Abstract
An improved supercell scheme has been proposed in this paper to efficiently and accurately process resonance self-shielding effect of gadolinia. Resonance effects are classified into global shadowing effect and local effects involving resonance interference, spatial self-shielding effects. Two categories of effects are decoupled and treated respectively based on different 1-D cylindrical pins. Hyperfine group method is applied to obtain multi-group cross sections for each 1-D pin. Afterwards, two categories of effects are coupled based on a correction formula. Because of the low efficiency for Carlvik method to compute collision probabilities in hyperfine group method, online tabulation and interpolation method is developed to accelerate gaining collision probabilities. The proposed scheme is verified against the problems of 3×3 pins with gadolinia rod, VERA 2O assembly with 12 gadolinia rods and VERA 2P with 24 gadolinia rods. The numerical results suggest promising consistence of multi-group cross sections and eigenvalues between the proposed scheme and reference solutions.
Highlights
The rapid development of computational ability allows us to perform fine neutronics calculation and have a better understanding of the detailed behavior of the whole nuclear reactor
High fidelity neutronics calculation requires accurate MG effective self-shielded XSs obtained from resonance calculation
In view of the fine mesh partition in gadolinia rod, calculation of CPs for the third pin should be further accelerated to enhance the practicability of the improved supercell scheme
Summary
The rapid development of computational ability allows us to perform fine neutronics calculation and have a better understanding of the detailed behavior of the whole nuclear reactor. High fidelity neutronics calculation requires accurate MG effective self-shielded XSs obtained from resonance calculation. The hyperfine group method will be timeconsuming to treat the supercell containing the gadolinia rod. In order to extend the supercell scheme to gadolinia rods in the frame of the self-shielding calculation of NECP-X, the previous supercell scheme has been improved to accelerate the computation efficiency to satisfy the practical application. The main reason for this treatment is that some techniques can be applied to accelerate the hyperfine group calculation, which allows the practical application of the supercell scheme. The aim of this paper is to treat resonance self-shielding effect of gadolinia To achieve this goal, the derivation of the improved supercell scheme is demonstrated. Accuracy of results are compared with reference solution and the improved performance on efficiency is presented
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