Proceeding of ICAPP07, May 13-18, 2007
The SANM solution, a new transverse leakage approximation and a sub-plane scheme
are introduced to the axial solver of the DeCART code to improve the solution accuracy and to
obtain the nodal solutions efficiently, and their solutions are examined for a demonstrative
problem of Ref. 2 and the C5G7MOX 3-D extension benchmark problems. The proposed
transverse leakage scheme determines the three expansion coefficients of the second-order
approximation by using the three intra-nodal sub-node fluxes, and it shows a good performance
for improving the accuracy of the nodal solution when compared with the conventional scheme.
The SANM solutions using the proposed transverse leakage approximation are shown to be much
more accurate than the NEM solutions. The sub-plane scheme in which multiple sub-planes are
introduced within a thick MOC plane and share the equivalence parameters determined for a thick
MOC plane shows a very good efficiency in that it produces as accurate solutions as the
conventional multi MOC planes scheme but it requires a slightly more computational burden than
the one sub-plane per MOC plane case. In the demonstrative problem, the SANM calculation with
the proposed transverse leakage approximation and using three sub-planes per MOC plane shows
less than 6 pcm eigenvalue and 0.7 % power errors. In the C5G7MOX benchmark problem, the
SANM calculation with the proposed transverse leakage approximation and using three subplanes per MOC plane also shows a good performance by reducing a large eigenvalue and the pin
power errors to a trivial error level of less than 5 pcm eigenvalue and 0.1 % power errors.
Therefore, it is concluded that the SANM calculation with the proposed transverse leakage
approximation and introducing a few sub-planes is very effective in obtaining a very accurate
solution efficiently.
