S-Space College of Engineering/Engineering Practice School (공과대학/대학원) Dept. of Energy Systems Engineering (에너지시스템공학부) Nuclear Engineering (원자핵공학전공) Journal Papers (저널논문_원자핵공학과)
Multigroup pin power reconstruction with two-dimensional source expansion and corner flux discontinuity
- Joo, Han Gyu; Yoon, Joo Il; Baek, Seung Gyou
- Issue Date
- Ann. Nucl. Eng. 36, 85
- A pin power reconstruction method that is readily applicable to multigroup problems with superior accuracy
is presented for applications involving rectangular fuel assemblies. It employs a two-dimensional
(2D), fourth order Legendre expansion of the source distribution that naturally leads to a group-decoupled,
2D semi-analytic solution of the neutron diffusion equation. The four surface average currents
and four corner fluxes are used as the boundary conditions to uniquely specify the homogenous solution.
The corner fluxes and source expansion coefficients are iteratively determined using the condition of corner
point balance and the orthogonal property of the Lengedre functions. Corner discontinuity is incorporated
in the calculation of the corner fluxes which turns out to be very effective in the cases of
enrichment zoning. The accuracy of the proposed method is assessed by performing the two-step core
calculations for the L336C5, C5G7MOX, and MOX core transient benchmark problems and then by comparing
with the direct whole-core transport solutions. The results indicate that the proposed method is as
accurate as the fully analytic method and works well irrespective the number of groups. However, it is
also noted that somewhat larger errors are inevitable at the peripheral assemblies near the reflector in
which the error associated with a prioi generation of the homogenized cross-sections and form functions
is not trivial.
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