Proceeding of ICAPP06, June 4-8, 2006
The geometry module of the DeCART direct whole core calculation code has been
extended in order to analyze BWR cores which might have a mixed loading of different fuel types.
First, an assembly based modular ray tracing scheme was implemented for the Method of
Characteristic (MOC) calculation, and a CMFD formulation applicable for unaligned mesh
conditions was then developed for acceleration the MOC calculation. The new calculation feature
has been validated by comparing DeCART BWR assembly calculations with the MCU Monte
Carlo calculations. A good agreement identified by the maximum eigenvalue difference of 120
pcm and the maximum pin power error of about 1% has been achieved. The CMFD scheme is
shown to reduce the number of MOC iterations by factors of 12-25 without loss of accuracy.
