Improvements and validation of the linear surface characteristics scheme

Apollo2 Year 2010

“…Indeed, for most of the assemblies considered the effect of the anisotropy on the keff value requires the use of a P5 order to get Monte Carlo accuracy. [71] However, this effect is less important on the detailed reaction-rate map and, in particular, on the power distribution fully optimized yet. For this method the time needed for the evaluation of the matrices rapidly increases with the number of groups and reaches near one half of the total computation time for the cases here discussed.…”

“…A further improvement is achieved by calculating the weight associated with the intersection of a trajectory with a surface as the product of the weight associated with the trajectory (usually a constant for uniformly spaced parallel trajectories) times the effective proportion of the surfaces 'viewed' by the trajectory. [71] This technique was inspired from a previous analysis whose aim was to minimize tracking for whole-core MOC calculations. [72] As an example calculation we consider two typical 17 17 PWR UOX and MOX assemblies [71].…”

“…[71] This technique was inspired from a previous analysis whose aim was to minimize tracking for whole-core MOC calculations. [72] As an example calculation we consider two typical 17 17 PWR UOX and MOX assemblies [71]. The calculations were done with 281-group SHEM multigroup cross sections based on JEFF3.1 [73] nuclear data evaluation, with self-shielding of resonant mixtures in the energy domains 22.5eV-2.2KeV and 22.5eV-7.5KeV for the UO2 and MOX assemblies, respectively, and P1 scattering anisotropy.…”

“…Finally, an improved surface representation for the angular flux moments was achieved by replacing the previous constant-surface approximation by a piecewise-constant approximation obtained by subdividing each surface of a region into several pieces. [71] The homogenization technique with the LS approximation was first tested against a reference TRIPOLI-4 calculation. We present in Fig.…”

Изследване На Изчислителни Схеми С Повишена Разделителна Способност За Неутронно-Физични Пресмятания На ВВЕР

“…Подробно описание на двата метода е дадено в статиите [34,45,46,47], а тук е направена представителна извадка на заложените идеи.…”