Development of the triangle-based nodal algorithm for reconstructing pin power distributions

Omid Safarzadeh

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URL :   http://research.shahed.ac.ir/WSR/WebPages/Report/PaperView.aspx?PaperID=137423
Date :  2020/02/14
Publish in :    Progress in Nuclear Energy
DOI :  https://doi.org/10.1016/j.pnucene.2020.103282
Link :  http://dx.doi.org/10.1016/j.pnucene.2020.103282
Keywords :Pin-wise power TPEN method Form function Hexagonal core

Abstract :

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The fuel pin power is an essential parameter for increasing the safety and reliability features of the reactor. Although the high-order triangle-based polynomial expansion nodal (TPEN) algorithm had been suggested for incredible accuracy and computational speed in hexagonal core analyses, the pin power reconstruction of this algorithm is not developed and assessed. This paper presents the characteristics and performances of the TPEN algorithm for pin power reconstruction. The converged nodal information obtained from sweep between coarsemesh finite difference (CMFD) and TPEN methods is used to reconstruct the neutron flux distribution in a homogeneous fuel assembly. The modulation technique is used to obtain the heterogeneous distribution of power density. In this technique, the power density homogeneous distribution, calculated with the reconstructed neutron flux is multiplied by a form function. These functions are generated by DRAGON5. The results obtained by this algorithm are verified for various core configurations of a VVER-1000 reactor. The pin power factors show good agreement with the reference solution obtained by heterogeneous fine mesh finite element method. The largest and average relative errors found were of the order of 5 and 0.5 for TPEN, in a peripheral cell of a fuel element with the faces towards the region of the baffle/reflector. We also compared the results with those obtained from the nodal expansion method (NEM). The maximum and mean relative error of 10 and 1 are found by the NEM method.