification of the models was performed by generating cross sections with the DRAGON and HELIOS codes, using the cross section data in 2-D and 3-D DIF3D nodal calculations, and comparing the results to MCNP4C ones. The results show that the use of discontinuity factors reduces errors in nodal solutions for the multiplication factor and power distribution. Surface-dependent discontinuity factors are found essential for improving the accuracy of the power distribution of cores with asymmetrically rodded blocks when nodal calculations are performed with one node per hexagonal block.
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